Don't error when function has an implicit return but its return type is assignable to undefined

[MariaSolOs]

Fixes #53473

[ahejlsberg]

I don't think this is the right fix for the issue. The following now doesn't error:

function foo(x: boolean): string | undefined {
}

This previously would report "A function whose declared type is neither 'void' nor 'any' must return a value."

[ahejlsberg]

The right fix is to put the assignability check back where it was originally.

[ahejlsberg]

Specifically, we need to undo the change I mention here. And then also undo the change in this PR.

[MariaSolOs]

I'm confused with @jakebailey's comment. Is this a fix or a bug? 😄

[ahejlsberg]

Is this a fix or a bug?

Is what a fix or a bug?

[MariaSolOs]

Is what a fix or a bug?

@ahejlsberg Sorry I wasn't clear, I was referring to this PR. The way I read Jake's comment, this change fixes the issue you brought up here, but you're suggesting we undo it.

[ahejlsberg]

Yes, I'm suggesting we undo this PR because, while it fixes the issue here, it causes a new issue that I mention here.

The real fix is to revert the deletion of the assignability check I mention here. Once that's done there is no need for this PR.

[MariaSolOs]

Got it, thanks for explaining! I can prepare that change.