gcc/

[official-gcc.git] / gcc / ada / sem_ch8.adb

------------------------------------------------------------------------------
--                                                                          --
--                         GNAT COMPILER COMPONENTS                         --
--                                                                          --
--                              S E M . C H 8                               --
--                                                                          --
--                                 B o d y                                  --
--                                                                          --
--          Copyright (C) 1992-2007, Free Software Foundation, Inc.         --
--                                                                          --
-- GNAT is free software;  you can  redistribute it  and/or modify it under --
-- terms of the  GNU General Public License as published  by the Free Soft- --
-- ware  Foundation;  either version 3,  or (at your option) any later ver- --
-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
-- for  more details.  You should have  received  a copy of the GNU General --
-- Public License  distributed with GNAT; see file COPYING3.  If not, go to --
-- http://www.gnu.org/licenses for a complete copy of the license.          --
--                                                                          --
-- GNAT was originally developed  by the GNAT team at  New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc.      --
--                                                                          --
------------------------------------------------------------------------------

with Atree;    use Atree;
with Debug;    use Debug;
with Einfo;    use Einfo;
with Elists;   use Elists;
with Errout;   use Errout;
with Exp_Tss;  use Exp_Tss;
with Exp_Util; use Exp_Util;
with Fname;    use Fname;
with Freeze;   use Freeze;
with Impunit;  use Impunit;
with Lib;      use Lib;
with Lib.Load; use Lib.Load;
with Lib.Xref; use Lib.Xref;
with Namet;    use Namet;
with Namet.Sp; use Namet.Sp;
with Nlists;   use Nlists;
with Nmake;    use Nmake;
with Opt;      use Opt;
with Output;   use Output;
with Restrict; use Restrict;
with Rident;   use Rident;
with Rtsfind;  use Rtsfind;
with Sem;      use Sem;
with Sem_Cat;  use Sem_Cat;
with Sem_Ch3;  use Sem_Ch3;
with Sem_Ch4;  use Sem_Ch4;
with Sem_Ch6;  use Sem_Ch6;
with Sem_Ch12; use Sem_Ch12;
with Sem_Disp; use Sem_Disp;
with Sem_Dist; use Sem_Dist;
with Sem_Res;  use Sem_Res;
with Sem_Util; use Sem_Util;
with Sem_Type; use Sem_Type;
with Stand;    use Stand;
with Sinfo;    use Sinfo;
with Sinfo.CN; use Sinfo.CN;
with Snames;   use Snames;
with Style;    use Style;
with Table;
with Tbuild;   use Tbuild;
with Uintp;    use Uintp;

package body Sem_Ch8 is

   ------------------------------------
   -- Visibility and Name Resolution --
   ------------------------------------

   --  This package handles name resolution and the collection of
   --  interpretations for overloaded names, prior to overload resolution.

   --  Name resolution is the process that establishes a mapping between source
   --  identifiers and the entities they denote at each point in the program.
   --  Each entity is represented by a defining occurrence. Each identifier
   --  that denotes an entity points to the corresponding defining occurrence.
   --  This is the entity of the applied occurrence. Each occurrence holds
   --  an index into the names table, where source identifiers are stored.

   --  Each entry in the names table for an identifier or designator uses the
   --  Info pointer to hold a link to the currently visible entity that has
   --  this name (see subprograms Get_Name_Entity_Id and Set_Name_Entity_Id
   --  in package Sem_Util). The visibility is initialized at the beginning of
   --  semantic processing to make entities in package Standard immediately
   --  visible. The visibility table is used in a more subtle way when
   --  compiling subunits (see below).

   --  Entities that have the same name (i.e. homonyms) are chained. In the
   --  case of overloaded entities, this chain holds all the possible meanings
   --  of a given identifier. The process of overload resolution uses type
   --  information to select from this chain the unique meaning of a given
   --  identifier.

   --  Entities are also chained in their scope, through the Next_Entity link.
   --  As a consequence, the name space is organized as a sparse matrix, where
   --  each row corresponds to a scope, and each column to a source identifier.
   --  Open scopes, that is to say scopes currently being compiled, have their
   --  corresponding rows of entities in order, innermost scope first.

   --  The scopes of packages that are mentioned in  context clauses appear in
   --  no particular order, interspersed among open scopes. This is because
   --  in the course of analyzing the context of a compilation, a package
   --  declaration is first an open scope, and subsequently an element of the
   --  context. If subunits or child units are present, a parent unit may
   --  appear under various guises at various times in the compilation.

   --  When the compilation of the innermost scope is complete, the entities
   --  defined therein are no longer visible. If the scope is not a package
   --  declaration, these entities are never visible subsequently, and can be
   --  removed from visibility chains. If the scope is a package declaration,
   --  its visible declarations may still be accessible. Therefore the entities
   --  defined in such a scope are left on the visibility chains, and only
   --  their visibility (immediately visibility or potential use-visibility)
   --  is affected.

   --  The ordering of homonyms on their chain does not necessarily follow
   --  the order of their corresponding scopes on the scope stack. For
   --  example, if package P and the enclosing scope both contain entities
   --  named E, then when compiling the package body the chain for E will
   --  hold the global entity first,  and the local one (corresponding to
   --  the current inner scope) next. As a result, name resolution routines
   --  do not assume any relative ordering of the homonym chains, either
   --  for scope nesting or to order of appearance of context clauses.

   --  When compiling a child unit, entities in the parent scope are always
   --  immediately visible. When compiling the body of a child unit, private
   --  entities in the parent must also be made immediately visible. There
   --  are separate routines to make the visible and private declarations
   --  visible at various times (see package Sem_Ch7).

   --              +--------+         +-----+
   --              | In use |-------->| EU1 |-------------------------->
   --              +--------+         +-----+
   --                                    |                      |
   --      +--------+                 +-----+                +-----+
   --      | Stand. |---------------->| ES1 |--------------->| ES2 |--->
   --      +--------+                 +-----+                +-----+
   --                                    |                      |
   --              +---------+           |                   +-----+
   --              | with'ed |------------------------------>| EW2 |--->
   --              +---------+           |                   +-----+
   --                                    |                      |
   --      +--------+                 +-----+                +-----+
   --      | Scope2 |---------------->| E12 |--------------->| E22 |--->
   --      +--------+                 +-----+                +-----+
   --                                    |                      |
   --      +--------+                 +-----+                +-----+
   --      | Scope1 |---------------->| E11 |--------------->| E12 |--->
   --      +--------+                 +-----+                +-----+
   --          ^                         |                      |
   --          |                         |                      |
   --          |   +---------+           |                      |
   --          |   | with'ed |----------------------------------------->
   --          |   +---------+           |                      |
   --          |                         |                      |
   --      Scope stack                   |                      |
   --      (innermost first)             |                      |
   --                                 +----------------------------+
   --      Names  table =>            | Id1 |     |    |     | Id2 |
   --                                 +----------------------------+

   --  Name resolution must deal with several syntactic forms: simple names,
   --  qualified names, indexed names, and various forms of calls.

   --  Each identifier points to an entry in the names table. The resolution
   --  of a simple name consists in traversing the homonym chain, starting
   --  from the names table. If an entry is immediately visible, it is the one
   --  designated by the identifier. If only potentially use-visible entities
   --  are on the chain, we must verify that they do not hide each other. If
   --  the entity we find is overloadable, we collect all other overloadable
   --  entities on the chain as long as they are not hidden.
   --
   --  To resolve expanded names, we must find the entity at the intersection
   --  of the entity chain for the scope (the prefix) and the homonym chain
   --  for the selector. In general, homonym chains will be much shorter than
   --  entity chains, so it is preferable to start from the names table as
   --  well. If the entity found is overloadable, we must collect all other
   --  interpretations that are defined in the scope denoted by the prefix.

   --  For records, protected types, and tasks, their local entities are
   --  removed from visibility chains on exit from the corresponding scope.
   --  From the outside, these entities are always accessed by selected
   --  notation, and the entity chain for the record type, protected type,
   --  etc. is traversed sequentially in  order to find the designated entity.

   --  The discriminants of a type and the operations of a protected type or
   --  task are unchained on  exit from the first view of the type, (such as
   --  a private or incomplete type declaration, or a protected type speci-
   --  fication) and re-chained when compiling the second view.

   --  In the case of operators,  we do not make operators on derived types
   --  explicit. As a result, the notation P."+" may denote either a user-
   --  defined function with name "+", or else an implicit declaration of the
   --  operator "+" in package P. The resolution of expanded names always
   --  tries to resolve an operator name as such an implicitly defined entity,
   --  in addition to looking for explicit declarations.

   --  All forms of names that denote entities (simple names, expanded names,
   --  character literals in some cases) have a Entity attribute, which
   --  identifies the entity denoted by the name.

   ---------------------
   -- The Scope Stack --
   ---------------------

   --  The Scope stack keeps track of the scopes currently been compiled.
   --  Every entity that contains declarations (including records) is placed
   --  on the scope stack while it is being processed, and removed at the end.
   --  Whenever a non-package scope is exited, the entities defined therein
   --  are removed from the visibility table, so that entities in outer scopes
   --  become visible (see previous description). On entry to Sem, the scope
   --  stack only contains the package Standard. As usual, subunits complicate
   --  this picture ever so slightly.

   --  The Rtsfind mechanism can force a call to Semantics while another
   --  compilation is in progress. The unit retrieved by Rtsfind must be
   --  compiled in  its own context, and has no access to the visibility of
   --  the unit currently being compiled. The procedures Save_Scope_Stack and
   --  Restore_Scope_Stack make entities in current open scopes invisible
   --  before compiling the retrieved unit, and restore the compilation
   --  environment afterwards.

   ------------------------
   -- Compiling subunits --
   ------------------------

   --  Subunits must be compiled in the environment of the corresponding stub,
   --  that is to say with the same visibility into the parent (and its
   --  context) that is available at the point of the stub declaration, but
   --  with the additional visibility provided by the context clause of the
   --  subunit itself. As a result, compilation of a subunit forces compilation
   --  of the parent (see description in lib-). At the point of the stub
   --  declaration, Analyze is called recursively to compile the proper body of
   --  the subunit, but without reinitializing the names table, nor the scope
   --  stack (i.e. standard is not pushed on the stack). In this fashion the
   --  context of the subunit is added to the context of the parent, and the
   --  subunit is compiled in the correct environment. Note that in the course
   --  of processing the context of a subunit, Standard will appear twice on
   --  the scope stack: once for the parent of the subunit, and once for the
   --  unit in the context clause being compiled. However, the two sets of
   --  entities are not linked by homonym chains, so that the compilation of
   --  any context unit happens in a fresh visibility environment.

   -------------------------------
   -- Processing of USE Clauses --
   -------------------------------

   --  Every defining occurrence has a flag indicating if it is potentially use
   --  visible. Resolution of simple names examines this flag. The processing
   --  of use clauses consists in setting this flag on all visible entities
   --  defined in the corresponding package. On exit from the scope of the use
   --  clause, the corresponding flag must be reset. However, a package may
   --  appear in several nested use clauses (pathological but legal, alas!)
   --  which forces us to use a slightly more involved scheme:

   --    a) The defining occurrence for a package holds a flag -In_Use- to
   --    indicate that it is currently in the scope of a use clause. If a
   --    redundant use clause is encountered, then the corresponding occurrence
   --    of the package name is flagged -Redundant_Use-.

   --    b) On exit from a scope, the use clauses in its declarative part are
   --    scanned. The visibility flag is reset in all entities declared in
   --    package named in a use clause, as long as the package is not flagged
   --    as being in a redundant use clause (in which case the outer use
   --    clause is still in effect, and the direct visibility of its entities
   --    must be retained).

   --  Note that entities are not removed from their homonym chains on exit
   --  from the package specification. A subsequent use clause does not need
   --  to rechain the visible entities, but only to establish their direct
   --  visibility.

   -----------------------------------
   -- Handling private declarations --
   -----------------------------------

   --  The principle that each entity has a single defining occurrence clashes
   --  with the presence of two separate definitions for private types: the
   --  first is the private type declaration, and second is the full type
   --  declaration. It is important that all references to the type point to
   --  the same defining occurrence, namely the first one. To enforce the two
   --  separate views of the entity, the corresponding information is swapped
   --  between the two declarations. Outside of the package, the defining
   --  occurrence only contains the private declaration information, while in
   --  the private part and the body of the package the defining occurrence
   --  contains the full declaration. To simplify the swap, the defining
   --  occurrence that currently holds the private declaration points to the
   --  full declaration. During semantic processing the defining occurrence
   --  also points to a list of private dependents, that is to say access types
   --  or composite types whose designated types or component types are
   --  subtypes or derived types of the private type in question. After the
   --  full declaration has been seen, the private dependents are updated to
   --  indicate that they have full definitions.

   ------------------------------------
   -- Handling of Undefined Messages --
   ------------------------------------

   --  In normal mode, only the first use of an undefined identifier generates
   --  a message. The table Urefs is used to record error messages that have
   --  been issued so that second and subsequent ones do not generate further
   --  messages. However, the second reference causes text to be added to the
   --  original undefined message noting "(more references follow)". The
   --  full error list option (-gnatf) forces messages to be generated for
   --  every reference and disconnects the use of this table.

   type Uref_Entry is record
      Node : Node_Id;
      --  Node for identifier for which original message was posted. The
      --  Chars field of this identifier is used to detect later references
      --  to the same identifier.

      Err : Error_Msg_Id;
      --  Records error message Id of original undefined message. Reset to
      --  No_Error_Msg after the second occurrence, where it is used to add
      --  text to the original message as described above.

      Nvis : Boolean;
      --  Set if the message is not visible rather than undefined

      Loc : Source_Ptr;
      --  Records location of error message. Used to make sure that we do
      --  not consider a, b : undefined as two separate instances, which
      --  would otherwise happen, since the parser converts this sequence
      --  to a : undefined; b : undefined.

   end record;

   package Urefs is new Table.Table (
     Table_Component_Type => Uref_Entry,
     Table_Index_Type     => Nat,
     Table_Low_Bound      => 1,
     Table_Initial        => 10,
     Table_Increment      => 100,
     Table_Name           => "Urefs");

   Candidate_Renaming : Entity_Id;
   --  Holds a candidate interpretation that appears in a subprogram renaming
   --  declaration and does not match the given specification, but matches at
   --  least on the first formal. Allows better error message when given
   --  specification omits defaulted parameters, a common error.

   -----------------------
   -- Local Subprograms --
   -----------------------

   procedure Analyze_Generic_Renaming
     (N : Node_Id;
      K : Entity_Kind);
   --  Common processing for all three kinds of generic renaming declarations.
   --  Enter new name and indicate that it renames the generic unit.

   procedure Analyze_Renamed_Character
     (N       : Node_Id;
      New_S   : Entity_Id;
      Is_Body : Boolean);
   --  Renamed entity is given by a character literal, which must belong
   --  to the return type of the new entity. Is_Body indicates whether the
   --  declaration is a renaming_as_body. If the original declaration has
   --  already been frozen (because of an intervening body, e.g.) the body of
   --  the function must be built now. The same applies to the following
   --  various renaming procedures.

   procedure Analyze_Renamed_Dereference
     (N       : Node_Id;
      New_S   : Entity_Id;
      Is_Body : Boolean);
   --  Renamed entity is given by an explicit dereference. Prefix must be a
   --  conformant access_to_subprogram type.

   procedure Analyze_Renamed_Entry
     (N       : Node_Id;
      New_S   : Entity_Id;
      Is_Body : Boolean);
   --  If the renamed entity in a subprogram renaming is an entry or protected
   --  subprogram, build a body for the new entity whose only statement is a
   --  call to the renamed entity.

   procedure Analyze_Renamed_Family_Member
     (N       : Node_Id;
      New_S   : Entity_Id;
      Is_Body : Boolean);
   --  Used when the renamed entity is an indexed component. The prefix must
   --  denote an entry family.

   procedure Analyze_Renamed_Primitive_Operation
     (N       : Node_Id;
      New_S   : Entity_Id;
      Is_Body : Boolean);
   --  If the renamed entity in a subprogram renaming is a primitive operation
   --  or a class-wide operation in prefix form, save the target object, which
   --  must be added to the list of actuals in any subsequent call.

   function Applicable_Use (Pack_Name : Node_Id) return Boolean;
   --  Common code to Use_One_Package and Set_Use, to determine whether
   --  use clause must be processed. Pack_Name is an entity name that
   --  references the package in question.

   procedure Attribute_Renaming (N : Node_Id);
   --  Analyze renaming of attribute as function. The renaming declaration N
   --  is rewritten as a function body that returns the attribute reference
   --  applied to the formals of the function.

   procedure Check_Frozen_Renaming (N : Node_Id; Subp : Entity_Id);
   --  A renaming_as_body may occur after the entity of the original decla-
   --  ration has been frozen. In that case, the body of the new entity must
   --  be built now, because the usual mechanism of building the renamed
   --  body at the point of freezing will not work. Subp is the subprogram
   --  for which N provides the Renaming_As_Body.

   procedure Check_In_Previous_With_Clause
     (N   : Node_Id;
      Nam : Node_Id);
   --  N is a use_package clause and Nam the package name, or N is a use_type
   --  clause and Nam is the prefix of the type name. In either case, verify
   --  that the package is visible at that point in the context: either  it
   --  appears in a previous with_clause, or because it is a fully qualified
   --  name and the root ancestor appears in a previous with_clause.

   procedure Check_Library_Unit_Renaming (N : Node_Id; Old_E : Entity_Id);
   --  Verify that the entity in a renaming declaration that is a library unit
   --  is itself a library unit and not a nested unit or subunit. Also check
   --  that if the renaming is a child unit of a generic parent, then the
   --  renamed unit must also be a child unit of that parent. Finally, verify
   --  that a renamed generic unit is not an implicit child declared within
   --  an instance of the parent.

   procedure Chain_Use_Clause (N : Node_Id);
   --  Chain use clause onto list of uses clauses headed by First_Use_Clause in
   --  the proper scope table entry. This is usually the current scope, but it
   --  will be an inner scope when installing the use clauses of the private
   --  declarations of a parent unit prior to compiling the private part of a
   --  child unit. This chain is traversed when installing/removing use clauses
   --  when compiling a subunit or instantiating a generic body on the fly,
   --  when it is necessary to save and restore full environments.

   function Has_Implicit_Character_Literal (N : Node_Id) return Boolean;
   --  Find a type derived from Character or Wide_Character in the prefix of N.
   --  Used to resolved qualified names whose selector is a character literal.

   function Has_Private_With (E : Entity_Id) return Boolean;
   --  Ada 2005 (AI-262): Determines if the current compilation unit has a
   --  private with on E.

   procedure Find_Expanded_Name (N : Node_Id);
   --  Selected component is known to be expanded name. Verify legality
   --  of selector given the scope denoted by prefix.

   function Find_Renamed_Entity
     (N         : Node_Id;
      Nam       : Node_Id;
      New_S     : Entity_Id;
      Is_Actual : Boolean := False) return Entity_Id;
   --  Find the renamed entity that corresponds to the given parameter profile
   --  in a subprogram renaming declaration. The renamed entity may be an
   --  operator, a subprogram, an entry, or a protected operation. Is_Actual
   --  indicates that the renaming is the one generated for an actual subpro-
   --  gram in an instance, for which special visibility checks apply.

   function Has_Implicit_Operator (N : Node_Id) return Boolean;
   --  N is an expanded name whose selector is an operator name (eg P."+").
   --  declarative part contains an implicit declaration of an operator if it
   --  has a declaration of a type to which one of the predefined operators
   --  apply. The existence of this routine is an implementation artifact. A
   --  more straightforward but more space-consuming choice would be to make
   --  all inherited operators explicit in the symbol table.

   procedure Inherit_Renamed_Profile (New_S : Entity_Id; Old_S : Entity_Id);
   --  A subprogram defined by a renaming declaration inherits the parameter
   --  profile of the renamed entity. The subtypes given in the subprogram
   --  specification are discarded and replaced with those of the renamed
   --  subprogram, which are then used to recheck the default values.

   function Is_Appropriate_For_Record (T : Entity_Id) return Boolean;
   --  Prefix is appropriate for record if it is of a record type, or an access
   --  to such.

   function Is_Appropriate_For_Entry_Prefix (T : Entity_Id) return Boolean;
   --  True if it is of a task type, a protected type, or else an access to one
   --  of these types.

   procedure Note_Redundant_Use (Clause : Node_Id);
   --  Mark the name in a use clause as redundant if the corresponding entity
   --  is already use-visible. Emit a warning if the use clause comes from
   --  source and the proper warnings are enabled.

   procedure Premature_Usage (N : Node_Id);
   --  Diagnose usage of an entity before it is visible

   procedure Use_One_Package (P : Entity_Id; N : Node_Id);
   --  Make visible entities declared in package P potentially use-visible
   --  in the current context. Also used in the analysis of subunits, when
   --  re-installing use clauses of parent units. N is the use_clause that
   --  names P (and possibly other packages).

   procedure Use_One_Type (Id : Node_Id);
   --  Id is the subtype mark from a use type clause. This procedure makes
   --  the primitive operators of the type potentially use-visible.

   procedure Write_Info;
   --  Write debugging information on entities declared in current scope

   procedure Write_Scopes;
   pragma Warnings (Off, Write_Scopes);
   --  Debugging information: dump all entities on scope stack

   --------------------------------
   -- Analyze_Exception_Renaming --
   --------------------------------

   --  The language only allows a single identifier, but the tree holds an
   --  identifier list. The parser has already issued an error message if
   --  there is more than one element in the list.

   procedure Analyze_Exception_Renaming (N : Node_Id) is
      Id  : constant Node_Id := Defining_Identifier (N);
      Nam : constant Node_Id := Name (N);

   begin
      Enter_Name (Id);
      Analyze (Nam);

      Set_Ekind          (Id, E_Exception);
      Set_Exception_Code (Id, Uint_0);
      Set_Etype          (Id, Standard_Exception_Type);
      Set_Is_Pure        (Id, Is_Pure (Current_Scope));

      if not Is_Entity_Name (Nam) or else
        Ekind (Entity (Nam)) /= E_Exception
      then
         Error_Msg_N ("invalid exception name in renaming", Nam);
      else
         if Present (Renamed_Object (Entity (Nam))) then
            Set_Renamed_Object (Id, Renamed_Object (Entity (Nam)));
         else
            Set_Renamed_Object (Id, Entity (Nam));
         end if;
      end if;
   end Analyze_Exception_Renaming;

   ---------------------------
   -- Analyze_Expanded_Name --
   ---------------------------

   procedure Analyze_Expanded_Name (N : Node_Id) is
   begin
      --  If the entity pointer is already set, this is an internal node, or a
      --  node that is analyzed more than once, after a tree modification. In
      --  such a case there is no resolution to perform, just set the type. For
      --  completeness, analyze prefix as well.

      if Present (Entity (N)) then
         if Is_Type (Entity (N)) then
            Set_Etype (N, Entity (N));
         else
            Set_Etype (N, Etype (Entity (N)));
         end if;

         Analyze (Prefix (N));
         return;
      else
         Find_Expanded_Name (N);
      end if;
   end Analyze_Expanded_Name;

   ---------------------------------------
   -- Analyze_Generic_Function_Renaming --
   ---------------------------------------

   procedure Analyze_Generic_Function_Renaming  (N : Node_Id) is
   begin
      Analyze_Generic_Renaming (N, E_Generic_Function);
   end Analyze_Generic_Function_Renaming;

   --------------------------------------
   -- Analyze_Generic_Package_Renaming --
   --------------------------------------

   procedure Analyze_Generic_Package_Renaming   (N : Node_Id) is
   begin
      --  Apply the Text_IO Kludge here, since we may be renaming one of the
      --  subpackages of Text_IO, then join common routine.

