| ------------------------------------------------------------------------------ |
| -- -- |
| -- GNAT COMPILER COMPONENTS -- |
| -- -- |
| -- S E M _ C A S E -- |
| -- -- |
| -- S p e c -- |
| -- -- |
| -- Copyright (C) 1996-2022, 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 discriminant 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. |
| |
| -- 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. 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; |
| |
| function Is_Case_Choice_Pattern (Expr : Node_Id) return Boolean; |
| -- GNAT language extensions allow casing on a non-discrete value, with |
| -- patterns as case choices. Return True iff Expr is such a pattern, or |
| -- a subexpression thereof. |
| |
| end Sem_Case; |
