Microsoft/TypeScript
[ID-Prep] Type of variable is widened in declaration with !strictNullChecks
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#57 441 ouverte le 19 févr. 2024
Domain: flag: isolatedDeclarationsHelp WantedPossible Improvement
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Description
The [ID-prep] set of issues aligns Declaration Emit with the forthcoming Isolated Declarations feature.
🔎 Search Terms
const declaration widen
🕗 Version & Regression Information
- This is the behavior in every version I tried
⏯ Playground Link
💻 Code
declare function f3<T>(a: T, b: T): T;
const x3 = f3("abc", "def"); // "abc" | "def"
🙁 Actual behavior
x3 is emitted as declare const x3: string; in declaration files but it's actually "abc" | "def" in source
🙂 Expected behavior
x3 is emitted as declare const x3: "abc" | "def"
Additional information about the issue
No response