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From: Jakub Jelinek <jakub@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc r11-8210] c++: Fix up C++23 [] <...> requires primary -> type {} parsing [PR99850] Date: Fri, 16 Apr 2021 07:35:14 +0000 (GMT) [thread overview] Message-ID: <20210416073514.C4B02388E83A@sourceware.org> (raw) https://gcc.gnu.org/g:784de5292c34e287c848b382b431599b818ea76e commit r11-8210-g784de5292c34e287c848b382b431599b818ea76e Author: Jakub Jelinek <jakub@redhat.com> Date: Fri Apr 16 09:34:26 2021 +0200 c++: Fix up C++23 [] <...> requires primary -> type {} parsing [PR99850] The requires clause parsing has code to suggest users wrapping non-primary expressions in (), so if it e.g. parses a primary expression and sees it is followed by ++, --, ., ( or -> among other things it will try to reparse it as assignment expression or what and if that works suggests wrapping it inside of parens. When it is requires-clause that is after <typename T> etc. it already has an exception from that as ( can occur in valid C++20 expression there - starting the parameters of the lambda. In C++23 another case can occur, as the parameters with the ()s can be omitted, requires C can be followed immediately by -> which starts a trailing return type. Even in that case, we don't want to parse that as C->... 2021-04-16 Jakub Jelinek <jakub@redhat.com> PR c++/99850 * parser.c (cp_parser_constraint_requires_parens) <case CPP_DEREF>: If lambda_p, return pce_ok instead of pce_maybe_postfix. * g++.dg/cpp23/lambda-specifiers2.C: New test. Diff: --- gcc/cp/parser.c | 13 +++++++++++++ gcc/testsuite/g++.dg/cpp23/lambda-specifiers2.C | 7 +++++++ 2 files changed, 20 insertions(+) diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c index 940751b5f05..dfc9b8251a7 100644 --- a/gcc/cp/parser.c +++ b/gcc/cp/parser.c @@ -28530,7 +28530,20 @@ cp_parser_constraint_requires_parens (cp_parser *parser, bool lambda_p) case CPP_PLUS_PLUS: case CPP_MINUS_MINUS: case CPP_DOT: + /* Unenclosed postfix operator. */ + return pce_maybe_postfix; + case CPP_DEREF: + /* A primary constraint that precedes the lambda-declarator of a + lambda expression is followed by trailing return type. + + []<typename T> requires C -> void {} + + Don't try to re-parse this as a postfix expression in + C++23 and later. In C++20 ( needs to come in between but we + allow it to be omitted with pedwarn. */ + if (lambda_p) + return pce_ok; /* Unenclosed postfix operator. */ return pce_maybe_postfix; } diff --git a/gcc/testsuite/g++.dg/cpp23/lambda-specifiers2.C b/gcc/testsuite/g++.dg/cpp23/lambda-specifiers2.C new file mode 100644 index 00000000000..0cc69bebc64 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp23/lambda-specifiers2.C @@ -0,0 +1,7 @@ +// PR c++/99850 +// P1102R2 - Down with ()! +// { dg-do compile { target c++23 } } + +auto l = []<auto> requires true -> void {}; +template <typename...> concept C = true; +auto m = []<typename... Ts> requires (C<Ts> && ...) -> void {};
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