Allows comparison of types that are not comparable

[ghost]

TypeScript Version: nightly (2.5.0-dev.20170613)

Code

const a = new Date();
const b = new Date();
console.log(a < b); // false
console.log(a > b); // false
console.log(a === b); // false

Expected behavior:

Compile error: can't compare Dates.

Actual behavior:

No error.

[mhegazy]

Looks like it should be covered under #15506