https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66841
Bug ID: 66841
Summary: [concepts] bogus error "invalid reference to function
concept" when function concept is overloaded
Product: gcc
Version: c++-concepts
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: eric.niebler at gmail dot com
Target Milestone: ---
This is related to the discussion in
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66834. Because of the kind
mismatch error described in 66834, the straightforward implementation of
Constructible doesn't work, and the concept must be overloaded. But once it's
overloaded, uses of it cause of "invalid reference to function concept" error.
template <class T, class U>
concept bool Same =
__is_same_as(T, U);
template <class T, class U>
concept bool ExplicitlyConvertible() { return
Same<T, U> ||
requires(T&& t) {
static_cast<U>((T&&)t);
};
}
template <class T>
concept bool Constructible() { return
requires {
T{ };
};
}
template <class T, class U>
concept bool Constructible() { return
ExplicitlyConvertible<U, T>() ||
requires (U&& u) {
T{ (U&&)u };
};
}
template <class T, class U, class V, class...Args>
concept bool Constructible() { return
requires (U&& u, V&& v, Args&&...args) {
T{ (U&&)u, (V&&)v, (Args&&)args... };
};
}
template <class, class...>
constexpr bool core_constructible() { return false; }
template <class T, class...Args>
requires Constructible<T, Args...>() // ERROR HERE
constexpr bool core_constructible() { return false; }
Yields:
../cmcstl2/scratch/constructible.cpp:40:23: error: invalid reference to
function concept ‘template<class T, class U, class V, class ... Args> constexpr
bool Constructible()’
requires Constructible<T, Args...>()
^
