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Inferred type equivalent to #167

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danvk opened this issue Sep 29, 2023 · 0 comments · Fixed by #252
Closed

Inferred type equivalent to #167

danvk opened this issue Sep 29, 2023 · 0 comments · Fixed by #252
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Effective TypeScr...

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@danvk
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danvk commented Sep 29, 2023

#145 added support for "equivalent to" assertions for type aliases. But what about values?

interface ABC { a: string; b: string; c: string; }
function foo(abc: ABC) {
  let k: keyof ABC;
  for (k in abc) {
    // ^? let k: keyof ABC (equivalent to "a" | "b" | "c")
  }
}
@danvk danvk added this to the Effective TypeScript 2nd Edition milestone Mar 7, 2024
@danvk danvk mentioned this issue Mar 10, 2024
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danvk added a commit that referenced this issue Mar 10, 2024
@danvk
Support "equivalent to" for values (#252)
944d48d 
Fixes #167 

Weirdly the `Resolve` helper only resolves types at the top level, not
in functions:

```ts
interface Point {
  x: number;
  y: number;
}

type Resolve<Raw> = Raw extends Function ? Raw : { [K in keyof Raw]: Raw[K] };
function foo(pt: Point) {
  let k: keyof Point;
  for (k in pt) {
    // ^? let k: keyof Point
    type SynthK = Resolve<keyof Point>;
    //   ^? type SynthK = keyof Point
  }
}

type SynthT2 = Resolve<keyof Point>;
//   ^? type SynthT2 = "x" | "y"`);
```

This might be microsoft/TypeScript#49852
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Support "equivalent to" for values danvk/literate-ts
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@danvk