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) 1992-2021, 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
29with Types; use Types;
30package 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 subprogram Subp was defined for the incomplete view of
61   --  Typ, and the full type declaration is a derived type, then Subp may
62   --  override a subprogram inherited from the parent type. In that case,
63   --  the inherited subprogram will have been hidden by the current one at
64   --  the point of the type derivation, so it does not appear in the list
65   --  of primitive operations of the type, and this procedure inserts the
66   --  overriding subprogram in the the full type's list of primitives by
67   --  iterating over the list for the parent type. If instead Subp is a new
68   --  primitive, then it's simply appended to the primitive list.
69
70   procedure Check_Operation_From_Private_View (Subp, Old_Subp : Entity_Id);
71   --  No action performed if Subp is not an alias of a dispatching operation.
72   --  Add Old_Subp (if not already present) to the list of primitives of the
73   --  tagged type T of Subp if T is the full view of a private tagged type.
74   --  The Alias of Old_Subp is adjusted to point to the inherited procedure
75   --  of the full view because it is always this one which has to be called.
76
77   function Covered_Interface_Primitives (Prim : Entity_Id) return Elist_Id;
78   --  Returns all the interface primitives covered by Prim, when its
79   --  controlling type has progenitors.
80
81   function Covered_Interface_Op (Prim : Entity_Id) return Entity_Id;
82   --  Returns the interface primitive that Prim covers, when its controlling
83   --  type has progenitors.
84
85   function Find_Controlling_Arg (N : Node_Id) return Node_Id;
86   --  Returns the actual controlling argument if N is dynamically tagged, and
87   --  Empty if it is not dynamically tagged.
88
89   function Find_Dispatching_Type (Subp : Entity_Id) return Entity_Id;
90   --  Check whether the subprogram Subp is dispatching, and find the tagged
91   --  type of the controlling argument or arguments. Returns Empty if Subp
92   --  is not a dispatching operation.
93
94   function Find_Primitive_Covering_Interface
95     (Tagged_Type : Entity_Id;
96      Iface_Prim  : Entity_Id) return Entity_Id;
97   --  Search the homonym chain for the primitive of Tagged_Type that covers
98   --  Iface_Prim. The homonym chain traversal is required to catch primitives
99   --  associated with the partial view of private types when processing the
100   --  corresponding full view. If the entity is not found, then search for it
101   --  in the list of primitives of Tagged_Type. This latter search is needed
102   --  when the interface primitive is covered by a private subprogram. If the
103   --  primitive has not been covered yet then return the entity that will be
104   --  overridden when the primitive is covered (that is, return the entity
105   --  whose alias attribute references the interface primitive). If none of
106   --  these entities is found then return Empty.
107
108   type Subprogram_List is array (Nat range <>) of Entity_Id;
109   --  Type returned by Inherited_Subprograms function
110
111   generic
112      with function Find_DT (Subp : Entity_Id) return Entity_Id;
113   package Inheritance_Utilities is
114
115      --  This package provides generic versions of inheritance utilities
116      --  provided here. These versions are used in GNATprove backend to adapt
117      --  these utilities to GNATprove specific version of visibility of types.
118
119      function Inherited_Subprograms
120        (S               : Entity_Id;
121         No_Interfaces   : Boolean := False;
122         Interfaces_Only : Boolean := False;
123         One_Only        : Boolean := False) return Subprogram_List;
124
125      function Is_Overriding_Subprogram (E : Entity_Id) return Boolean;
126   end Inheritance_Utilities;
127
128   function Inherited_Subprograms
129     (S               : Entity_Id;
130      No_Interfaces   : Boolean := False;
131      Interfaces_Only : Boolean := False;
132      One_Only        : Boolean := False) return Subprogram_List;
133   --  Given the spec of a subprogram, this function gathers any inherited
134   --  subprograms from direct inheritance or via interfaces. The result is an
135   --  array of Entity_Ids of the specs of inherited subprograms. Returns a
136   --  null array if passed an Empty spec id. Note that the returned array
137   --  only includes subprograms and generic subprograms (and excludes any
138   --  other inherited entities, in particular enumeration literals). If
139   --  No_Interfaces is True, only return inherited subprograms not coming
140   --  from an interface. If Interfaces_Only is True, only return inherited
141   --  subprograms from interfaces. Otherwise, subprograms inherited directly
142   --  come first, starting with the closest ancestors, and are followed by
143   --  subprograms inherited from interfaces. At most one of No_Interfaces
144   --  and Interfaces_Only should be True.
145   --
146   --  If One_Only is set, the search is discontinued as soon as one entry
147   --  is found. In this case the resulting array is either null or contains
148   --  exactly one element.
149
150   function Is_Dynamically_Tagged (N : Node_Id) return Boolean;
151   --  Used to determine whether a call is dispatching, i.e. if it is
152   --  an expression of a class_Wide type, or a call to a function with
153   --  controlling result where at least one operand is dynamically tagged.
154   --  Also used to determine whether an entity has a class-wide type, or a
155   --  function call that dispatches on the result. Used to verify that all the
156   --  dependent expressions in a conditional expression are equally tagged.
157
158   function Is_Null_Interface_Primitive (E : Entity_Id) return Boolean;
159   --  Returns True if E is a null procedure that is an interface primitive
160
161   function Is_Overriding_Subprogram (E : Entity_Id) return Boolean;
162   --  Returns True if E is an overriding subprogram and False otherwise, in
163   --  particular for an inherited subprogram.
164
165   function Is_Tag_Indeterminate (N : Node_Id) return Boolean;
166   --  Returns true if the expression N is tag-indeterminate. An expression
167   --  is tag-indeterminate if it is a call that dispatches on result, and all
168   --  controlling operands are also indeterminate. Such a function call may
169   --  inherit a tag from an enclosing call.
170
171   procedure Override_Dispatching_Operation
172     (Tagged_Type : Entity_Id;
173      Prev_Op     : Entity_Id;
174      New_Op      : Entity_Id);
175   --  Replace an implicit dispatching operation of the type Tagged_Type
176   --  with an explicit one. Prev_Op is an inherited primitive operation which
177   --  is overridden by the explicit declaration of New_Op.
178
179   procedure Propagate_Tag (Control : Node_Id; Actual : Node_Id);
180   --  If a function call given by Actual is tag-indeterminate, its controlling
181   --  argument is found in the context, given by Control: either from an
182   --  operand of an enclosing call, or the left-hand side of the enclosing
183   --  assignment statement. The tag of Control will be propagated recursively
184   --  to Actual and to its tag-indeterminate operands, if any.
185
186end Sem_Disp;
187