[Bug c++/100482] namespaces as int in decltype expression

[sand at rifkin dot dev via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100482

--- Comment #1 from Jeremy R. <sand at rifkin dot dev> ---
This appears to be valid for function return types as well but the compiler
does error when decltype is used in a function parameter

namespace std{}
int A(int a) { // fine
    decltype(std) b = a;
    return b;
}
decltype(std) B(int a) {  // fine
    decltype(std) b = a;
    return b;
}
auto C(int a) -> decltype(std) {  // fine
    decltype(std) b = a;
    return b;
}
int D(decltype(std) a) { // error: expected initializer before 'a'
    decltype(std) b = a;
    return b;
}