msvc compiles the following code(with /permissive- compiler switch), clang and gcc do not:
template<auto val>
struct S{
static constexpr auto val = val;
};
int main() {
return S<4>::val;
}
I presume that this is just a msvc bug, but I am curious if maybe standard is ambiguous here.
The standard is unambiguous on this, a template parameter can't be redeclared for any reason, see [temp.local]/6:
A template-parameter shall not be redeclared within its scope (including nested scopes). A template-parameter shall not have the same name as the template name.
[ Example:
template<class T, int i> class Y { int T; // error: template-parameter redeclared void f() { char T; // error: template-parameter redeclared } }; template<class X> class X; // error: template-parameter redeclared— end example ]
So MSVC behavior (given the /permissive- flag) looks like a bug.
The name of a template-parameter shall not be bound to any following declaration contained by the scope to which the template-parameter belongs.
[Example 5:
template<class T, int i> class Y { int T; // error: template-parameter hidden void f() { char T; // error: template-parameter hidden } friend void T(); // OK: no name bound }; template<class X> class X; // error: hidden by template-parameter— end example]
A declaration of a static data member plainly binds a name, so it is just as ill-formed.