      Text_IO_Kludge (Name (N));

      Analyze_Generic_Renaming (N, E_Generic_Package);
   end Analyze_Generic_Package_Renaming;

   ----------------------------------------
   -- Analyze_Generic_Procedure_Renaming --
   ----------------------------------------

   procedure Analyze_Generic_Procedure_Renaming (N : Node_Id) is
   begin
      Analyze_Generic_Renaming (N, E_Generic_Procedure);
   end Analyze_Generic_Procedure_Renaming;

   ------------------------------
   -- Analyze_Generic_Renaming --
   ------------------------------

   procedure Analyze_Generic_Renaming
     (N : Node_Id;
      K : Entity_Kind)
   is
      New_P : constant Entity_Id := Defining_Entity (N);
      Old_P : Entity_Id;
      Inst  : Boolean   := False; -- prevent junk warning

   begin
      if Name (N) = Error then
         return;
      end if;

      Generate_Definition (New_P);

      if Current_Scope /= Standard_Standard then
         Set_Is_Pure (New_P, Is_Pure (Current_Scope));
      end if;

      if Nkind (Name (N)) = N_Selected_Component then
         Check_Generic_Child_Unit (Name (N), Inst);
      else
         Analyze (Name (N));
      end if;

      if not Is_Entity_Name (Name (N)) then
         Error_Msg_N ("expect entity name in renaming declaration", Name (N));
         Old_P := Any_Id;
      else
         Old_P := Entity (Name (N));
      end if;

      Enter_Name (New_P);
      Set_Ekind (New_P, K);

      if Etype (Old_P) = Any_Type then
         null;

      elsif Ekind (Old_P) /= K then
         Error_Msg_N ("invalid generic unit name", Name (N));

      else
         if Present (Renamed_Object (Old_P)) then
            Set_Renamed_Object (New_P,  Renamed_Object (Old_P));
         else
            Set_Renamed_Object (New_P, Old_P);
         end if;

         Set_Is_Pure          (New_P, Is_Pure          (Old_P));
         Set_Is_Preelaborated (New_P, Is_Preelaborated (Old_P));

         Set_Etype (New_P, Etype (Old_P));
         Set_Has_Completion (New_P);

         if In_Open_Scopes (Old_P) then
            Error_Msg_N ("within its scope, generic denotes its instance", N);
         end if;

         Check_Library_Unit_Renaming (N, Old_P);
      end if;
   end Analyze_Generic_Renaming;

   -----------------------------
   -- Analyze_Object_Renaming --
   -----------------------------

   procedure Analyze_Object_Renaming (N : Node_Id) is
      Id  : constant Entity_Id := Defining_Identifier (N);
      Dec : Node_Id;
      Nam : constant Node_Id   := Name (N);
      T   : Entity_Id;
      T2  : Entity_Id;

      function In_Generic_Scope (E : Entity_Id) return Boolean;
      --  Determine whether entity E is inside a generic cope

      ----------------------
      -- In_Generic_Scope --
      ----------------------

      function In_Generic_Scope (E : Entity_Id) return Boolean is
         S : Entity_Id;

      begin
         S := Scope (E);
         while Present (S) and then S /= Standard_Standard loop
            if Is_Generic_Unit (S) then
               return True;
            end if;

            S := Scope (S);
         end loop;

         return False;
      end In_Generic_Scope;

   --  Start of processing for Analyze_Object_Renaming

   begin
      if Nam = Error then
         return;
      end if;

      Set_Is_Pure (Id, Is_Pure (Current_Scope));
      Enter_Name (Id);

      --  The renaming of a component that depends on a discriminant requires
      --  an actual subtype, because in subsequent use of the object Gigi will
      --  be unable to locate the actual bounds. This explicit step is required
      --  when the renaming is generated in removing side effects of an
      --  already-analyzed expression.

      if Nkind (Nam) = N_Selected_Component
        and then Analyzed (Nam)
      then
         T := Etype (Nam);
         Dec :=  Build_Actual_Subtype_Of_Component (Etype (Nam), Nam);

         if Present (Dec) then
            Insert_Action (N, Dec);
            T := Defining_Identifier (Dec);
            Set_Etype (Nam, T);
         end if;

         --  Complete analysis of the subtype mark in any case, for ASIS use

         if Present (Subtype_Mark (N)) then
            Find_Type (Subtype_Mark (N));
         end if;

      elsif Present (Subtype_Mark (N)) then
         Find_Type (Subtype_Mark (N));
         T := Entity (Subtype_Mark (N));
         Analyze (Nam);

         if Nkind (Nam) = N_Type_Conversion
            and then not Is_Tagged_Type (T)
         then
            Error_Msg_N
              ("renaming of conversion only allowed for tagged types", Nam);
         end if;

         Resolve (Nam, T);

      --  Ada 2005 (AI-230/AI-254): Access renaming

      else pragma Assert (Present (Access_Definition (N)));
         T := Access_Definition
                (Related_Nod => N,
                 N           => Access_Definition (N));

         Analyze_And_Resolve (Nam, T);

         --  Ada 2005 (AI-231): "In the case where the type is defined by an
         --  access_definition, the renamed entity shall be of an access-to-
         --  constant type if and only if the access_definition defines an
         --  access-to-constant type" ARM 8.5.1(4)

         if Constant_Present (Access_Definition (N))
           and then not Is_Access_Constant (Etype (Nam))
         then
            Error_Msg_N ("(Ada 2005): the renamed object is not "
                         & "access-to-constant (RM 8.5.1(6))", N);
         end if;
      end if;

      --  Special processing for renaming function return object

      if Nkind (Nam) = N_Function_Call
        and then Comes_From_Source (Nam)
      then
         case Ada_Version is

            --  Usage is illegal in Ada 83

            when Ada_83 =>
               Error_Msg_N
                 ("(Ada 83) cannot rename function return object", Nam);

            --  In Ada 95, warn for odd case of renaming parameterless function
            --  call if this is not a limited type (where this is useful)

            when others =>
               if Warn_On_Object_Renames_Function
                 and then No (Parameter_Associations (Nam))
                 and then not Is_Limited_Type (Etype (Nam))
               then
                  Error_Msg_N
                    ("?renaming function result object is suspicious",
                     Nam);
                  Error_Msg_NE
                    ("\?function & will be called only once",
                     Nam, Entity (Name (Nam)));
                  Error_Msg_N
                    ("\?suggest using an initialized constant object instead",
                     Nam);
               end if;
         end case;
      end if;

      --  An object renaming requires an exact match of the type. Class-wide
      --  matching is not allowed.

      if Is_Class_Wide_Type (T)
        and then Base_Type (Etype (Nam)) /= Base_Type (T)
      then
         Wrong_Type (Nam, T);
      end if;

      T2 := Etype (Nam);

      --  (Ada 2005: AI-326): Handle wrong use of incomplete type

      if Nkind (Nam) = N_Explicit_Dereference
        and then Ekind (Etype (T2)) = E_Incomplete_Type
      then
         Error_Msg_N ("invalid use of incomplete type", Id);
         return;
      end if;

      --  Ada 2005 (AI-327)

      if Ada_Version >= Ada_05
        and then Nkind (Nam) = N_Attribute_Reference
        and then Attribute_Name (Nam) = Name_Priority
      then
         null;

      elsif Ada_Version >= Ada_05
        and then Nkind (Nam) in N_Has_Entity
      then
         declare
            Error_Node  : Node_Id;
            Nam_Decl    : Node_Id;
            Nam_Ent     : Entity_Id;
            Subtyp_Decl : Node_Id;

         begin
            if Nkind (Nam) = N_Attribute_Reference then
               Nam_Ent := Entity (Prefix (Nam));
            else
               Nam_Ent := Entity (Nam);
            end if;

            Nam_Decl    := Parent (Nam_Ent);
            Subtyp_Decl := Parent (Etype (Nam_Ent));

            if Has_Null_Exclusion (N)
              and then not Has_Null_Exclusion (Nam_Decl)
            then
               --  Ada 2005 (AI-423): If the object name denotes a generic
               --  formal object of a generic unit G, and the object renaming
               --  declaration occurs within the body of G or within the body
               --  of a generic unit declared within the declarative region
               --  of G, then the declaration of the formal object of G must
               --  have a null exclusion.

               if Is_Formal_Object (Nam_Ent)
                 and then In_Generic_Scope (Id)
               then
                  if Present (Subtype_Mark (Nam_Decl)) then
                     Error_Node := Subtype_Mark (Nam_Decl);
                  else
                     pragma Assert
                       (Ada_Version >= Ada_05
                          and then Present (Access_Definition (Nam_Decl)));

                     Error_Node := Access_Definition (Nam_Decl);
                  end if;

                  Error_Msg_N
                    ("`NOT NULL` required in formal object declaration",
                     Error_Node);
                  Error_Msg_Sloc := Sloc (N);
                  Error_Msg_N
                    ("\because of renaming # (RM 8.5.4(4))", Error_Node);

               --  Ada 2005 (AI-423): Otherwise, the subtype of the object name
               --  shall exclude null.

               elsif Nkind (Subtyp_Decl) = N_Subtype_Declaration
                 and then not Has_Null_Exclusion (Subtyp_Decl)
               then
                  Error_Msg_N
                    ("`NOT NULL` required for subtype & (RM 8.5.1(4.6/2))",
                     Defining_Identifier (Subtyp_Decl));
               end if;
            end if;
         end;
      end if;

      Set_Ekind (Id, E_Variable);
      Init_Size_Align (Id);

      if T = Any_Type or else Etype (Nam) = Any_Type then
         return;

      --  Verify that the renamed entity is an object or a function call. It
      --  may have been rewritten in several ways.

      elsif Is_Object_Reference (Nam) then
         if Comes_From_Source (N)
           and then Is_Dependent_Component_Of_Mutable_Object (Nam)
         then
            Error_Msg_N
              ("illegal renaming of discriminant-dependent component", Nam);
         else
            null;
         end if;

      --  A static function call may have been folded into a literal

      elsif Nkind (Original_Node (Nam)) = N_Function_Call

            --  When expansion is disabled, attribute reference is not
            --  rewritten as function call. Otherwise it may be rewritten
            --  as a conversion, so check original node.

        or else (Nkind (Original_Node (Nam)) = N_Attribute_Reference
                  and then Is_Function_Attribute_Name
                             (Attribute_Name (Original_Node (Nam))))

            --  Weird but legal, equivalent to renaming a function call.
            --  Illegal if the literal is the result of constant-folding an
            --  attribute reference that is not a function.

        or else (Is_Entity_Name (Nam)
                  and then Ekind (Entity (Nam)) = E_Enumeration_Literal
                  and then
                    Nkind (Original_Node (Nam)) /= N_Attribute_Reference)

        or else (Nkind (Nam) = N_Type_Conversion
                    and then Is_Tagged_Type (Entity (Subtype_Mark (Nam))))
      then
         null;

      elsif Nkind (Nam) = N_Type_Conversion then
         Error_Msg_N
           ("renaming of conversion only allowed for tagged types", Nam);

      --  Ada 2005 (AI-327)

      elsif Ada_Version >= Ada_05
        and then Nkind (Nam) = N_Attribute_Reference
        and then Attribute_Name (Nam) = Name_Priority
      then
         null;

      else
         Error_Msg_N ("expect object name in renaming", Nam);
      end if;

      Set_Etype (Id, T2);

      if not Is_Variable (Nam) then
         Set_Ekind               (Id, E_Constant);
         Set_Never_Set_In_Source (Id, True);
         Set_Is_True_Constant    (Id, True);
      end if;

      Set_Renamed_Object (Id, Nam);
   end Analyze_Object_Renaming;

   ------------------------------
   -- Analyze_Package_Renaming --
   ------------------------------

   procedure Analyze_Package_Renaming (N : Node_Id) is
      New_P : constant Entity_Id := Defining_Entity (N);
      Old_P : Entity_Id;
      Spec  : Node_Id;

   begin
      if Name (N) = Error then
         return;
      end if;

      --  Apply Text_IO kludge here, since we may be renaming one of the
      --  children of Text_IO.

      Text_IO_Kludge (Name (N));

      if Current_Scope /= Standard_Standard then
         Set_Is_Pure (New_P, Is_Pure (Current_Scope));
      end if;

      Enter_Name (New_P);
      Analyze (Name (N));

      if Is_Entity_Name (Name (N)) then
         Old_P := Entity (Name (N));
      else
         Old_P := Any_Id;
      end if;

      if Etype (Old_P) = Any_Type then
         Error_Msg_N
           ("expect package name in renaming", Name (N));

      elsif Ekind (Old_P) /= E_Package
        and then not (Ekind (Old_P) = E_Generic_Package
                       and then In_Open_Scopes (Old_P))
      then
         if Ekind (Old_P) = E_Generic_Package then
            Error_Msg_N
               ("generic package cannot be renamed as a package", Name (N));
         else
            Error_Msg_Sloc := Sloc (Old_P);
            Error_Msg_NE
             ("expect package name in renaming, found& declared#",
               Name (N), Old_P);
         end if;

         --  Set basic attributes to minimize cascaded errors

         Set_Ekind (New_P, E_Package);
         Set_Etype (New_P, Standard_Void_Type);

      --  Here for OK package renaming

      else
         --  Entities in the old package are accessible through the renaming
         --  entity. The simplest implementation is to have both packages share
         --  the entity list.

         Set_Ekind (New_P, E_Package);
         Set_Etype (New_P, Standard_Void_Type);

         if Present (Renamed_Object (Old_P)) then
            Set_Renamed_Object (New_P,  Renamed_Object (Old_P));
         else
            Set_Renamed_Object (New_P, Old_P);
         end if;

         Set_Has_Completion (New_P);

         Set_First_Entity (New_P,  First_Entity (Old_P));
         Set_Last_Entity  (New_P,  Last_Entity  (Old_P));
         Set_First_Private_Entity (New_P, First_Private_Entity (Old_P));
         Check_Library_Unit_Renaming (N, Old_P);
         Generate_Reference (Old_P, Name (N));

         --  If the renaming is in the visible part of a package, then we set
         --  In_Package_Spec for the renamed package, to prevent giving
         --  warnings about no entities referenced. Such a warning would be
         --  overenthusiastic, since clients can see entities in the renamed
         --  package via the visible package renaming.

         declare
            Ent : constant Entity_Id := Cunit_Entity (Current_Sem_Unit);
         begin
            if Ekind (Ent) = E_Package
              and then not In_Private_Part (Ent)
              and then In_Extended_Main_Source_Unit (N)
              and then Ekind (Old_P) = E_Package
            then
               Set_Renamed_In_Spec (Old_P);
            end if;
         end;

         --  If this is the renaming declaration of a package instantiation
         --  within itself, it is the declaration that ends the list of actuals
         --  for the instantiation. At this point, the subtypes that rename
         --  the actuals are flagged as generic, to avoid spurious ambiguities
         --  if the actuals for two distinct formals happen to coincide. If
         --  the actual is a private type, the subtype has a private completion
         --  that is flagged in the same fashion.

         --  Resolution is identical to what is was in the original generic.
         --  On exit from the generic instance, these are turned into regular
         --  subtypes again, so they are compatible with types in their class.

         if not Is_Generic_Instance (Old_P) then
            return;
         else
            Spec := Specification (Unit_Declaration_Node (Old_P));
         end if;

         if Nkind (Spec) = N_Package_Specification
           and then Present (Generic_Parent (Spec))
           and then Old_P = Current_Scope
           and then Chars (New_P) = Chars (Generic_Parent (Spec))
         then
            declare
               E : Entity_Id;

            begin
               E := First_Entity (Old_P);
               while Present (E)
                 and then E /= New_P
               loop
                  if Is_Type (E)
                    and then Nkind (Parent (E)) = N_Subtype_Declaration
                  then
                     Set_Is_Generic_Actual_Type (E);

                     if Is_Private_Type (E)
                       and then Present (Full_View (E))
                     then
                        Set_Is_Generic_Actual_Type (Full_View (E));
                     end if;
                  end if;

                  Next_Entity (E);
               end loop;
            end;
         end if;
      end if;
   end Analyze_Package_Renaming;

   -------------------------------
   -- Analyze_Renamed_Character --
   -------------------------------

   procedure Analyze_Renamed_Character
     (N       : Node_Id;
      New_S   : Entity_Id;
      Is_Body : Boolean)
   is
      C : constant Node_Id := Name (N);

   begin
      if Ekind (New_S) = E_Function then
         Resolve (C, Etype (New_S));

         if Is_Body then
            Check_Frozen_Renaming (N, New_S);
         end if;

      else
         Error_Msg_N ("character literal can only be renamed as function", N);
      end if;
   end Analyze_Renamed_Character;

   ---------------------------------
   -- Analyze_Renamed_Dereference --
   ---------------------------------

   procedure Analyze_Renamed_Dereference
     (N       : Node_Id;
      New_S   : Entity_Id;
      Is_Body : Boolean)
   is
      Nam : constant Node_Id := Name (N);
      P   : constant Node_Id := Prefix (Nam);
      Typ : Entity_Id;
      Ind : Interp_Index;
      It  : Interp;

   begin
      if not Is_Overloaded (P) then
         if Ekind (Etype (Nam)) /= E_Subprogram_Type
           or else not Type_Conformant (Etype (Nam), New_S) then
            Error_Msg_N ("designated type does not match specification", P);
         else
            Resolve (P);
         end if;

         return;

      else
         Typ := Any_Type;
         Get_First_Interp (Nam, Ind, It);

         while Present (It.Nam) loop

            if Ekind (It.Nam) = E_Subprogram_Type
              and then Type_Conformant (It.Nam, New_S) then

               if Typ /= Any_Id then
                  Error_Msg_N ("ambiguous renaming", P);
                  return;
               else
                  Typ := It.Nam;
               end if;
            end if;

            Get_Next_Interp (Ind, It);
         end loop;

         if Typ = Any_Type then
            Error_Msg_N ("designated type does not match specification", P);
         else
            Resolve (N, Typ);

            if Is_Body then
               Check_Frozen_Renaming (N, New_S);
            end if;
         end if;
      end if;
   end Analyze_Renamed_Dereference;

   ---------------------------
   -- Analyze_Renamed_Entry --
   ---------------------------

   procedure Analyze_Renamed_Entry
     (N       : Node_Id;
      New_S   : Entity_Id;
      Is_Body : Boolean)
   is
      Nam   : constant Node_Id := Name (N);
      Sel   : constant Node_Id := Selector_Name (Nam);
      Old_S : Entity_Id;

   begin
      if Entity (Sel) = Any_Id then

         --  Selector is undefined on prefix. Error emitted already

         Set_Has_Completion (New_S);
         return;
      end if;

      --  Otherwise find renamed entity and build body of New_S as a call to it

      Old_S := Find_Renamed_Entity (N, Selector_Name (Nam), New_S);

      if Old_S = Any_Id then
         Error_Msg_N (" no subprogram or entry matches specification",  N);
      else
         if Is_Body then
            Check_Subtype_Conformant (New_S, Old_S, N);
            Generate_Reference (New_S, Defining_Entity (N), 'b');
            Style.Check_Identifier (Defining_Entity (N), New_S);

         else
            --  Only mode conformance required for a renaming_as_declaration

            Check_Mode_Conformant (New_S, Old_S, N);
         end if;

         Inherit_Renamed_Profile (New_S, Old_S);

         --  The prefix can be an arbitrary expression that yields a task
         --  type, so it must be resolved.

         Resolve (Prefix (Nam), Scope (Old_S));
      end if;

      Set_Convention (New_S, Convention (Old_S));
      Set_Has_Completion (New_S, Inside_A_Generic);

      if Is_Body then
         Check_Frozen_Renaming (N, New_S);
      end if;
   end Analyze_Renamed_Entry;

   -----------------------------------
   -- Analyze_Renamed_Family_Member --
   -----------------------------------

   procedure Analyze_Renamed_Family_Member
     (N       : Node_Id;
      New_S   : Entity_Id;
      Is_Body : Boolean)
   is
      Nam   : constant Node_Id := Name (N);
      P     : constant Node_Id := Prefix (Nam);
      Old_S : Entity_Id;

   begin
      if (Is_Entity_Name (P) and then Ekind (Entity (P)) = E_Entry_Family)
        or else (Nkind (P) = N_Selected_Component
                   and then
                 Ekind (Entity (Selector_Name (P))) = E_Entry_Family)
      then
         if Is_Entity_Name (P) then
            Old_S := Entity (P);
         else
            Old_S := Entity (Selector_Name (P));
         end if;

         if not Entity_Matches_Spec (Old_S, New_S) then
            Error_Msg_N ("entry family does not match specification", N);

         elsif Is_Body then
            Check_Subtype_Conformant (New_S, Old_S, N);
            Generate_Reference (New_S, Defining_Entity (N), 'b');
            Style.Check_Identifier (Defining_Entity (N), New_S);
         end if;

      else
         Error_Msg_N ("no entry family matches specification", N);
      end if;

      Set_Has_Completion (New_S, Inside_A_Generic);

      if Is_Body then
         Check_Frozen_Renaming (N, New_S);
      end if;
   end Analyze_Renamed_Family_Member;

   -----------------------------------------
   -- Analyze_Renamed_Primitive_Operation --
   -----------------------------------------

   procedure Analyze_Renamed_Primitive_Operation
     (N       : Node_Id;
      New_S   : Entity_Id;
      Is_Body : Boolean)
   is
      Old_S : Entity_Id;

      function Conforms
        (Subp : Entity_Id;
         Ctyp : Conformance_Type) return Boolean;
      --  Verify that the signatures of the renamed entity and the new entity
      --  match. The first formal of the renamed entity is skipped because it
      --  is the target object in any subsequent call.

      function Conforms
        (Subp : Entity_Id;
         Ctyp : Conformance_Type) return Boolean
      is
         Old_F : Entity_Id;
         New_F : Entity_Id;

      begin
         if Ekind (Subp) /= Ekind (New_S) then
            return False;
         end if;

         Old_F := Next_Formal (First_Formal (Subp));
         New_F := First_Formal (New_S);
         while Present (Old_F) and then Present (New_F) loop
            if not Conforming_Types (Etype (Old_F), Etype (New_F), Ctyp) then
               return False;
            end if;

            if Ctyp >= Mode_Conformant
              and then Ekind (Old_F) /= Ekind (New_F)
            then
               return False;
            end if;

            Next_Formal (New_F);
            Next_Formal (Old_F);
         end loop;

         return True;
      end Conforms;

   begin
      if not Is_Overloaded (Selector_Name (Name (N))) then
         Old_S := Entity (Selector_Name (Name (N)));

         if not Conforms (Old_S, Type_Conformant) then
            Old_S := Any_Id;
         end if;

      else
         --  Find the operation that matches the given signature

         declare
            It  : Interp;
            Ind : Interp_Index;

         begin
            Old_S := Any_Id;
            Get_First_Interp (Selector_Name (Name (N)), Ind, It);

            while Present (It.Nam) loop
               if Conforms (It.Nam, Type_Conformant) then
                  Old_S := It.Nam;
               end if;

               Get_Next_Interp (Ind, It);
            end loop;
         end;
      end if;

      if Old_S = Any_Id then
         Error_Msg_N (" no subprogram or entry matches specification",  N);

      else
         if Is_Body then
            if not Conforms (Old_S, Subtype_Conformant) then
               Error_Msg_N ("subtype conformance error in renaming", N);
            end if;

            Generate_Reference (New_S, Defining_Entity (N), 'b');
            Style.Check_Identifier (Defining_Entity (N), New_S);

         else
            --  Only mode conformance required for a renaming_as_declaration

            if not Conforms (Old_S, Mode_Conformant) then
               Error_Msg_N ("mode conformance error in renaming", N);
            end if;
         end if;

         --  Inherit_Renamed_Profile (New_S, Old_S);

         --  The prefix can be an arbitrary expression that yields an
         --  object, so it must be resolved.

         Resolve (Prefix (Name (N)));
      end if;
   end Analyze_Renamed_Primitive_Operation;

   ---------------------------------
   -- Analyze_Subprogram_Renaming --
   ---------------------------------

   procedure Analyze_Subprogram_Renaming (N : Node_Id) is
      Formal_Spec : constant Node_Id          := Corresponding_Formal_Spec (N);
      Is_Actual   : constant Boolean          := Present (Formal_Spec);
      Inst_Node   : Node_Id                   := Empty;
      Nam         : constant Node_Id          := Name (N);
      New_S       : Entity_Id;
      Old_S       : Entity_Id                 := Empty;
      Rename_Spec : Entity_Id;
      Save_AV     : constant Ada_Version_Type := Ada_Version;
      Save_AV_Exp : constant Ada_Version_Type := Ada_Version_Explicit;
      Spec        : constant Node_Id          := Specification (N);

      procedure Check_Null_Exclusion
        (Ren : Entity_Id;
         Sub : Entity_Id);
      --  Ada 2005 (AI-423): Given renaming Ren of subprogram Sub, check the
      --  following AI rules:
      --
      --    If Ren is a renaming of a formal subprogram and one of its
      --    parameters has a null exclusion, then the corresponding formal
      --    in Sub must also have one. Otherwise the subtype of the Sub's
      --    formal parameter must exclude null.
      --
      --    If Ren is a renaming of a formal function and its retrun
      --    profile has a null exclusion, then Sub's return profile must
      --    have one. Otherwise the subtype of Sub's return profile must
      --    exclude null.

      function Original_Subprogram (Subp : Entity_Id) return Entity_Id;
      --  Find renamed entity when the declaration is a renaming_as_body and
      --  the renamed entity may itself be a renaming_as_body. Used to enforce
      --  rule that a renaming_as_body is illegal if the declaration occurs
      --  before the subprogram it completes is frozen, and renaming indirectly
      --  renames the subprogram itself.(Defect Report 8652/0027).

      --------------------------
      -- Check_Null_Exclusion --
      --------------------------

      procedure Check_Null_Exclusion
        (Ren : Entity_Id;
         Sub : Entity_Id)
      is
         Ren_Formal : Entity_Id;
         Sub_Formal : Entity_Id;

      begin
         --  Parameter check

         Ren_Formal := First_Formal (Ren);
         Sub_Formal := First_Formal (Sub);
         while Present (Ren_Formal)
           and then Present (Sub_Formal)
         loop
            if Has_Null_Exclusion (Parent (Ren_Formal))
              and then
                not (Has_Null_Exclusion (Parent (Sub_Formal))
                       or else Can_Never_Be_Null (Etype (Sub_Formal)))
            then
               Error_Msg_NE
                 ("`NOT NULL` required for parameter &",
                  Parent (Sub_Formal), Sub_Formal);
            end if;

            Next_Formal (Ren_Formal);
            Next_Formal (Sub_Formal);
         end loop;

         --  Return profile check

         if Nkind (Parent (Ren)) = N_Function_Specification
           and then Nkind (Parent (Sub)) = N_Function_Specification
           and then Has_Null_Exclusion (Parent (Ren))
           and then
             not (Has_Null_Exclusion (Parent (Sub))
                    or else Can_Never_Be_Null (Etype (Sub)))
         then
            Error_Msg_N
              ("return must specify `NOT NULL`",
               Result_Definition (Parent (Sub)));
         end if;
      end Check_Null_Exclusion;

      -------------------------
      -- Original_Subprogram --
      -------------------------

      function Original_Subprogram (Subp : Entity_Id) return Entity_Id is
         Orig_Decl : Node_Id;
         Orig_Subp : Entity_Id;

      begin
         --  First case: renamed entity is itself a renaming

         if Present (Alias (Subp)) then
            return Alias (Subp);

         elsif
           Nkind (Unit_Declaration_Node (Subp)) = N_Subprogram_Declaration
             and then Present
              (Corresponding_Body (Unit_Declaration_Node (Subp)))
         then
            --  Check if renamed entity is a renaming_as_body

            Orig_Decl :=
              Unit_Declaration_Node
                (Corresponding_Body (Unit_Declaration_Node (Subp)));

            if Nkind (Orig_Decl) = N_Subprogram_Renaming_Declaration then
               Orig_Subp := Entity (Name (Orig_Decl));

               if Orig_Subp = Rename_Spec then

                  --  Circularity detected

                  return Orig_Subp;

               else
                  return (Original_Subprogram (Orig_Subp));
               end if;
            else
               return Subp;
            end if;
         else
            return Subp;
         end if;
      end Original_Subprogram;

   --  Start of processing for Analyze_Subprogram_Renaming

   begin
      --  We must test for the attribute renaming case before the Analyze
      --  call because otherwise Sem_Attr will complain that the attribute
      --  is missing an argument when it is analyzed.

      if Nkind (Nam) = N_Attribute_Reference then

         --  In the case of an abstract formal subprogram association, rewrite
         --  an actual given by a stream attribute as the name of the
         --  corresponding stream primitive of the type.

         --  In a generic context the stream operations are not generated, and
         --  this must be treated as a normal attribute reference, to be
         --  expanded in subsequent instantiations.

         if Is_Actual and then Is_Abstract_Subprogram (Formal_Spec)
           and then Expander_Active
         then
            declare
               Stream_Prim : Entity_Id;
               Prefix_Type : constant Entity_Id := Entity (Prefix (Nam));

            begin
               --  The class-wide forms of the stream attributes are not
               --  primitive dispatching operations (even though they
               --  internally dispatch to a stream attribute).

               if Is_Class_Wide_Type (Prefix_Type) then
                  Error_Msg_N
                    ("attribute must be a primitive dispatching operation",
                     Nam);
                  return;
               end if;

               --  Retrieve the primitive subprogram associated with the
               --  attribute. This can only be a stream attribute, since those
               --  are the only ones that are dispatching (and the actual for
               --  an abstract formal subprogram must be dispatching
               --  operation).

               case Attribute_Name (Nam) is
                  when Name_Input  =>
                     Stream_Prim :=
                       Find_Prim_Op (Prefix_Type, TSS_Stream_Input);
                  when Name_Output =>
                     Stream_Prim :=
                       Find_Prim_Op (Prefix_Type, TSS_Stream_Output);
                  when Name_Read   =>
                     Stream_Prim :=
                       Find_Prim_Op (Prefix_Type, TSS_Stream_Read);
                  when Name_Write  =>
                     Stream_Prim :=
                       Find_Prim_Op (Prefix_Type, TSS_Stream_Write);
                  when others      =>
                     Error_Msg_N
                       ("attribute must be a primitive dispatching operation",
                        Nam);
                     return;
               end case;

               --  Rewrite the attribute into the name of its corresponding
               --  primitive dispatching subprogram. We can then proceed with
               --  the usual processing for subprogram renamings.

               declare
                  Prim_Name : constant Node_Id :=
                                Make_Identifier (Sloc (Nam),
                                  Chars => Chars (Stream_Prim));
               begin
                  Set_Entity (Prim_Name, Stream_Prim);
                  Rewrite (Nam, Prim_Name);
                  Analyze (Nam);
               end;
            end;

         --  Normal processing for a renaming of an attribute

         else
            Attribute_Renaming (N);
            return;
         end if;
      end if;

      --  Check whether this declaration corresponds to the instantiation
      --  of a formal subprogram.

