1------------------------------------------------------------------------------ 2-- -- 3-- GNAT COMPILER COMPONENTS -- 4-- -- 5-- S E M _ C A S E -- 6-- -- 7-- S p e c -- 8-- -- 9-- Copyright (C) 1996-2013, 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-- Package containing the routines to process a list of discrete choices. 27-- Such lists can occur in two different constructs: case statements and 28-- record variants. We have factorized what used to be two very similar 29-- sets of routines in one place. These are not currently used for the 30-- aggregate case, since issues with nested aggregates make that case 31-- substantially different. 32 33-- The following processing is required for such cases: 34 35-- 1. Analysis of names of subtypes, constants, expressions appearing within 36-- the choices. This must be done when the construct is encountered to get 37-- proper visibility of names. 38 39-- 2. Checking for semantic correctness of the choices. A lot of this could 40-- be done at the time when the construct is encountered, but not all, since 41-- in the case of variants, statically predicated subtypes won't be frozen 42-- (and the choice sets known) till the enclosing record type is frozen. So 43-- at least the check for no overlaps and covering the range must be delayed 44-- till the freeze point in this case. 45 46-- 3. Set the Others_Discrete_Choices list for an others choice. This is 47-- used in various ways, e.g. to construct the disriminant checking function 48-- for the case of a variant with an others choice. 49 50-- 4. In the case of static predicates, we need to expand out choices that 51-- correspond to the predicate for the back end. This expansion destroys 52-- the list of choices, so it should be delayed to expansion time. We do 53-- not want to mess up the -gnatct ASIS tree, which needs to be able to 54 55-- Step 1 is performed by the generic procedure Analyze_Choices, which is 56-- called when the variant record or case statement/expression is first 57-- encountered. 58 59-- Step 2 is performed by the generic procedure Check_Choices. We decide to 60-- do all semantic checking in that step, since as noted above some of this 61-- has to be deferred to the freeze point in any case for variants. For case 62-- statements and expressions, this procedure can be called at the time the 63-- case construct is encountered (after calling Analyze_Choices). 64 65-- Step 3 is also performed by Check_Choices, since we need the static ranges 66-- for predicated subtypes to accurately construct this. 67 68-- Step 4 is performed by the procedure Expand_Static_Predicates_In_Choices. 69-- For case statements, this call only happens during expansion, so the tree 70-- generated for ASIS does not have this expansion. For the Variant case, the 71-- expansion is done in the ASIS -gnatct case, but with a proper Rewrite call 72-- on the N_Variant node, so ASIS can retrieve the original. The reason we do 73-- the expansion unconditionally for variants is that other processing, for 74-- example for aggregates, relies on having a complete list of choices. 75 76-- Historical note: We used to perform all four of these functions at once in 77-- a single procedure called Analyze_Choices. This routine was called at the 78-- time the construct was first encountered. That seemed to work OK up to Ada 79-- 2005, but the introduction of statically predicated subtypes with delayed 80-- evaluation of the static ranges made this completely wrong, both because 81-- the ASIS tree got destroyed by step 4, and steps 2 and 3 were too early 82-- in the variant record case. 83 84with Types; use Types; 85 86package Sem_Case is 87 88 procedure No_OP (C : Node_Id); 89 -- The no-operation routine. Does absolutely nothing. Can be used 90 -- in the following generics for the parameters Process_Empty_Choice, 91 -- or Process_Associated_Node. 92 93 generic 94 with procedure Process_Associated_Node (A : Node_Id); 95 -- Associated with each case alternative or record variant A there is 96 -- a node or list of nodes that need additional processing. This routine 97 -- implements that processing. 98 99 package Generic_Analyze_Choices is 100 101 procedure Analyze_Choices 102 (Alternatives : List_Id; 103 Subtyp : Entity_Id); 104 -- From a case expression, case statement, or record variant, this 105 -- routine analyzes the corresponding list of discrete choices which 106 -- appear in each element of the list Alternatives (for the variant 107 -- part case, this is the variants, for a case expression or statement, 108 -- this is the Alternatives). 109 -- 110 -- Subtyp is the subtype of the discrete choices. The type against which 111 -- the discrete choices must be resolved is its base type. 112 113 end Generic_Analyze_Choices; 114 115 generic 116 with procedure Process_Empty_Choice (Choice : Node_Id); 117 -- Processing to carry out for an empty Choice. Set to No_Op (declared 118 -- above) if no such processing is required. 119 120 with procedure Process_Non_Static_Choice (Choice : Node_Id); 121 -- Processing to carry out for a non static Choice (gives an error msg) 122 123 with procedure Process_Associated_Node (A : Node_Id); 124 -- Associated with each case alternative or record variant A there is 125 -- a node or list of nodes that need semantic processing. This routine 126 -- implements that processing. 127 128 package Generic_Check_Choices is 129 130 procedure Check_Choices 131 (N : Node_Id; 132 Alternatives : List_Id; 133 Subtyp : Entity_Id; 134 Others_Present : out Boolean); 135 -- From a case expression, case statement, or record variant N, this 136 -- routine analyzes the corresponding list of discrete choices which 137 -- appear in each element of the list Alternatives (for the variant 138 -- part case, this is the variants, for a case expression or statement, 139 -- this is the Alternatives). 140 -- 141 -- Subtyp is the subtype of the discrete choices. The type against which 142 -- the discrete choices must be resolved is its base type. 143 -- 144 -- Others_Present is set to True if an Others choice is present in the 145 -- list of choices, and in this case Others_Discrete_Choices is set in 146 -- the N_Others_Choice node. 147 -- 148 -- If a Discrete_Choice list contains at least one instance of a subtype 149 -- with a static predicate, then the Has_SP_Choice flag is set true in 150 -- the parent node (N_Variant, N_Case_Expression/Statement_Alternative). 151 152 end Generic_Check_Choices; 153end Sem_Case; 154