String type to introspect.
static assert( isTrulyString!string); static assert( isTrulyString!dstring); static assert( isTrulyString!wstring); static assert(!isTrulyString!(char[])); static assert(!isTrulyString!(dchar[])); static assert(!isTrulyString!(wchar[]));
True if a type is string, dstring or wstring; otherwise false.
Does not consider e.g. char[] a string, as isSomeString does.