      --  If this is an instantiation, the corresponding actual is frozen and
      --  error messages can be made more precise. If this is a default
      --  subprogram, the entity is already established in the generic, and is
      --  not retrieved by visibility. If it is a default with a box, the
      --  candidate interpretations, if any, have been collected when building
      --  the renaming declaration. If overloaded, the proper interpretation is
      --  determined in Find_Renamed_Entity. If the entity is an operator,
      --  Find_Renamed_Entity applies additional visibility checks.

      if Is_Actual then
         Inst_Node := Unit_Declaration_Node (Formal_Spec);

         if Is_Entity_Name (Nam)
           and then Present (Entity (Nam))
           and then not Comes_From_Source (Nam)
           and then not Is_Overloaded (Nam)
         then
            Old_S := Entity (Nam);
            New_S := Analyze_Subprogram_Specification (Spec);

            --  Operator case

            if Ekind (Entity (Nam)) = E_Operator then

               --  Box present

               if Box_Present (Inst_Node) then
                  Old_S := Find_Renamed_Entity (N, Name (N), New_S, Is_Actual);

               --  If there is an immediately visible homonym of the operator
               --  and the declaration has a default, this is worth a warning
               --  because the user probably did not intend to get the pre-
               --  defined operator, visible in the generic declaration. To
               --  find if there is an intended candidate, analyze the renaming
               --  again in the current context.

               elsif Scope (Old_S) = Standard_Standard
                 and then Present (Default_Name (Inst_Node))
               then
                  declare
                     Decl   : constant Node_Id := New_Copy_Tree (N);
                     Hidden : Entity_Id;

                  begin
                     Set_Entity (Name (Decl), Empty);
                     Analyze (Name (Decl));
                     Hidden :=
                       Find_Renamed_Entity (Decl, Name (Decl), New_S, True);

                     if Present (Hidden)
                       and then In_Open_Scopes (Scope (Hidden))
                       and then Is_Immediately_Visible (Hidden)
                       and then Comes_From_Source (Hidden)
                       and then Hidden /= Old_S
                     then
                        Error_Msg_Sloc := Sloc (Hidden);
                        Error_Msg_N ("?default subprogram is resolved " &
                                     "in the generic declaration " &
                                     "(RM 12.6(17))", N);
                        Error_Msg_NE ("\?and will not use & #", N, Hidden);
                     end if;
                  end;
               end if;
            end if;

         else
            Analyze (Nam);
            New_S := Analyze_Subprogram_Specification (Spec);
         end if;

      else
         --  Renamed entity must be analyzed first, to avoid being hidden by
         --  new name (which might be the same in a generic instance).

         Analyze (Nam);

         --  The renaming defines a new overloaded entity, which is analyzed
         --  like a subprogram declaration.

         New_S := Analyze_Subprogram_Specification (Spec);
      end if;

      if Current_Scope /= Standard_Standard then
         Set_Is_Pure (New_S, Is_Pure (Current_Scope));
      end if;

      Rename_Spec := Find_Corresponding_Spec (N);

      --  Case of Renaming_As_Body

      if Present (Rename_Spec) then

         --  Renaming declaration is the completion of the declaration of
         --  Rename_Spec. We build an actual body for it at the freezing point.

         Set_Corresponding_Spec (N, Rename_Spec);

         --  Deal with special case of Input and Output stream functions

         if Nkind (Unit_Declaration_Node (Rename_Spec)) =
                                     N_Abstract_Subprogram_Declaration
         then
            --  Input and Output stream functions are abstract if the object
            --  type is abstract. However, these functions may receive explicit
            --  declarations in representation clauses, making the attribute
            --  subprograms usable  as defaults in subsequent type extensions.
            --  In this case we rewrite the declaration to make the subprogram
            --  non-abstract. We remove the previous declaration, and insert
            --  the new one at the point of the renaming, to prevent premature
            --  access to unfrozen types. The new declaration reuses the
            --  specification of the previous one, and must not be analyzed.

            pragma Assert (Is_TSS (Rename_Spec, TSS_Stream_Output)
                           or else Is_TSS (Rename_Spec, TSS_Stream_Input));

            declare
               Old_Decl : constant Node_Id :=
                            Unit_Declaration_Node (Rename_Spec);
               New_Decl : constant Node_Id :=
                            Make_Subprogram_Declaration (Sloc (N),
                              Specification =>
                                Relocate_Node (Specification (Old_Decl)));
            begin
               Remove (Old_Decl);
               Insert_After (N, New_Decl);
               Set_Is_Abstract_Subprogram (Rename_Spec, False);
               Set_Analyzed (New_Decl);
            end;
         end if;

         Set_Corresponding_Body (Unit_Declaration_Node (Rename_Spec), New_S);

         if Ada_Version = Ada_83 and then Comes_From_Source (N) then
            Error_Msg_N ("(Ada 83) renaming cannot serve as a body", N);
         end if;

         Set_Convention (New_S, Convention (Rename_Spec));
         Check_Fully_Conformant (New_S, Rename_Spec);
         Set_Public_Status (New_S);

         --  The specification does not introduce new formals, but only
         --  repeats the formals of the original subprogram declaration.
         --  For cross-reference purposes, and for refactoring tools, we
         --  treat the formals of the renaming declaration as body formals.

         Reference_Body_Formals (Rename_Spec, New_S);

         --  Indicate that the entity in the declaration functions like the
         --  corresponding body, and is not a new entity. The body will be
         --  constructed later at the freeze point, so indicate that the
         --  completion has not been seen yet.

         Set_Ekind (New_S, E_Subprogram_Body);
         New_S := Rename_Spec;
         Set_Has_Completion (Rename_Spec, False);

         --  Ada 2005: check overriding indicator

         if Must_Override (Specification (N))
           and then not Is_Overriding_Operation (Rename_Spec)
         then
            Error_Msg_NE ("subprogram& is not overriding", N, Rename_Spec);

         elsif Must_Not_Override (Specification (N))
           and then Is_Overriding_Operation (Rename_Spec)
         then
            Error_Msg_NE
              ("subprogram& overrides inherited operation", N, Rename_Spec);
         end if;

      --  Normal subprogram renaming (not renaming as body)

      else
         Generate_Definition (New_S);
         New_Overloaded_Entity (New_S);

         if Is_Entity_Name (Nam)
           and then Is_Intrinsic_Subprogram (Entity (Nam))
         then
            null;
         else
            Check_Delayed_Subprogram (New_S);
         end if;
      end if;

      --  There is no need for elaboration checks on the new entity, which may
      --  be called before the next freezing point where the body will appear.
      --  Elaboration checks refer to the real entity, not the one created by
      --  the renaming declaration.

      Set_Kill_Elaboration_Checks (New_S, True);

      if Etype (Nam) = Any_Type then
         Set_Has_Completion (New_S);
         return;

      elsif Nkind (Nam) = N_Selected_Component then

         --  A prefix of the form  A.B can designate an entry of task A, a
         --  protected operation of protected object A, or finally a primitive
         --  operation of object A. In the later case, A is an object of some
         --  tagged type, or an access type that denotes one such. To further
         --  distinguish these cases, note that the scope of a task entry or
         --  protected operation is type of the prefix.

         --  The prefix could be an overloaded function call that returns both
         --  kinds of operations. This overloading pathology is left to the
         --  dedicated reader ???

         declare
            T : constant Entity_Id := Etype (Prefix (Nam));

         begin
            if Present (T)
              and then
                (Is_Tagged_Type (T)
                  or else
                    (Is_Access_Type (T)
                      and then
                        Is_Tagged_Type (Designated_Type (T))))
              and then Scope (Entity (Selector_Name (Nam))) /= T
            then
               Analyze_Renamed_Primitive_Operation
                 (N, New_S, Present (Rename_Spec));
               return;

            else
               --  Renamed entity is an entry or protected operation. For those
               --  cases an explicit body is built (at the point of freezing of
               --  this entity) that contains a call to the renamed entity.

               --  This is not allowed for renaming as body if the renamed
               --  spec is already frozen (see RM 8.5.4(5) for details).

               if Present (Rename_Spec)
                 and then Is_Frozen (Rename_Spec)
               then
                  Error_Msg_N
                    ("renaming-as-body cannot rename entry as subprogram", N);
                  Error_Msg_NE
                    ("\since & is already frozen (RM 8.5.4(5))",
                     N, Rename_Spec);
               else
                  Analyze_Renamed_Entry (N, New_S, Present (Rename_Spec));
               end if;

               return;
            end if;
         end;

      elsif Nkind (Nam) = N_Explicit_Dereference then

         --  Renamed entity is designated by access_to_subprogram expression.
         --  Must build body to encapsulate call, as in the entry case.

         Analyze_Renamed_Dereference (N, New_S, Present (Rename_Spec));
         return;

      elsif Nkind (Nam) = N_Indexed_Component then
         Analyze_Renamed_Family_Member (N, New_S, Present (Rename_Spec));
         return;

      elsif Nkind (Nam) = N_Character_Literal then
         Analyze_Renamed_Character (N, New_S, Present (Rename_Spec));
         return;

      elsif (not Is_Entity_Name (Nam)
              and then Nkind (Nam) /= N_Operator_Symbol)
        or else not Is_Overloadable (Entity (Nam))
      then
         Error_Msg_N ("expect valid subprogram name in renaming", N);
         return;
      end if;

      --  Find the renamed entity that matches the given specification. Disable
      --  Ada_83 because there is no requirement of full conformance between
      --  renamed entity and new entity, even though the same circuit is used.

      --  This is a bit of a kludge, which introduces a really irregular use of
      --  Ada_Version[_Explicit]. Would be nice to find cleaner way to do this
      --  ???

      Ada_Version := Ada_Version_Type'Max (Ada_Version, Ada_95);
      Ada_Version_Explicit := Ada_Version;

      if No (Old_S) then
         Old_S := Find_Renamed_Entity (N, Name (N), New_S, Is_Actual);

         --  When the renamed subprogram is overloaded and used as an actual
         --  of a generic, its entity is set to the first available homonym.
         --  We must first disambiguate the name, then set the proper entity.

         if Is_Actual
           and then Is_Overloaded (Nam)
         then
            Set_Entity (Nam, Old_S);
         end if;
      end if;

      --  Most common case: subprogram renames subprogram. No body is generated
      --  in this case, so we must indicate the declaration is complete as is.

      if No (Rename_Spec) then
         Set_Has_Completion   (New_S);
         Set_Is_Pure          (New_S, Is_Pure          (Entity (Nam)));
         Set_Is_Preelaborated (New_S, Is_Preelaborated (Entity (Nam)));

         --  Ada 2005 (AI-423): Check the consistency of null exclusions
         --  between a subprogram and its correct renaming.

         --  Note: the Any_Id check is a guard that prevents compiler crashes
         --  when performing a null exclusion check between a renaming and a
         --  renamed subprogram that has been found to be illegal.

         if Ada_Version >= Ada_05
           and then Entity (Nam) /= Any_Id
         then
            Check_Null_Exclusion
              (Ren => New_S,
               Sub => Entity (Nam));
         end if;

         --  Enforce the Ada 2005 rule that the renamed entity cannot require
         --  overriding. The flag Requires_Overriding is set very selectively
         --  and misses some other illegal cases. The additional conditions
         --  checked below are sufficient but not necessary ???

         --  The rule does not apply to the renaming generated for an actual
         --  subprogram in an instance.

         if Is_Actual then
            null;

         --  Guard agaisnt previous errors, and omit renamings of predefined
         --  operators.

         elsif Ekind (Old_S) /= E_Function
           and then Ekind (Old_S) /= E_Procedure
         then
            null;

         elsif Requires_Overriding (Old_S)
           or else
              (Is_Abstract_Subprogram (Old_S)
                 and then Present (Find_Dispatching_Type (Old_S))
                 and then
                   not Is_Abstract_Type (Find_Dispatching_Type (Old_S)))
         then
            Error_Msg_N
              ("renamed entity cannot be "
               & "subprogram that requires overriding (RM 8.5.4 (5.1))", N);
         end if;
      end if;

      if Old_S /= Any_Id then
         if Is_Actual
           and then From_Default (N)
         then
            --  This is an implicit reference to the default actual

            Generate_Reference (Old_S, Nam, Typ => 'i', Force => True);
         else
            Generate_Reference (Old_S, Nam);
         end if;

         --  For a renaming-as-body, require subtype conformance, but if the
         --  declaration being completed has not been frozen, then inherit the
         --  convention of the renamed subprogram prior to checking conformance
         --  (unless the renaming has an explicit convention established; the
         --  rule stated in the RM doesn't seem to address this ???).

         if Present (Rename_Spec) then
            Generate_Reference (Rename_Spec, Defining_Entity (Spec), 'b');
            Style.Check_Identifier (Defining_Entity (Spec), Rename_Spec);

            if not Is_Frozen (Rename_Spec) then
               if not Has_Convention_Pragma (Rename_Spec) then
                  Set_Convention (New_S, Convention (Old_S));
               end if;

               if Ekind (Old_S) /= E_Operator then
                  Check_Mode_Conformant (New_S, Old_S, Spec);
               end if;

               if Original_Subprogram (Old_S) = Rename_Spec then
                  Error_Msg_N ("unfrozen subprogram cannot rename itself ", N);
               end if;
            else
               Check_Subtype_Conformant (New_S, Old_S, Spec);
            end if;

            Check_Frozen_Renaming (N, Rename_Spec);

            --  Check explicitly that renamed entity is not intrinsic, because
            --  in in a generic the renamed body is not built. In this case,
            --  the renaming_as_body is a completion.

            if Inside_A_Generic then
               if Is_Frozen (Rename_Spec)
                 and then Is_Intrinsic_Subprogram (Old_S)
               then
                  Error_Msg_N
                    ("subprogram in renaming_as_body cannot be intrinsic",
                       Name (N));
               end if;

               Set_Has_Completion (Rename_Spec);
            end if;

         elsif Ekind (Old_S) /= E_Operator then
            Check_Mode_Conformant (New_S, Old_S);

            if Is_Actual
              and then Error_Posted (New_S)
            then
               Error_Msg_NE ("invalid actual subprogram: & #!", N, Old_S);
            end if;
         end if;

         if No (Rename_Spec) then

            --  The parameter profile of the new entity is that of the renamed
            --  entity: the subtypes given in the specification are irrelevant.

            Inherit_Renamed_Profile (New_S, Old_S);

            --  A call to the subprogram is transformed into a call to the
            --  renamed entity. This is transitive if the renamed entity is
            --  itself a renaming.

            if Present (Alias (Old_S)) then
               Set_Alias (New_S, Alias (Old_S));
            else
               Set_Alias (New_S, Old_S);
            end if;

            --  Note that we do not set Is_Intrinsic_Subprogram if we have a
            --  renaming as body, since the entity in this case is not an
            --  intrinsic (it calls an intrinsic, but we have a real body for
            --  this call, and it is in this body that the required intrinsic
            --  processing will take place).

            --  Also, if this is a renaming of inequality, the renamed operator
            --  is intrinsic, but what matters is the corresponding equality
            --  operator, which may be user-defined.

            Set_Is_Intrinsic_Subprogram
              (New_S,
                Is_Intrinsic_Subprogram (Old_S)
                  and then
                    (Chars (Old_S) /= Name_Op_Ne
                       or else Ekind (Old_S) = E_Operator
                       or else
                         Is_Intrinsic_Subprogram
                            (Corresponding_Equality (Old_S))));

            if Ekind (Alias (New_S)) = E_Operator then
               Set_Has_Delayed_Freeze (New_S, False);
            end if;

            --  If the renaming corresponds to an association for an abstract
            --  formal subprogram, then various attributes must be set to
            --  indicate that the renaming is an abstract dispatching operation
            --  with a controlling type.

            if Is_Actual and then Is_Abstract_Subprogram (Formal_Spec) then

               --  Mark the renaming as abstract here, so Find_Dispatching_Type
               --  see it as corresponding to a generic association for a
               --  formal abstract subprogram

               Set_Is_Abstract_Subprogram (New_S);

               declare
                  New_S_Ctrl_Type : constant Entity_Id :=
                                      Find_Dispatching_Type (New_S);
                  Old_S_Ctrl_Type : constant Entity_Id :=
                                      Find_Dispatching_Type (Old_S);

               begin
                  if Old_S_Ctrl_Type /= New_S_Ctrl_Type then
                     Error_Msg_NE
                       ("actual must be dispatching subprogram for type&",
                        Nam, New_S_Ctrl_Type);

                  else
                     Set_Is_Dispatching_Operation (New_S);
                     Check_Controlling_Formals (New_S_Ctrl_Type, New_S);

                     --  If the actual in the formal subprogram is itself a
                     --  formal abstract subprogram association, there's no
                     --  dispatch table component or position to inherit.

                     if Present (DTC_Entity (Old_S)) then
                        Set_DTC_Entity  (New_S, DTC_Entity (Old_S));
                        Set_DT_Position (New_S, DT_Position (Old_S));
                     end if;
                  end if;
               end;
            end if;
         end if;

         if not Is_Actual
           and then (Old_S = New_S
                      or else (Nkind (Nam) /= N_Expanded_Name
                        and then  Chars (Old_S) = Chars (New_S)))
         then
            Error_Msg_N ("subprogram cannot rename itself", N);
         end if;

         Set_Convention (New_S, Convention (Old_S));

         if Is_Abstract_Subprogram (Old_S) then
            if Present (Rename_Spec) then
               Error_Msg_N
                 ("a renaming-as-body cannot rename an abstract subprogram",
                  N);
               Set_Has_Completion (Rename_Spec);
            else
               Set_Is_Abstract_Subprogram (New_S);
            end if;
         end if;

         Check_Library_Unit_Renaming (N, Old_S);

         --  Pathological case: procedure renames entry in the scope of its
         --  task. Entry is given by simple name, but body must be built for
         --  procedure. Of course if called it will deadlock.

         if Ekind (Old_S) = E_Entry then
            Set_Has_Completion (New_S, False);
            Set_Alias (New_S, Empty);
         end if;

         if Is_Actual then
            Freeze_Before (N, Old_S);
            Set_Has_Delayed_Freeze (New_S, False);
            Freeze_Before (N, New_S);

            --  An abstract subprogram is only allowed as an actual in the case
            --  where the formal subprogram is also abstract.

            if (Ekind (Old_S) = E_Procedure or else Ekind (Old_S) = E_Function)
              and then Is_Abstract_Subprogram (Old_S)
              and then not Is_Abstract_Subprogram (Formal_Spec)
            then
               Error_Msg_N
                 ("abstract subprogram not allowed as generic actual", Nam);
            end if;
         end if;

      else
         --  A common error is to assume that implicit operators for types are
         --  defined in Standard, or in the scope of a subtype. In those cases
         --  where the renamed entity is given with an expanded name, it is
         --  worth mentioning that operators for the type are not declared in
         --  the scope given by the prefix.

         if Nkind (Nam) = N_Expanded_Name
           and then Nkind (Selector_Name (Nam)) = N_Operator_Symbol
           and then Scope (Entity (Nam)) = Standard_Standard
         then
            declare
               T : constant Entity_Id :=
                     Base_Type (Etype (First_Formal (New_S)));
            begin
               Error_Msg_Node_2 := Prefix (Nam);
               Error_Msg_NE
                 ("operator for type& is not declared in&", Prefix (Nam), T);
            end;

         else
            Error_Msg_NE
              ("no visible subprogram matches the specification for&",
                Spec, New_S);
         end if;

         if Present (Candidate_Renaming) then
            declare
               F1 : Entity_Id;
               F2 : Entity_Id;

            begin
               F1 := First_Formal (Candidate_Renaming);
               F2 := First_Formal (New_S);

               while Present (F1) and then Present (F2) loop
                  Next_Formal (F1);
                  Next_Formal (F2);
               end loop;

               if Present (F1) and then Present (Default_Value (F1)) then
                  if Present (Next_Formal (F1)) then
                     Error_Msg_NE
                       ("\missing specification for &" &
                          " and other formals with defaults", Spec, F1);
                  else
                     Error_Msg_NE
                    ("\missing specification for &", Spec, F1);
                  end if;
               end if;
            end;
         end if;
      end if;

      --  Ada 2005 AI 404: if the new subprogram is dispatching, verify that
      --  controlling access parameters are known non-null for the renamed
      --  subprogram. Test also applies to a subprogram instantiation that
      --  is dispatching. Test is skipped if some previous error was detected
      --  that set Old_S to Any_Id.

      if Ada_Version >= Ada_05
        and then Old_S /= Any_Id
        and then not Is_Dispatching_Operation (Old_S)
        and then Is_Dispatching_Operation (New_S)
      then
         declare
            Old_F : Entity_Id;
            New_F : Entity_Id;

         begin
            Old_F := First_Formal (Old_S);
            New_F := First_Formal (New_S);
            while Present (Old_F) loop
               if Ekind (Etype (Old_F)) = E_Anonymous_Access_Type
                 and then Is_Controlling_Formal (New_F)
                 and then not Can_Never_Be_Null (Old_F)
               then
                  Error_Msg_N ("access parameter is controlling,", New_F);
                  Error_Msg_NE
                    ("\corresponding parameter of& "
                     & "must be explicitly null excluding", New_F, Old_S);
               end if;

               Next_Formal (Old_F);
               Next_Formal (New_F);
            end loop;
         end;
      end if;

      --  A useful warning, suggested by Ada Bug Finder (Ada-Europe 2005)

      if Comes_From_Source (N)
        and then Present (Old_S)
        and then Nkind (Old_S) = N_Defining_Operator_Symbol
        and then Nkind (New_S) = N_Defining_Operator_Symbol
        and then Chars (Old_S) /= Chars (New_S)
      then
         Error_Msg_NE
           ("?& is being renamed as a different operator",
             New_S, Old_S);
      end if;

      --  Another warning or some utility: if the new subprogram as the same
      --  name as the old one, the old one is not hidden by an outer homograph,
      --  the new one is not a public symbol, and the old one is otherwise
      --  directly visible, the renaming is superfluous.

      if Chars (Old_S) = Chars (New_S)
        and then Comes_From_Source (N)
        and then Scope (Old_S) /= Standard_Standard
        and then Warn_On_Redundant_Constructs
        and then
          (Is_Immediately_Visible (Old_S)
            or else Is_Potentially_Use_Visible (Old_S))
        and then Is_Overloadable (Current_Scope)
        and then Chars (Current_Scope) /= Chars (Old_S)
      then
         Error_Msg_N
          ("?redundant renaming, entity is directly visible", Name (N));
      end if;

      Ada_Version := Save_AV;
      Ada_Version_Explicit := Save_AV_Exp;
   end Analyze_Subprogram_Renaming;

   -------------------------
   -- Analyze_Use_Package --
   -------------------------

   --  Resolve the package names in the use clause, and make all the visible
   --  entities defined in the package potentially use-visible. If the package
   --  is already in use from a previous use clause, its visible entities are
   --  already use-visible. In that case, mark the occurrence as a redundant
   --  use. If the package is an open scope, i.e. if the use clause occurs
   --  within the package itself, ignore it.

   procedure Analyze_Use_Package (N : Node_Id) is
      Pack_Name : Node_Id;
      Pack      : Entity_Id;

   --  Start of processing for Analyze_Use_Package

   begin
      Set_Hidden_By_Use_Clause (N, No_Elist);

      --  Use clause is not allowed in a spec of a predefined package
      --  declaration except that packages whose file name starts a-n are OK
      --  (these are children of Ada.Numerics, and such packages are never
      --  loaded by Rtsfind).

      if Is_Predefined_File_Name (Unit_File_Name (Current_Sem_Unit))
        and then Name_Buffer (1 .. 3) /= "a-n"
        and then
          Nkind (Unit (Cunit (Current_Sem_Unit))) = N_Package_Declaration
      then
         Error_Msg_N ("use clause not allowed in predefined spec", N);
      end if;

      --  Chain clause to list of use clauses in current scope

      if Nkind (Parent (N)) /= N_Compilation_Unit then
         Chain_Use_Clause (N);
      end if;

      --  Loop through package names to identify referenced packages

      Pack_Name := First (Names (N));
      while Present (Pack_Name) loop
         Analyze (Pack_Name);

         if Nkind (Parent (N)) = N_Compilation_Unit
           and then Nkind (Pack_Name) = N_Expanded_Name
         then
            declare
               Pref : Node_Id;

            begin
               Pref := Prefix (Pack_Name);
               while Nkind (Pref) = N_Expanded_Name loop
                  Pref := Prefix (Pref);
               end loop;

               if Entity (Pref) = Standard_Standard then
                  Error_Msg_N
                   ("predefined package Standard cannot appear"
                     & " in a context clause", Pref);
               end if;
            end;
         end if;

         Next (Pack_Name);
      end loop;

      --  Loop through package names to mark all entities as potentially
      --  use visible.

