Class type parameter is not flowed to class property

[bcherny]

class Class<T> {
  a: (b: T) => string
}

class Class2 extends Class<number> {
  a = b => 'b' // ERROR: Parameter 'b' implicitly has an 'any' type.
}

Expected: b should be a number
Actual: b is any

This is likely tracked already, but I was not able to find it. Filing here just in case.

[RyanCavanaugh]

#10570