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) 1992-2015, 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, that
  34    --  defaults for controlling parameters are tag-indeterminate, and that the
  35    --  nominal subtype of the parameters and result statically match the first
  36    --  subtype of the controlling type. Issues appropriate error messages if
  37    --  any of these requirements is not met.
  38
  39    procedure Check_Dispatching_Call (N : Node_Id);
  40    --  Check if the call N is a dispatching call. The subprogram is known to be
  41    --  a dispatching operation. The call is dispatching if all the controlling
  42    --  actuals are dynamically tagged. This procedure is called after overload
  43    --  resolution, so the call is known to be unambiguous.
  44
  45    procedure Check_Dispatching_Operation (Subp, Old_Subp : Entity_Id);
  46    --  Add Subp to the list of primitive operations of the corresponding type
  47    --  if it has a parameter of this type and is defined at a proper place for
  48    --  primitive operations (new primitives are only defined in package spec,
  49    --  overridden operation can be defined in any scope). If Old_Subp is not
  50    --  Empty we are in the overriding case. If the tagged type associated with
  51    --  Subp is a concurrent type (case that occurs when the type is declared
  52    --  in a generic because the analysis of generics disables generation of the
  53    --  corresponding record) then this routine does not add Subp to the list of
  54    --  primitive operations but leaves Subp decorated as dispatching operation
  55    --  to enable checks associated with the Object.Operation notation.
  56
  57    procedure Check_Operation_From_Incomplete_Type
  58      (Subp : Entity_Id;
  59       Typ  : Entity_Id);
  60    --  If a primitive operation was defined for the incomplete view of the
  61    --  type, and the full type declaration is a derived type definition,
  62    --  the operation may override an inherited one.
  63    --  Need more description here, what are the parameters, and what does
  64    --  this call actually do???
  65
  66    procedure Check_Operation_From_Private_View (Subp, Old_Subp : Entity_Id);
  67    --  Add Old_Subp to the list of primitive operations of the corresponding
  68    --  tagged type if it is the full view of a private tagged type. The Alias
  69    --  of Old_Subp is adjusted to point to the inherited procedure of the
  70    --  full view because it is always this one which has to be called.
  71    --  What is Subp used for???
  72
  73    function Covers_Some_Interface (Prim : Entity_Id) return Boolean;
  74    --  Returns true if Prim covers some interface primitive of its associated
  75    --  tagged type. The tagged type of Prim must be frozen when this function
  76    --  is invoked.
  77
  78    function Find_Controlling_Arg (N : Node_Id) return Node_Id;
  79    --  Returns the actual controlling argument if N is dynamically tagged, and
  80    --  Empty if it is not dynamically tagged.
  81
  82    function Find_Dispatching_Type (Subp : Entity_Id) return Entity_Id;
  83    --  Check whether the subprogram Subp is dispatching, and find the tagged
  84    --  type of the controlling argument or arguments. Returns Empty if Subp
  85    --  is not a dispatching operation.
  86
  87    function Find_Primitive_Covering_Interface
  88      (Tagged_Type : Entity_Id;
  89       Iface_Prim  : Entity_Id) return Entity_Id;
  90    --  Search the homonym chain for the primitive of Tagged_Type that covers
  91    --  Iface_Prim. The homonym chain traversal is required to catch primitives
  92    --  associated with the partial view of private types when processing the
  93    --  corresponding full view. If the entity is not found, then search for it
  94    --  in the list of primitives of Tagged_Type. This latter search is needed
  95    --  when the interface primitive is covered by a private subprogram. If the
  96    --  primitive has not been covered yet then return the entity that will be
  97    --  overridden when the primitive is covered (that is, return the entity
  98    --  whose alias attribute references the interface primitive). If none of
  99    --  these entities is found then return Empty.
 100
 101    type Subprogram_List is array (Nat range <>) of Entity_Id;
 102    --  Type returned by Inherited_Subprograms function
 103
 104    function Inherited_Subprograms
 105      (S               : Entity_Id;
 106       No_Interfaces   : Boolean := False;
 107       Interfaces_Only : Boolean := False;
 108       One_Only        : Boolean := False) return Subprogram_List;
 109    --  Given the spec of a subprogram, this function gathers any inherited
 110    --  subprograms from direct inheritance or via interfaces. The result is an
 111    --  array of Entity_Ids of the specs of inherited subprograms. Returns a
 112    --  null array if passed an Empty spec id. Note that the returned array
 113    --  only includes subprograms and generic subprograms (and excludes any
 114    --  other inherited entities, in particular enumeration literals). If
 115    --  No_Interfaces is True, only return inherited subprograms not coming
 116    --  from an interface. If Interfaces_Only is True, only return inherited
 117    --  subprograms from interfaces. Otherwise, subprograms inherited directly
 118    --  come first, starting with the closest ancestors, and are followed by
 119    --  subprograms inherited from interfaces. At most one of No_Interfaces
 120    --  and Interfaces_Only should be True.
 121    --
 122    --  If One_Only is set, the search is discontinued as soon as one entry
 123    --  is found. In this case the resulting array is either null or contains
 124    --  exactly one element.
 125
 126    function Is_Dynamically_Tagged (N : Node_Id) return Boolean;
 127    --  Used to determine whether a call is dispatching, i.e. if it is
 128    --  an expression of a class_Wide type, or a call to a function with
 129    --  controlling result where at least one operand is dynamically tagged.
 130    --  Also used to determine whether an entity has a class-wide type, or a
 131    --  function call that dispatches on the result. Used to verify that all the
 132    --  dependent expressions in a conditional expression are equally tagged.
 133
 134    function Is_Null_Interface_Primitive (E : Entity_Id) return Boolean;
 135    --  Returns True if E is a null procedure that is an interface primitive
 136
 137    function Is_Overriding_Subprogram (E : Entity_Id) return Boolean;
 138    --  Returns True if E is an overriding subprogram
 139
 140    function Is_Tag_Indeterminate (N : Node_Id) return Boolean;
 141    --  Returns true if the expression N is tag-indeterminate. An expression
 142    --  is tag-indeterminate if it is a call that dispatches on result, and all
 143    --  controlling operands are also indeterminate. Such a function call may
 144    --  inherit a tag from an enclosing call.
 145
 146    procedure Override_Dispatching_Operation
 147      (Tagged_Type : Entity_Id;
 148       Prev_Op     : Entity_Id;
 149       New_Op      : Entity_Id;
 150       Is_Wrapper  : Boolean := False);
 151    --  Replace an implicit dispatching operation of the type Tagged_Type
 152    --  with an explicit one. Prev_Op is an inherited primitive operation which
 153    --  is overridden by the explicit declaration of New_Op. Is_Wrapper is
 154    --  True when New_Op is an internally generated wrapper of a controlling
 155    --  function. The caller checks that Tagged_Type is indeed a tagged type.
 156
 157    procedure Propagate_Tag (Control : Node_Id; Actual : Node_Id);
 158    --  If a function call is tag-indeterminate, its controlling argument is
 159    --  found in the context: either an enclosing call, or the left-hand side
 160    --  of the enclosing assignment statement. The tag must be propagated
 161    --  recursively to the tag-indeterminate actuals of the call.
 162    --  Need clear description of the parameters Control and Actual, especially
 163    --  since the comments above refer to actuals in the plural ???
 164
 165 end Sem_Disp;