[Bug c++/102721] out-of-line member function definition fails to allow lambda in unevaluated-context of new feature in c++20

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102721

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #1)
> Confirmed,
> Here is a better example of what is going wrong:
> template<class T>
> struct A
> {    
>     void foo(const T){}
> };
> 
> using t = decltype(+[]{})[3];
> using t1 = const decltype(+[]{})[3];
> 
> template<>
> void A<t>::foo(t1)
> {}
> 
> template<>
> void A<decltype(+[]{})[4]>::foo(const decltype(+[]{})[4])
> {}
> 
> The first template specialization is accepted but the second one is not.
Note it is not array related either:
template<>
void A<decltype(+[]{})>::foo(const decltype(+[]{}))
{}