C++ function-to-pointer implicit conversion: which compiler is right? Clang and GCC disagree

Question

template <typename Type, Type Func>
struct A
{
};

void func();

A<void(), func> a; // same result with A<void(), &func> a;

This code compiles with Clang (including latest 8.0.0), but not with GCC (including latest 9.1).

GCC says: error: 'void()' is not a valid type for a template non-type parameter

Which compiler is right and why?

Update

I am guessing GCC is wrong, because the following compiles on both Clang and GCC:

template <void()>
struct A
{
};

void func();

A<func> a; // same result with A<&func> a;

So contrary to what GCC reports in the first example, void() seems to be "a valid type for a template non-type parameter"

Answer 1

Similarly to what happens to function parameter type, if the type of a non-type template parameter is a function type, it is adjusted to pointer to function type [temp.param]/8:

A non-type template-parameter of type “array of T” or of function type T is adjusted to be of type “pointer to T”.

So clang is right. GCC bug report already exists bug #82773

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Only the current working draft of the c++ standard recognizes the process of substitution of template argument into following template parameters. So it could be argued that the standard is not clear because it does not specify that the type adjustment is performed after each of those substitutions.