      Pack_Name := First (Names (N));
      while Present (Pack_Name) loop
         if Is_Entity_Name (Pack_Name) then
            Pack := Entity (Pack_Name);

            if Ekind (Pack) /= E_Package
              and then Etype (Pack) /= Any_Type
            then
               if Ekind (Pack) = E_Generic_Package then
                  Error_Msg_N
                   ("a generic package is not allowed in a use clause",
                      Pack_Name);
               else
                  Error_Msg_N ("& is not a usable package", Pack_Name);
               end if;

            else
               if Nkind (Parent (N)) = N_Compilation_Unit then
                  Check_In_Previous_With_Clause (N, Pack_Name);
               end if;

               if Applicable_Use (Pack_Name) then
                  Use_One_Package (Pack, N);
               end if;
            end if;
         end if;

         Next (Pack_Name);
      end loop;
   end Analyze_Use_Package;

   ----------------------
   -- Analyze_Use_Type --
   ----------------------

   procedure Analyze_Use_Type (N : Node_Id) is
      E  : Entity_Id;
      Id : Entity_Id;

   begin
      Set_Hidden_By_Use_Clause (N, No_Elist);

      --  Chain clause to list of use clauses in current scope

      if Nkind (Parent (N)) /= N_Compilation_Unit then
         Chain_Use_Clause (N);
      end if;

      Id := First (Subtype_Marks (N));
      while Present (Id) loop
         Find_Type (Id);
         E := Entity (Id);

         if E /= Any_Type then
            Use_One_Type (Id);

            if Nkind (Parent (N)) = N_Compilation_Unit then
               if Nkind (Id) = N_Identifier then
                  Error_Msg_N ("type is not directly visible", Id);

               elsif Is_Child_Unit (Scope (E))
                 and then Scope (E) /= System_Aux_Id
               then
                  Check_In_Previous_With_Clause (N, Prefix (Id));
               end if;
            end if;
         end if;

         Next (Id);
      end loop;
   end Analyze_Use_Type;

   --------------------
   -- Applicable_Use --
   --------------------

   function Applicable_Use (Pack_Name : Node_Id) return Boolean is
      Pack : constant Entity_Id := Entity (Pack_Name);

   begin
      if In_Open_Scopes (Pack) then
         if Warn_On_Redundant_Constructs
           and then Pack = Current_Scope
         then
            Error_Msg_NE
              ("& is already use-visible within itself?", Pack_Name, Pack);
         end if;

         return False;

      elsif In_Use (Pack) then
         Note_Redundant_Use (Pack_Name);
         return False;

      elsif Present (Renamed_Object (Pack))
        and then In_Use (Renamed_Object (Pack))
      then
         Note_Redundant_Use (Pack_Name);
         return False;

      else
         return True;
      end if;
   end Applicable_Use;

   ------------------------
   -- Attribute_Renaming --
   ------------------------

   procedure Attribute_Renaming (N : Node_Id) is
      Loc        : constant Source_Ptr := Sloc (N);
      Nam        : constant Node_Id    := Name (N);
      Spec       : constant Node_Id    := Specification (N);
      New_S      : constant Entity_Id  := Defining_Unit_Name (Spec);
      Aname      : constant Name_Id    := Attribute_Name (Nam);

      Form_Num   : Nat      := 0;
      Expr_List  : List_Id  := No_List;

      Attr_Node  : Node_Id;
      Body_Node  : Node_Id;
      Param_Spec : Node_Id;

   begin
      Generate_Definition (New_S);

      --  This procedure is called in the context of subprogram renaming,
      --  and thus the attribute must be one that is a subprogram. All of
      --  those have at least one formal parameter, with the singular
      --  exception of AST_Entry (which is a real oddity, it is odd that
      --  this can be renamed at all!)

      if not Is_Non_Empty_List (Parameter_Specifications (Spec)) then
         if Aname /= Name_AST_Entry then
            Error_Msg_N
              ("subprogram renaming an attribute must have formals", N);
            return;
         end if;

      else
         Param_Spec := First (Parameter_Specifications (Spec));
         while Present (Param_Spec) loop
            Form_Num := Form_Num + 1;

            if Nkind (Parameter_Type (Param_Spec)) /= N_Access_Definition then
               Find_Type (Parameter_Type (Param_Spec));

               --  The profile of the new entity denotes the base type (s) of
               --  the types given in the specification. For access parameters
               --  there are no subtypes involved.

               Rewrite (Parameter_Type (Param_Spec),
                New_Reference_To
                  (Base_Type (Entity (Parameter_Type (Param_Spec))), Loc));
            end if;

            if No (Expr_List) then
               Expr_List := New_List;
            end if;

            Append_To (Expr_List,
              Make_Identifier (Loc,
                Chars => Chars (Defining_Identifier (Param_Spec))));

            --  The expressions in the attribute reference are not freeze
            --   points. Neither is the attribute as a whole, see below.

            Set_Must_Not_Freeze (Last (Expr_List));
            Next (Param_Spec);
         end loop;
      end if;

      --  Immediate error if too many formals. Other mismatches in numbers
      --  of number of types of parameters are detected when we analyze the
      --  body of the subprogram that we construct.

      if Form_Num > 2 then
         Error_Msg_N ("too many formals for attribute", N);

      --  Error if the attribute reference has expressions that look
      --  like formal parameters.

      elsif Present (Expressions (Nam)) then
         Error_Msg_N ("illegal expressions in attribute reference", Nam);

      elsif
        Aname = Name_Compose      or else
        Aname = Name_Exponent     or else
        Aname = Name_Leading_Part or else
        Aname = Name_Pos          or else
        Aname = Name_Round        or else
        Aname = Name_Scaling      or else
        Aname = Name_Val
      then
         if Nkind (N) = N_Subprogram_Renaming_Declaration
           and then Present (Corresponding_Formal_Spec (N))
         then
            Error_Msg_N
              ("generic actual cannot be attribute involving universal type",
               Nam);
         else
            Error_Msg_N
              ("attribute involving a universal type cannot be renamed",
               Nam);
         end if;
      end if;

      --  AST_Entry is an odd case. It doesn't really make much sense to
      --  allow it to be renamed, but that's the DEC rule, so we have to
      --  do it right. The point is that the AST_Entry call should be made
      --  now, and what the function will return is the returned value.

      --  Note that there is no Expr_List in this case anyway

      if Aname = Name_AST_Entry then
         declare
            Ent  : Entity_Id;
            Decl : Node_Id;

         begin
            Ent := Make_Defining_Identifier (Loc, New_Internal_Name ('R'));

            Decl :=
              Make_Object_Declaration (Loc,
                Defining_Identifier => Ent,
                Object_Definition =>
                  New_Occurrence_Of (RTE (RE_AST_Handler), Loc),
                Expression => Nam,
                Constant_Present => True);

            Set_Assignment_OK (Decl, True);
            Insert_Action (N, Decl);
            Attr_Node := Make_Identifier (Loc, Chars (Ent));
         end;

      --  For all other attributes, we rewrite the attribute node to have
      --  a list of expressions corresponding to the subprogram formals.
      --  A renaming declaration is not a freeze point, and the analysis of
      --  the attribute reference should not freeze the type of the prefix.

      else
         Attr_Node :=
           Make_Attribute_Reference (Loc,
             Prefix         => Prefix (Nam),
             Attribute_Name => Aname,
             Expressions    => Expr_List);

         Set_Must_Not_Freeze (Attr_Node);
         Set_Must_Not_Freeze (Prefix (Nam));
      end if;

      --  Case of renaming a function

      if Nkind (Spec) = N_Function_Specification then
         if Is_Procedure_Attribute_Name (Aname) then
            Error_Msg_N ("attribute can only be renamed as procedure", Nam);
            return;
         end if;

         Find_Type (Result_Definition (Spec));
         Rewrite (Result_Definition (Spec),
             New_Reference_To (
               Base_Type (Entity (Result_Definition (Spec))), Loc));

         Body_Node :=
           Make_Subprogram_Body (Loc,
             Specification => Spec,
             Declarations => New_List,
             Handled_Statement_Sequence =>
               Make_Handled_Sequence_Of_Statements (Loc,
                   Statements => New_List (
                     Make_Simple_Return_Statement (Loc,
                       Expression => Attr_Node))));

      --  Case of renaming a procedure

      else
         if not Is_Procedure_Attribute_Name (Aname) then
            Error_Msg_N ("attribute can only be renamed as function", Nam);
            return;
         end if;

         Body_Node :=
           Make_Subprogram_Body (Loc,
             Specification => Spec,
             Declarations => New_List,
             Handled_Statement_Sequence =>
               Make_Handled_Sequence_Of_Statements (Loc,
                   Statements => New_List (Attr_Node)));
      end if;

      --  In case of tagged types we add the body of the generated function to
      --  the freezing actions of the type (because in the general case such
      --  type is still not frozen). We exclude from this processing generic
      --  formal subprograms found in instantiations and AST_Entry renamings.

      if not Present (Corresponding_Formal_Spec (N))
        and then Etype (Nam) /= RTE (RE_AST_Handler)
      then
         declare
            P : constant Entity_Id := Prefix (Nam);

         begin
            Find_Type (P);

            if Is_Tagged_Type (Etype (P)) then
               Ensure_Freeze_Node (Etype (P));
               Append_Freeze_Action (Etype (P), Body_Node);
            else
               Rewrite (N, Body_Node);
               Analyze (N);
               Set_Etype (New_S, Base_Type (Etype (New_S)));
            end if;
         end;

      --  Generic formal subprograms or AST_Handler renaming

      else
         Rewrite (N, Body_Node);
         Analyze (N);
         Set_Etype (New_S, Base_Type (Etype (New_S)));
      end if;

      if Is_Compilation_Unit (New_S) then
         Error_Msg_N
           ("a library unit can only rename another library unit", N);
      end if;

      --  We suppress elaboration warnings for the resulting entity, since
      --  clearly they are not needed, and more particularly, in the case
      --  of a generic formal subprogram, the resulting entity can appear
      --  after the instantiation itself, and thus look like a bogus case
      --  of access before elaboration.

      Set_Suppress_Elaboration_Warnings (New_S);

   end Attribute_Renaming;

   ----------------------
   -- Chain_Use_Clause --
   ----------------------

   procedure Chain_Use_Clause (N : Node_Id) is
      Pack : Entity_Id;
      Level : Int := Scope_Stack.Last;

   begin
      if not Is_Compilation_Unit (Current_Scope)
        or else not Is_Child_Unit (Current_Scope)
      then
         null;   --  Common case

      elsif Defining_Entity (Parent (N)) = Current_Scope then
         null;   --  Common case for compilation unit

      else
         --  If declaration appears in some other scope, it must be in some
         --  parent unit when compiling a child.

         Pack := Defining_Entity (Parent (N));
         if not In_Open_Scopes (Pack) then
            null;  --  default as well

         else
            --  Find entry for parent unit in scope stack

            while Scope_Stack.Table (Level).Entity /= Pack loop
               Level := Level - 1;
            end loop;
         end if;
      end if;

      Set_Next_Use_Clause (N,
        Scope_Stack.Table (Level).First_Use_Clause);
      Scope_Stack.Table (Level).First_Use_Clause := N;
   end Chain_Use_Clause;

   ---------------------------
   -- Check_Frozen_Renaming --
   ---------------------------

   procedure Check_Frozen_Renaming (N : Node_Id; Subp : Entity_Id) is
      B_Node : Node_Id;
      Old_S  : Entity_Id;

   begin
      if Is_Frozen (Subp)
        and then not Has_Completion (Subp)
      then
         B_Node :=
           Build_Renamed_Body
             (Parent (Declaration_Node (Subp)), Defining_Entity (N));

         if Is_Entity_Name (Name (N)) then
            Old_S := Entity (Name (N));

            if not Is_Frozen (Old_S)
              and then Operating_Mode /= Check_Semantics
            then
               Append_Freeze_Action (Old_S, B_Node);
            else
               Insert_After (N, B_Node);
               Analyze (B_Node);
            end if;

            if Is_Intrinsic_Subprogram (Old_S)
              and then not In_Instance
            then
               Error_Msg_N
                 ("subprogram used in renaming_as_body cannot be intrinsic",
                    Name (N));
            end if;

         else
            Insert_After (N, B_Node);
            Analyze (B_Node);
         end if;
      end if;
   end Check_Frozen_Renaming;

   -----------------------------------
   -- Check_In_Previous_With_Clause --
   -----------------------------------

   procedure Check_In_Previous_With_Clause
     (N   : Node_Id;
      Nam : Entity_Id)
   is
      Pack : constant Entity_Id := Entity (Original_Node (Nam));
      Item : Node_Id;
      Par  : Node_Id;

   begin
      Item := First (Context_Items (Parent (N)));

      while Present (Item)
        and then Item /= N
      loop
         if Nkind (Item) = N_With_Clause

            --  Protect the frontend against previous critical errors

           and then Nkind (Name (Item)) /= N_Selected_Component
           and then Entity (Name (Item)) = Pack
         then
            Par := Nam;

            --  Find root library unit in with_clause

            while Nkind (Par) = N_Expanded_Name loop
               Par := Prefix (Par);
            end loop;

            if Is_Child_Unit (Entity (Original_Node (Par))) then
               Error_Msg_NE
                 ("& is not directly visible", Par, Entity (Par));
            else
               return;
            end if;
         end if;

         Next (Item);
      end loop;

      --  On exit, package is not mentioned in a previous with_clause.
      --  Check if its prefix is.

      if Nkind (Nam) = N_Expanded_Name then
         Check_In_Previous_With_Clause (N, Prefix (Nam));

      elsif Pack /= Any_Id then
         Error_Msg_NE ("& is not visible", Nam, Pack);
      end if;
   end Check_In_Previous_With_Clause;

   ---------------------------------
   -- Check_Library_Unit_Renaming --
   ---------------------------------

   procedure Check_Library_Unit_Renaming (N : Node_Id; Old_E : Entity_Id) is
      New_E : Entity_Id;

   begin
      if Nkind (Parent (N)) /= N_Compilation_Unit then
         return;

      --  Check for library unit. Note that we used to check for the scope
      --  being Standard here, but that was wrong for Standard itself.

      elsif not Is_Compilation_Unit (Old_E)
        and then not Is_Child_Unit (Old_E)
      then
         Error_Msg_N ("renamed unit must be a library unit", Name (N));

      --  Entities defined in Standard (operators and boolean literals) cannot
      --  be renamed as library units.

      elsif Scope (Old_E) = Standard_Standard
        and then Sloc (Old_E) = Standard_Location
      then
         Error_Msg_N ("renamed unit must be a library unit", Name (N));

      elsif Present (Parent_Spec (N))
        and then Nkind (Unit (Parent_Spec (N))) = N_Generic_Package_Declaration
        and then not Is_Child_Unit (Old_E)
      then
         Error_Msg_N
           ("renamed unit must be a child unit of generic parent", Name (N));

      elsif Nkind (N) in N_Generic_Renaming_Declaration
         and then  Nkind (Name (N)) = N_Expanded_Name
         and then Is_Generic_Instance (Entity (Prefix (Name (N))))
         and then Is_Generic_Unit (Old_E)
      then
         Error_Msg_N
           ("renamed generic unit must be a library unit", Name (N));

      elsif Ekind (Old_E) = E_Package
        or else Ekind (Old_E) = E_Generic_Package
      then
         --  Inherit categorization flags

         New_E := Defining_Entity (N);
         Set_Is_Pure                  (New_E, Is_Pure           (Old_E));
         Set_Is_Preelaborated         (New_E, Is_Preelaborated  (Old_E));
         Set_Is_Remote_Call_Interface (New_E,
                                       Is_Remote_Call_Interface (Old_E));
         Set_Is_Remote_Types          (New_E, Is_Remote_Types   (Old_E));
         Set_Is_Shared_Passive        (New_E, Is_Shared_Passive (Old_E));
      end if;
   end Check_Library_Unit_Renaming;

   ---------------
   -- End_Scope --
   ---------------

   procedure End_Scope is
      Id    : Entity_Id;
      Prev  : Entity_Id;
      Outer : Entity_Id;

   begin
      Id := First_Entity (Current_Scope);
      while Present (Id) loop
         --  An entity in the current scope is not necessarily the first one
         --  on its homonym chain. Find its predecessor if any,
         --  If it is an internal entity, it will not be in the visibility
         --  chain altogether,  and there is nothing to unchain.

         if Id /= Current_Entity (Id) then
            Prev := Current_Entity (Id);
            while Present (Prev)
              and then Present (Homonym (Prev))
              and then Homonym (Prev) /= Id
            loop
               Prev := Homonym (Prev);
            end loop;

            --  Skip to end of loop if Id is not in the visibility chain

            if No (Prev) or else Homonym (Prev) /= Id then
               goto Next_Ent;
            end if;

         else
            Prev := Empty;
         end if;

         Set_Is_Immediately_Visible (Id, False);

         Outer := Homonym (Id);
         while Present (Outer) and then Scope (Outer) = Current_Scope loop
            Outer := Homonym (Outer);
         end loop;

         --  Reset homonym link of other entities, but do not modify link
         --  between entities in current scope, so that the back-end can have
         --  a proper count of local overloadings.

         if No (Prev) then
            Set_Name_Entity_Id (Chars (Id), Outer);

         elsif Scope (Prev) /= Scope (Id) then
            Set_Homonym (Prev,  Outer);
         end if;

         <<Next_Ent>>
            Next_Entity (Id);
      end loop;

      --  If the scope generated freeze actions, place them before the
      --  current declaration and analyze them. Type declarations and
      --  the bodies of initialization procedures can generate such nodes.
      --  We follow the parent chain until we reach a list node, which is
      --  the enclosing list of declarations. If the list appears within
      --  a protected definition, move freeze nodes outside the protected
      --  type altogether.

      if Present
         (Scope_Stack.Table (Scope_Stack.Last).Pending_Freeze_Actions)
      then
         declare
            Decl : Node_Id;
            L    : constant List_Id := Scope_Stack.Table
                    (Scope_Stack.Last).Pending_Freeze_Actions;

         begin
            if Is_Itype (Current_Scope) then
               Decl := Associated_Node_For_Itype (Current_Scope);
            else
               Decl := Parent (Current_Scope);
            end if;

            Pop_Scope;

            while not (Is_List_Member (Decl))
              or else Nkind_In (Parent (Decl), N_Protected_Definition,
                                               N_Task_Definition)
            loop
               Decl := Parent (Decl);
            end loop;

            Insert_List_Before_And_Analyze (Decl, L);
         end;

      else
         Pop_Scope;
      end if;

   end End_Scope;

   ---------------------
   -- End_Use_Clauses --
   ---------------------

   procedure End_Use_Clauses (Clause : Node_Id) is
      U   : Node_Id;

   begin
      --  Remove Use_Type clauses first, because they affect the
      --  visibility of operators in subsequent used packages.

      U := Clause;
      while Present (U) loop
         if Nkind (U) = N_Use_Type_Clause then
            End_Use_Type (U);
         end if;

         Next_Use_Clause (U);
      end loop;

      U := Clause;
      while Present (U) loop
         if Nkind (U) = N_Use_Package_Clause then
            End_Use_Package (U);
         end if;

         Next_Use_Clause (U);
      end loop;
   end End_Use_Clauses;

   ---------------------
   -- End_Use_Package --
   ---------------------

   procedure End_Use_Package (N : Node_Id) is
      Pack_Name : Node_Id;
      Pack      : Entity_Id;
      Id        : Entity_Id;
      Elmt      : Elmt_Id;

      function Is_Primitive_Operator
        (Op : Entity_Id;
         F  : Entity_Id) return Boolean;
      --  Check whether Op is a primitive operator of a use-visible type

      ---------------------------
      -- Is_Primitive_Operator --
      ---------------------------

      function Is_Primitive_Operator
        (Op : Entity_Id;
         F  : Entity_Id) return Boolean
      is
         T : constant Entity_Id := Etype (F);
      begin
         return In_Use (T)
           and then Scope (T) = Scope (Op);
      end Is_Primitive_Operator;

   --  Start of processing for End_Use_Package

   begin
      Pack_Name := First (Names (N));
      while Present (Pack_Name) loop
         Pack := Entity (Pack_Name);

         if Ekind (Pack) = E_Package then
            if In_Open_Scopes (Pack) then
               null;

            elsif not Redundant_Use (Pack_Name) then
               Set_In_Use (Pack, False);
               Set_Current_Use_Clause (Pack, Empty);

               Id := First_Entity (Pack);
               while Present (Id) loop

                  --  Preserve use-visibility of operators that are primitive
                  --  operators of a type that is use-visible through an active
                  --  use_type clause.

                  if Nkind (Id) = N_Defining_Operator_Symbol
                       and then
                         (Is_Primitive_Operator (Id, First_Formal (Id))
                            or else
                          (Present (Next_Formal (First_Formal (Id)))
                             and then
                               Is_Primitive_Operator
                                 (Id, Next_Formal (First_Formal (Id)))))
                  then
                     null;

                  else
                     Set_Is_Potentially_Use_Visible (Id, False);
                  end if;

                  if Is_Private_Type (Id)
                    and then Present (Full_View (Id))
                  then
                     Set_Is_Potentially_Use_Visible (Full_View (Id), False);
                  end if;

                  Next_Entity (Id);
               end loop;

               if Present (Renamed_Object (Pack)) then
                  Set_In_Use (Renamed_Object (Pack), False);
                  Set_Current_Use_Clause (Renamed_Object (Pack), Empty);
               end if;

               if Chars (Pack) = Name_System
                 and then Scope (Pack) = Standard_Standard
                 and then Present_System_Aux
               then
                  Id := First_Entity (System_Aux_Id);
                  while Present (Id) loop
                     Set_Is_Potentially_Use_Visible (Id, False);

                     if Is_Private_Type (Id)
                       and then Present (Full_View (Id))
                     then
                        Set_Is_Potentially_Use_Visible (Full_View (Id), False);
                     end if;

                     Next_Entity (Id);
                  end loop;

                  Set_In_Use (System_Aux_Id, False);
               end if;

            else
               Set_Redundant_Use (Pack_Name, False);
            end if;
         end if;

         Next (Pack_Name);
      end loop;

      if Present (Hidden_By_Use_Clause (N)) then
         Elmt := First_Elmt (Hidden_By_Use_Clause (N));
         while Present (Elmt) loop
            Set_Is_Immediately_Visible (Node (Elmt));
            Next_Elmt (Elmt);
         end loop;

         Set_Hidden_By_Use_Clause (N, No_Elist);
      end if;
   end End_Use_Package;

   ------------------
   -- End_Use_Type --
   ------------------

   procedure End_Use_Type (N : Node_Id) is
      Id      : Entity_Id;
      Op_List : Elist_Id;
      Elmt    : Elmt_Id;
      T       : Entity_Id;

   begin
      Id := First (Subtype_Marks (N));
      while Present (Id) loop

         --  A call to rtsfind may occur while analyzing a use_type clause,
         --  in which case the type marks are not resolved yet, and there is
         --  nothing to remove.

         if not Is_Entity_Name (Id)
           or else No (Entity (Id))
         then
            goto Continue;
         end if;

         T := Entity (Id);

         if T = Any_Type
           or else From_With_Type (T)
         then
            null;

         --  Note that the use_Type clause may mention a subtype of the type
         --  whose primitive operations have been made visible. Here as
         --  elsewhere, it is the base type that matters for visibility.

         elsif In_Open_Scopes (Scope (Base_Type (T))) then
            null;

         elsif not Redundant_Use (Id) then
            Set_In_Use (T, False);
            Set_In_Use (Base_Type (T), False);
            Op_List := Collect_Primitive_Operations (T);

            Elmt := First_Elmt (Op_List);
            while Present (Elmt) loop
               if Nkind (Node (Elmt)) = N_Defining_Operator_Symbol then
                  Set_Is_Potentially_Use_Visible (Node (Elmt), False);
               end if;

               Next_Elmt (Elmt);
            end loop;
         end if;

         <<Continue>>
         Next (Id);
      end loop;
   end End_Use_Type;

   ----------------------
   -- Find_Direct_Name --
   ----------------------

   procedure Find_Direct_Name (N : Node_Id) is
      E    : Entity_Id;
      E2   : Entity_Id;
      Msg  : Boolean;

      Inst : Entity_Id := Empty;
      --  Enclosing instance, if any

      Homonyms : Entity_Id;
      --  Saves start of homonym chain

      Nvis_Entity : Boolean;
      --  Set True to indicate that at there is at least one entity on the
      --  homonym chain which, while not visible, is visible enough from the
      --  user point of view to warrant an error message of "not visible"
      --  rather than undefined.

      Nvis_Is_Private_Subprg : Boolean := False;
      --  Ada 2005 (AI-262): Set True to indicate that a form of Beaujolais
      --  effect concerning library subprograms has been detected. Used to
      --  generate the precise error message.

      function From_Actual_Package (E : Entity_Id) return Boolean;
      --  Returns true if the entity is declared in a package that is
      --  an actual for a formal package of the current instance. Such an
      --  entity requires special handling because it may be use-visible
      --  but hides directly visible entities defined outside the instance.

      function Is_Actual_Parameter return Boolean;
      --  This function checks if the node N is an identifier that is an actual
      --  parameter of a procedure call. If so it returns True, otherwise it
      --  return False. The reason for this check is that at this stage we do
      --  not know what procedure is being called if the procedure might be
      --  overloaded, so it is premature to go setting referenced flags or
      --  making calls to Generate_Reference. We will wait till Resolve_Actuals
      --  for that processing

      function Known_But_Invisible (E : Entity_Id) return Boolean;
      --  This function determines whether the entity E (which is not
      --  visible) can reasonably be considered to be known to the writer
      --  of the reference. This is a heuristic test, used only for the
      --  purposes of figuring out whether we prefer to complain that an
      --  entity is undefined or invisible (and identify the declaration
      --  of the invisible entity in the latter case). The point here is
      --  that we don't want to complain that something is invisible and
      --  then point to something entirely mysterious to the writer.

      procedure Nvis_Messages;
      --  Called if there are no visible entries for N, but there is at least
      --  one non-directly visible, or hidden declaration. This procedure
      --  outputs an appropriate set of error messages.

      procedure Undefined (Nvis : Boolean);
      --  This function is called if the current node has no corresponding
      --  visible entity or entities. The value set in Msg indicates whether
      --  an error message was generated (multiple error messages for the
      --  same variable are generally suppressed, see body for details).
      --  Msg is True if an error message was generated, False if not. This
      --  value is used by the caller to determine whether or not to output
      --  additional messages where appropriate. The parameter is set False
      --  to get the message "X is undefined", and True to get the message
      --  "X is not visible".

      -------------------------
      -- From_Actual_Package --
      -------------------------

      function From_Actual_Package (E : Entity_Id) return Boolean is
         Scop : constant Entity_Id := Scope (E);
         Act  : Entity_Id;

      begin
         if not In_Instance then
            return False;
         else
            Inst := Current_Scope;
            while Present (Inst)
              and then Ekind (Inst) /= E_Package
              and then not Is_Generic_Instance (Inst)
            loop
               Inst := Scope (Inst);
            end loop;

            if No (Inst) then
               return False;
            end if;

            Act := First_Entity (Inst);
            while Present (Act) loop
               if Ekind (Act) = E_Package then

                  --  Check for end of actuals list

                  if Renamed_Object (Act) = Inst then
                     return False;

                  elsif Present (Associated_Formal_Package (Act))
                    and then Renamed_Object (Act) = Scop
                  then
                     --  Entity comes from (instance of) formal package

                     return True;

                  else
                     Next_Entity (Act);
                  end if;

               else
                  Next_Entity (Act);
               end if;
            end loop;

            return False;
         end if;
      end From_Actual_Package;

      -------------------------
      -- Is_Actual_Parameter --
      -------------------------

      function Is_Actual_Parameter return Boolean is
      begin
         return
           Nkind (N) = N_Identifier
             and then
               (Nkind (Parent (N)) = N_Procedure_Call_Statement
                  or else
                    (Nkind (Parent (N)) = N_Parameter_Association
                       and then N = Explicit_Actual_Parameter (Parent (N))
                       and then Nkind (Parent (Parent (N))) =
                                          N_Procedure_Call_Statement));
      end Is_Actual_Parameter;

      -------------------------
      -- Known_But_Invisible --
      -------------------------

      function Known_But_Invisible (E : Entity_Id) return Boolean is
         Fname : File_Name_Type;

      begin
         --  Entities in Standard are always considered to be known

         if Sloc (E) <= Standard_Location then
            return True;

         --  An entity that does not come from source is always considered
         --  to be unknown, since it is an artifact of code expansion.

         elsif not Comes_From_Source (E) then
            return False;

         --  In gnat internal mode, we consider all entities known

         elsif GNAT_Mode then
            return True;
         end if;

         --  Here we have an entity that is not from package Standard, and
         --  which comes from Source. See if it comes from an internal file.

