auto template parameters: g++ 7.3 vs clang++ 6.0 : Which compiler is correct?

Question

Two compilers produce different results for this code example. Clang generates two different types. G++ uses same type for fu and fi. Which one is standard compliant?

#include <iostream>

template< auto IVAL>
struct foo {
    decltype(IVAL) x = -IVAL;
};

int main()
{
    foo<10u> fu;
    foo<10> fi;
    std::cout << fi.x << " " << fu.x << '\n';
    return 0;
}

g++-7.3 output:

4294967286 4294967286

clang-6.0 output:

-10 4294967286

Answer 1

gcc is wrong here, these are clearly two distinct types.

And to confirm - this bug is fixed in gcc 8.0.1

Sample code