On Mon, Aug 05, 2024 at 12:00:04PM -0400, Jason Merrill wrote:
> On 8/2/24 2:12 PM, Marek Polacek wrote:
> > Bootstrapped/regtested on x86_64-pc-linux-gnu. Comments?
> >
> > -- >8 --
> > This patch removes vestigial Concepts TS code as discussed in
> > <https://gcc.gnu.org/pipermail/gcc-patches/2024-July/657937.html>.
> >
> > In particular, it removes code related to function/variable concepts.
> > That includes variable_concept_p and function_concept_p, which then
> > cascades into removing DECL_DECLARED_CONCEPT_P etc. So I think we
> > no longer need to say "standard concept" since there are no non-standard
> > ones anymore.
> >
> > I've added two new errors saying that "variable/function concepts are
> > no longer supported".
> >
> > gcc/cp/ChangeLog:
> >
> > * constexpr.cc (cxx_eval_constant_expression): Don't call
> > unpack_concept_check. Add a concept_check_p assert. Remove
> > function_concept_p code.
> > * constraint.cc (check_constraint_atom): Remove function concepts code.
> > (unpack_concept_check): Remove.
> > (get_concept_check_template): Remove Concepts TS code.
> > (resolve_function_concept_overload): Remove.
> > (resolve_function_concept_check): Remove.
> > (resolve_concept_check): Remove Concepts TS code.
> > (get_returned_expression): Remove.
> > (get_variable_initializer): Remove.
> > (get_concept_definition): Remove Concepts TS code.
> > (normalize_concept_check): Likewise.
> > (build_function_check): Remove.
> > (build_variable_check): Remove.
> > (build_standard_check): Use concept_definition_p instead of
> > standard_concept_p.
> > (build_concept_check): Remove variable_concept_p/function_concept_p
> > code.
> > (build_concept_id): Simplify.
> > (build_type_constraint): Likewise.
> > (placeholder_extract_concept_and_args): Likewise.
> > (satisfy_nondeclaration_constraints): Likewise.
> > (check_function_concept): Remove.
> > (get_constraint_error_location): Remove Concepts TS code.
> > * cp-tree.h (DECL_DECLARED_CONCEPT_P): Remove.
> > (check_function_concept): Remove.
> > (unpack_concept_check): Remove.
> > (standard_concept_p): Remove.
> > (variable_concept_p): Remove.
> > (function_concept_p): Remove.
> > (concept_definition_p): Simplify.
> > (concept_check_p): Don't check for CALL_EXPR.
> > * decl.cc (check_concept_refinement): Remove.
> > (duplicate_decls): Remove check_concept_refinement code.
> > (is_concept_var): Remove.
> > (cp_finish_decl): Remove is_concept_var.
> > (check_concept_fn): Remove.
> > (grokfndecl): Give an error about function concepts not being supported
> > anymore. Remove unused code.
> > (grokvardecl): Give an error about variable concepts not being
> > supported anymore.
> > (finish_function): Remove DECL_DECLARED_CONCEPT_P code.
> > * decl2.cc (min_vis_expr_r): Use concept_definition_p instead of
> > standard_concept_p.
> > (maybe_instantiate_decl): Remove DECL_DECLARED_CONCEPT_P check.
> > (mark_used): Likewise.
> > * error.cc (dump_simple_decl): Use concept_definition_p instead of
> > standard_concept_p.
> > (dump_function_decl): Remove DECL_DECLARED_CONCEPT_P code.
> > (print_concept_check_info): Don't call unpack_concept_check.
> > * mangle.cc (write_type_constraint): Likewise.
> > * parser.cc (cp_parser_nested_name_specifier_opt): Remove
> > function_concept_p code. Only check concept_definition_p, not
> > variable_concept_p/standard_concept_p.
> > (add_debug_begin_stmt): Remove DECL_DECLARED_CONCEPT_P code.
> > (cp_parser_template_declaration_after_parameters): Remove a stale
> > comment.
> > * pt.cc (check_explicit_specialization): Remove
> > DECL_DECLARED_CONCEPT_P code.
> > (process_partial_specialization): Remove variable_concept_p code.
> > (lookup_template_variable): Likewise.
> > (tsubst_expr) <case CALL_EXPR>: Remove Concepts TS code and simplify.
> > (do_decl_instantiation): Remove DECL_DECLARED_CONCEPT_P code.
> > (instantiate_decl): Likewise.
> > (placeholder_type_constraint_dependent_p): Don't call
> > unpack_concept_check. Add a concept_check_p assert.
> > (convert_generic_types_to_packs): Likewise.
> > * semantics.cc (finish_call_expr): Remove Concepts TS code and simplify.
> >
> > gcc/testsuite/ChangeLog:
> >
> > * g++.dg/concepts/decl-diagnose.C: Adjust dg-error.
> > * g++.dg/concepts/fn-concept2.C: Likewise.