         Fname := Unit_File_Name (Get_Source_Unit (E));

         --  Case of from internal file

         if Is_Internal_File_Name (Fname) then

            --  Private part entities in internal files are never considered
            --  to be known to the writer of normal application code.

            if Is_Hidden (E) then
               return False;
            end if;

            --  Entities from System packages other than System and
            --  System.Storage_Elements are not considered to be known.
            --  System.Auxxxx files are also considered known to the user.

            --  Should refine this at some point to generally distinguish
            --  between known and unknown internal files ???

            Get_Name_String (Fname);

            return
              Name_Len < 2
                or else
              Name_Buffer (1 .. 2) /= "s-"
                or else
              Name_Buffer (3 .. 8) = "stoele"
                or else
              Name_Buffer (3 .. 5) = "aux";

         --  If not an internal file, then entity is definitely known,
         --  even if it is in a private part (the message generated will
         --  note that it is in a private part)

         else
            return True;
         end if;
      end Known_But_Invisible;

      -------------------
      -- Nvis_Messages --
      -------------------

      procedure Nvis_Messages is
         Comp_Unit : Node_Id;
         Ent       : Entity_Id;
         Hidden    : Boolean := False;
         Item      : Node_Id;

      begin
         --  Ada 2005 (AI-262): Generate a precise error concerning the
         --  Beaujolais effect that was previously detected

         if Nvis_Is_Private_Subprg then

            pragma Assert (Nkind (E2) = N_Defining_Identifier
                            and then Ekind (E2) = E_Function
                            and then Scope (E2) = Standard_Standard
                            and then Has_Private_With (E2));

            --  Find the sloc corresponding to the private with'ed unit

            Comp_Unit := Cunit (Current_Sem_Unit);
            Error_Msg_Sloc := No_Location;

            Item := First (Context_Items (Comp_Unit));
            while Present (Item) loop
               if Nkind (Item) = N_With_Clause
                 and then Private_Present (Item)
                 and then Entity (Name (Item)) = E2
               then
                  Error_Msg_Sloc := Sloc (Item);
                  exit;
               end if;

               Next (Item);
            end loop;

            pragma Assert (Error_Msg_Sloc /= No_Location);

            Error_Msg_N ("(Ada 2005): hidden by private with clause #", N);
            return;
         end if;

         Undefined (Nvis => True);

         if Msg then

            --  First loop does hidden declarations

            Ent := Homonyms;
            while Present (Ent) loop
               if Is_Potentially_Use_Visible (Ent) then
                  if not Hidden then
                     Error_Msg_N ("multiple use clauses cause hiding!", N);
                     Hidden := True;
                  end if;

                  Error_Msg_Sloc := Sloc (Ent);
                  Error_Msg_N ("hidden declaration#!", N);
               end if;

               Ent := Homonym (Ent);
            end loop;

            --  If we found hidden declarations, then that's enough, don't
            --  bother looking for non-visible declarations as well.

            if Hidden then
               return;
            end if;

            --  Second loop does non-directly visible declarations

            Ent := Homonyms;
            while Present (Ent) loop
               if not Is_Potentially_Use_Visible (Ent) then

                  --  Do not bother the user with unknown entities

                  if not Known_But_Invisible (Ent) then
                     goto Continue;
                  end if;

                  Error_Msg_Sloc := Sloc (Ent);

                  --  Output message noting that there is a non-visible
                  --  declaration, distinguishing the private part case.

                  if Is_Hidden (Ent) then
                     Error_Msg_N ("non-visible (private) declaration#!", N);
                  else
                     Error_Msg_N ("non-visible declaration#!", N);

                     if Is_Compilation_Unit (Ent)
                       and then
                         Nkind (Parent (Parent (N))) = N_Use_Package_Clause
                     then
                        Error_Msg_Qual_Level := 99;
                        Error_Msg_NE ("\\missing `WITH &;`", N, Ent);
                        Error_Msg_Qual_Level := 0;
                     end if;
                  end if;

                  --  Set entity and its containing package as referenced. We
                  --  can't be sure of this, but this seems a better choice
                  --  to avoid unused entity messages.

                  if Comes_From_Source (Ent) then
                     Set_Referenced (Ent);
                     Set_Referenced (Cunit_Entity (Get_Source_Unit (Ent)));
                  end if;
               end if;

               <<Continue>>
               Ent := Homonym (Ent);
            end loop;
         end if;
      end Nvis_Messages;

      ---------------
      -- Undefined --
      ---------------

      procedure Undefined (Nvis : Boolean) is
         Emsg : Error_Msg_Id;

      begin
         --  We should never find an undefined internal name. If we do, then
         --  see if we have previous errors. If so, ignore on the grounds that
         --  it is probably a cascaded message (e.g. a block label from a badly
         --  formed block). If no previous errors, then we have a real internal
         --  error of some kind so raise an exception.

         if Is_Internal_Name (Chars (N)) then
            if Total_Errors_Detected /= 0 then
               return;
            else
               raise Program_Error;
            end if;
         end if;

         --  A very specialized error check, if the undefined variable is
         --  a case tag, and the case type is an enumeration type, check
         --  for a possible misspelling, and if so, modify the identifier

         --  Named aggregate should also be handled similarly ???

         if Nkind (N) = N_Identifier
           and then Nkind (Parent (N)) = N_Case_Statement_Alternative
         then
            declare
               Case_Stm : constant Node_Id   := Parent (Parent (N));
               Case_Typ : constant Entity_Id := Etype (Expression (Case_Stm));
               Case_Rtp : constant Entity_Id := Root_Type (Case_Typ);

               Lit : Node_Id;

            begin
               if Is_Enumeration_Type (Case_Typ)
                 and then Case_Rtp /= Standard_Character
                 and then Case_Rtp /= Standard_Wide_Character
                 and then Case_Rtp /= Standard_Wide_Wide_Character
               then
                  Lit := First_Literal (Case_Typ);
                  Get_Name_String (Chars (Lit));

                  if Chars (Lit) /= Chars (N)
                    and then Is_Bad_Spelling_Of (Chars (N), Chars (Lit)) then
                     Error_Msg_Node_2 := Lit;
                     Error_Msg_N
                       ("& is undefined, assume misspelling of &", N);
                     Rewrite (N, New_Occurrence_Of (Lit, Sloc (N)));
                     return;
                  end if;

                  Lit := Next_Literal (Lit);
               end if;
            end;
         end if;

         --  Normal processing

         Set_Entity (N, Any_Id);
         Set_Etype  (N, Any_Type);

         --  We use the table Urefs to keep track of entities for which we
         --  have issued errors for undefined references. Multiple errors
         --  for a single name are normally suppressed, however we modify
         --  the error message to alert the programmer to this effect.

         for J in Urefs.First .. Urefs.Last loop
            if Chars (N) = Chars (Urefs.Table (J).Node) then
               if Urefs.Table (J).Err /= No_Error_Msg
                 and then Sloc (N) /= Urefs.Table (J).Loc
               then
                  Error_Msg_Node_1 := Urefs.Table (J).Node;

                  if Urefs.Table (J).Nvis then
                     Change_Error_Text (Urefs.Table (J).Err,
                       "& is not visible (more references follow)");
                  else
                     Change_Error_Text (Urefs.Table (J).Err,
                       "& is undefined (more references follow)");
                  end if;

                  Urefs.Table (J).Err := No_Error_Msg;
               end if;

               --  Although we will set Msg False, and thus suppress the
               --  message, we also set Error_Posted True, to avoid any
               --  cascaded messages resulting from the undefined reference.

               Msg := False;
               Set_Error_Posted (N, True);
               return;
            end if;
         end loop;

         --  If entry not found, this is first undefined occurrence

         if Nvis then
            Error_Msg_N ("& is not visible!", N);
            Emsg := Get_Msg_Id;

         else
            Error_Msg_N ("& is undefined!", N);
            Emsg := Get_Msg_Id;

            --  A very bizarre special check, if the undefined identifier
            --  is put or put_line, then add a special error message (since
            --  this is a very common error for beginners to make).

            if Chars (N) = Name_Put or else Chars (N) = Name_Put_Line then
               Error_Msg_N
                 ("\\possible missing `WITH Ada.Text_'I'O; " &
                  "USE Ada.Text_'I'O`!", N);

            --  Another special check if N is the prefix of a selected
            --  component which is a known unit, add message complaining
            --  about missing with for this unit.

            elsif Nkind (Parent (N)) = N_Selected_Component
              and then N = Prefix (Parent (N))
              and then Is_Known_Unit (Parent (N))
            then
               Error_Msg_Node_2 := Selector_Name (Parent (N));
               Error_Msg_N ("\\missing `WITH &.&;`", Prefix (Parent (N)));
            end if;

            --  Now check for possible misspellings

            declare
               E      : Entity_Id;
               Ematch : Entity_Id := Empty;

               Last_Name_Id : constant Name_Id :=
                                Name_Id (Nat (First_Name_Id) +
                                           Name_Entries_Count - 1);

            begin
               for Nam in First_Name_Id .. Last_Name_Id loop
                  E := Get_Name_Entity_Id (Nam);

                  if Present (E)
                     and then (Is_Immediately_Visible (E)
                                 or else
                               Is_Potentially_Use_Visible (E))
                  then
                     if Is_Bad_Spelling_Of (Chars (N), Nam) then
                        Ematch := E;
                        exit;
                     end if;
                  end if;
               end loop;

               if Present (Ematch) then
                  Error_Msg_NE ("\possible misspelling of&", N, Ematch);
               end if;
            end;
         end if;

         --  Make entry in undefined references table unless the full errors
         --  switch is set, in which case by refraining from generating the
         --  table entry, we guarantee that we get an error message for every
         --  undefined reference.

         if not All_Errors_Mode then
            Urefs.Append (
              (Node => N,
               Err  => Emsg,
               Nvis => Nvis,
               Loc  => Sloc (N)));
         end if;

         Msg := True;
      end Undefined;

   --  Start of processing for Find_Direct_Name

   begin
      --  If the entity pointer is already set, this is an internal node, or
      --  a node that is analyzed more than once, after a tree modification.
      --  In such a case there is no resolution to perform, just set the type.

      if Present (Entity (N)) then
         if Is_Type (Entity (N)) then
            Set_Etype (N, Entity (N));

         else
            declare
               Entyp : constant Entity_Id := Etype (Entity (N));

            begin
               --  One special case here. If the Etype field is already set,
               --  and references the packed array type corresponding to the
               --  etype of the referenced entity, then leave it alone. This
               --  happens for trees generated from Exp_Pakd, where expressions
               --  can be deliberately "mis-typed" to the packed array type.

               if Is_Array_Type (Entyp)
                 and then Is_Packed (Entyp)
                 and then Present (Etype (N))
                 and then Etype (N) = Packed_Array_Type (Entyp)
               then
                  null;

               --  If not that special case, then just reset the Etype

               else
                  Set_Etype (N, Etype (Entity (N)));
               end if;
            end;
         end if;

         return;
      end if;

      --  Here if Entity pointer was not set, we need full visibility analysis
      --  First we generate debugging output if the debug E flag is set.

      if Debug_Flag_E then
         Write_Str ("Looking for ");
         Write_Name (Chars (N));
         Write_Eol;
      end if;

      Homonyms := Current_Entity (N);
      Nvis_Entity := False;

      E := Homonyms;
      while Present (E) loop

         --  If entity is immediately visible or potentially use
         --  visible, then process the entity and we are done.

         if Is_Immediately_Visible (E) then
            goto Immediately_Visible_Entity;

         elsif Is_Potentially_Use_Visible (E) then
            goto Potentially_Use_Visible_Entity;

         --  Note if a known but invisible entity encountered

         elsif Known_But_Invisible (E) then
            Nvis_Entity := True;
         end if;

         --  Move to next entity in chain and continue search

         E := Homonym (E);
      end loop;

      --  If no entries on homonym chain that were potentially visible,
      --  and no entities reasonably considered as non-visible, then
      --  we have a plain undefined reference, with no additional
      --  explanation required!

      if not Nvis_Entity then
         Undefined (Nvis => False);

      --  Otherwise there is at least one entry on the homonym chain that
      --  is reasonably considered as being known and non-visible.

      else
         Nvis_Messages;
      end if;

      return;

      --  Processing for a potentially use visible entry found. We must search
      --  the rest of the homonym chain for two reasons. First, if there is a
      --  directly visible entry, then none of the potentially use-visible
      --  entities are directly visible (RM 8.4(10)). Second, we need to check
      --  for the case of multiple potentially use-visible entries hiding one
      --  another and as a result being non-directly visible (RM 8.4(11)).

      <<Potentially_Use_Visible_Entity>> declare
         Only_One_Visible : Boolean := True;
         All_Overloadable : Boolean := Is_Overloadable (E);

      begin
         E2 := Homonym (E);
         while Present (E2) loop
            if Is_Immediately_Visible (E2) then

               --  If the use-visible entity comes from the actual for a
               --  formal package, it hides a directly visible entity from
               --  outside the instance.

               if From_Actual_Package (E)
                 and then Scope_Depth (E2) < Scope_Depth (Inst)
               then
                  goto Found;
               else
                  E := E2;
                  goto Immediately_Visible_Entity;
               end if;

            elsif Is_Potentially_Use_Visible (E2) then
               Only_One_Visible := False;
               All_Overloadable := All_Overloadable and Is_Overloadable (E2);

            --  Ada 2005 (AI-262): Protect against a form of Beujolais effect
            --  that can occurr in private_with clauses. Example:

            --    with A;
            --    private with B;              package A is
            --    package C is                   function B return Integer;
            --      use A;                     end A;
            --      V1 : Integer := B;
            --    private                      function B return Integer;
            --      V2 : Integer := B;
            --    end C;

            --  V1 resolves to A.B, but V2 resolves to library unit B

            elsif Ekind (E2) = E_Function
              and then Scope (E2) = Standard_Standard
              and then Has_Private_With (E2)
            then
               Only_One_Visible       := False;
               All_Overloadable       := False;
               Nvis_Is_Private_Subprg := True;
               exit;
            end if;

            E2 := Homonym (E2);
         end loop;

         --  On falling through this loop, we have checked that there are no
         --  immediately visible entities. Only_One_Visible is set if exactly
         --  one potentially use visible entity exists. All_Overloadable is
         --  set if all the potentially use visible entities are overloadable.
         --  The condition for legality is that either there is one potentially
         --  use visible entity, or if there is more than one, then all of them
         --  are overloadable.

         if Only_One_Visible or All_Overloadable then
            goto Found;

         --  If there is more than one potentially use-visible entity and at
         --  least one of them non-overloadable, we have an error (RM 8.4(11).
         --  Note that E points to the first such entity on the homonym list.
         --  Special case: if one of the entities is declared in an actual
         --  package, it was visible in the generic, and takes precedence over
         --  other entities that are potentially use-visible. Same if it is
         --  declared in a local instantiation of the current instance.

         else
            if In_Instance then

               --  Find current instance

               Inst := Current_Scope;
               while Present (Inst)
                 and then Inst /= Standard_Standard
               loop
                  if Is_Generic_Instance (Inst) then
                     exit;
                  end if;

                  Inst := Scope (Inst);
               end loop;

               E2 := E;
               while Present (E2) loop
                  if From_Actual_Package (E2)
                    or else
                      (Is_Generic_Instance (Scope (E2))
                        and then Scope_Depth (Scope (E2)) > Scope_Depth (Inst))
                  then
                     E := E2;
                     goto Found;
                  end if;

                  E2 := Homonym (E2);
               end loop;

               Nvis_Messages;
               return;

            elsif
              Is_Predefined_File_Name (Unit_File_Name (Current_Sem_Unit))
            then
               --  A use-clause in the body of a system file creates conflict
               --  with some entity in a user scope, while rtsfind is active.
               --  Keep only the entity coming from another predefined unit.

               E2 := E;
               while Present (E2) loop
                  if Is_Predefined_File_Name
                    (Unit_File_Name (Get_Source_Unit (Sloc (E2))))
                  then
                     E := E2;
                     goto Found;
                  end if;

                  E2 := Homonym (E2);
               end loop;

               --  Entity must exist because predefined unit is correct

               raise Program_Error;

            else
               Nvis_Messages;
               return;
            end if;
         end if;
      end;

      --  Come here with E set to the first immediately visible entity on
      --  the homonym chain. This is the one we want unless there is another
      --  immediately visible entity further on in the chain for a more
      --  inner scope (RM 8.3(8)).

      <<Immediately_Visible_Entity>> declare
         Level : Int;
         Scop  : Entity_Id;

      begin
         --  Find scope level of initial entity. When compiling  through
         --  Rtsfind, the previous context is not completely invisible, and
         --  an outer entity may appear on the chain, whose scope is below
         --  the entry for Standard that delimits the current scope stack.
         --  Indicate that the level for this spurious entry is outside of
         --  the current scope stack.

         Level := Scope_Stack.Last;
         loop
            Scop := Scope_Stack.Table (Level).Entity;
            exit when Scop = Scope (E);
            Level := Level - 1;
            exit when Scop = Standard_Standard;
         end loop;

         --  Now search remainder of homonym chain for more inner entry
         --  If the entity is Standard itself, it has no scope, and we
         --  compare it with the stack entry directly.

         E2 := Homonym (E);
         while Present (E2) loop
            if Is_Immediately_Visible (E2) then

               --  If a generic package contains a local declaration that
               --  has the same name as the generic, there may be a visibility
               --  conflict in an instance, where the local declaration must
               --  also hide the name of the corresponding package renaming.
               --  We check explicitly for a package declared by a renaming,
               --  whose renamed entity is an instance that is on the scope
               --  stack, and that contains a homonym in the same scope. Once
               --  we have found it, we know that the package renaming is not
               --  immediately visible, and that the identifier denotes the
               --  other entity (and its homonyms if overloaded).

               if Scope (E) = Scope (E2)
                 and then Ekind (E) = E_Package
                 and then Present (Renamed_Object (E))
                 and then Is_Generic_Instance (Renamed_Object (E))
                 and then In_Open_Scopes (Renamed_Object (E))
                 and then Comes_From_Source (N)
               then
                  Set_Is_Immediately_Visible (E, False);
                  E := E2;

               else
                  for J in Level + 1 .. Scope_Stack.Last loop
                     if Scope_Stack.Table (J).Entity = Scope (E2)
                       or else Scope_Stack.Table (J).Entity = E2
                     then
                        Level := J;
                        E := E2;
                        exit;
                     end if;
                  end loop;
               end if;
            end if;

            E2 := Homonym (E2);
         end loop;

         --  At the end of that loop, E is the innermost immediately
         --  visible entity, so we are all set.
      end;

      --  Come here with entity found, and stored in E

      <<Found>> begin

         --  When distribution features are available (Get_PCS_Name /=
         --  Name_No_DSA), a remote access-to-subprogram type is converted
         --  into a record type holding whatever information is needed to
         --  perform a remote call on an RCI suprogram. In that case we
         --  rewrite any occurrence of the RAS type into the equivalent record
         --  type here. 'Access attribute references and RAS dereferences are
         --  then implemented using specific TSSs. However when distribution is
         --  not available (case of Get_PCS_Name = Name_No_DSA), we bypass the
         --  generation of these TSSs, and we must keep the RAS type in its
         --  original access-to-subprogram form (since all calls through a
         --  value of such type will be local anyway in the absence of a PCS).

         if Comes_From_Source (N)
           and then Is_Remote_Access_To_Subprogram_Type (E)
           and then Expander_Active
           and then Get_PCS_Name /= Name_No_DSA
         then
            Rewrite (N,
              New_Occurrence_Of (Equivalent_Type (E), Sloc (N)));
            return;
         end if;

         Set_Entity (N, E);
         --  Why no Style_Check here???

         if Is_Type (E) then
            Set_Etype (N, E);
         else
            Set_Etype (N, Get_Full_View (Etype (E)));
         end if;

         if Debug_Flag_E then
            Write_Str (" found  ");
            Write_Entity_Info (E, "      ");
         end if;

         --  If the Ekind of the entity is Void, it means that all homonyms
         --  are hidden from all visibility (RM 8.3(5,14-20)). However, this
         --  test is skipped if the current scope is a record and the name is
         --  a pragma argument expression (case of Atomic and Volatile pragmas
         --  and possibly other similar pragmas added later, which are allowed
         --  to reference components in the current record).

         if Ekind (E) = E_Void
           and then
             (not Is_Record_Type (Current_Scope)
               or else Nkind (Parent (N)) /= N_Pragma_Argument_Association)
         then
            Premature_Usage (N);

         --  If the entity is overloadable, collect all interpretations of the
         --  name for subsequent overload resolution. We optimize a bit here to
         --  do this only if we have an overloadable entity that is not on its
         --  own on the homonym chain.

         elsif Is_Overloadable (E)
           and then (Present (Homonym (E)) or else Current_Entity (N) /= E)
         then
            Collect_Interps (N);

            --  If no homonyms were visible, the entity is unambiguous

            if not Is_Overloaded (N) then
               if not Is_Actual_Parameter then
                  Generate_Reference (E, N);
               end if;
            end if;

         --  Case of non-overloadable entity, set the entity providing that
         --  we do not have the case of a discriminant reference within a
         --  default expression. Such references are replaced with the
         --  corresponding discriminal, which is the formal corresponding to
         --  to the discriminant in the initialization procedure.

         else
            --  Entity is unambiguous, indicate that it is referenced here

            --  For a renaming of an object, always generate simple reference,
            --  we don't try to keep track of assignments in this case.

            if Is_Object (E) and then Present (Renamed_Object (E)) then
               Generate_Reference (E, N);

            --  One odd case is that we do not want to set the Referenced flag
            --  if the entity is a label, and the identifier is the label in
            --  the source, since this is not a reference from the point of
            --  view of the user.

            elsif Nkind (Parent (N)) = N_Label then
               declare
                  R : constant Boolean := Referenced (E);

               begin
                  --  Generate reference unless this is an actual parameter
                  --  (see comment below)

                  if Is_Actual_Parameter then
                     Generate_Reference (E, N);
                     Set_Referenced (E, R);
                  end if;
               end;

            --  Normal case, not a label: generate reference

            --  ??? It is too early to generate a reference here even if
            --    the entity is unambiguous, because the tree is not
            --    sufficiently typed at this point for Generate_Reference to
            --    determine whether this reference modifies the denoted object
            --    (because implicit derefences cannot be identified prior to
            --    full type resolution).
            --
            --  ??? The Is_Actual_Parameter routine takes care of one of these
            --    cases but there are others probably

            else
               if not Is_Actual_Parameter then
                  Generate_Reference (E, N);
               end if;

               Check_Nested_Access (E);
            end if;

            --  Set Entity, with style check if need be. For a discriminant
            --  reference, replace by the corresponding discriminal, i.e. the
            --  parameter of the initialization procedure that corresponds to
            --  the discriminant. If this replacement is being performed, there
            --  is no style check to perform.

            --  This replacement must not be done if we are currently
            --  processing a generic spec or body, because the discriminal
            --  has not been not generated in this case.

            if not In_Default_Expression
              or else Ekind (E) /= E_Discriminant
              or else Inside_A_Generic
            then
               Set_Entity_With_Style_Check (N, E);

            --  The replacement is not done either for a task discriminant that
            --  appears in a default expression of an entry parameter. See
            --  Expand_Discriminant in exp_ch2 for details on their handling.

            elsif Is_Concurrent_Type (Scope (E)) then
               declare
                  P : Node_Id;

               begin
                  P := Parent (N);
                  while Present (P)
                    and then not Nkind_In (P, N_Parameter_Specification,
                                              N_Component_Declaration)
                  loop
                     P := Parent (P);
                  end loop;

                  if Present (P)
                     and then Nkind (P) = N_Parameter_Specification
                  then
                     null;
                  else
                     Set_Entity (N, Discriminal (E));
                  end if;
               end;

            --  Otherwise, this is a discriminant in a context in which
            --  it is a reference to the corresponding parameter of the
            --  init proc for the enclosing type.

            else
               Set_Entity (N, Discriminal (E));
            end if;
         end if;
      end;
   end Find_Direct_Name;

   ------------------------
   -- Find_Expanded_Name --
   ------------------------

   --  This routine searches the homonym chain of the entity until it finds
   --  an entity declared in the scope denoted by the prefix. If the entity
   --  is private, it may nevertheless be immediately visible, if we are in
   --  the scope of its declaration.

   procedure Find_Expanded_Name (N : Node_Id) is
      Selector  : constant Node_Id := Selector_Name (N);
      Candidate : Entity_Id        := Empty;
      P_Name    : Entity_Id;
      O_Name    : Entity_Id;
      Id        : Entity_Id;

   begin
      P_Name := Entity (Prefix (N));
      O_Name := P_Name;

      --  If the prefix is a renamed package, look for the entity
      --  in the original package.

      if Ekind (P_Name) = E_Package
        and then Present (Renamed_Object (P_Name))
      then
         P_Name := Renamed_Object (P_Name);

         --  Rewrite node with entity field pointing to renamed object

         Rewrite (Prefix (N), New_Copy (Prefix (N)));
         Set_Entity (Prefix (N), P_Name);

      --  If the prefix is an object of a concurrent type, look for
      --  the entity in the associated task or protected type.

      elsif Is_Concurrent_Type (Etype (P_Name)) then
         P_Name := Etype (P_Name);
      end if;

      Id := Current_Entity (Selector);

      declare
         Is_New_Candidate : Boolean;

      begin
         while Present (Id) loop
            if Scope (Id) = P_Name then
               Candidate        := Id;
               Is_New_Candidate := True;

            --  Ada 2005 (AI-217): Handle shadow entities associated with types
            --  declared in limited-withed nested packages. We don't need to
            --  handle E_Incomplete_Subtype entities because the entities in
            --  the limited view are always E_Incomplete_Type entities (see
            --  Build_Limited_Views). Regarding the expression used to evaluate
            --  the scope, it is important to note that the limited view also
            --  has shadow entities associated nested packages. For this reason
            --  the correct scope of the entity is the scope of the real entity
            --  The non-limited view may itself be incomplete, in which case
            --  get the full view if available.

            elsif From_With_Type (Id)
              and then Is_Type (Id)
              and then Ekind (Id) = E_Incomplete_Type
              and then Present (Non_Limited_View (Id))
              and then Scope (Non_Limited_View (Id)) = P_Name
            then
               Candidate        := Get_Full_View (Non_Limited_View (Id));
               Is_New_Candidate := True;

            else
               Is_New_Candidate := False;
            end if;

            if Is_New_Candidate then
               if Is_Child_Unit (Id) then
                  exit when Is_Visible_Child_Unit (Id)
                    or else Is_Immediately_Visible (Id);

               else
                  exit when not Is_Hidden (Id)
                    or else Is_Immediately_Visible (Id);
               end if;
            end if;

            Id := Homonym (Id);
         end loop;
      end;

      if No (Id)
        and then (Ekind (P_Name) = E_Procedure
                    or else
                  Ekind (P_Name) = E_Function)
        and then Is_Generic_Instance (P_Name)
      then
         --  Expanded name denotes entity in (instance of) generic subprogram.
         --  The entity may be in the subprogram instance, or may denote one of
         --  the formals, which is declared in the enclosing wrapper package.

