IsNegativeNumber

Sometimes when working with numeric literals, we need to rule out (or enforce) that the provided number is a positive integer.

To do that, we first need a way to tell if the number is negative.

Write a type-level function IsNegativeNumber that accepts a number N and returns:

• true if N is negative
• false if N is positive
• false if N is 0,
• never if N is number
• never if N is a union