Microsoft/TypeScript

`satisfies` changes the generic type, "resolves" it immediately

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#52.394 aberto em 24 de jan. de 2023

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 (12 comments) (0 reactions) (0 assignees)TypeScript (6.726 forks)batch import
BugDomain: check: Type InferenceHelp Wanted

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Description

Bug Report

It seems that using satisfies on a value that is bound to a generic type, in some way resolves the generic type at that place.

const foo = <T extends 1 | 2>(bar: T) => {
  // PROBLEM: a and b should have the same type.
  const a = bar satisfies any; // using any type that doesn't use the generic T here creates this problem
  //    ^? 1 | 2
  const b = bar;
  //    ^? T extends 1 | 2
}

Playground link

🔎 Search Terms

satisfies changes type, generic, widening

🕗 Version & Regression Information

Using 4.9.4 now with satisfies and noticed this.

  • This changed between versions 4.9 and 4.8 when satisfies was introduced
  • This is the behavior in every version I tried, and I reviewed the FAQ
  • I was unable to test this on prior versions because satisfies didn't exist

⏯ Playground Link

Playground link

🙁 Actual behavior

a and b have different types as seen in the playground

🙂 Expected behavior

satisfies should be a no-op

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