Struggling with Redux code, I've encountered a peculiar behavior regarding type assignment that has left me puzzled.
In the following code snippet, it's clear that you cannot assign anyaction to iaction. Yet, surprisingly, assigning anyaction to iaction2 works without any issues. Despite attempting to adhere to the "Assignment Compatibility" part of the specification, I can't quite grasp the reason behind this inconsistency.
What exactly is happening here? It seems apparent that there are instances of type AnyAction that cannot be assigned to IAction2.
export interface ILoadUserBegin {
type: "LOAD_USER_BEGIN";
}
export interface ILoadUserSuccess {
type: "LOAD_USER_SUCCESS";
response: number;
}
type IAction = ILoadUserSuccess;
type IAction2 = ILoadUserBegin | ILoadUserSuccess;
// these are redux types
interface Action {
type: any;
}
interface AnyAction extends Action {
[extraProps: string]: any;
}
// tests
let iaction: IAction = { type: "LOAD_USER_SUCCESS", response: 2 };
let iaction2: IAction2 = { type: "LOAD_USER_BEGIN" };
let anyaction: AnyAction = { type: "foo" };
// ERROR
// Type 'AnyAction' is not assignable to type 'ILoadUserSuccess'.
// Property 'response' is missing in type 'AnyAction'.
iaction = anyaction;
// But this is OK!
iaction2 = anyaction;