Out-of-class definition of member of constrained specialization

[jwakely]

template<class T> concept C1 = true;
template<class T> concept C2 = C1<T> && true;

template<C1> struct X { };
template<C2 T> struct X<T> { struct Y; };

template<C2 T> struct X<T>::Y { }; // (1)

Clang rejects (1) saying:

<source>:7:10: error: type constraint differs in template redeclaration
template<C2 T> struct X<T>::Y { };
         ^
<source>:4:10: note: previous template declaration is here
template<C1 T> struct X { };
         ^
<source>:7:29: error: no struct named 'Y' in 'X<T>'
template<C2 T> struct X<T>::Y { };
                      ~~~~~~^

This is wrong, Y is a member of the partial specialization on line 5, not the primary template on line 4.

[llvmbot]

@llvm/issue-subscribers-clang-frontend

[royjacobson]

Looks like duplicate of #50208.

[llvmbot]

@llvm/issue-subscribers-c-20

[jwakely]

#50208 is now closed as a dup of #49620

[usx95]

Duplicate of #49620