Microsoft/TypeScript
Incorrectly reported `TS2322` error on array items after spread
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#55 340 ouverte le 11 août 2023
BugDomain: Error MessagesHelp Wanted
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Description
🔎 Search Terms
"array spread", "TS2322"
🕗 Version & Regression Information
- This is the behavior in every version I tried, and I reviewed the FAQ for entries about
⏯ Playground Link
💻 Code
const a: Array<number | string> = [];
const b: Array<number> = [...a, 1];
🙁 Actual behavior
The compiler gives the following two errors, of which only one is appropriate:
~/prog/typescript ❯ tsc ./array-spread-error.ts
array-spread-error.ts:2:27 - error TS2322: Type 'string | number' is not assignable to type 'number'.
Type 'string' is not assignable to type 'number'.
2 const b: Array<number> = [...a, 1];
~~~~
array-spread-error.ts:2:33 - error TS2322: Type 'string | number' is not assignable to type 'number'.
Type 'string' is not assignable to type 'number'.
2 const b: Array<number> = [...a, 1];
~
🙂 Expected behavior
The spread is clearly incorrect, as the original array could potentially contain strings as well, but the number literal should not be marked with the same error.