Comments (4)
Duplicate of #39600.
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UnionToIntersection
has been called an ill formed type by the team. It's not supported and it could stop working with any new version.
from typescript.
// I assumed the above solution is equal to overloading
That assumption is wrong. Keep in mind that E
can be a union type as well. It's perfectly valid that the type for E
is "invalidate" | "reassign"
. That also means it's possible to provide an invalid mesg
for the event
.
from typescript.
@MartinJohns Yes that is correct, I do account for this through these
// helper types
// https://stackoverflow.com/questions/50374908/transform-union-type-to-intersection-type
type UnionToIntersection<U> =
(U extends any ? (k: U) => void : never) extends ((k: infer I) => void) ? I : never
// https://stackoverflow.com/questions/53953814/typescript-check-if-a-type-is-a-union
type IsUnion<T, U extends T = T> =
(T extends any ?
(U extends T ? false : true)
: never) extends false ? false : true
export type OneOf<T, K> = IsUnion<K> extends false ? keyof T : never;
recv<E extends OneOf<Events, E>>(event: E, cb: (mesg: Events[E]>) => void) {}
I meant equal in the context of the problem, which is how they handle void.
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