Function shapes with union typed params incorrectly accept more restrictive functions #9765

interface Callback {
  (value: string | number): void;
}

// expect this to work
const many: Callback = (value: string | number | boolean) => {
  // ...
}

// expect a type error here
const one: Callback = (value: string) => {
  // ...
}

many(1);       // should work, does work
one(1);        // shouldn't work, does work *
many("hello"); // should work, does work
one("hello");  // should work, does work
many(true);    // shouldn't work, doesn't work
one(true);     // shouldn't work, doesn't work

interface SomeLib {
  onChange: (callback: (newValue: string | null) => void) => void;
}

const foo: SomeLib = ...;
foo.onChange((newValue: string) => {
  // oops, I forgot newValue may not be defined, but this compiles
});