Out-of-class member template definition rejected when a non-type template parameter type uses a member typedef

[Saldivarcher]

Issue Summary

An out-of-class definition of a member template is rejected as incompatible
with its declaration when a non-type template parameter has a member typedef
of the enclosing class template as its type. In the class, the type is written
as V. Outside the class, the type must be written as typename S<T>::V.
These name the same type, so the two template parameter lists are equivalent
([temp.over.link]).

GCC 15, Clang 21 and MSVC v19.latest accept the program. EDG 6.5 and trunk
reject it in default mode. EDG also rejects it with --microsoft. EDG accepts
it with --gnu_version and --clang_version.

Reproducing Source Code

template <typename T>
struct S {
  typedef T V;
  template <V N> void f ();
};
template <typename T>
template <typename S<T>::V N>
void S<T>::f () {}

template void S<int>::f<1> ();

https://godbolt.org/z/63eG8h1fb

Command-line Options

cpfe --c++17 --no_wrap_diagnostics --no_code_gen nttp.cc

Type of Issue

[Front End] This code SHOULD compile with these options.

Additional Details

Output:

"nttp.cc", line 8: error: declaration is incompatible with function template "void S<T>::f<N>()" (declared at line 4)
  void S<T>::f () {}
             ^

"nttp.cc", line 10: error: function "S<T>::f<N>() [with T=int, N=1]" cannot be instantiated -- no template definition was supplied
  template void S<int>::f<1> ();
           ^

2 errors detected in the compilation of "nttp.cc".

Variants

Change	Result
Out-of-class parameter written as T N	OK
Function parameter of type typename S<T>::V * instead of a template parameter	OK
Non-type template parameter of function pointer type int (*)(V *) vs int (*)(typename S<T>::V *)	error
Member class template: template <V N> struct M; defined as template <typename S<T>::V N> struct S<T>::M {};	error

The member class template gives this error:

"nttp_class.cc", line 7: error: declaration is incompatible with constant "T N" (declared at line 4)
  template <typename S<T>::V N>
                             ^

Reproducing (Standard) Configuration(s)

linux-gcc-debug

Reproducing (Non-standard) Configuration

No response

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• I have checked open issues and existing discussions before filing this report.
• The reproducing source code that I have provided does not depend on headers that I have not included with my submission.
• I have reduced the reproducing source code to the best of my ability.
• I have selected at least one standard configuration or uploaded a non-standard configuration dump.
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