https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96821
Daniil Dudkin <dudkindaniilm2 at yandex dot ru> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|INVALID |---
Status|RESOLVED |REOPENED
--- Comment #5 from Daniil Dudkin <dudkindaniilm2 at yandex dot ru> ---
(In reply to Patrick Palka from comment #4)
> GCC's behaviour is correct, I think. Since the concept constant_expression
> doesn't use its template parameter, the normal form of foo's associated
> constraint is just 'true (with an empty parameter mapping)', so the
> satisfaction value of with_value_constant<T> for any T is trivially true and
> independent of T.
No, I don't think that GCC behaviour is correct.
http://eel.is/c++draft/temp.constr#atomic-3
> If substitution results in an invalid type or expression, the constraint is
> not satisfied.
The substitution with_value_constant<WithNotConstant::value> results in an
invalid expression because WithNotConstant::value is not a constant expression,
so it cannot be used as a non-type template argument. That means
with_value_constant<WithNotConstant::value> should be false regardless how
with_value_constant is defined.
