typedef type checking?

Consider using a strong typedef: https://www.boost.org/doc/libs/release/boost/serialization/strong_typedef.hpp

To expand upon Nawaz's answer: when you typedef A B, then B is just an alias for A, not a separate type. x and y are just int's in your example.

If you want to create a new type, use a one-member struct.

As long as T1 and T2 are typedefs of same type, you will not get any warning!