Defining generic functional type fails

[xp500]

TypeScript Version: 2.4.1

Code

class A {
}

class B extends A {
  prop: number
}

type C = <S extends A>(p: S) => void;

const a: C = (p: B) => {}

Expected behavior:
The function a (p :B) => {} should be a valid C because B extends A
Actual behavior:
Build fails with the following error

error TS2322: Type '(p: B) => void' is not assignable to type 'C'.
  Types of parameters 'p' and 'p' are incompatible.
    Type 'S' is not assignable to type 'B'.
      Type 'A' is not assignable to type 'B'.
        Property 'prop' is missing in type 'A'.

This used to work in 2.3.4.

[kitsonk]

Dupe of #16985

[HerringtonDarkholme]

See this #16797 (comment)

[mhegazy]

Automatically closing this issue for housekeeping purposes. The issue labels indicate that it is unactionable at the moment or has already been addressed.