Function template overload resolution fails in Visual C++ 2017 - c++

Question

I am trying to figure out if what I wrote is legal C++14 w.r.t. unambiguous function template overload resolution.
In my opinion, the below program should compile and return 3.
Various versions of Clang and GCC compute just that at compile time (using -std=c++14 -O2), but Visual C++ 2017 (Version 15.5.2; latest update at time of writing) chokes on it with the below error message.
enum class Enum0 { State };
enum class Enum1 { State };
template <Enum0 Param0 = Enum0::State>
int get()
{
return 1;
}
template <Enum1 Param1>
int get()
{
return 2;
}
int main()
{
int sum = 0;
sum += get(); // should call instantiation of first function template
sum += get<Enum1::State>(); // should call instantiation of second function template
return sum;
}
This is the emitted error message by the Visual C++ compiler:
20 : <source>(20): error C2668: 'get': ambiguous call to overloaded function
11 : <source>(11): note: could be 'int get<Enum1::State>(void)'
5 : <source>(5): note: or 'int get<Enum0::State>(void)'
20 : <source>(20): note: while trying to match the argument list '()'
See https://godbolt.org/g/PhH2VY for a live demonstration (and https://godbolt.org/g/BVEv79 for the previous code example before editing the question).
Change the compiler to MVSC to see the compilation failing. GCC and Clang do not indicate any issue. Both nicely emit the following x86 assembly:
mov eax, 3
ret
Are GCC and Clang too lenient, or is this an issue with Visual C++?

Answer 1

That's a good question, isn't it. If I change the second call to get with:
sum += get<Enum1::State, int>(0.0); // should call instantiation of second function template
... then it compiles...
Notice, I add a second template argument. In my day to day work, I use an old dialect of C++ compatible with MFC...so take my reasoning with a grain of salt. But, since you are only providing one argument to the template, and the second template requires two arguments, ISTM that the VC++ compiler is trying to use the first template because it has default arguments and can take only one argument. So it chooses that template but cannot do the conversion from Enum1 to Enum0.