------------------------------------------------------------------------------ -- -- -- GNAT COMPILER COMPONENTS -- -- -- -- S E M _ C A S E -- -- -- -- S p e c -- -- -- -- Copyright (C) 1996-2018, 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 mostly nothing. Can be used -- in the following generics for the parameters Process_Empty_Choice, -- or Process_Associated_Node. In the case of an empty range choice, -- routine emits a warning when Warn_On_Redundant_Constructs is enabled. 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;