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Missing generator's type parameter in functions and constructors #32248
Description
TypeScript Version: master
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Code
export class Coroutine<T = unknown, R = unknown, S = unknown> {
constructor(gen: (this: Coroutine<T, R, S>) => Generator<R, T, S> | AsyncGenerator<R, T, S>) {
}
}
new Coroutine<0, 0, 1>(async function* g() {
const a = yield 0;
return 0;
});Expected behavior:
Type g is AsyncGenerator<0, 0, 1>.
Type a is 1.
Actual behavior:
Type g is AsyncGenerator<0, 0, unknown>.
Type a is any.
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rbuckton commentedon Jul 4, 2019
This is an issue with contextual typing. The contextual type from the constructor isn't flowing to the async generator.
falsandtru commentedon Jul 4, 2019
Since the constructor has been given all type parameters the type of the parameter gen must be AsyncGenerator<0, 0, 1>. All type parameters are clearly decided. And the return type of yield must be unknown with the current behavior, as is defined by the context type.
falsandtru commentedon Jul 4, 2019
Note that the type declaration for
thisdoesn't affect this bug. This is one of the verbose elements for effectivity of regression tests.falsandtru commentedon Jul 4, 2019
Same also with functions.
falsandtru commentedon Jul 16, 2019
Ron Buckton (@rbuckton) Why you still haven't fixed this bug?
falsandtru commentedon Jul 17, 2019
Thanks Ron Buckton (@rbuckton) !
falsandtru commentedon Jul 26, 2019
Ryan Cavanaugh (@RyanCavanaugh) Label this.