         P_Name := Scope (P_Name);

         Id := Current_Entity (Selector);
         while Present (Id) loop
            exit when Scope (Id) = P_Name;
            Id := Homonym (Id);
         end loop;
      end if;

      if No (Id) or else Chars (Id) /= Chars (Selector) then
         Set_Etype (N, Any_Type);

         --  If we are looking for an entity defined in System, try to
         --  find it in the child package that may have been provided as
         --  an extension to System. The Extend_System pragma will have
         --  supplied the name of the extension, which may have to be loaded.

         if Chars (P_Name) = Name_System
           and then Scope (P_Name) = Standard_Standard
           and then Present (System_Extend_Unit)
           and then Present_System_Aux (N)
         then
            Set_Entity (Prefix (N), System_Aux_Id);
            Find_Expanded_Name (N);
            return;

         elsif Nkind (Selector) = N_Operator_Symbol
           and then Has_Implicit_Operator (N)
         then
            --  There is an implicit instance of the predefined operator in
            --  the given scope. The operator entity is defined in Standard.
            --  Has_Implicit_Operator makes the node into an Expanded_Name.

            return;

         elsif Nkind (Selector) = N_Character_Literal
           and then Has_Implicit_Character_Literal (N)
         then
            --  If there is no literal defined in the scope denoted by the
            --  prefix, the literal may belong to (a type derived from)
            --  Standard_Character, for which we have no explicit literals.

            return;

         else
            --  If the prefix is a single concurrent object, use its
            --  name in  the error message, rather than that of the
            --  anonymous type.

            if Is_Concurrent_Type (P_Name)
              and then Is_Internal_Name (Chars (P_Name))
            then
               Error_Msg_Node_2 := Entity (Prefix (N));
            else
               Error_Msg_Node_2 := P_Name;
            end if;

            if P_Name = System_Aux_Id then
               P_Name := Scope (P_Name);
               Set_Entity (Prefix (N), P_Name);
            end if;

            if Present (Candidate) then

               --  If we know that the unit is a child unit we can give a more
               --  accurate error message.

               if Is_Child_Unit (Candidate) then

                  --  If the candidate is a private child unit and we are in
                  --  the visible part of a public unit, specialize the error
                  --  message. There might be a private with_clause for it,
                  --  but it is not currently active.

                  if Is_Private_Descendant (Candidate)
                    and then Ekind (Current_Scope) = E_Package
                    and then not In_Private_Part (Current_Scope)
                    and then not Is_Private_Descendant (Current_Scope)
                  then
                     Error_Msg_N ("private child unit& is not visible here",
                                  Selector);

                  --  Normal case where we have a missing with for a child unit

                  else
                     Error_Msg_Qual_Level := 99;
                     Error_Msg_NE ("missing `WITH &;`", Selector, Candidate);
                     Error_Msg_Qual_Level := 0;
                  end if;

                  --  Here we don't know that this is a child unit

               else
                  Error_Msg_NE ("& is not a visible entity of&", N, Selector);
               end if;

            else
               --  Within the instantiation of a child unit, the prefix may
               --  denote the parent instance, but the selector has the name
               --  of the original child. Find whether we are within the
               --  corresponding instance, and get the proper entity, which
               --  can only be an enclosing scope.

               if O_Name /= P_Name
                 and then In_Open_Scopes (P_Name)
                 and then Is_Generic_Instance (P_Name)
               then
                  declare
                     S : Entity_Id := Current_Scope;
                     P : Entity_Id;

                  begin
                     for J in reverse 0 .. Scope_Stack.Last loop
                        S := Scope_Stack.Table (J).Entity;

                        exit when S = Standard_Standard;

                        if Ekind (S) = E_Function
                          or else Ekind (S) = E_Package
                          or else Ekind (S) = E_Procedure
                        then
                           P := Generic_Parent (Specification
                                  (Unit_Declaration_Node (S)));

                           if Present (P)
                             and then Chars (Scope (P)) = Chars (O_Name)
                             and then Chars (P) = Chars (Selector)
                           then
                              Id := S;
                              goto Found;
                           end if;
                        end if;

                     end loop;
                  end;
               end if;

               --  If this is a selection from Ada, System or Interfaces, then
               --  we assume a missing with for the corresponding package.

               if Is_Known_Unit (N) then
                  if not Error_Posted (N) then
                     Error_Msg_Node_2 := Selector;
                     Error_Msg_N ("missing `WITH &.&;`", Prefix (N));
                  end if;

               --  If this is a selection from a dummy package, then suppress
               --  the error message, of course the entity is missing if the
               --  package is missing!

               elsif Sloc (Error_Msg_Node_2) = No_Location then
                  null;

               --  Here we have the case of an undefined component

               else
                  Error_Msg_NE ("& not declared in&", N, Selector);

                  --  Check for misspelling of some entity in prefix

                  Id := First_Entity (P_Name);
                  while Present (Id) loop
                     if Is_Bad_Spelling_Of (Chars (Id), Chars (Selector))
                       and then not Is_Internal_Name (Chars (Id))
                     then
                        Error_Msg_NE
                          ("possible misspelling of&", Selector, Id);
                        exit;
                     end if;

                     Next_Entity (Id);
                  end loop;

                  --  Specialize the message if this may be an instantiation
                  --  of a child unit that was not mentioned in the context.

                  if Nkind (Parent (N)) = N_Package_Instantiation
                    and then Is_Generic_Instance (Entity (Prefix (N)))
                    and then Is_Compilation_Unit
                               (Generic_Parent (Parent (Entity (Prefix (N)))))
                  then
                     Error_Msg_Node_2 := Selector;
                     Error_Msg_N ("\missing `WITH &.&;`", Prefix (N));
                  end if;
               end if;
            end if;

            Id := Any_Id;
         end if;
      end if;

      <<Found>>
      if Comes_From_Source (N)
        and then Is_Remote_Access_To_Subprogram_Type (Id)
        and then Present (Equivalent_Type (Id))
      then
         --  If we are not actually generating distribution code (i.e. the
         --  current PCS is the dummy non-distributed version), then the
         --  Equivalent_Type will be missing, and Id should be treated as
         --  a regular access-to-subprogram type.

         Id := Equivalent_Type (Id);
         Set_Chars (Selector, Chars (Id));
      end if;

      --  Ada 2005 (AI-50217): Check usage of entities in limited withed units

      if Ekind (P_Name) = E_Package
        and then From_With_Type (P_Name)
      then
         if From_With_Type (Id)
           or else Is_Type (Id)
           or else Ekind (Id) = E_Package
         then
            null;
         else
            Error_Msg_N
              ("limited withed package can only be used to access "
               & " incomplete types",
                N);
         end if;
      end if;

      if Is_Task_Type (P_Name)
        and then ((Ekind (Id) = E_Entry
                     and then Nkind (Parent (N)) /= N_Attribute_Reference)
                   or else
                    (Ekind (Id) = E_Entry_Family
                      and then
                        Nkind (Parent (Parent (N))) /= N_Attribute_Reference))
      then
         --  It is an entry call after all, either to the current task (which
         --  will deadlock) or to an enclosing task.

         Analyze_Selected_Component (N);
         return;
      end if;

      Change_Selected_Component_To_Expanded_Name (N);

      --  Do style check and generate reference, but skip both steps if this
      --  entity has homonyms, since we may not have the right homonym set yet.
      --  The proper homonym will be set during the resolve phase.

      if Has_Homonym (Id) then
         Set_Entity (N, Id);
      else
         Set_Entity_With_Style_Check (N, Id);
         Generate_Reference (Id, N);
      end if;

      if Is_Type (Id) then
         Set_Etype (N, Id);
      else
         Set_Etype (N, Get_Full_View (Etype (Id)));
      end if;

      --  If the Ekind of the entity is Void, it means that all homonyms are
      --  hidden from all visibility (RM 8.3(5,14-20)).

      if Ekind (Id) = E_Void then
         Premature_Usage (N);

      elsif Is_Overloadable (Id)
        and then Present (Homonym (Id))
      then
         declare
            H : Entity_Id := Homonym (Id);

         begin
            while Present (H) loop
               if Scope (H) = Scope (Id)
                 and then
                   (not Is_Hidden (H)
                      or else Is_Immediately_Visible (H))
               then
                  Collect_Interps (N);
                  exit;
               end if;

               H := Homonym (H);
            end loop;

            --  If an extension of System is present, collect possible explicit
            --  overloadings declared in the extension.

            if Chars (P_Name) = Name_System
              and then Scope (P_Name) = Standard_Standard
              and then Present (System_Extend_Unit)
              and then Present_System_Aux (N)
            then
               H := Current_Entity (Id);

               while Present (H) loop
                  if Scope (H) = System_Aux_Id then
                     Add_One_Interp (N, H, Etype (H));
                  end if;

                  H := Homonym (H);
               end loop;
            end if;
         end;
      end if;

      if Nkind (Selector_Name (N)) = N_Operator_Symbol
        and then Scope (Id) /= Standard_Standard
      then
         --  In addition to user-defined operators in the given scope, there
         --  may be an implicit instance of the predefined operator. The
         --  operator (defined in Standard) is found in Has_Implicit_Operator,
         --  and added to the interpretations. Procedure Add_One_Interp will
         --  determine which hides which.

         if Has_Implicit_Operator (N) then
            null;
         end if;
      end if;
   end Find_Expanded_Name;

   -------------------------
   -- Find_Renamed_Entity --
   -------------------------

   function Find_Renamed_Entity
     (N         : Node_Id;
      Nam       : Node_Id;
      New_S     : Entity_Id;
      Is_Actual : Boolean := False) return Entity_Id
   is
      Ind   : Interp_Index;
      I1    : Interp_Index := 0; -- Suppress junk warnings
      It    : Interp;
      It1   : Interp;
      Old_S : Entity_Id;
      Inst  : Entity_Id;

      function Enclosing_Instance return Entity_Id;
      --  If the renaming determines the entity for the default of a formal
      --  subprogram nested within another instance, choose the innermost
      --  candidate. This is because if the formal has a box, and we are within
      --  an enclosing instance where some candidate interpretations are local
      --  to this enclosing instance, we know that the default was properly
      --  resolved when analyzing the generic, so we prefer the local
      --  candidates to those that are external. This is not always the case
      --  but is a reasonable heuristic on the use of nested generics. The
      --  proper solution requires a full renaming model.

      function Is_Visible_Operation (Op : Entity_Id) return Boolean;
      --  If the renamed entity is an implicit operator, check whether it is
      --  visible because its operand type is properly visible. This check
      --  applies to explicit renamed entities that appear in the source in a
      --  renaming declaration or a formal subprogram instance, but not to
      --  default generic actuals with a name.

      function Report_Overload return Entity_Id;
      --  List possible interpretations, and specialize message in the
      --  case of a generic actual.

      function Within (Inner, Outer : Entity_Id) return Boolean;
      --  Determine whether a candidate subprogram is defined within the
      --  enclosing instance. If yes, it has precedence over outer candidates.

      ------------------------
      -- Enclosing_Instance --
      ------------------------

      function Enclosing_Instance return Entity_Id is
         S : Entity_Id;

      begin
         if not Is_Generic_Instance (Current_Scope)
           and then not Is_Actual
         then
            return Empty;
         end if;

         S := Scope (Current_Scope);
         while S /= Standard_Standard loop
            if Is_Generic_Instance (S) then
               return S;
            end if;

            S := Scope (S);
         end loop;

         return Empty;
      end Enclosing_Instance;

      --------------------------
      -- Is_Visible_Operation --
      --------------------------

      function Is_Visible_Operation (Op : Entity_Id) return Boolean is
         Scop : Entity_Id;
         Typ  : Entity_Id;
         Btyp : Entity_Id;

      begin
         if Ekind (Op) /= E_Operator
           or else Scope (Op) /= Standard_Standard
           or else (In_Instance
                      and then
                        (not Is_Actual
                           or else Present (Enclosing_Instance)))
         then
            return True;

         else
            --  For a fixed point type operator, check the resulting type,
            --  because it may be a mixed mode integer * fixed operation.

            if Present (Next_Formal (First_Formal (New_S)))
              and then Is_Fixed_Point_Type (Etype (New_S))
            then
               Typ := Etype (New_S);
            else
               Typ := Etype (First_Formal (New_S));
            end if;

            Btyp := Base_Type (Typ);

            if Nkind (Nam) /= N_Expanded_Name then
               return (In_Open_Scopes (Scope (Btyp))
                        or else Is_Potentially_Use_Visible (Btyp)
                        or else In_Use (Btyp)
                        or else In_Use (Scope (Btyp)));

            else
               Scop := Entity (Prefix (Nam));

               if Ekind (Scop) = E_Package
                 and then Present (Renamed_Object (Scop))
               then
                  Scop := Renamed_Object (Scop);
               end if;

               --  Operator is visible if prefix of expanded name denotes
               --  scope of type, or else type type is defined in System_Aux
               --  and the prefix denotes System.

               return Scope (Btyp) = Scop
                 or else (Scope (Btyp) = System_Aux_Id
                           and then Scope (Scope (Btyp)) = Scop);
            end if;
         end if;
      end Is_Visible_Operation;

      ------------
      -- Within --
      ------------

      function Within (Inner, Outer : Entity_Id) return Boolean is
         Sc : Entity_Id;

      begin
         Sc := Scope (Inner);
         while Sc /= Standard_Standard loop
            if Sc = Outer then
               return True;
            else
               Sc := Scope (Sc);
            end if;
         end loop;

         return False;
      end Within;

      ---------------------
      -- Report_Overload --
      ---------------------

      function Report_Overload return Entity_Id is
      begin
         if Is_Actual then
            Error_Msg_NE
              ("ambiguous actual subprogram&, " &
                 "possible interpretations:", N, Nam);
         else
            Error_Msg_N
              ("ambiguous subprogram, " &
                 "possible interpretations:", N);
         end if;

         List_Interps (Nam, N);
         return Old_S;
      end Report_Overload;

   --  Start of processing for Find_Renamed_Entry

   begin
      Old_S := Any_Id;
      Candidate_Renaming := Empty;

      if not Is_Overloaded (Nam) then
         if Entity_Matches_Spec (Entity (Nam), New_S)
           and then Is_Visible_Operation (Entity (Nam))
         then
            Old_S := Entity (Nam);

         elsif
           Present (First_Formal (Entity (Nam)))
             and then Present (First_Formal (New_S))
             and then (Base_Type (Etype (First_Formal (Entity (Nam))))
                        = Base_Type (Etype (First_Formal (New_S))))
         then
            Candidate_Renaming := Entity (Nam);
         end if;

      else
         Get_First_Interp (Nam, Ind, It);
         while Present (It.Nam) loop
            if Entity_Matches_Spec (It.Nam, New_S)
               and then Is_Visible_Operation (It.Nam)
            then
               if Old_S /= Any_Id then

                  --  Note: The call to Disambiguate only happens if a
                  --  previous interpretation was found, in which case I1
                  --  has received a value.

                  It1 := Disambiguate (Nam, I1, Ind, Etype (Old_S));

                  if It1 = No_Interp then
                     Inst := Enclosing_Instance;

                     if Present (Inst) then
                        if Within (It.Nam, Inst) then
                           return (It.Nam);
                        elsif Within (Old_S, Inst) then
                           return (Old_S);
                        else
                           return Report_Overload;
                        end if;

                     else
                        return Report_Overload;
                     end if;

                  else
                     Old_S := It1.Nam;
                     exit;
                  end if;

               else
                  I1 := Ind;
                  Old_S := It.Nam;
               end if;

            elsif
              Present (First_Formal (It.Nam))
                and then Present (First_Formal (New_S))
                and then  (Base_Type (Etype (First_Formal (It.Nam)))
                            = Base_Type (Etype (First_Formal (New_S))))
            then
               Candidate_Renaming := It.Nam;
            end if;

            Get_Next_Interp (Ind, It);
         end loop;

         Set_Entity (Nam, Old_S);
         Set_Is_Overloaded (Nam, False);
      end if;

      return Old_S;
   end Find_Renamed_Entity;

   -----------------------------
   -- Find_Selected_Component --
   -----------------------------

   procedure Find_Selected_Component (N : Node_Id) is
      P : constant Node_Id := Prefix (N);

      P_Name : Entity_Id;
      --  Entity denoted by prefix

      P_Type : Entity_Id;
      --  and its type

      Nam : Node_Id;

   begin
      Analyze (P);

      if Nkind (P) = N_Error then
         return;

      --  If the selector already has an entity, the node has been constructed
      --  in the course of expansion, and is known to be valid. Do not verify
      --  that it is defined for the type (it may be a private component used
      --  in the expansion of record equality).

      elsif Present (Entity (Selector_Name (N))) then

         if No (Etype (N))
           or else Etype (N) = Any_Type
         then
            declare
               Sel_Name : constant Node_Id   := Selector_Name (N);
               Selector : constant Entity_Id := Entity (Sel_Name);
               C_Etype  : Node_Id;

            begin
               Set_Etype (Sel_Name, Etype (Selector));

               if not Is_Entity_Name (P) then
                  Resolve (P);
               end if;

               --  Build an actual subtype except for the first parameter
               --  of an init proc, where this actual subtype is by
               --  definition incorrect, since the object is uninitialized
               --  (and does not even have defined discriminants etc.)

               if Is_Entity_Name (P)
                 and then Ekind (Entity (P)) = E_Function
               then
                  Nam := New_Copy (P);

                  if Is_Overloaded (P) then
                     Save_Interps (P, Nam);
                  end if;

                  Rewrite (P,
                    Make_Function_Call (Sloc (P), Name => Nam));
                  Analyze_Call (P);
                  Analyze_Selected_Component (N);
                  return;

               elsif Ekind (Selector) = E_Component
                 and then (not Is_Entity_Name (P)
                            or else Chars (Entity (P)) /= Name_uInit)
               then
                  C_Etype :=
                    Build_Actual_Subtype_Of_Component (
                      Etype (Selector), N);
               else
                  C_Etype := Empty;
               end if;

               if No (C_Etype) then
                  C_Etype := Etype (Selector);
               else
                  Insert_Action (N, C_Etype);
                  C_Etype := Defining_Identifier (C_Etype);
               end if;

               Set_Etype (N, C_Etype);
            end;

            --  If this is the name of an entry or protected operation, and
            --  the prefix is an access type, insert an explicit dereference,
            --  so that entry calls are treated uniformly.

            if Is_Access_Type (Etype (P))
              and then Is_Concurrent_Type (Designated_Type (Etype (P)))
            then
               declare
                  New_P : constant Node_Id :=
                            Make_Explicit_Dereference (Sloc (P),
                              Prefix => Relocate_Node (P));
               begin
                  Rewrite (P, New_P);
                  Set_Etype (P, Designated_Type (Etype (Prefix (P))));
               end;
            end if;

         --  If the selected component appears within a default expression
         --  and it has an actual subtype, the pre-analysis has not yet
         --  completed its analysis, because Insert_Actions is disabled in
         --  that context. Within the init proc of the enclosing type we
         --  must complete this analysis, if an actual subtype was created.

         elsif Inside_Init_Proc then
            declare
               Typ  : constant Entity_Id := Etype (N);
               Decl : constant Node_Id   := Declaration_Node (Typ);
            begin
               if Nkind (Decl) = N_Subtype_Declaration
                 and then not Analyzed (Decl)
                 and then Is_List_Member (Decl)
                 and then No (Parent (Decl))
               then
                  Remove (Decl);
                  Insert_Action (N, Decl);
               end if;
            end;
         end if;

         return;

      elsif Is_Entity_Name (P) then
         P_Name := Entity (P);

         --  The prefix may denote an enclosing type which is the completion
         --  of an incomplete type declaration.

         if Is_Type (P_Name) then
            Set_Entity (P, Get_Full_View (P_Name));
            Set_Etype  (P, Entity (P));
            P_Name := Entity (P);
         end if;

         P_Type := Base_Type (Etype (P));

         if Debug_Flag_E then
            Write_Str ("Found prefix type to be ");
            Write_Entity_Info (P_Type, "      "); Write_Eol;
         end if;

         --  First check for components of a record object (not the
         --  result of a call, which is handled below).

         if Is_Appropriate_For_Record (P_Type)
           and then not Is_Overloadable (P_Name)
           and then not Is_Type (P_Name)
         then
            --  Selected component of record. Type checking will validate
            --  name of selector.
            --  ??? could we rewrite an implicit dereference into an explicit
            --  one here?

            Analyze_Selected_Component (N);

         elsif Is_Appropriate_For_Entry_Prefix (P_Type)
           and then not In_Open_Scopes (P_Name)
           and then (not Is_Concurrent_Type (Etype (P_Name))
                       or else not In_Open_Scopes (Etype (P_Name)))
         then
            --  Call to protected operation or entry. Type checking is
            --  needed on the prefix.

            Analyze_Selected_Component (N);

         elsif (In_Open_Scopes (P_Name)
                  and then Ekind (P_Name) /= E_Void
                  and then not Is_Overloadable (P_Name))
           or else (Is_Concurrent_Type (Etype (P_Name))
                      and then In_Open_Scopes (Etype (P_Name)))
         then
            --  Prefix denotes an enclosing loop, block, or task, i.e. an
            --  enclosing construct that is not a subprogram or accept.

            Find_Expanded_Name (N);

         elsif Ekind (P_Name) = E_Package then
            Find_Expanded_Name (N);

         elsif Is_Overloadable (P_Name) then

            --  The subprogram may be a renaming (of an enclosing scope) as
            --  in the case of the name of the generic within an instantiation.

            if (Ekind (P_Name) = E_Procedure
                 or else Ekind (P_Name) = E_Function)
              and then Present (Alias (P_Name))
              and then Is_Generic_Instance (Alias (P_Name))
            then
               P_Name := Alias (P_Name);
            end if;

            if Is_Overloaded (P) then

               --  The prefix must resolve to a unique enclosing construct

               declare
                  Found : Boolean := False;
                  Ind   : Interp_Index;
                  It    : Interp;

               begin
                  Get_First_Interp (P, Ind, It);
                  while Present (It.Nam) loop
                     if In_Open_Scopes (It.Nam) then
                        if Found then
                           Error_Msg_N (
                              "prefix must be unique enclosing scope", N);
                           Set_Entity (N, Any_Id);
                           Set_Etype  (N, Any_Type);
                           return;

                        else
                           Found := True;
                           P_Name := It.Nam;
                        end if;
                     end if;

                     Get_Next_Interp (Ind, It);
                  end loop;
               end;
            end if;

            if In_Open_Scopes (P_Name) then
               Set_Entity (P, P_Name);
               Set_Is_Overloaded (P, False);
               Find_Expanded_Name (N);

            else
               --  If no interpretation as an expanded name is possible, it
               --  must be a selected component of a record returned by a
               --  function call. Reformat prefix as a function call, the rest
               --  is done by type resolution. If the prefix is procedure or
               --  entry, as is P.X; this is an error.

               if Ekind (P_Name) /= E_Function
                 and then (not Is_Overloaded (P)
                             or else
                           Nkind (Parent (N)) = N_Procedure_Call_Statement)
               then
                  --  Prefix may mention a package that is hidden by a local
                  --  declaration: let the user know. Scan the full homonym
                  --  chain, the candidate package may be anywhere on it.

                  if Present (Homonym (Current_Entity (P_Name))) then

                     P_Name := Current_Entity (P_Name);

                     while Present (P_Name) loop
                        exit when Ekind (P_Name) = E_Package;
                        P_Name := Homonym (P_Name);
                     end loop;

                     if Present (P_Name) then
                        Error_Msg_Sloc := Sloc (Entity (Prefix (N)));

                        Error_Msg_NE
                          ("package& is hidden by declaration#",
                            N, P_Name);

                        Set_Entity (Prefix (N), P_Name);
                        Find_Expanded_Name (N);
                        return;
                     else
                        P_Name := Entity (Prefix (N));
                     end if;
                  end if;

                  Error_Msg_NE
                    ("invalid prefix in selected component&", N, P_Name);
                  Change_Selected_Component_To_Expanded_Name (N);
                  Set_Entity (N, Any_Id);
                  Set_Etype (N, Any_Type);

               else
                  Nam := New_Copy (P);
                  Save_Interps (P, Nam);
                  Rewrite (P,
                    Make_Function_Call (Sloc (P), Name => Nam));
                  Analyze_Call (P);
                  Analyze_Selected_Component (N);
               end if;
            end if;

         --  Remaining cases generate various error messages

         else
            --  Format node as expanded name, to avoid cascaded errors

            Change_Selected_Component_To_Expanded_Name (N);
            Set_Entity  (N, Any_Id);
            Set_Etype   (N, Any_Type);

            --  Issue error message, but avoid this if error issued already.
            --  Use identifier of prefix if one is available.

            if P_Name = Any_Id  then
               null;

            elsif Ekind (P_Name) = E_Void then
               Premature_Usage (P);

            elsif Nkind (P) /= N_Attribute_Reference then
               Error_Msg_N (
                "invalid prefix in selected component&", P);

               if Is_Access_Type (P_Type)
                 and then Ekind (Designated_Type (P_Type)) = E_Incomplete_Type
               then
                  Error_Msg_N
                    ("\dereference must not be of an incomplete type " &
                       "(RM 3.10.1)", P);
               end if;

            else
               Error_Msg_N (
                "invalid prefix in selected component", P);
            end if;
         end if;

      else
         --  If prefix is not the name of an entity, it must be an expression,
         --  whose type is appropriate for a record. This is determined by
         --  type resolution.

         Analyze_Selected_Component (N);
      end if;
   end Find_Selected_Component;

   ---------------
   -- Find_Type --
   ---------------

   procedure Find_Type (N : Node_Id) is
      C      : Entity_Id;
      Typ    : Entity_Id;
      T      : Entity_Id;
      T_Name : Entity_Id;

   begin
      if N = Error then
         return;

      elsif Nkind (N) = N_Attribute_Reference then

         --  Class attribute. This is not valid in Ada 83 mode, but we do not
         --  need to enforce that at this point, since the declaration of the
         --  tagged type in the prefix would have been flagged already.

         if Attribute_Name (N) = Name_Class then
            Check_Restriction (No_Dispatch, N);
            Find_Type (Prefix (N));

            --  Propagate error from bad prefix

            if Etype (Prefix (N)) = Any_Type then
               Set_Entity (N, Any_Type);
               Set_Etype  (N, Any_Type);
               return;
            end if;

            T := Base_Type (Entity (Prefix (N)));

            --  Case where type is not known to be tagged. Its appearance in
            --  the prefix of the 'Class attribute indicates that the full view
            --  will be tagged.

            if not Is_Tagged_Type (T) then
               if Ekind (T) = E_Incomplete_Type then

                  --  It is legal to denote the class type of an incomplete
                  --  type. The full type will have to be tagged, of course.
                  --  In Ada 2005 this usage is declared obsolescent, so we
                  --  warn accordingly.

