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Only the last overloaded signature is picked when passing an overloaded function to Array.mapΒ #55840

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@vfsfitvnm

Description

@vfsfitvnm

πŸ”Ž Search Terms

"overload", "last overload", "is not assignable to parameter of type", "Array.map"

πŸ•— Version & Regression Information

  • This is the behavior in every version I tried, and I reviewed the FAQ

⏯ Playground Link

https://www.typescriptlang.org/play?ts=5.3.0-dev.20230923&ssl=2&ssc=1&pln=3&pc=1#code/CYUwxgNghgTiAEAzArgOzAFwJYHtVJxwAoA3KCZEALngGcMYtUBzAShvsZYG4BYAKFCRYCFOmx4CxMhWrxUyALYAjEDHbylqmH34CweevBgAGDgybMA2gF14AXnhWARFGcAaeM+XObAOkUoAAciAH0HAD4pMNZWbngAegT4HABrfUMMYwBGcy5rO0cXN09vXwDgokRCOMTktRgcGAEgA

πŸ’» Code

declare function foo(value: string): string;
declare function foo(value: number): number;

const r0: string[] = ["a", "b"].map(_ => foo(_)); // ok
const r1: string[] = ["a", "b"].map(foo); // error, number is inferred

πŸ™ Actual behavior

It looks like when foo is passed "directly" (that is without a wrapper arrow function), its signature is the last one that was declared. Swapping the first two lines works around the issue, indeed.

πŸ™‚ Expected behavior

It should iterate through all the possible overloads.

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