| Message ID | 20210414191837.GW1179226@tucnak |
|---|---|
| State | New |
| Headers | show |
| Series | c++: Fix up C++23 [] <...> requires primary -> type {} parsing [PR99850] | expand |
On 4/14/21 3:18 PM, Jakub Jelinek wrote: > 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->... > Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux (with > GXX_TESTSUITE_STDS=98,11,14,17,20,2b ), ok for trunk? > > 2021-04-14 Jakub Jelinek <jakub@redhat.com> > > PR c++/99850 > * parser.c (cp_parser_constraint_requires_parens) <case CPP_DEREF>: > If lambda_p, return pce_ok for C++23 or later instead of > pce_maybe_postfix. > > * g++.dg/cpp23/lambda-specifiers2.C: New test. > > --- gcc/cp/parser.c.jj 2021-04-14 10:48:41.318103715 +0200 > +++ gcc/cp/parser.c 2021-04-14 14:52:03.220235527 +0200 > @@ -28526,7 +28526,19 @@ cp_parser_constraint_requires_parens (cp > 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. */ > + if (lambda_p && cxx_dialect >= cxx23) > + return pce_ok; I think let's not make this depend on cxx_dialect, since we allow this in C++20 mode as well with a pedwarn. OK with that change. > /* Unenclosed postfix operator. */ > return pce_maybe_postfix; > } > --- gcc/testsuite/g++.dg/cpp23/lambda-specifiers2.C.jj 2021-04-14 15:01:41.728714721 +0200 > +++ gcc/testsuite/g++.dg/cpp23/lambda-specifiers2.C 2021-04-14 15:01:32.959813534 +0200 > @@ -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 {}; > > Jakub >
--- gcc/cp/parser.c.jj 2021-04-14 10:48:41.318103715 +0200 +++ gcc/cp/parser.c 2021-04-14 14:52:03.220235527 +0200 @@ -28526,7 +28526,19 @@ cp_parser_constraint_requires_parens (cp 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. */ + if (lambda_p && cxx_dialect >= cxx23) + return pce_ok; /* Unenclosed postfix operator. */ return pce_maybe_postfix; } --- gcc/testsuite/g++.dg/cpp23/lambda-specifiers2.C.jj 2021-04-14 15:01:41.728714721 +0200 +++ gcc/testsuite/g++.dg/cpp23/lambda-specifiers2.C 2021-04-14 15:01:32.959813534 +0200 @@ -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 {};