Pop quiz, what does this do?

[Steven Schveighoffer]

The FieldNameTuple from std.traits returns a tuple of names of all the 
fields that are present on a type instance.

What about the result on things that can't have fields?

import std.traits;

interface I
{
    int foo();
}

pragma(msg, FieldNameTuple!I);

Without looking up the docs, or trying it, what do you think it does?

-Steve