Return type of some functions is incorrect.

[tomc974]

Hi!

I have a function with a logic similar to the below function

function f(x: number) {
  if (x < 5) return true
  if (x > 20) return false
  return undefined
}

• The return type inferred by the TypeScript compiler is boolean | undefined
• The return type produced by TypeDoc is undefined | true | false

No big deal but still annoying...

[aciccarello]

@tomc974, I'm curious, why would you want a true | false type rather than a boolean type? In my mind those are the same with the possible exception of allowing null.

[tomc974]

@aciccarello It's the other way around. I do want the boolean | undefined type but TypeDoc generates documentation with undefined | true | false. Try to run it on the provided example ;-)

[aciccarello]

@tomc974 Sorry, I misunderstood.

I've confirmed TypeDoc is outputting differently than TypeScript's implicit definition. If the function is explicitly given a boolean | undefined return type, that is respected by TypeDoc.

[calebsander]

I see this with an interface method that has the signature writeValue(buffer: GrowableBuffer, value: VALUE, root?: boolean): void. The type for root shows up instead as root?: undefined | true | false. I have an abstract class that implements this interface with an abstract version of the method. Interestingly, it is also broken for the abstract class, but subclasses of the abstract class that implement this method have the correct documentation.

[Gerrit0]

Fixed in 0.20.0 beta 30