Implicit conversion failure under Clang

conversion.cpp

class To{};

#include <utility>

class From{
public:
	/* This will cause compilation error under Clang (3.5) with c++11 standard */

	operator const To() { return To(); }

	/* Any one of below works fine */

	//explicit operator const To() { return To(); }
	//operator To() { return To(); }
	//operator To &&() { return std::move(To()); }
};

int main() {
	From f;
	To t (f);
	return 0;
}