https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84140
Casey Carter <Casey at Carter dot net> changed:
What |Removed |Added
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CC| |Casey at Carter dot net
--- Comment #1 from Casey Carter <Casey at Carter dot net> ---
Another repro:
template<class, class> constexpr bool is_same_v = false;
template<class T> constexpr bool is_same_v<T, T> = true;
template<class T, class U>
concept bool Same = is_same_v<T, U>;
template<class T, class U>
concept bool Diff = requires(T& t, U& u) { u - t; };
template<class I, class S>
int distance(I, S) { return 0; }
template<class I, Diff<I> S>
int distance(I first, S last) {
return last - first;
}
template<class T>
struct I {
template<class U>
requires Same<T, U>
friend int operator-(I const&, I<U> const&) {
static_assert(Same<T, U>);
return 42;
}
};
int main() {
return distance(I<int>{}, I<void>{});
}
Compiling fails when the static_assert in the body of the friend function
template - which simply asserts that the constraint on the template is
satisfied - fires. It would appear the constraints aren't being checked for
satisfaction at all on hidden friends found during overload resolution.
FWIW, this makes it impossible to implement the Ranges proposal as specified.
