No contextual typing on yield expression when generator function is contextually typed as union of normal function and generator function

[uhyo]

Bug Report

🔎 Search Terms

generator function union contextual typing yield

🕗 Version & Regression Information

4.1.5, 4.4.2

• This changed between versions 4.0.5 and 4.1.5

⏯ Playground Link

Playground link with relevant code

💻 Code

type FuncOrGeneratorFunc = () => (number | Generator<(arg: number) => void, any, void>)

const f: FuncOrGeneratorFunc = function*() {
  // Error: Parameter 'num' implicitly has an 'any' type.
  yield (num) => console.log(num);
}

🙁 Actual behavior

A noImplicitAny error is reported.

Note: the same happens for async generator functions too.

🙂 Expected behavior

Type of num is inferred as number. This is the behavior of TS 4.0.