                  --  ??? This test is temporarily disabled (always False)
                  --  because it causes an unwanted warning on GNAT sources
                  --  (built with -gnatg, which includes Warn_On_Obsolescent_
                  --  Feature). Once this issue is cleared in the sources, it
                  --  can be enabled.

                  if not Is_Tagged_Type (T)
                    and then Ada_Version >= Ada_05
                    and then Warn_On_Obsolescent_Feature
                    and then False
                  then
                     Error_Msg_N
                       ("applying 'Class to an untagged imcomplete type"
                         & " is an obsolescent feature  (RM J.11)", N);
                  end if;

                  Set_Is_Tagged_Type (T);
                  Set_Primitive_Operations (T, New_Elmt_List);
                  Make_Class_Wide_Type (T);
                  Set_Entity (N, Class_Wide_Type (T));
                  Set_Etype  (N, Class_Wide_Type (T));

               elsif Ekind (T) = E_Private_Type
                 and then not Is_Generic_Type (T)
                 and then In_Private_Part (Scope (T))
               then
                  --  The Class attribute can be applied to an untagged private
                  --  type fulfilled by a tagged type prior to the full type
                  --  declaration (but only within the parent package's private
                  --  part). Create the class-wide type now and check that the
                  --  full type is tagged later during its analysis. Note that
                  --  we do not mark the private type as tagged, unlike the
                  --  case of incomplete types, because the type must still
                  --  appear untagged to outside units.

                  if No (Class_Wide_Type (T)) then
                     Make_Class_Wide_Type (T);
                  end if;

                  Set_Entity (N, Class_Wide_Type (T));
                  Set_Etype  (N, Class_Wide_Type (T));

               else
                  --  Should we introduce a type Any_Tagged and use Wrong_Type
                  --  here, it would be a bit more consistent???

                  Error_Msg_NE
                    ("tagged type required, found}",
                     Prefix (N), First_Subtype (T));
                  Set_Entity (N, Any_Type);
                  return;
               end if;

            --  Case of tagged type

            else
               if Is_Concurrent_Type (T) then
                  if No (Corresponding_Record_Type (Entity (Prefix (N)))) then

                     --  Previous error. Use current type, which at least
                     --  provides some operations.

                     C := Entity (Prefix (N));

                  else
                     C := Class_Wide_Type
                            (Corresponding_Record_Type (Entity (Prefix (N))));
                  end if;

               else
                  C := Class_Wide_Type (Entity (Prefix (N)));
               end if;

               Set_Entity_With_Style_Check (N, C);
               Generate_Reference (C, N);
               Set_Etype (N, C);
            end if;

         --  Base attribute, not allowed in Ada 83

         elsif Attribute_Name (N) = Name_Base then
            if Ada_Version = Ada_83 and then Comes_From_Source (N) then
               Error_Msg_N
                 ("(Ada 83) Base attribute not allowed in subtype mark", N);

            else
               Find_Type (Prefix (N));
               Typ := Entity (Prefix (N));

               if Ada_Version >= Ada_95
                 and then not Is_Scalar_Type (Typ)
                 and then not Is_Generic_Type (Typ)
               then
                  Error_Msg_N
                    ("prefix of Base attribute must be scalar type",
                      Prefix (N));

               elsif Sloc (Typ) = Standard_Location
                 and then Base_Type (Typ) = Typ
                 and then Warn_On_Redundant_Constructs
               then
                  Error_Msg_NE
                    ("?redudant attribute, & is its own base type", N, Typ);
               end if;

               T := Base_Type (Typ);

               --  Rewrite attribute reference with type itself (see similar
               --  processing in Analyze_Attribute, case Base). Preserve
               --  prefix if present, for other legality checks.

               if Nkind (Prefix (N)) = N_Expanded_Name then
                  Rewrite (N,
                     Make_Expanded_Name (Sloc (N),
                       Chars         => Chars (T),
                       Prefix        => New_Copy (Prefix (Prefix (N))),
                       Selector_Name => New_Reference_To (T, Sloc (N))));

               else
                  Rewrite (N, New_Reference_To (T, Sloc (N)));
               end if;

               Set_Entity (N, T);
               Set_Etype (N, T);
            end if;

         elsif Attribute_Name (N) = Name_Stub_Type then

            --  This is handled in Analyze_Attribute

            Analyze (N);

         --  All other attributes are invalid in a subtype mark

         else
            Error_Msg_N ("invalid attribute in subtype mark", N);
         end if;

      else
         Analyze (N);

         if Is_Entity_Name (N) then
            T_Name := Entity (N);
         else
            Error_Msg_N ("subtype mark required in this context", N);
            Set_Etype (N, Any_Type);
            return;
         end if;

         if T_Name  = Any_Id or else Etype (N) = Any_Type then

            --  Undefined id. Make it into a valid type

            Set_Entity (N, Any_Type);

         elsif not Is_Type (T_Name)
           and then T_Name /= Standard_Void_Type
         then
            Error_Msg_Sloc := Sloc (T_Name);
            Error_Msg_N ("subtype mark required in this context", N);
            Error_Msg_NE ("\\found & declared#", N, T_Name);
            Set_Entity (N, Any_Type);

         else
            --  If the type is an incomplete type created to handle
            --  anonymous access components of a record type, then the
            --  incomplete type is the visible entity and subsequent
            --  references will point to it. Mark the original full
            --  type as referenced, to prevent spurious warnings.

            if Is_Incomplete_Type (T_Name)
              and then Present (Full_View (T_Name))
              and then not Comes_From_Source (T_Name)
            then
               Set_Referenced (Full_View (T_Name));
            end if;

            T_Name := Get_Full_View (T_Name);

            --  Ada 2005 (AI-251, AI-50217): Handle interfaces visible through
            --  limited-with clauses

            if From_With_Type (T_Name)
              and then Ekind (T_Name) in Incomplete_Kind
              and then Present (Non_Limited_View (T_Name))
              and then Is_Interface (Non_Limited_View (T_Name))
            then
               T_Name := Non_Limited_View (T_Name);
            end if;

            if In_Open_Scopes (T_Name) then
               if Ekind (Base_Type (T_Name)) = E_Task_Type then

                  --  In Ada 2005, a task name can be used in an access
                  --  definition within its own body.

                  if Ada_Version >= Ada_05
                    and then Nkind (Parent (N)) = N_Access_Definition
                  then
                     Set_Entity (N, T_Name);
                     Set_Etype  (N, T_Name);
                     return;

                  else
                     Error_Msg_N
                       ("task type cannot be used as type mark " &
                        "within its own spec or body", N);
                  end if;

               elsif Ekind (Base_Type (T_Name)) = E_Protected_Type then

                  --  In Ada 2005, a protected name can be used in an access
                  --  definition within its own body.

                  if Ada_Version >= Ada_05
                    and then Nkind (Parent (N)) = N_Access_Definition
                  then
                     Set_Entity (N, T_Name);
                     Set_Etype  (N, T_Name);
                     return;

                  else
                     Error_Msg_N
                       ("protected type cannot be used as type mark " &
                        "within its own spec or body", N);
                  end if;

               else
                  Error_Msg_N ("type declaration cannot refer to itself", N);
               end if;

               Set_Etype (N, Any_Type);
               Set_Entity (N, Any_Type);
               Set_Error_Posted (T_Name);
               return;
            end if;

            Set_Entity (N, T_Name);
            Set_Etype  (N, T_Name);
         end if;
      end if;

      if Present (Etype (N)) and then Comes_From_Source (N) then
         if Is_Fixed_Point_Type (Etype (N)) then
            Check_Restriction (No_Fixed_Point, N);
         elsif Is_Floating_Point_Type (Etype (N)) then
            Check_Restriction (No_Floating_Point, N);
         end if;
      end if;
   end Find_Type;

   ------------------------------------
   -- Has_Implicit_Character_Literal --
   ------------------------------------

   function Has_Implicit_Character_Literal (N : Node_Id) return Boolean is
      Id      : Entity_Id;
      Found   : Boolean := False;
      P       : constant Entity_Id := Entity (Prefix (N));
      Priv_Id : Entity_Id := Empty;

   begin
      if Ekind (P) = E_Package
        and then not In_Open_Scopes (P)
      then
         Priv_Id := First_Private_Entity (P);
      end if;

      if P = Standard_Standard then
         Change_Selected_Component_To_Expanded_Name (N);
         Rewrite (N, Selector_Name (N));
         Analyze (N);
         Set_Etype (Original_Node (N), Standard_Character);
         return True;
      end if;

      Id := First_Entity (P);

      while Present (Id)
        and then Id /= Priv_Id
      loop
         if Is_Character_Type (Id)
           and then (Root_Type (Id) = Standard_Character
                       or else Root_Type (Id) = Standard_Wide_Character
                       or else Root_Type (Id) = Standard_Wide_Wide_Character)
           and then Id = Base_Type (Id)
         then
            --  We replace the node with the literal itself, resolve as a
            --  character, and set the type correctly.

            if not Found then
               Change_Selected_Component_To_Expanded_Name (N);
               Rewrite (N, Selector_Name (N));
               Analyze (N);
               Set_Etype (N, Id);
               Set_Etype (Original_Node (N), Id);
               Found := True;

            else
               --  More than one type derived from Character in given scope.
               --  Collect all possible interpretations.

               Add_One_Interp (N, Id, Id);
            end if;
         end if;

         Next_Entity (Id);
      end loop;

      return Found;
   end Has_Implicit_Character_Literal;

   ----------------------
   -- Has_Private_With --
   ----------------------

   function Has_Private_With (E : Entity_Id) return Boolean is
      Comp_Unit : constant Node_Id := Cunit (Current_Sem_Unit);
      Item      : Node_Id;

   begin
      Item := First (Context_Items (Comp_Unit));
      while Present (Item) loop
         if Nkind (Item) = N_With_Clause
           and then Private_Present (Item)
           and then Entity (Name (Item)) = E
         then
            return True;
         end if;

         Next (Item);
      end loop;

      return False;
   end Has_Private_With;

   ---------------------------
   -- Has_Implicit_Operator --
   ---------------------------

   function Has_Implicit_Operator (N : Node_Id) return Boolean is
      Op_Id   : constant Name_Id   := Chars (Selector_Name (N));
      P       : constant Entity_Id := Entity (Prefix (N));
      Id      : Entity_Id;
      Priv_Id : Entity_Id := Empty;

      procedure Add_Implicit_Operator
        (T       : Entity_Id;
         Op_Type : Entity_Id := Empty);
      --  Add implicit interpretation to node N, using the type for which a
      --  predefined operator exists. If the operator yields a boolean type,
      --  the Operand_Type is implicitly referenced by the operator, and a
      --  reference to it must be generated.

      ---------------------------
      -- Add_Implicit_Operator --
      ---------------------------

      procedure Add_Implicit_Operator
        (T       : Entity_Id;
         Op_Type : Entity_Id := Empty)
      is
         Predef_Op : Entity_Id;

      begin
         Predef_Op := Current_Entity (Selector_Name (N));

         while Present (Predef_Op)
           and then Scope (Predef_Op) /= Standard_Standard
         loop
            Predef_Op := Homonym (Predef_Op);
         end loop;

         if Nkind (N) = N_Selected_Component then
            Change_Selected_Component_To_Expanded_Name (N);
         end if;

         Add_One_Interp (N, Predef_Op, T);

         --  For operators with unary and binary interpretations, add both

         if Present (Homonym (Predef_Op)) then
            Add_One_Interp (N, Homonym (Predef_Op), T);
         end if;

         --  The node is a reference to a predefined operator, and
         --  an implicit reference to the type of its operands.

         if Present (Op_Type) then
            Generate_Operator_Reference (N, Op_Type);
         else
            Generate_Operator_Reference (N, T);
         end if;
      end Add_Implicit_Operator;

   --  Start of processing for Has_Implicit_Operator

   begin
      if Ekind (P) = E_Package
        and then not In_Open_Scopes (P)
      then
         Priv_Id := First_Private_Entity (P);
      end if;

      Id := First_Entity (P);

      case Op_Id is

         --  Boolean operators: an implicit declaration exists if the scope
         --  contains a declaration for a derived Boolean type, or for an
         --  array of Boolean type.

         when Name_Op_And | Name_Op_Not | Name_Op_Or  | Name_Op_Xor =>
            while Id  /= Priv_Id loop
               if Valid_Boolean_Arg (Id)
                 and then Id = Base_Type (Id)
               then
                  Add_Implicit_Operator (Id);
                  return True;
               end if;

               Next_Entity (Id);
            end loop;

         --  Equality: look for any non-limited type (result is Boolean)

         when Name_Op_Eq | Name_Op_Ne =>
            while Id  /= Priv_Id loop
               if Is_Type (Id)
                 and then not Is_Limited_Type (Id)
                 and then Id = Base_Type (Id)
               then
                  Add_Implicit_Operator (Standard_Boolean, Id);
                  return True;
               end if;

               Next_Entity (Id);
            end loop;

         --  Comparison operators: scalar type, or array of scalar

         when Name_Op_Lt | Name_Op_Le | Name_Op_Gt | Name_Op_Ge =>
            while Id  /= Priv_Id loop
               if (Is_Scalar_Type (Id)
                 or else (Is_Array_Type (Id)
                           and then Is_Scalar_Type (Component_Type (Id))))
                 and then Id = Base_Type (Id)
               then
                  Add_Implicit_Operator (Standard_Boolean, Id);
                  return True;
               end if;

               Next_Entity (Id);
            end loop;

         --  Arithmetic operators: any numeric type

         when Name_Op_Abs      |
              Name_Op_Add      |
              Name_Op_Mod      |
              Name_Op_Rem      |
              Name_Op_Subtract |
              Name_Op_Multiply |
              Name_Op_Divide   |
              Name_Op_Expon    =>
            while Id  /= Priv_Id loop
               if Is_Numeric_Type (Id)
                 and then Id = Base_Type (Id)
               then
                  Add_Implicit_Operator (Id);
                  return True;
               end if;

               Next_Entity (Id);
            end loop;

         --  Concatenation: any one-dimensional array type

         when Name_Op_Concat =>
            while Id  /= Priv_Id loop
               if Is_Array_Type (Id) and then Number_Dimensions (Id) = 1
                 and then Id = Base_Type (Id)
               then
                  Add_Implicit_Operator (Id);
                  return True;
               end if;

               Next_Entity (Id);
            end loop;

         --  What is the others condition here? Should we be using a
         --  subtype of Name_Id that would restrict to operators ???

         when others => null;
      end case;

      --  If we fall through, then we do not have an implicit operator

      return False;

   end Has_Implicit_Operator;

   --------------------
   -- In_Open_Scopes --
   --------------------

   function In_Open_Scopes (S : Entity_Id) return Boolean is
   begin
      --  Several scope stacks are maintained by Scope_Stack. The base of the
      --  currently active scope stack is denoted by the Is_Active_Stack_Base
      --  flag in the scope stack entry. Note that the scope stacks used to
      --  simply be delimited implicitly by the presence of Standard_Standard
      --  at their base, but there now are cases where this is not sufficient
      --  because Standard_Standard actually may appear in the middle of the
      --  active set of scopes.

      for J in reverse 0 .. Scope_Stack.Last loop
         if Scope_Stack.Table (J).Entity = S then
            return True;
         end if;

         --  Check Is_Active_Stack_Base to tell us when to stop, as there are
         --  cases where Standard_Standard appears in the middle of the active
         --  set of scopes. This affects the declaration and overriding of
         --  private inherited operations in instantiations of generic child
         --  units.

         exit when Scope_Stack.Table (J).Is_Active_Stack_Base;
      end loop;

      return False;
   end In_Open_Scopes;

   -----------------------------
   -- Inherit_Renamed_Profile --
   -----------------------------

   procedure Inherit_Renamed_Profile (New_S : Entity_Id; Old_S : Entity_Id) is
      New_F : Entity_Id;
      Old_F : Entity_Id;
      Old_T : Entity_Id;
      New_T : Entity_Id;

   begin
      if Ekind (Old_S) = E_Operator then
         New_F := First_Formal (New_S);

         while Present (New_F) loop
            Set_Etype (New_F, Base_Type (Etype (New_F)));
            Next_Formal (New_F);
         end loop;

         Set_Etype (New_S, Base_Type (Etype (New_S)));

      else
         New_F := First_Formal (New_S);
         Old_F := First_Formal (Old_S);

         while Present (New_F) loop
            New_T := Etype (New_F);
            Old_T := Etype (Old_F);

            --  If the new type is a renaming of the old one, as is the
            --  case for actuals in instances, retain its name, to simplify
            --  later disambiguation.

            if Nkind (Parent (New_T)) = N_Subtype_Declaration
              and then Is_Entity_Name (Subtype_Indication (Parent (New_T)))
              and then Entity (Subtype_Indication (Parent (New_T))) = Old_T
            then
               null;
            else
               Set_Etype (New_F, Old_T);
            end if;

            Next_Formal (New_F);
            Next_Formal (Old_F);
         end loop;

         if Ekind (Old_S) = E_Function
           or else Ekind (Old_S) = E_Enumeration_Literal
         then
            Set_Etype (New_S, Etype (Old_S));
         end if;
      end if;
   end Inherit_Renamed_Profile;

   ----------------
   -- Initialize --
   ----------------

   procedure Initialize is
   begin
      Urefs.Init;
   end Initialize;

   -------------------------
   -- Install_Use_Clauses --
   -------------------------

   procedure Install_Use_Clauses
     (Clause             : Node_Id;
      Force_Installation : Boolean := False)
   is
      U  : Node_Id;
      P  : Node_Id;
      Id : Entity_Id;

   begin
      U := Clause;
      while Present (U) loop

         --  Case of USE package

         if Nkind (U) = N_Use_Package_Clause then
            P := First (Names (U));
            while Present (P) loop
               Id := Entity (P);

               if Ekind (Id) = E_Package then
                  if In_Use (Id) then
                     Note_Redundant_Use (P);

                  elsif Present (Renamed_Object (Id))
                    and then In_Use (Renamed_Object (Id))
                  then
                     Note_Redundant_Use (P);

                  elsif Force_Installation or else Applicable_Use (P) then
                     Use_One_Package (Id, U);

                  end if;
               end if;

               Next (P);
            end loop;

         --  Case of USE TYPE

         else
            P := First (Subtype_Marks (U));
            while Present (P) loop
               if not Is_Entity_Name (P)
                 or else No (Entity (P))
               then
                  null;

               elsif Entity (P) /= Any_Type then
                  Use_One_Type (P);
               end if;

               Next (P);
            end loop;
         end if;

         Next_Use_Clause (U);
      end loop;
   end Install_Use_Clauses;

   -------------------------------------
   -- Is_Appropriate_For_Entry_Prefix --
   -------------------------------------

   function Is_Appropriate_For_Entry_Prefix (T : Entity_Id) return Boolean is
      P_Type : Entity_Id := T;

   begin
      if Is_Access_Type (P_Type) then
         P_Type := Designated_Type (P_Type);
      end if;

      return Is_Task_Type (P_Type) or else Is_Protected_Type (P_Type);
   end Is_Appropriate_For_Entry_Prefix;

   -------------------------------
   -- Is_Appropriate_For_Record --
   -------------------------------

   function Is_Appropriate_For_Record (T : Entity_Id) return Boolean is

      function Has_Components (T1 : Entity_Id) return Boolean;
      --  Determine if given type has components (i.e. is either a record
      --  type or a type that has discriminants).

      --------------------
      -- Has_Components --
      --------------------

      function Has_Components (T1 : Entity_Id) return Boolean is
      begin
         return Is_Record_Type (T1)
           or else (Is_Private_Type (T1) and then Has_Discriminants (T1))
           or else (Is_Task_Type (T1) and then Has_Discriminants (T1))
           or else (Is_Incomplete_Type (T1)
                     and then From_With_Type (T1)
                     and then Present (Non_Limited_View (T1))
                     and then Is_Record_Type
                                (Get_Full_View (Non_Limited_View (T1))));
      end Has_Components;

   --  Start of processing for Is_Appropriate_For_Record

   begin
      return
        Present (T)
          and then (Has_Components (T)
                     or else (Is_Access_Type (T)
                               and then Has_Components (Designated_Type (T))));
   end Is_Appropriate_For_Record;

   ------------------------
   -- Note_Redundant_Use --
   ------------------------

   procedure Note_Redundant_Use (Clause : Node_Id) is
      Pack_Name : constant Entity_Id := Entity (Clause);
      Cur_Use   : constant Node_Id   := Current_Use_Clause (Pack_Name);
      Decl      : constant Node_Id   := Parent (Clause);

      Prev_Use   : Node_Id := Empty;
      Redundant  : Node_Id := Empty;
      --  The Use_Clause which is actually redundant. In the simplest case
      --  it is Pack itself, but when we compile a body we install its
      --  context before that of its spec, in which case it is the use_clause
      --  in the spec that will appear to be redundant, and we want the
      --  warning to be placed on the body. Similar complications appear when
      --  the redundancy is between a child unit and one of its ancestors.

   begin
      Set_Redundant_Use (Clause, True);

      if not Comes_From_Source (Clause)
        or else In_Instance
        or else not Warn_On_Redundant_Constructs
      then
         return;
      end if;

      if not Is_Compilation_Unit (Current_Scope) then

         --  If the use_clause is in an inner scope, it is made redundant
         --  by some clause in the current context, with one exception:
         --  If we're compiling a nested package body, and the use_clause
         --  comes from the corresponding spec, the clause is not necessarily
         --  fully redundant, so we should not warn.  If a warning was
         --  warranted, it would have been given when the spec was processed.

         if Nkind (Parent (Decl)) = N_Package_Specification then
            declare
               Package_Spec_Entity : constant Entity_Id :=
                                       Defining_Unit_Name (Parent (Decl));
            begin
               if In_Package_Body (Package_Spec_Entity) then
                  return;
               end if;
            end;
         end if;

         Redundant := Clause;
         Prev_Use  := Cur_Use;

      elsif Nkind (Unit (Cunit (Current_Sem_Unit))) = N_Package_Body then
         declare
            Cur_Unit : constant Unit_Number_Type := Get_Source_Unit (Cur_Use);
            New_Unit : constant Unit_Number_Type := Get_Source_Unit (Clause);
            Scop     : Entity_Id;

         begin
            if Cur_Unit = New_Unit then

               --  Redundant clause in same body

               Redundant := Clause;
               Prev_Use  := Cur_Use;

            elsif Cur_Unit = Current_Sem_Unit then

               --  If the new clause is not in the current unit it has been
               --  analyzed first, and it makes the other one redundant.
               --  However, if the new clause appears in a subunit, Cur_Unit
               --  is still the parent, and in that case the redundant one
               --  is the one appearing in the subunit.

               if Nkind (Unit (Cunit (New_Unit))) = N_Subunit then
                  Redundant := Clause;
                  Prev_Use  := Cur_Use;

               --  Most common case: redundant clause in body,
               --  original clause in spec. Current scope is spec entity.

               elsif
                 Current_Scope =
                   Defining_Entity (
                     Unit (Library_Unit (Cunit (Current_Sem_Unit))))
               then
                  Redundant := Cur_Use;
                  Prev_Use  := Clause;

               else
                  --  The new clause may appear in an unrelated unit, when
                  --  the parents of a generic are being installed prior to
                  --  instantiation. In this case there must be no warning.
                  --  We detect this case by checking whether the current top
                  --  of the stack is related to the current compilation.

