[cfe-dev] Why is compiler support needed for std::underlying_type?

[Stephen Kelly]

Richard Smith wrote:

> enum E1 : long {};
> static_assert(std::is_same<std::underlying_type<E>::type, long>::value,
> ""); // ok
> static_assert(std::is_same<UnderLyingType<E>::Type, long>::value, ""); //
> fails
> 
> enum E2 : char {};
> static_assert(std::is_same<std::underlying_type<E>::type, char>::value,
> ""); // ok
> static_assert(std::is_same<UnderLyingType<E>::Type, char>::value, ""); //
> fails
> 

Am I right to say this? :

Even if sizeof(long)==sizeof(long long), they are not the same type. The 
compiler intrinsic knows that, but my solution does not.

Similarly, signed char, char and unsigned char are three different distinct 
types. The compiler knows this, but my solution does not.

Thanks,

Steve.