1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
9 -- Copyright (C) 1992-2011, Free Software Foundation, Inc. --
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. --
21 -- GNAT was originally developed by the GNAT team at New York University. --
22 -- Extensive contributions were provided by Ada Core Technologies Inc. --
24 ------------------------------------------------------------------------------
26 -- This unit contains the routines used to handle type determination,
27 -- including the routine used to support overload resolution.
29 with Types; use Types;
33 ---------------------------------------------
34 -- Data Structures for Overload Resolution --
35 ---------------------------------------------
37 -- To determine the unique meaning of an identifier, overload resolution
38 -- may have to be performed if the visibility rules alone identify more
39 -- than one possible entity as the denotation of a given identifier. When
40 -- the visibility rules find such a potential ambiguity, the set of
41 -- possible interpretations must be attached to the identifier, and
42 -- overload resolution must be performed over the innermost enclosing
43 -- complete context. At the end of the resolution, either a single
44 -- interpretation is found for all identifiers in the context, or else a
45 -- type error (invalid type or ambiguous reference) must be signalled.
47 -- The set of interpretations of a given name is stored in a data structure
48 -- that is separate from the syntax tree, because it corresponds to
49 -- transient information. The interpretations themselves are stored in
50 -- table All_Interp. A mapping from tree nodes to sets of interpretations
51 -- called Interp_Map, is maintained by the overload resolution routines.
52 -- Both these structures are initialized at the beginning of every complete
55 -- Corresponding to the set of interpretations for a given overloadable
56 -- identifier, there is a set of possible types corresponding to the types
57 -- that the overloaded call may return. We keep a 1-to-1 correspondence
58 -- between interpretations and types: for user-defined subprograms the type
59 -- is the declared return type. For operators, the type is determined by
60 -- the type of the arguments. If the arguments themselves are overloaded,
61 -- we enter the operator name in the names table for each possible result
62 -- type. In most cases, arguments are not overloaded and only one
63 -- interpretation is present anyway.
68 Abstract_Op : Entity_Id := Empty;
71 -- Entity Abstract_Op is set to the abstract operation which potentially
72 -- disables the interpretation in Ada 2005 mode.
74 No_Interp : constant Interp := (Empty, Empty, Empty);
76 type Interp_Index is new Int;
82 -- A common error is the use of an operator in infix notation on arguments
83 -- of a type that is not directly visible. Rather than diagnosing a type
84 -- mismatch, it is better to indicate that the type can be made use-visible
85 -- with the appropriate use clause. The global variable Candidate_Type is
86 -- set in Add_One_Interp whenever an interpretation might be legal for an
87 -- operator if the type were directly visible. This variable is used in
88 -- sem_ch4 when no legal interpretation is found.
90 Candidate_Type : Entity_Id;
96 procedure Init_Interp_Tables;
97 -- Invoked by gnatf when processing multiple files
99 procedure Collect_Interps (N : Node_Id);
100 -- Invoked when the name N has more than one visible interpretation. This
101 -- is the high level routine which accumulates the possible interpretations
102 -- of the node. The first meaning and type of N have already been stored
103 -- in N. If the name is an expanded name, the homonyms are only those that
104 -- belong to the same scope.
106 function Is_Invisible_Operator (N : Node_Id; T : Entity_Id) return Boolean;
107 -- Check whether a predefined operation with universal operands appears in
108 -- a context in which the operators of the expected type are not visible.
110 procedure List_Interps (Nam : Node_Id; Err : Node_Id);
111 -- List candidate interpretations of an overloaded name. Used for various
114 procedure Add_One_Interp
118 Opnd_Type : Entity_Id := Empty);
119 -- Add (E, T) to the list of interpretations of the node being resolved.
120 -- For calls and operators, i.e. for nodes that have a name field, E is an
121 -- overloadable entity, and T is its type. For constructs such as indexed
122 -- expressions, the caller sets E equal to T, because the overloading comes
123 -- from other fields, and the node itself has no name to resolve. Hidden
124 -- denotes whether an interpretation has been disabled by an abstract
125 -- operator. Add_One_Interp includes semantic processing to deal with
126 -- adding entries that hide one another etc.
128 -- For operators, the legality of the operation depends on the visibility
129 -- of T and its scope. If the operator is an equality or comparison, T is
130 -- always Boolean, and we use Opnd_Type, which is a candidate type for one
131 -- of the operands of N, to check visibility.
133 procedure End_Interp_List;
134 -- End the list of interpretations of current node
136 procedure Get_First_Interp
138 I : out Interp_Index;
140 -- Initialize iteration over set of interpretations for Node N. The first
141 -- interpretation is placed in It, and I is initialized for subsequent
142 -- calls to Get_Next_Interp.
144 procedure Get_Next_Interp (I : in out Interp_Index; It : out Interp);
145 -- Iteration step over set of interpretations. Using the value in I, which
146 -- was set by a previous call to Get_First_Interp or Get_Next_Interp, the
147 -- next interpretation is placed in It, and I is updated for the next call.
148 -- The end of the list of interpretations is signalled by It.Nam = Empty.
150 procedure Remove_Interp (I : in out Interp_Index);
151 -- Remove an interpretation that is hidden by another, or that does not
152 -- match the context. The value of I on input was set by a call to either
153 -- Get_First_Interp or Get_Next_Interp and references the interpretation
154 -- to be removed. The only allowed use of the exit value of I is as input
155 -- to a subsequent call to Get_Next_Interp, which yields the interpretation
156 -- following the removed one.
