Can friend function of a local class be defined in namespace scope?

A local class in C++ can have friend functions, but these functions cannot be defined neither inside the class [class.friend] p5:

A function may be defined in a friend declaration of a class if and only if the class is a non-local class and the function name is unqualified.

nor inside the enclosing function [dcl.fct.def.general] p2:

[...] A function shall be defined only in namespace or class scope. [...]

And what if a friend function of a local class is defined in the global scope as follows:

auto foo() {
    struct A;
    void bar(const A&);
    struct A { 
        friend void bar(const A&);
    };
    bar(A{});
    return A{};
}

using A = decltype(foo());
void bar(const A&) {}

int main() {
    foo();
}

Compilers diverge here:

• MSVC shows a compilation warning and fails during linking:

warning C5046: 'bar': Symbol involving type with internal linkage not defined
error LNK2019: unresolved external symbol "void __cdecl bar(struct `__cdecl foo(void)'::`2'::A const &)" (?bar@@YAXAEBUA@?1??foo@@YA@XZ@@Z) referenced in function "__cdecl foo(void)" (?foo@@YA@XZ)

• EDG shows compilation error:

error: function "bar", declared using a local type, must be defined in this translation unit

• GCC already accepts the program, but only with -fpermissive flag, printing the warning:

warning: 'void bar(const foo()::A&)', declared using local type 'const foo()::A', is used but never defined [-fpermissive]

• and only Clang permits this program just fine without single warning: online demo.

Which implementation is correct here?