Interfaces don't guide inference for functions that end in throw

[appreciate-devon]

Bug Report

🔎 Search Terms

implements doesn't influence throw
function that only throws implicitly returns void

(I did find #7538 but there were no associated issues)

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries. I tried 4.3.5 as well as next

⏯ Playground Link

Playground link with relevant code

💻 Code

interface Foo {
  func(): number
}

class Bar implements Foo {
  func() {
    throw new Error("Bogus")
  }
}

🙁 Actual behavior

Property 'func' in type 'Bar' is not assignable to the same property in base type 'Foo'.
  Type '() => void' is not assignable to type '() => number'.
    Type 'void' is not assignable to type 'number'.

🙂 Expected behavior

I expected () => number to be used to inform Bar's definition for func(), since the interface sets the lower bound for acceptable return values.

[fatcerberus]

Method types aren’t currently inferred based on implements or extends. Related to #32082

[MartinJohns]

And the function ending in a throw is irrelevant. This errors as well:

interface Foo {
  func(): 1
}

export class Bar implements Foo {
  func() {
    return 1
  }
}

[blast-hardcheese]

Ah, thank you. Seeing as my issue is completely covered by the other issue, I'll watch that and close this.

Unrelated: I've been using TS on and off for close to ten years, thanks very much to everyone involved.