                  Scop := Current_Scope;
                  while Present (Scop)
                    and then Scop /= Standard_Standard
                  loop
                     if Is_Compilation_Unit (Scop)
                       and then not Is_Child_Unit (Scop)
                     then
                        return;

                     elsif Scop = Cunit_Entity (Current_Sem_Unit) then
                        exit;
                     end if;

                     Scop := Scope (Scop);
                  end loop;

                  Redundant := Cur_Use;
                  Prev_Use  := Clause;
               end if;

            elsif New_Unit = Current_Sem_Unit then
               Redundant := Clause;
               Prev_Use  := Cur_Use;

            else
               --  Neither is the current unit, so they appear in parent or
               --  sibling units. Warning will be emitted elsewhere.

               return;
            end if;
         end;

      elsif Nkind (Unit (Cunit (Current_Sem_Unit))) = N_Package_Declaration
        and then Present (Parent_Spec (Unit (Cunit (Current_Sem_Unit))))
      then
         --  Use_clause is in child unit of current unit, and the child
         --  unit appears in the context of the body of the parent, so it
         --  has been installed first, even though it is the redundant one.
         --  Depending on their placement in the context, the visible or the
         --  private parts of the two units, either might appear as redundant,
         --  but the message has to be on the current unit.

         if Get_Source_Unit (Cur_Use) = Current_Sem_Unit then
            Redundant := Cur_Use;
            Prev_Use  := Clause;
         else
            Redundant := Clause;
            Prev_Use  := Cur_Use;
         end if;

         --  If the new use clause appears in the private part of a parent unit
         --  it may appear to be redudant w.r.t. a use clause in a child unit,
         --  but the previous use clause was needed in the visible part of the
         --  child, and no warning should be emitted.

         if Nkind (Parent (Decl)) = N_Package_Specification
           and then
             List_Containing (Decl) = Private_Declarations (Parent (Decl))
         then
            declare
               Par : constant Entity_Id := Defining_Entity (Parent (Decl));
               Spec : constant Node_Id  :=
                        Specification (Unit (Cunit (Current_Sem_Unit)));

            begin
               if Is_Compilation_Unit (Par)
                 and then Par /= Cunit_Entity (Current_Sem_Unit)
                 and then Parent (Cur_Use) = Spec
                 and then
                   List_Containing (Cur_Use) = Visible_Declarations (Spec)
               then
                  return;
               end if;
            end;
         end if;

      else
         null;
      end if;

      if Present (Redundant) then
         Error_Msg_Sloc := Sloc (Prev_Use);
         Error_Msg_NE
           ("& is already use-visible through previous use clause #?",
            Redundant, Pack_Name);
      end if;
   end Note_Redundant_Use;

   ---------------
   -- Pop_Scope --
   ---------------

   procedure Pop_Scope is
      SST : Scope_Stack_Entry renames Scope_Stack.Table (Scope_Stack.Last);

   begin
      if Debug_Flag_E then
         Write_Info;
      end if;

      Scope_Suppress := SST.Save_Scope_Suppress;
      Local_Suppress_Stack_Top := SST.Save_Local_Suppress_Stack_Top;

      if Debug_Flag_W then
         Write_Str ("--> exiting scope: ");
         Write_Name (Chars (Current_Scope));
         Write_Str (", Depth=");
         Write_Int (Int (Scope_Stack.Last));
         Write_Eol;
      end if;

      End_Use_Clauses (SST.First_Use_Clause);

      --  If the actions to be wrapped are still there they will get lost
      --  causing incomplete code to be generated. It is better to abort in
      --  this case (and we do the abort even with assertions off since the
      --  penalty is incorrect code generation)

      if SST.Actions_To_Be_Wrapped_Before /= No_List
           or else
         SST.Actions_To_Be_Wrapped_After  /= No_List
      then
         return;
      end if;

      --  Free last subprogram name if allocated, and pop scope

      Free (SST.Last_Subprogram_Name);
      Scope_Stack.Decrement_Last;
   end Pop_Scope;

   ---------------
   -- Push_Scope --
   ---------------

   procedure Push_Scope (S : Entity_Id) is
      E : Entity_Id;

   begin
      if Ekind (S) = E_Void then
         null;

      --  Set scope depth if not a non-concurrent type, and we have not
      --  yet set the scope depth. This means that we have the first
      --  occurrence of the scope, and this is where the depth is set.

      elsif (not Is_Type (S) or else Is_Concurrent_Type (S))
        and then not Scope_Depth_Set (S)
      then
         if S = Standard_Standard then
            Set_Scope_Depth_Value (S, Uint_0);

         elsif Is_Child_Unit (S) then
            Set_Scope_Depth_Value (S, Uint_1);

         elsif not Is_Record_Type (Current_Scope) then
            if Ekind (S) = E_Loop then
               Set_Scope_Depth_Value (S, Scope_Depth (Current_Scope));
            else
               Set_Scope_Depth_Value (S, Scope_Depth (Current_Scope) + 1);
            end if;
         end if;
      end if;

      Scope_Stack.Increment_Last;

      declare
         SST : Scope_Stack_Entry renames Scope_Stack.Table (Scope_Stack.Last);

      begin
         SST.Entity                        := S;
         SST.Save_Scope_Suppress           := Scope_Suppress;
         SST.Save_Local_Suppress_Stack_Top := Local_Suppress_Stack_Top;

         if Scope_Stack.Last > Scope_Stack.First then
            SST.Component_Alignment_Default := Scope_Stack.Table
                                                 (Scope_Stack.Last - 1).
                                                   Component_Alignment_Default;
         end if;

         SST.Last_Subprogram_Name           := null;
         SST.Is_Transient                   := False;
         SST.Node_To_Be_Wrapped             := Empty;
         SST.Pending_Freeze_Actions         := No_List;
         SST.Actions_To_Be_Wrapped_Before   := No_List;
         SST.Actions_To_Be_Wrapped_After    := No_List;
         SST.First_Use_Clause               := Empty;
         SST.Is_Active_Stack_Base           := False;
         SST.Previous_Visibility            := False;
      end;

      if Debug_Flag_W then
         Write_Str ("--> new scope: ");
         Write_Name (Chars (Current_Scope));
         Write_Str (", Id=");
         Write_Int (Int (Current_Scope));
         Write_Str (", Depth=");
         Write_Int (Int (Scope_Stack.Last));
         Write_Eol;
      end if;

      --  Deal with copying flags from the previous scope to this one. This
      --  is not necessary if either scope is standard, or if the new scope
      --  is a child unit.

      if S /= Standard_Standard
        and then Scope (S) /= Standard_Standard
        and then not Is_Child_Unit (S)
      then
         E := Scope (S);

         if Nkind (E) not in N_Entity then
            return;
         end if;

         --  Copy categorization flags from Scope (S) to S, this is not done
         --  when Scope (S) is Standard_Standard since propagation is from
         --  library unit entity inwards. Copy other relevant attributes as
         --  well (Discard_Names in particular).

         --  We only propagate inwards for library level entities,
         --  inner level subprograms do not inherit the categorization.

         if Is_Library_Level_Entity (S) then
            Set_Is_Preelaborated  (S, Is_Preelaborated (E));
            Set_Is_Shared_Passive (S, Is_Shared_Passive (E));
            Set_Discard_Names     (S, Discard_Names (E));
            Set_Suppress_Value_Tracking_On_Call
                                  (S, Suppress_Value_Tracking_On_Call (E));
            Set_Categorization_From_Scope (E => S, Scop => E);
         end if;
      end if;
   end Push_Scope;

   ---------------------
   -- Premature_Usage --
   ---------------------

   procedure Premature_Usage (N : Node_Id) is
      Kind : constant Node_Kind := Nkind (Parent (Entity (N)));
      E    : Entity_Id := Entity (N);

   begin
      --  Within an instance, the analysis of the actual for a formal object
      --  does not see the name of the object itself. This is significant only
      --  if the object is an aggregate, where its analysis does not do any
      --  name resolution on component associations. (see 4717-008). In such a
      --  case, look for the visible homonym on the chain.

      if In_Instance
        and then Present (Homonym (E))
      then
         E := Homonym (E);

         while Present (E)
           and then not In_Open_Scopes (Scope (E))
         loop
            E := Homonym (E);
         end loop;

         if Present (E) then
            Set_Entity (N, E);
            Set_Etype (N, Etype (E));
            return;
         end if;
      end if;

      if Kind  = N_Component_Declaration then
         Error_Msg_N
           ("component&! cannot be used before end of record declaration", N);

      elsif Kind  = N_Parameter_Specification then
         Error_Msg_N
           ("formal parameter&! cannot be used before end of specification",
            N);

      elsif Kind  = N_Discriminant_Specification then
         Error_Msg_N
           ("discriminant&! cannot be used before end of discriminant part",
            N);

      elsif Kind  = N_Procedure_Specification
        or else Kind = N_Function_Specification
      then
         Error_Msg_N
           ("subprogram&! cannot be used before end of its declaration",
            N);

      elsif Kind = N_Full_Type_Declaration then
         Error_Msg_N
           ("type& cannot be used before end of its declaration!", N);

      else
         Error_Msg_N
           ("object& cannot be used before end of its declaration!", N);
      end if;
   end Premature_Usage;

   ------------------------
   -- Present_System_Aux --
   ------------------------

   function Present_System_Aux (N : Node_Id := Empty) return Boolean is
      Loc      : Source_Ptr;
      Aux_Name : Unit_Name_Type;
      Unum     : Unit_Number_Type;
      Withn    : Node_Id;
      With_Sys : Node_Id;
      The_Unit : Node_Id;

      function Find_System (C_Unit : Node_Id) return Entity_Id;
      --  Scan context clause of compilation unit to find with_clause
      --  for System.

      -----------------
      -- Find_System --
      -----------------

      function Find_System (C_Unit : Node_Id) return Entity_Id is
         With_Clause : Node_Id;

      begin
         With_Clause := First (Context_Items (C_Unit));
         while Present (With_Clause) loop
            if (Nkind (With_Clause) = N_With_Clause
              and then Chars (Name (With_Clause)) = Name_System)
              and then Comes_From_Source (With_Clause)
            then
               return With_Clause;
            end if;

            Next (With_Clause);
         end loop;

         return Empty;
      end Find_System;

   --  Start of processing for Present_System_Aux

   begin
      --  The child unit may have been loaded and analyzed already

      if Present (System_Aux_Id) then
         return True;

      --  If no previous pragma for System.Aux, nothing to load

      elsif No (System_Extend_Unit) then
         return False;

      --  Use the unit name given in the pragma to retrieve the unit.
      --  Verify that System itself appears in the context clause of the
      --  current compilation. If System is not present, an error will
      --  have been reported already.

      else
         With_Sys := Find_System (Cunit (Current_Sem_Unit));

         The_Unit := Unit (Cunit (Current_Sem_Unit));

         if No (With_Sys)
           and then
             (Nkind (The_Unit) = N_Package_Body
                or else (Nkind (The_Unit) = N_Subprogram_Body
                           and then
                             not Acts_As_Spec (Cunit (Current_Sem_Unit))))
         then
            With_Sys := Find_System (Library_Unit (Cunit (Current_Sem_Unit)));
         end if;

         if No (With_Sys)
           and then Present (N)
         then
            --  If we are compiling a subunit, we need to examine its
            --  context as well (Current_Sem_Unit is the parent unit);

            The_Unit := Parent (N);
            while Nkind (The_Unit) /= N_Compilation_Unit loop
               The_Unit := Parent (The_Unit);
            end loop;

            if Nkind (Unit (The_Unit)) = N_Subunit then
               With_Sys := Find_System (The_Unit);
            end if;
         end if;

         if No (With_Sys) then
            return False;
         end if;

         Loc := Sloc (With_Sys);
         Get_Name_String (Chars (Expression (System_Extend_Unit)));
         Name_Buffer (8 .. Name_Len + 7) := Name_Buffer (1 .. Name_Len);
         Name_Buffer (1 .. 7) := "system.";
         Name_Buffer (Name_Len + 8) := '%';
         Name_Buffer (Name_Len + 9) := 's';
         Name_Len := Name_Len + 9;
         Aux_Name := Name_Find;

         Unum :=
           Load_Unit
             (Load_Name  => Aux_Name,
              Required   => False,
              Subunit    => False,
              Error_Node => With_Sys);

         if Unum /= No_Unit then
            Semantics (Cunit (Unum));
            System_Aux_Id :=
              Defining_Entity (Specification (Unit (Cunit (Unum))));

            Withn :=
              Make_With_Clause (Loc,
                Name =>
                  Make_Expanded_Name (Loc,
                    Chars  => Chars (System_Aux_Id),
                    Prefix => New_Reference_To (Scope (System_Aux_Id), Loc),
                    Selector_Name => New_Reference_To (System_Aux_Id, Loc)));

            Set_Entity (Name (Withn), System_Aux_Id);

            Set_Library_Unit       (Withn, Cunit (Unum));
            Set_Corresponding_Spec (Withn, System_Aux_Id);
            Set_First_Name         (Withn, True);
            Set_Implicit_With      (Withn, True);

            Insert_After (With_Sys, Withn);
            Mark_Rewrite_Insertion (Withn);
            Set_Context_Installed (Withn);

            return True;

         --  Here if unit load failed

         else
            Error_Msg_Name_1 := Name_System;
            Error_Msg_Name_2 := Chars (Expression (System_Extend_Unit));
            Error_Msg_N
              ("extension package `%.%` does not exist",
               Opt.System_Extend_Unit);
            return False;
         end if;
      end if;
   end Present_System_Aux;

   -------------------------
   -- Restore_Scope_Stack --
   -------------------------

   procedure Restore_Scope_Stack (Handle_Use : Boolean := True) is
      E         : Entity_Id;
      S         : Entity_Id;
      Comp_Unit : Node_Id;
      In_Child  : Boolean := False;
      Full_Vis  : Boolean := True;
      SS_Last   : constant Int := Scope_Stack.Last;

   begin
      --  Restore visibility of previous scope stack, if any

      for J in reverse 0 .. Scope_Stack.Last loop
         exit when  Scope_Stack.Table (J).Entity = Standard_Standard
            or else No (Scope_Stack.Table (J).Entity);

         S := Scope_Stack.Table (J).Entity;

         if not Is_Hidden_Open_Scope (S) then

            --  If the parent scope is hidden, its entities are hidden as
            --  well, unless the entity is the instantiation currently
            --  being analyzed.

            if not Is_Hidden_Open_Scope (Scope (S))
              or else not Analyzed (Parent (S))
              or else Scope (S) = Standard_Standard
            then
               Set_Is_Immediately_Visible (S, True);
            end if;

            E := First_Entity (S);
            while Present (E) loop
               if Is_Child_Unit (E) then
                  Set_Is_Immediately_Visible (E,
                    Is_Visible_Child_Unit (E) or else In_Open_Scopes (E));
               else
                  Set_Is_Immediately_Visible (E, True);
               end if;

               Next_Entity (E);

               if not Full_Vis then
                  exit when E = First_Private_Entity (S);
               end if;
            end loop;

            --  The visibility of child units (siblings of current compilation)
            --  must be restored in any case. Their declarations may appear
            --  after the private part of the parent.

            if not Full_Vis then
               while Present (E) loop
                  if Is_Child_Unit (E) then
                     Set_Is_Immediately_Visible (E,
                       Is_Visible_Child_Unit (E) or else In_Open_Scopes (E));
                  end if;

                  Next_Entity (E);
               end loop;
            end if;
         end if;

         if Is_Child_Unit (S)
            and not In_Child     --  check only for current unit
         then
            In_Child := True;

            --  Restore visibility of parents according to whether the child
            --  is private and whether we are in its visible part.

            Comp_Unit := Parent (Unit_Declaration_Node (S));

            if Nkind (Comp_Unit) = N_Compilation_Unit
              and then Private_Present (Comp_Unit)
            then
               Full_Vis := True;

            elsif (Ekind (S) = E_Package
                    or else Ekind (S) = E_Generic_Package)
              and then (In_Private_Part (S)
                         or else In_Package_Body (S))
            then
               Full_Vis := True;

            elsif (Ekind (S) = E_Procedure
                    or else Ekind (S) = E_Function)
              and then Has_Completion (S)
            then
               Full_Vis := True;
            else
               Full_Vis := False;
            end if;
         else
            Full_Vis := True;
         end if;
      end loop;

      if SS_Last >= Scope_Stack.First
        and then Scope_Stack.Table (SS_Last).Entity /= Standard_Standard
        and then Handle_Use
      then
         Install_Use_Clauses (Scope_Stack.Table (SS_Last).First_Use_Clause);
      end if;
   end Restore_Scope_Stack;

   ----------------------
   -- Save_Scope_Stack --
   ----------------------

   procedure Save_Scope_Stack (Handle_Use : Boolean := True) is
      E       : Entity_Id;
      S       : Entity_Id;
      SS_Last : constant Int := Scope_Stack.Last;

   begin
      if SS_Last >= Scope_Stack.First
        and then Scope_Stack.Table (SS_Last).Entity /= Standard_Standard
      then
         if Handle_Use then
            End_Use_Clauses (Scope_Stack.Table (SS_Last).First_Use_Clause);
         end if;

         --  If the call is from within a compilation unit, as when called from
         --  Rtsfind, make current entries in scope stack invisible while we
         --  analyze the new unit.

         for J in reverse 0 .. SS_Last loop
            exit when  Scope_Stack.Table (J).Entity = Standard_Standard
               or else No (Scope_Stack.Table (J).Entity);

            S := Scope_Stack.Table (J).Entity;
            Set_Is_Immediately_Visible (S, False);

            E := First_Entity (S);
            while Present (E) loop
               Set_Is_Immediately_Visible (E, False);
               Next_Entity (E);
            end loop;
         end loop;

      end if;
   end Save_Scope_Stack;

   -------------
   -- Set_Use --
   -------------

   procedure Set_Use (L : List_Id) is
      Decl      : Node_Id;
      Pack_Name : Node_Id;
      Pack      : Entity_Id;
      Id        : Entity_Id;

   begin
      if Present (L) then
         Decl := First (L);
         while Present (Decl) loop
            if Nkind (Decl) = N_Use_Package_Clause then
               Chain_Use_Clause (Decl);

               Pack_Name := First (Names (Decl));
               while Present (Pack_Name) loop
                  Pack := Entity (Pack_Name);

                  if Ekind (Pack) = E_Package
                    and then Applicable_Use (Pack_Name)
                  then
                     Use_One_Package (Pack, Decl);
                  end if;

                  Next (Pack_Name);
               end loop;

            elsif Nkind (Decl) = N_Use_Type_Clause  then
               Chain_Use_Clause (Decl);

               Id := First (Subtype_Marks (Decl));
               while Present (Id) loop
                  if Entity (Id) /= Any_Type then
                     Use_One_Type (Id);
                  end if;

                  Next (Id);
               end loop;
            end if;

            Next (Decl);
         end loop;
      end if;
   end Set_Use;

   ---------------------
   -- Use_One_Package --
   ---------------------

   procedure Use_One_Package (P : Entity_Id; N : Node_Id) is
      Id               : Entity_Id;
      Prev             : Entity_Id;
      Current_Instance : Entity_Id := Empty;
      Real_P           : Entity_Id;
      Private_With_OK  : Boolean   := False;

   begin
      if Ekind (P) /= E_Package then
         return;
      end if;

      Set_In_Use (P);
      Set_Current_Use_Clause (P, N);

      --  Ada 2005 (AI-50217): Check restriction

      if From_With_Type (P) then
         Error_Msg_N ("limited withed package cannot appear in use clause", N);
      end if;

      --  Find enclosing instance, if any

      if In_Instance then
         Current_Instance := Current_Scope;
         while not Is_Generic_Instance (Current_Instance) loop
            Current_Instance := Scope (Current_Instance);
         end loop;

         if No (Hidden_By_Use_Clause (N)) then
            Set_Hidden_By_Use_Clause (N, New_Elmt_List);
         end if;
      end if;

      --  If unit is a package renaming, indicate that the renamed
      --  package is also in use (the flags on both entities must
      --  remain consistent, and a subsequent use of either of them
      --  should be recognized as redundant).

      if Present (Renamed_Object (P)) then
         Set_In_Use (Renamed_Object (P));
         Set_Current_Use_Clause (Renamed_Object (P), N);
         Real_P := Renamed_Object (P);
      else
         Real_P := P;
      end if;

      --  Ada 2005 (AI-262): Check the use_clause of a private withed package
      --  found in the private part of a package specification

      if In_Private_Part (Current_Scope)
        and then Has_Private_With (P)
        and then Is_Child_Unit (Current_Scope)
        and then Is_Child_Unit (P)
        and then Is_Ancestor_Package (Scope (Current_Scope), P)
      then
         Private_With_OK := True;
      end if;

      --  Loop through entities in one package making them potentially
      --  use-visible.

      Id := First_Entity (P);
      while Present (Id)
        and then (Id /= First_Private_Entity (P)
                    or else Private_With_OK) -- Ada 2005 (AI-262)
      loop
         Prev := Current_Entity (Id);
         while Present (Prev) loop
            if Is_Immediately_Visible (Prev)
              and then (not Is_Overloadable (Prev)
                         or else not Is_Overloadable (Id)
                         or else (Type_Conformant (Id, Prev)))
            then
               if No (Current_Instance) then

                  --  Potentially use-visible entity remains hidden

                  goto Next_Usable_Entity;

               --  A use clause within an instance hides outer global entities,
               --  which are not used to resolve local entities in the
               --  instance. Note that the predefined entities in Standard
               --  could not have been hidden in the generic by a use clause,
               --  and therefore remain visible. Other compilation units whose
               --  entities appear in Standard must be hidden in an instance.

               --  To determine whether an entity is external to the instance
               --  we compare the scope depth of its scope with that of the
               --  current instance. However, a generic actual of a subprogram
               --  instance is declared in the wrapper package but will not be
               --  hidden by a use-visible entity.

               --  If Id is called Standard, the predefined package with the
               --  same name is in the homonym chain. It has to be ignored
               --  because it has no defined scope (being the only entity in
               --  the system with this mandated behavior).

               elsif not Is_Hidden (Id)
                 and then Present (Scope (Prev))
                 and then not Is_Wrapper_Package (Scope (Prev))
                 and then Scope_Depth (Scope (Prev)) <
                          Scope_Depth (Current_Instance)
                 and then (Scope (Prev) /= Standard_Standard
                            or else Sloc (Prev) > Standard_Location)
               then
                  Set_Is_Potentially_Use_Visible (Id);
                  Set_Is_Immediately_Visible (Prev, False);
                  Append_Elmt (Prev, Hidden_By_Use_Clause (N));
               end if;

            --  A user-defined operator is not use-visible if the predefined
            --  operator for the type is immediately visible, which is the case
            --  if the type of the operand is in an open scope. This does not
            --  apply to user-defined operators that have operands of different
            --  types, because the predefined mixed mode operations (multiply
            --  and divide) apply to universal types and do not hide anything.

            elsif Ekind (Prev) = E_Operator
              and then Operator_Matches_Spec (Prev, Id)
              and then In_Open_Scopes
               (Scope (Base_Type (Etype (First_Formal (Id)))))
              and then (No (Next_Formal (First_Formal (Id)))
                         or else Etype (First_Formal (Id))
                           = Etype (Next_Formal (First_Formal (Id)))
                         or else Chars (Prev) = Name_Op_Expon)
            then
               goto Next_Usable_Entity;
            end if;

            Prev := Homonym (Prev);
         end loop;

         --  On exit, we know entity is not hidden, unless it is private

         if not Is_Hidden (Id)
           and then ((not Is_Child_Unit (Id))
                       or else Is_Visible_Child_Unit (Id))
         then
            Set_Is_Potentially_Use_Visible (Id);

            if Is_Private_Type (Id)
              and then Present (Full_View (Id))
            then
               Set_Is_Potentially_Use_Visible (Full_View (Id));
            end if;
         end if;

         <<Next_Usable_Entity>>
            Next_Entity (Id);
      end loop;

      --  Child units are also made use-visible by a use clause, but they may
      --  appear after all visible declarations in the parent entity list.

      while Present (Id) loop
         if Is_Child_Unit (Id)
           and then Is_Visible_Child_Unit (Id)
         then
            Set_Is_Potentially_Use_Visible (Id);
         end if;

         Next_Entity (Id);
      end loop;

      if Chars (Real_P) = Name_System
        and then Scope (Real_P) = Standard_Standard
        and then Present_System_Aux (N)
      then
         Use_One_Package (System_Aux_Id, N);
      end if;

   end Use_One_Package;

   ------------------
   -- Use_One_Type --
   ------------------

   procedure Use_One_Type (Id : Node_Id) is
      Elmt          : Elmt_Id;
      Is_Known_Used : Boolean;
      Op_List       : Elist_Id;
      T             : Entity_Id;

      function Spec_Reloaded_For_Body return Boolean;
      --  Determine whether the compilation unit is a package body and the use
      --  type clause is in the spec of the same package. Even though the spec
      --  was analyzed first, its context is reloaded when analysing the body.

      ----------------------------
      -- Spec_Reloaded_For_Body --
      ----------------------------

      function Spec_Reloaded_For_Body return Boolean is
      begin
         if Nkind (Unit (Cunit (Current_Sem_Unit))) = N_Package_Body then
            declare
               Spec : constant Node_Id :=
                        Parent (List_Containing (Parent (Id)));
            begin
               return
                 Nkind (Spec) = N_Package_Specification
                   and then Corresponding_Body (Parent (Spec)) =
                              Cunit_Entity (Current_Sem_Unit);
            end;
         end if;

         return False;
      end Spec_Reloaded_For_Body;

   --  Start of processing for Use_One_Type;

   begin
      --  It is the type determined by the subtype mark (8.4(8)) whose
      --  operations become potentially use-visible.

      T := Base_Type (Entity (Id));

      --  Either the type itself is used, the package where it is declared
      --  is in use or the entity is declared in the current package, thus
      --  use-visible.

      Is_Known_Used :=
        In_Use (T)
          or else In_Use (Scope (T))
          or else Scope (T) = Current_Scope;

      Set_Redundant_Use (Id,
        Is_Known_Used or else Is_Potentially_Use_Visible (T));

      if In_Open_Scopes (Scope (T)) then
         null;

      --  A limited view cannot appear in a use_type clause. However, an
      --  access type whose designated type is limited has the flag but
      --  is not itself a limited view unless we only have a limited view
      --  of its enclosing package.

      elsif From_With_Type (T)
        and then From_With_Type (Scope (T))
      then
         Error_Msg_N
           ("incomplete type from limited view "
             & "cannot appear in use clause", Id);

      --  If the subtype mark designates a subtype in a different package,
      --  we have to check that the parent type is visible, otherwise the
      --  use type clause is a noop. Not clear how to do that???

      elsif not Redundant_Use (Id) then
         Set_In_Use (T);
         Op_List := Collect_Primitive_Operations (T);

         Elmt := First_Elmt (Op_List);
         while Present (Elmt) loop
            if (Nkind (Node (Elmt)) = N_Defining_Operator_Symbol
                 or else Chars (Node (Elmt)) in Any_Operator_Name)
              and then not Is_Hidden (Node (Elmt))
            then
               Set_Is_Potentially_Use_Visible (Node (Elmt));
            end if;

            Next_Elmt (Elmt);
         end loop;
      end if;

      --  If warning on redundant constructs, check for unnecessary WITH

      if Warn_On_Redundant_Constructs
        and then Is_Known_Used

         --                     with P;         with P; use P;
         --    package P is     package X is    package body X is
         --       type T ...       use P.T;

         --  The compilation unit is the body of X. GNAT first compiles the
         --  spec of X, then procedes to the body. At that point P is marked
         --  as use visible. The analysis then reinstalls the spec along with
         --  its context. The use clause P.T is now recognized as redundant,
         --  but in the wrong context. Do not emit a warning in such cases.

        and then not Spec_Reloaded_For_Body
      then
         --  The type already has a use clause

         if In_Use (T) then
            Error_Msg_NE
              ("& is already use-visible through previous use type clause?",
               Id, Id);

         --  The package where T is declared is already used

         elsif In_Use (Scope (T)) then
            Error_Msg_Sloc := Sloc (Current_Use_Clause (Scope (T)));
            Error_Msg_NE
              ("& is already use-visible through package use clause #?",
               Id, Id);

         --  The current scope is the package where T is declared

         else
            Error_Msg_Node_2 := Scope (T);
            Error_Msg_NE
              ("& is already use-visible inside package &?", Id, Id);
         end if;
      end if;
   end Use_One_Type;

   ----------------
   -- Write_Info --
   ----------------

   procedure Write_Info is
      Id : Entity_Id := First_Entity (Current_Scope);

   begin
      --  No point in dumping standard entities

      if Current_Scope = Standard_Standard then
         return;
      end if;

      Write_Str ("========================================================");
      Write_Eol;
      Write_Str ("        Defined Entities in ");
      Write_Name (Chars (Current_Scope));
      Write_Eol;
      Write_Str ("========================================================");
      Write_Eol;

      if No (Id) then
         Write_Str ("-- none --");
         Write_Eol;

      else
         while Present (Id) loop
            Write_Entity_Info (Id, " ");
            Next_Entity (Id);
         end loop;
      end if;

      if Scope (Current_Scope) = Standard_Standard then

         --  Print information on the current unit itself

         Write_Entity_Info (Current_Scope, " ");
      end if;

      Write_Eol;
   end Write_Info;

   -----------------
   -- Write_Scopes --
   -----------------

   procedure Write_Scopes is
      S : Entity_Id;
   begin
      for J in reverse 1 .. Scope_Stack.Last loop
         S :=  Scope_Stack.Table (J).Entity;
         Write_Int (Int (S));
         Write_Str (" === ");
         Write_Name (Chars (S));
         Write_Eol;
      end loop;
   end Write_Scopes;

end Sem_Ch8;