1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
|
------------------------------------------------------------------------------
-- --
-- GNAT COMPILER COMPONENTS --
-- --
-- S E M _ C A S E --
-- --
-- S p e c --
-- --
-- Copyright (C) 1996-2013, Free Software Foundation, Inc. --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
-- ware Foundation; either version 3, or (at your option) any later ver- --
-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
-- for more details. You should have received a copy of the GNU General --
-- Public License distributed with GNAT; see file COPYING3. If not, go to --
-- http://www.gnu.org/licenses for a complete copy of the license. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
------------------------------------------------------------------------------
-- Package containing the routines to process a list of discrete choices.
-- Such lists can occur in two different constructs: case statements and
-- record variants. We have factorized what used to be two very similar
-- sets of routines in one place. These are not currently used for the
-- aggregate case, since issues with nested aggregates make that case
-- substantially different.
-- The following processing is required for such cases:
-- 1. Analysis of names of subtypes, constants, expressions appearing within
-- the choices. This must be done when the construct is encountered to get
-- proper visibility of names.
-- 2. Checking for semantic correctness of the choices. A lot of this could
-- be done at the time when the construct is encountered, but not all, since
-- in the case of variants, statically predicated subtypes won't be frozen
-- (and the choice sets known) till the enclosing record type is frozen. So
-- at least the check for no overlaps and covering the range must be delayed
-- till the freeze point in this case.
-- 3. Set the Others_Discrete_Choices list for an others choice. This is
-- used in various ways, e.g. to construct the disriminant checking function
-- for the case of a variant with an others choice.
-- 4. In the case of static predicates, we need to expand out choices that
-- correspond to the predicate for the back end. This expansion destroys
-- the list of choices, so it should be delayed to expansion time. We do
-- not want to mess up the -gnatct ASIS tree, which needs to be able to
-- Step 1 is performed by the generic procedure Analyze_Choices, which is
-- called when the variant record or case statement/expression is first
-- encountered.
-- Step 2 is performed by the generic procedure Check_Choices. We decide to
-- do all semantic checking in that step, since as noted above some of this
-- has to be deferred to the freeze point in any case for variants. For case
-- statements and expressions, this procedure can be called at the time the
-- case construct is encountered (after calling Analyze_Choices).
-- Step 3 is also performed by Check_Choices, since we need the static ranges
-- for predicated subtypes to accurately construct this.
-- Step 4 is performed by the procedure Expand_Static_Predicates_In_Choices.
-- For case statements, this call only happens during expansion, so the tree
-- generated for ASIS does not have this expansion. For the Variant case, the
-- expansion is done in the ASIS -gnatct case, but with a proper Rewrite call
-- on the N_Variant node, so ASIS can retrieve the original. The reason we do
-- the expansion unconditionally for variants is that other processing, for
-- example for aggregates, relies on having a complete list of choices.
-- Historical note: We used to perform all four of these functions at once in
-- a single procedure called Analyze_Choices. This routine was called at the
-- time the construct was first encountered. That seemed to work OK up to Ada
-- 2005, but the introduction of statically predicated subtypes with delayed
-- evaluation of the static ranges made this completely wrong, both because
-- the ASIS tree got destroyed by step 4, and steps 2 and 3 were too early
-- in the variant record case.
with Types; use Types;
package Sem_Case is
procedure No_OP (C : Node_Id);
-- The no-operation routine. Does absolutely nothing. Can be used
-- in the following generics for the parameters Process_Empty_Choice,
-- or Process_Associated_Node.
generic
with procedure Process_Associated_Node (A : Node_Id);
-- Associated with each case alternative or record variant A there is
-- a node or list of nodes that need additional processing. This routine
-- implements that processing.
package Generic_Analyze_Choices is
procedure Analyze_Choices
(Alternatives : List_Id;
Subtyp : Entity_Id);
-- From a case expression, case statement, or record variant, this
-- routine analyzes the corresponding list of discrete choices which
-- appear in each element of the list Alternatives (for the variant
-- part case, this is the variants, for a case expression or statement,
-- this is the Alternatives).
--
-- Subtyp is the subtype of the discrete choices. The type against which
-- the discrete choices must be resolved is its base type.
end Generic_Analyze_Choices;
generic
with procedure Process_Empty_Choice (Choice : Node_Id);
-- Processing to carry out for an empty Choice. Set to No_Op (declared
-- above) if no such processing is required.
with procedure Process_Non_Static_Choice (Choice : Node_Id);
-- Processing to carry out for a non static Choice (gives an error msg)
with procedure Process_Associated_Node (A : Node_Id);
-- Associated with each case alternative or record variant A there is
-- a node or list of nodes that need semantic processing. This routine
-- implements that processing.
package Generic_Check_Choices is
procedure Check_Choices
(N : Node_Id;
Alternatives : List_Id;
Subtyp : Entity_Id;
Others_Present : out Boolean);
-- From a case expression, case statement, or record variant N, this
-- routine analyzes the corresponding list of discrete choices which
-- appear in each element of the list Alternatives (for the variant
-- part case, this is the variants, for a case expression or statement,
-- this is the Alternatives).
--
-- Subtyp is the subtype of the discrete choices. The type against which
-- the discrete choices must be resolved is its base type.
--
-- Others_Present is set to True if an Others choice is present in the
-- list of choices, and in this case Others_Discrete_Choices is set in
-- the N_Others_Choice node.
--
-- If a Discrete_Choice list contains at least one instance of a subtype
-- with a static predicate, then the Has_SP_Choice flag is set true in
-- the parent node (N_Variant, N_Case_Expression/Statement_Alternative).
end Generic_Check_Choices;
end Sem_Case;
|