> > * g++.dg/concepts/pr71128.C: Likewise.
> > * g++.dg/concepts/var-concept6.C: Likewise.
> > * g++.dg/cpp2a/concepts.C: Likewise.
> > ---
> > gcc/cp/constexpr.cc | 13 +-
> > gcc/cp/constraint.cc | 346 +-----------------
> > gcc/cp/cp-tree.h | 71 +---
> > gcc/cp/decl.cc | 118 +-----
> > gcc/cp/decl2.cc | 4 +-
> > gcc/cp/error.cc | 10 +-
> > gcc/cp/mangle.cc | 4 +-
> > gcc/cp/parser.cc | 16 +-
> > gcc/cp/pt.cc | 60 +--
> > gcc/cp/semantics.cc | 17 +-
> > gcc/testsuite/g++.dg/concepts/decl-diagnose.C | 8 +-
> > gcc/testsuite/g++.dg/concepts/fn-concept2.C | 4 +-
> > gcc/testsuite/g++.dg/concepts/pr71128.C | 8 +-
> > gcc/testsuite/g++.dg/concepts/var-concept6.C | 2 +-
> > gcc/testsuite/g++.dg/cpp2a/concepts.C | 4 +-
> > 15 files changed, 65 insertions(+), 620 deletions(-)
> >
> > diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
> > index 8277b3b79ba..b079be1b3d5 100644
> > --- a/gcc/cp/constexpr.cc
> > +++ b/gcc/cp/constexpr.cc
> > @@ -8508,20 +8508,11 @@ cxx_eval_constant_expression (const constexpr_ctx
> > *ctx, tree t,
> > {
> > /* We can evaluate template-id that refers to a concept only if
> > the template arguments are non-dependent. */
> > - tree id = unpack_concept_check (t);
> > - tree tmpl = TREE_OPERAND (id, 0);
> > + gcc_assert (concept_check_p (t));
> > + tree tmpl = TREE_OPERAND (t, 0);
> > if (!concept_definition_p (tmpl))
> > internal_error ("unexpected template-id %qE", t);
>
> It seems unnecessary to have both the assert and the internal_error here;
> I'd drop the internal_error.
Done.
> > -/* The normal form of an atom depends on the expression. The normal
> > - form of a function call to a function concept is a check constraint
> > - for that concept. The normal form of a reference to a variable
> > - concept is a check constraint for that concept. Otherwise, the
> > - constraint is a predicate constraint. */
> > +/* The normal form of an atom is a predicate constraint. */
>
> I think the term "predicate constraint" is also obsolete; it's now "atomic
> constraint".
Aha. Done.
> > @@ -3952,8 +3950,8 @@ print_concept_check_info (diagnostic_context
> > *context, tree expr, tree map, tree
> > {
> > gcc_assert (concept_check_p (expr));
> > - tree id = unpack_concept_check (expr);
> > - tree tmpl = TREE_OPERAND (id, 0);
> > + tree tmpl = TREE_OPERAND (expr, 0);
> > + // ??? Can this go now that fn/var concepts have been removed?
>
> I would definitely expect so, did you try?
Yeah, it can go.
> I think we also want to adjust the 'concept bool' handling in
> cp_parser_decl_specifier_seq:
>
> > /* Warn for concept as a decl-specifier. We'll rewrite these
> > as
> > concept declarations later. */
> > {
> > cp_token *next = cp_lexer_peek_token (parser->lexer);
> > if (next->keyword == RID_BOOL)
> > => permerror (next->location, "the %<bool%> keyword is not "
> > "allowed in a C++20 concept definition");
> > else
> > error_at (token->location, "C++20 concept definition syntax "
> > "is %<concept <name> = <expr>%>");
> > }
>
> After the permerror let's skip the 'bool' token and continue trying to parse
> a concept declaration. I think that should allow us to remove more of the
> code in grokfndecl/grokvardecl?
If by skip you mean cp_lexer_consume_token, then that results in worse
diagnostics for e.g.
concept bool f3();
where it adds the extra "with no type" error:
t.C:3:9: error: the 'bool' keyword is not allowed in a C++20 concept definition
[-fpermissive]
3 | concept bool f3();
| ^~~~
t.C:3:14: error: ISO C++ forbids declaration of 'f3' with no type [-fpermissive]
3 | concept bool f3();
| ^~
t.C:3:14: error: function concepts are no longer supported
Besides, I don't see what more I could remove in grokfndecl/grokvardecl.
Except this tiny bit, now added:
@@ -11307,7 +11307,7 @@ grokvardecl (tree type,
// Handle explicit specializations and instantiations of variable templates.
if (orig_declarator)
decl = check_explicit_specialization (orig_declarator, decl,
- template_count, conceptp * 8);
+ template_count, 0);
return decl != error_mark_node ? decl : NULL_TREE;
}
Marek
