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) 1996-2020, 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. 53 54-- Step 1 is performed by the generic procedure Analyze_Choices, which is 55-- called when the variant record or case statement/expression is first 56-- encountered. 57 58-- Step 2 is performed by the generic procedure Check_Choices. We decide to 59-- do all semantic checking in that step, since as noted above some of this 60-- has to be deferred to the freeze point in any case for variants. For case 61-- statements and expressions, this procedure can be called at the time the 62-- case construct is encountered (after calling Analyze_Choices). 63 64-- Step 3 is also performed by Check_Choices, since we need the static ranges 65-- for predicated subtypes to accurately construct this. 66 67-- Step 4 is performed by the procedure Expand_Static_Predicates_In_Choices. 68-- For case statements, this call only happens during expansion. The reason 69-- we do the expansion unconditionally for variants is that other processing, 70-- for example for aggregates, relies on having a complete list of choices. 71 72-- Historical note: We used to perform all four of these functions at once in 73-- a single procedure called Analyze_Choices. This routine was called at the 74-- time the construct was first encountered. That seemed to work OK up to Ada 75-- 2005, but the introduction of statically predicated subtypes with delayed 76-- evaluation of the static ranges made this completely wrong, both because 77-- the ASIS tree got destroyed by step 4, and steps 2 and 3 were too early 78-- in the variant record case. 79 80with Types; use Types; 81 82package Sem_Case is 83 84 procedure No_OP (C : Node_Id); 85 -- The no-operation routine. Does mostly nothing. Can be used 86 -- in the following generics for the parameters Process_Empty_Choice, 87 -- or Process_Associated_Node. In the case of an empty range choice, 88 -- routine emits a warning when Warn_On_Redundant_Constructs is enabled. 89 90 generic 91 with procedure Process_Associated_Node (A : Node_Id); 92 -- Associated with each case alternative or record variant A there is 93 -- a node or list of nodes that need additional processing. This routine 94 -- implements that processing. 95 96 package Generic_Analyze_Choices is 97 98 procedure Analyze_Choices 99 (Alternatives : List_Id; 100 Subtyp : Entity_Id); 101 -- From a case expression, case statement, or record variant, this 102 -- routine analyzes the corresponding list of discrete choices which 103 -- appear in each element of the list Alternatives (for the variant 104 -- part case, this is the variants, for a case expression or statement, 105 -- this is the Alternatives). 106 -- 107 -- Subtyp is the subtype of the discrete choices. The type against which 108 -- the discrete choices must be resolved is its base type. 109 110 end Generic_Analyze_Choices; 111 112 generic 113 with procedure Process_Empty_Choice (Choice : Node_Id); 114 -- Processing to carry out for an empty Choice. Set to No_Op (declared 115 -- above) if no such processing is required. 116 117 with procedure Process_Non_Static_Choice (Choice : Node_Id); 118 -- Processing to carry out for a non static Choice (gives an error msg) 119 120 with procedure Process_Associated_Node (A : Node_Id); 121 -- Associated with each case alternative or record variant A there is 122 -- a node or list of nodes that need semantic processing. This routine 123 -- implements that processing. 124 125 package Generic_Check_Choices is 126 127 procedure Check_Choices 128 (N : Node_Id; 129 Alternatives : List_Id; 130 Subtyp : Entity_Id; 131 Others_Present : out Boolean); 132 -- From a case expression, case statement, or record variant N, this 133 -- routine analyzes the corresponding list of discrete choices which 134 -- appear in each element of the list Alternatives (for the variant 135 -- part case, this is the variants, for a case expression or statement, 136 -- this is the Alternatives). 137 -- 138 -- Subtyp is the subtype of the discrete choices. The type against which 139 -- the discrete choices must be resolved is its base type. 140 -- 141 -- Others_Present is set to True if an Others choice is present in the 142 -- list of choices, and in this case Others_Discrete_Choices is set in 143 -- the N_Others_Choice node. 144 -- 145 -- If a Discrete_Choice list contains at least one instance of a subtype 146 -- with a static predicate, then the Has_SP_Choice flag is set true in 147 -- the parent node (N_Variant, N_Case_Expression/Statement_Alternative). 148 149 end Generic_Check_Choices; 150end Sem_Case; 151