158 procedure Save_Interps (Old_N : Node_Id; New_N : Node_Id);
159 -- If an overloaded node is rewritten during semantic analysis, its
160 -- possible interpretations must be linked to the copy. This procedure
161 -- transfers the overload information from Old_N, the old node, to
162 -- New_N, its new copy. It has no effect in the non-overloaded case.
164 function Covers (T1, T2 : Entity_Id) return Boolean;
165 -- This is the basic type compatibility routine. T1 is the expected type,
166 -- imposed by context, and T2 is the actual type. The processing reflects
167 -- both the definition of type coverage and the rules for operand matching;
168 -- that is, this does not exactly match the RM definition of "covers".
170 function Disambiguate
172 I1, I2 : Interp_Index;
173 Typ : Entity_Id) return Interp;
174 -- If more than one interpretation of a name in a call is legal, apply
175 -- preference rules (universal types first) and operator visibility in
176 -- order to remove ambiguity. I1 and I2 are the first two interpretations
177 -- that are compatible with the context, but there may be others.
179 function Entity_Matches_Spec (Old_S, New_S : Entity_Id) return Boolean;
180 -- To resolve subprogram renaming and default formal subprograms in generic
181 -- definitions. Old_S is a possible interpretation of the entity being
182 -- renamed, New_S has an explicit signature. If Old_S is a subprogram, as
183 -- opposed to an operator, type and mode conformance are required.
185 function Find_Unique_Type (L : Node_Id; R : Node_Id) return Entity_Id;
186 -- Used in second pass of resolution, for equality and comparison nodes. L
187 -- is the left operand, whose type is known to be correct, and R is the
188 -- right operand, which has one interpretation compatible with that of L.
189 -- Return the type intersection of the two.
191 function Has_Compatible_Type (N : Node_Id; Typ : Entity_Id) return Boolean;
192 -- Verify that some interpretation of the node N has a type compatible with
193 -- Typ. If N is not overloaded, then its unique type must be compatible
194 -- with Typ. Otherwise iterate through the interpretations of N looking for
197 function Hides_Op (F : Entity_Id; Op : Entity_Id) return Boolean;
198 -- A user-defined function hides a predefined operator if it is matches the
199 -- signature of the operator, and is declared in an open scope, or in the
200 -- scope of the result type.
202 function Interface_Present_In_Ancestor
204 Iface : Entity_Id) return Boolean;
205 -- Ada 2005 (AI-251): Typ must be a tagged record type/subtype and Iface
206 -- must be an abstract interface type (or a class-wide abstract interface).
207 -- This function is used to check if Typ or some ancestor of Typ implements
208 -- Iface (returning True only if so).
210 function Intersect_Types (L, R : Node_Id) return Entity_Id;
211 -- Find the common interpretation to two analyzed nodes. If one of the
212 -- interpretations is universal, choose the non-universal one. If either
213 -- node is overloaded, find single common interpretation.
215 function In_Generic_Actual (Exp : Node_Id) return Boolean;
216 -- Determine whether the expression is part of a generic actual. At the
217 -- time the actual is resolved the scope is already that of the instance,
218 -- but conceptually the resolution of the actual takes place in the
219 -- enclosing context and no special disambiguation rules should be applied.
224 Use_Full_View : Boolean := False) return Boolean;
225 -- T1 is a tagged type (not class-wide). Verify that it is one of the
226 -- ancestors of type T2 (which may or not be class-wide). If Use_Full_View
227 -- is True then the full-view of private parents is used when climbing
228 -- through the parents of T2.
230 -- Note: For analysis purposes the flag Use_Full_View must be set to False
231 -- (otherwise we break the privacy contract since this routine returns true
232 -- for hidden ancestors of private types). For expansion purposes this flag
233 -- is generally set to True since the expander must know with precision the
234 -- ancestors of a tagged type. For example, if a private type derives from
235 -- an interface type then the interface may not be an ancestor of its full
236 -- view since the full-view is only required to cover the interface (RM 7.3
237 -- (7.3/2))) and this knowledge affects construction of dispatch tables.
239 function Is_Progenitor
241 Typ : Entity_Id) return Boolean;
242 -- Determine whether the interface Iface is implemented by Typ. It requires
243 -- traversing the list of abstract interfaces of the type, as well as that
244 -- of the ancestor types. The predicate is used to determine when a formal
245 -- in the signature of an inherited operation must carry the derived type.
247 function Is_Subtype_Of (T1 : Entity_Id; T2 : Entity_Id) return Boolean;
248 -- Checks whether T1 is any subtype of T2 directly or indirectly. Applies
249 -- only to scalar subtypes???
251 function Operator_Matches_Spec (Op, New_S : Entity_Id) return Boolean;
252 -- Used to resolve subprograms renaming operators, and calls to user
253 -- defined operators. Determines whether a given operator Op, matches
254 -- a specification, New_S.
256 procedure Set_Abstract_Op (I : Interp_Index; V : Entity_Id);
257 -- Set the abstract operation field of an interpretation
259 function Valid_Comparison_Arg (T : Entity_Id) return Boolean;
260 -- A valid argument to an ordering operator must be a discrete type, a
261 -- real type, or a one dimensional array with a discrete component type.
263 function Valid_Boolean_Arg (T : Entity_Id) return Boolean;
264 -- A valid argument of a boolean operator is either some boolean type, or a
265 -- one-dimensional array of boolean type.
267 procedure Write_Interp (It : Interp);
268 -- Debugging procedure to display an Interp
270 procedure Write_Interp_Ref (Map_Ptr : Int);
271 -- Debugging procedure to display entry in Interp_Map. Would not be needed
272 -- if it were possible to debug instantiations of Table.
274 procedure Write_Overloads (N : Node_Id);
275 -- Debugging procedure to output info on possibly overloaded entities for
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