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any inferred as type parameter even with --noImplicitAny #11311
Description
TypeScript Version: nightly (2.1.0-dev.20161002)
Code
function second<T>(tuple: [any, T]): T
function second<T>(tuple: [any, T, any]): T
function second(tuple: any[]): any {
return tuple[1]
}
function segundo<T>(tuple: [any, T] | [any, T, any]): T {
return tuple[1]
}
const pairs: [number, string][] = [[1, "two"]]
const x: number[] = pairs.map(second)
const y: number[] = pairs.map(segundo)Expected behavior:
Both x and y are compile errors.
Actual behavior:
y fails with:
a.ts(13,7): error TS2322: Type 'string[]' is not assignable to type 'number[]'.
Type 'string' is not assignable to type 'number'.
but x does not fail, because the generic parameter of map is inferred as any rather than string, even with --noImplicitAny turned on.
On another note, I'm not sure what's happening below: either the type parameter of identity is inferred as any or it's inferred as string & number and function bivariance wreaks its magic:
function useStringToNumber(f: (s: string) => number): void {}
function identity<T>(t: T): T {
return t
}
useStringToNumber(identity)
Activity
sergey-shandar commentedon Oct 11, 2016
Related issue #3038
mhegazy commentedon May 17, 2017
looks like a duplicate of #11152
mhegazy commentedon May 18, 2017
looks like the same issue as #9366
mhegazy commentedon May 24, 2017
The last example is technically as spec'ed. see 4.15.2 Type Argument Inference:
mhegazy commentedon Jun 8, 2017
Automatically closing this issue for housekeeping purposes. The issue labels indicate that it is unactionable at the moment or has already been addressed.