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Unnecessary elaboration about not being assignable to type parameters #42849
Description
async function foo<T>(x: T): Promise<T> {
let yaddable = await getXOrYadda(x);
return yaddable;
}
interface Yadda {
stuff: string,
things: string,
}
declare function getXOrYadda<T>(x: T): T | Yadda;Here, you'll get an error like
Type 'T | Yadda' is not assignable to type 'T'.
'T' could be instantiated with an arbitrary type which could be unrelated to 'T | Yadda'.
Type 'Yadda' is not assignable to type 'T'.
'T' could be instantiated with an arbitrary type which could be unrelated to 'Yadda'.
Proposed
Either
Type 'T | Yadda' is not assignable to type 'T'.
Type 'Yadda' is not assignable to type 'T'.
'T' could be instantiated with an arbitrary type which could be unrelated to 'Yadda'.
or
Type 'T | Yadda' is not assignable to type 'T'.
'T' could be instantiated with an arbitrary type which could be unrelated to 'T | Yadda'.
Activity
[-]Unnecessary repetition about constraint types[/-][+]Unnecessary elaboration about not being assignable to type parameters[/+]jonhue commentedon Feb 25, 2021
I created a pull request that makes the proposed change (#42952) but had one small question about the behavior in scenarios related to the one discussed here.