https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90734
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |rejects-valid
Status|UNCONFIRMED |NEW
Last reconfirmed| |2019-10-29
CC| |redi at gcc dot gnu.org
See Also| |https://gcc.gnu.org/bugzill
| |a/show_bug.cgi?id=82507
Blocks| |67491
Ever confirmed|0 |1
--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Bug 82507 is fixed on trunk, but this isn't.
Refreshed for C++2a syntax (https://godbolt.org/z/M6D5k8):
template <bool B>
inline constexpr bool bool_ = B;
#if defined(WORKAROUND)
template<class T, class U>
concept Same_impl = __is_same_as(T, U);
#else
template <class T, class U>
concept Same_impl = bool_<__is_same_as(T, U)>;
#endif
template<class T, class U>
concept Same = Same_impl<T, U> && Same_impl<U, T>;
template<class T>
concept Foo = Same<const T&, const T&>;
template<class T>
concept Bar = Foo<T> && Same<T, T>;
template<class T>
struct S1 {
// overload set incorrectly is ambiguous (should resolve to second
overload)
static constexpr bool f() requires Foo<T> { return false; }
static constexpr bool f() requires Bar<T> { return true; }
};
template<class T>
struct S2 {
// overload set incorrectly is not ambiguous (resolves to third overload)
static constexpr bool f() requires Foo<T> { return false; }
static constexpr bool f() requires Bar<T> { return false; }
static constexpr bool f() requires bool_<true> && true { return true; }
};
template<class T>
concept can_f = requires { T::f(); };
int main() {
static_assert(Foo<int>);
static_assert(Bar<int>);
static_assert(can_f<S1<int>>); // Fails
static_assert(S1<int>::f()); // Bogus error
static_assert(!can_f<S2<int>>); // Fails
#ifndef WORKAROUND
static_assert(S2<int>::f()); // Bogus non-error
#endif
}
<source>: In function 'int main()':
<source>:48:30: error: call of overloaded 'f()' is ambiguous
48 | static_assert(S2<int>::f()); // Bogus non-error
| ^
<source>:31:27: note: candidate: 'static constexpr bool S2<T>::f() requires
Foo<T> [with T = int]'
31 | static constexpr bool f() requires Foo<T> { return false; }
| ^
<source>:32:27: note: candidate: 'static constexpr bool S2<T>::f() requires
Bar<T> [with T = int]'
32 | static constexpr bool f() requires Bar<T> { return false; }
| ^
<source>:33:27: note: candidate: 'static constexpr bool S2<T>::f() requires
(bool_<true>) && true [with T = int]'
33 | static constexpr bool f() requires bool_<true> && true { return
true; }
| ^
Compiler returned: 1
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67491
[Bug 67491] [meta-bug] concepts issues
