1------------------------------------------------------------------------------
2--                                                                          --
3--                         GNAT COMPILER COMPONENTS                         --
4--                                                                          --
5--                              S E M _ R E S                               --
6--                                                                          --
7--                                 S p e c                                  --
8--                                                                          --
9--          Copyright (C) 1992-2011, 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--  Resolution processing for all subexpression nodes. Note that the separate
27--  package Sem_Aggr contains the actual resolution routines for aggregates,
28--  which are separated off since aggregate processing is complex.
29
30with Types; use Types;
31
32package Sem_Res is
33
34   --  As described in Sem_Ch4, the type resolution proceeds in two phases.
35   --  The first phase is a bottom up pass that is achieved during the
36   --  recursive traversal performed by the Analyze procedures. This phase
37   --  determines unambiguous types, and collects sets of possible types
38   --  where the interpretation is potentially ambiguous.
39
40   --  On completing this bottom up pass, which corresponds to a call to
41   --  Analyze on a complete context, the Resolve routine is called which
42   --  performs a top down resolution with recursive calls to itself to
43   --  resolve operands.
44
45   --  Since in practice a lot of semantic analysis has to be postponed until
46   --  types are known (e.g. static folding, setting of suppress flags), the
47   --  Resolve routines also complete the semantic analysis, and call the
48   --  expander for possibly expansion of the completely type resolved node.
49
50   procedure Resolve (N : Node_Id; Typ : Entity_Id);
51   procedure Resolve (N : Node_Id; Typ : Entity_Id; Suppress : Check_Id);
52   --  Top level type-checking procedure, called in a complete context. The
53   --  construct N, which is a subexpression, has already been analyzed, and
54   --  is required to be of type Typ given the analysis of the context (which
55   --  uses the information gathered on the bottom up phase in Analyze). The
56   --  resolve routines do various other processing, e.g. static evaluation.
57   --  If a Suppress argument is present, then the resolution is done with the
58   --  specified check suppressed (can be All_Checks to suppress all checks).
59
60   procedure Resolve (N : Node_Id);
61   --  A version of Resolve where the type to be used for resolution is
62   --  taken from the Etype (N). This is commonly used in cases where the
63   --  context does not add anything and the first pass of analysis found
64   --  the correct expected type.
65
66   procedure Resolve_Discrete_Subtype_Indication
67     (N   : Node_Id;
68      Typ : Entity_Id);
69   --  Resolve subtype indications in choices (case statements and
70   --  aggregates) and in index constraints. Note that the resulting Etype
71   --  of the subtype indication node is set to the Etype of the contained
72   --  range (i.e. an Itype is not constructed for the actual subtype).
73
74   procedure Resolve_Entry (Entry_Name : Node_Id);
75   --  Find name of entry being called, and resolve prefix of name with its
76   --  own type. For now we assume that the prefix cannot be overloaded and
77   --  the name of the entry plays no role in the resolution.
78
79   procedure Analyze_And_Resolve (N : Node_Id);
80   procedure Analyze_And_Resolve (N : Node_Id; Typ : Entity_Id);
81   procedure Analyze_And_Resolve
82     (N        : Node_Id;
83      Typ      : Entity_Id;
84      Suppress : Check_Id);
85   procedure Analyze_And_Resolve
86     (N        : Node_Id;
87      Suppress : Check_Id);
88   --  These routines combine the effect of Analyze and Resolve. If a Suppress
89   --  argument is present, then the analysis is done with the specified check
90   --  suppressed (can be All_Checks to suppress all checks). These checks are
91   --  suppressed for both the analysis and resolution. If the type argument
92   --  is not present, then the Etype of the expression after the Analyze
93   --  call is used for the Resolve.
94
95   procedure Ambiguous_Character (C : Node_Id);
96   --  Give list of candidate interpretations when a character literal cannot
97   --  be resolved, for example in a (useless) comparison such as 'A' = 'B'.
98   --  In Ada 95 the literals in question can be of type Character or Wide_
99   --  Character. In Ada 2005 Wide_Wide_Character is also a candidate. The
100   --  node may also be overloaded with user-defined character types.
101
102   procedure Check_Parameterless_Call (N : Node_Id);
103   --  Several forms of names can denote calls to entities without para-
104   --  meters. The context determines whether the name denotes the entity
105   --  or a call to it. When it is a call, the node must be rebuilt
106   --  accordingly and reanalyzed to obtain possible interpretations.
107   --
108   --  The name may be that of an overloadable construct, or it can be an
109   --  explicit dereference of a prefix that denotes an access to subprogram.
110   --  In that case, we want to convert the name into a call only if the
111   --  context requires the return type of the subprogram.  Finally, a
112   --  parameterless protected subprogram appears as a selected component.
113   --
114   --  The parameter T is the Typ for the corresponding resolve call.
115
116   procedure Preanalyze_And_Resolve (N : Node_Id; T : Entity_Id);
117   --  Performs a pre-analysis of expression node N. During pre-analysis,
118   --  N is analyzed and then resolved against type T, but no expansion
119   --  is carried out for N or its children. For more info on pre-analysis
120   --  read the spec of Sem.
121
122   procedure Preanalyze_And_Resolve (N : Node_Id);
123   --  Same, but use type of node because context does not impose a single type
124
125   function Valid_Conversion
126     (N           : Node_Id;
127      Target      : Entity_Id;
128      Operand     : Node_Id;
129      Report_Errs : Boolean := True) return Boolean;
130   --  Verify legality rules given in 4.6 (8-23). Target is the target type
131   --  of the conversion, which may be an implicit conversion of an actual
132   --  parameter to an anonymous access type (in which case N denotes the
133   --  actual parameter and N = Operand). Returns a Boolean result indicating
134   --  whether the conversion is legal. Reports errors in the case of illegal
135   --  conversions, unless Report_Errs is False.
136
137private
138   procedure Resolve_Implicit_Type (N : Node_Id) renames Resolve;
139   pragma Inline (Resolve_Implicit_Type);
140   --  We use this renaming to make the application of Inline very explicit
141   --  to this version, since other versions of Resolve are not inlined.
142
143end Sem_Res;
144