gcc/ada/sem_disp.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --                             S E M _ D I S P                              --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2010, Free Software Foundation, Inc.         --
  10 --                                                                          --
  11 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  12 -- terms of the  GNU General Public License as published  by the Free Soft- --
  13 -- ware  Foundation;  either version 3,  or (at your option) any later ver- --
  14 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  15 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  16 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  17 -- for  more details.  You should have  received  a copy of the GNU General --
  18 -- Public License  distributed with GNAT; see file COPYING3.  If not, go to --
  19 -- http://www.gnu.org/licenses for a complete copy of the license.          --
  20 --                                                                          --
  21 -- GNAT was originally developed  by the GNAT team at  New York University. --
  22 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  23 --                                                                          --
  24 ------------------------------------------------------------------------------
  25
  26 --  This package contains routines involved in tagged types and dynamic
  27 --  dispatching.
  28
  29 with Types; use Types;
  30 package Sem_Disp is
  31
  32    procedure Check_Controlling_Formals (Typ : Entity_Id; Subp : Entity_Id);
  33    --  Check that all controlling parameters of Subp are of type Typ,
  34    --  that defaults for controlling parameters are tag-indeterminate,
  35    --  and that the nominal subtype of the parameters and result
  36    --  statically match the first subtype of the controlling type.
  37
  38    procedure Check_Dispatching_Call (N : Node_Id);
  39    --  Check if a call is a dispatching call. The subprogram is known to
  40    --  be a dispatching operation. The call is dispatching if all the
  41    --  controlling actuals are dynamically tagged. This procedure is called
  42    --  after overload resolution, so the call is known to be unambiguous.
  43
  44    procedure Check_Dispatching_Operation (Subp, Old_Subp : Entity_Id);
  45    --  Add "Subp" to the list of primitive operations of the corresponding type
  46    --  if it has a parameter of this type and is defined at a proper place for
  47    --  primitive operations (new primitives are only defined in package spec,
  48    --  overridden operation can be defined in any scope). If Old_Subp is not
  49    --  Empty we are in the overriding case. If the tagged type associated with
  50    --  Subp is a concurrent type (case that occurs when the type is declared in
  51    --  a generic because the analysis of generics disables generation of the
  52    --  corresponding record) then this routine does does not add "Subp" to the
  53    --  list of primitive operations but leaves Subp decorated as dispatching
  54    --  operation to enable checks associated with the Object.Operation notation
  55
  56    procedure Check_Operation_From_Incomplete_Type
  57      (Subp : Entity_Id;
  58       Typ  : Entity_Id);
  59    --  If a primitive operation was defined for the incomplete view of the
  60    --  type, and the full type declaration is a derived type definition,
  61    --  the operation may override an inherited one.
  62
  63    procedure Check_Operation_From_Private_View (Subp, Old_Subp : Entity_Id);
  64    --  Add "Old_Subp" to the list of primitive operations of the corresponding
  65    --  tagged type if it is the full view of a private tagged type. The Alias
  66    --  of "OldSubp" is adjusted to point to the inherited procedure of the
  67    --  full view because it is always this one which has to be called.
  68
  69    function Covers_Some_Interface (Prim : Entity_Id) return Boolean;
  70    --  Returns true if Prim covers some interface primitive of its associated
  71    --  tagged type. The tagged type of Prim must be frozen when this function
  72    --  is invoked.
  73
  74    function Find_Controlling_Arg (N : Node_Id) return Node_Id;
  75    --  Returns the actual controlling argument if N is dynamically tagged,
  76    --  and Empty if it is not dynamically tagged.
  77
  78    function Find_Dispatching_Type (Subp : Entity_Id) return Entity_Id;
  79    --  Check whether a subprogram is dispatching, and find the tagged type of
  80    --  the controlling argument or arguments. Returns Empty if Subp is not a
  81    --  dispatching operation.
  82
  83    function Find_Primitive_Covering_Interface
  84      (Tagged_Type : Entity_Id;
  85       Iface_Prim  : Entity_Id) return Entity_Id;
  86    --  Search in the homonym chain for the primitive of Tagged_Type that covers
  87    --  Iface_Prim. The homonym chain traversal is required to catch primitives
  88    --  associated with the partial view of private types when processing the
  89    --  corresponding full view. If the entity is not found then search for it
  90    --  in the list of primitives of Tagged_Type. This latter search is needed
  91    --  when the interface primitive is covered by a private subprogram. If the
  92    --  primitive has not been covered yet then return the entity that will be
  93    --  overridden when the primitive is covered (that is, return the entity
  94    --  whose alias attribute references the interface primitive). If none of
  95    --  these entities is found then return Empty.
  96
  97    type Subprogram_List is array (Nat range <>) of Entity_Id;
  98    --  Type returned by Inherited_Subprograms function
  99
 100    function Inherited_Subprograms (S : Entity_Id) return Subprogram_List;
 101    --  Given the spec of a subprogram, this function gathers any inherited
 102    --  subprograms from direct inheritance or via interfaces. The list is
 103    --  a list of entity id's of the specs of inherited subprograms. Returns
 104    --  a null array if passed an Empty spec id. Note that the returned array
 105    --  only includes subprograms and generic subprograms (and excludes any
 106    --  other inherited entities, in particular enumeration literals).
 107
 108    function Is_Dynamically_Tagged (N : Node_Id) return Boolean;
 109    --  Used to determine whether a call is dispatching, i.e. if is an
 110    --  an expression of a class_Wide type, or a call to a function with
 111    --  controlling result where at least one operand is dynamically tagged.
 112
 113    function Is_Null_Interface_Primitive (E : Entity_Id) return Boolean;
 114    --  Returns True if E is a null procedure that is an interface primitive
 115
 116    function Is_Tag_Indeterminate (N : Node_Id) return Boolean;
 117    --  An expression is tag-indeterminate if it is a call that dispatches
 118    --  on result, and all controlling operands are also indeterminate.
 119    --  Such a function call may inherit a tag from an enclosing call.
 120
 121    procedure Override_Dispatching_Operation
 122      (Tagged_Type : Entity_Id;
 123       Prev_Op     : Entity_Id;
 124       New_Op      : Entity_Id);
 125    --  Replace an implicit dispatching operation with an explicit one.
 126    --  Prev_Op is an inherited primitive operation which is overridden
 127    --  by the explicit declaration of New_Op.
 128
 129    procedure Propagate_Tag (Control : Node_Id; Actual : Node_Id);
 130    --  If a function call is tag-indeterminate,  its controlling argument is
 131    --  found in the context;  either an enclosing call, or the left-hand side
 132    --  of the enclosing assignment statement. The tag must be propagated
 133    --  recursively to the tag-indeterminate actuals of the call.
 134
 135 end Sem_Disp;