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Generic parameter types are incorrectly inferred as { } #26809
Description
TypeScript Version: 3.0.1, vscode 1.26.1
Search Terms:
Code
interface A<R> {
a(): R
}
function some1<R>(a: A<R>): R {
return null
}
function some2<R, D extends A<R>>(a: D): R {
return null
}
let out1 = some1({
a() {
return 'asd'
}
})
let out2 = some2({
a() {
return 'asd'
}
})Expected behavior: out1: string, out2: string
Actual behavior: out1: string, out2: {}
Activity
AlCalzone commentedon Aug 31, 2018
Seems there is not enough context for TS to infer
Rinsome2, since you are not passing any argument with typeR. You can fix this by explicitly telling TypeScript to inferRfrom the interface:2A5F commentedon Aug 31, 2018
But why would it be
{}instead of an errorAlCalzone commentedon Aug 31, 2018
As far as I understand,
{}is the default when inference fails. This keeps the type-checking enabled - as opposed toany, which doesn't.