Incorrectly inferred call signature

[boris-kolar]

🔎 Search Terms

call signature, overloaded call

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about call signature

⏯ Playground Link

https://www.typescriptlang.org/play/?ts=5.7.0-dev.20241101#code/JYOwLgpgTgZghgYwgAgGIHt3IN4ChnIAUAHgFzICMAlOQEz5FnK03IDMuAvrrmAJ4AHFAGE4AGzEBlYAHMQcMAFcoEADwAVAHzIAvMnXIIxSCAAmAZyIA6GwPKgY0ZAAUqu7Q6cAlZAH5rtuSu7sg+5Oq8gigA6lDoIDLqUbrIohLScgrKahjo2gD0+Yx0bjrabEA

💻 Code

interface Foo {
  (x: 1): 2
  (x: 2): 3
}

type CallSignature<T> = T extends (...p: infer P) => infer R ? (...p: P) => R : T
type WrongType = CallSignature<Foo> // (x: 2) => 3

🙁 Actual behavior

The inferred type is not compatible with actual type

🙂 Expected behavior

The inferred type should (at minimum) be compatible with actual type (ideally { (x: 1) => 2; (x: 2) => 3 }).

Additional information about the issue

No response

[MartinJohns]

This is working as intended / a design limitation. See the documentation: Inferring Within Conditional Types

When inferring from a type with multiple call signatures (such as the type of an overloaded function), inferences are made from the last signature (which, presumably, is the most permissive catch-all case). It is not possible to perform overload resolution based on a list of argument types.

[jcalz]

see #26591 and other issues

[typescript-bot]

This issue has been marked as "Duplicate" and has seen no recent activity. It has been automatically closed for house-keeping purposes.