https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67038
Bug ID: 67038
Summary: [c++-concepts] Viable function template despite
unsatisfied constraints
Product: gcc
Version: c++-concepts
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: Casey at Carter dot net
Target Milestone: ---
Created attachment 36077
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=36077&action=edit
Preprocessed test case
r226205 fails to compile this correct program:
#include <stl2/iterator.hpp>
template <stl2::WeakOutputIterator<int> I>
requires !stl2::WeakInputIterator<I>()
constexpr bool dispatch() { return false; }
template <stl2::WeakInputIterator I>
constexpr bool dispatch() { return true; }
template <stl2::WeakOutputIterator<int> I>
constexpr bool is_weak_out() { return true; }
template <stl2::WeakInputIterator I>
constexpr bool is_weak_in() { return true; }
int main() {
static_assert(is_weak_out<int*>());
static_assert(is_weak_in<int*>());
static_assert(dispatch<int*>());
}
with error:
~/concept-gcc/bin/g++ -std=gnu++1z -I ~/cmcstl2/include -I
~/cmcstl2/meta/include foo.cpp -c
foo.cpp: In function ‘int main()’:
foo.cpp:19:32: error: call of overloaded ‘dispatch()’ is ambiguous
static_assert(dispatch<int*>());
^
foo.cpp:5:16: note: candidate: constexpr bool dispatch() [with I = int*]
constexpr bool dispatch() { return false; }
^
foo.cpp:8:16: note: candidate: constexpr bool dispatch() [with I = int*]
constexpr bool dispatch() { return true; }
^
The compiler apparently considers both overloads of dispatch to be viable
despite that the first overload's constraint !stl2::WeakInputIterator<I>() is
clearly not satisfied when I is int*.
