https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101782
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |rejects-valid
Assignee|redi at gcc dot gnu.org |unassigned at gcc dot
gnu.org
Status|ASSIGNED |NEW
Component|testsuite |c++
--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
This is a C++ FE bug.
This valid C++20 code:
template<typename T> concept foo = true;
template<typename T> requires foo<T>
[[nodiscard]]
int bar(T) { return 1; }
is rejected with the -fconcepts-ts flag (as both C++20 and C++17):
conc.C:4:1: error: two consecutive ‘[’ shall only introduce an attribute before
‘[’ token
4 | [[nodiscard]]
| ^
For C++17 mode, -fconcepts-ts defines __cpp_concepts=201507L so we could use
that to suppress the [[nodiscard]] attributes when the flag is given.
But we can't detect it for C++20 mode (which is when the testsuite errors
happen) because C++20 defines __cpp_concepts=201907L and -fconcepts-ts doesn't
change that. So I'm not sure what we can do, other than not apply the attribute
to constrained functions with a requires-clause.
