Closed
Description
openedon Apr 10, 2019
TypeScript Version: 3.4.0-dev.201xxxxx
Search Terms:
Recursive
Conditional
Code
type Action<
Args extends any[],
Payload extends Record<string, any>,
T extends string
> = ((...args: Args) => (Payload & { type: T })) & {
readonly type: T
}
type AnyAction = Action<any[], any, string>
type CascadingActionMap = {
[name: string]: AnyAction | CascadingActionMap
}
type Reducer<S, T> = (state: S, action: T) => S
type CascadingActionType<T> = T extends CascadingActionMap
? { [K in keyof T]: ActionType<T[K]> }[keyof T]
: never
export type ActionType<T> = T extends AnyAction
? ReturnType<T>
: T extends Reducer<any, infer A>
? A
: CascadingActionType<T>Expected behavior:
No errors. It's worth noting that it works in 3.3.4, with the correct derived type.
Actual behavior:
Running tsc command line, it reports the following errors:
error TS2456: Type alias 'CascadingActionType' circularly references itself.
914 type CascadingActionType<T> = T extends CascadingActionMap
~~~~~~~~~~~~~~~~~~~
error TS2315: Type 'ActionType' is not generic.
915 ? { [K in keyof T]: ActionType<T[K]> }[keyof T]
~~~~~~~~~~~~~~~~
error TS2456: Type alias 'ActionType' circularly references itself.
918 export type ActionType<T> = T extends AnyAction
~~~~~~~~~~
error TS2315: Type 'CascadingActionType' is not generic.
924 : CascadingActionType<T>
~~~~~~~~~~~~~~~~~~~~~~
Playground Link:
Related Issues:
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment