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NonNullable is not resolved for a mapped type in a contextual parameter type from instantiated type aliasΒ #51331
Description
Bug Report
π Search Terms
NonNullable, Omit, mapped type, contextual type
π Version & Regression Information
- This changed between versions 4.7 and 4.8
β― Playground Link
Playground link with relevant code
Original repro case
π» Code
type GestureKey = "drag";
type DragState = { movement: [number, number]; };
interface State {
drag?: DragState;
}
type SharedGestureState = {
dragging?: boolean;
};
type FullGestureState<Key extends GestureKey> = SharedGestureState &
NonNullable<State[Key]>;
type Handler<Key extends GestureKey> = (
state: Omit<FullGestureState<Key>, "event">
) => void;
const works = (state: Omit<FullGestureState<"drag">, "event">) => {
state;
// ^? (parameter) state: Omit<SharedGestureState & DragState, "event">
type StateKeys = keyof typeof state;
// ^? type StateKeys = "dragging" | "movement"
console.log(state.movement);
};
const doesntWork: Handler<"drag"> = (state) => {
state; (parameter) state: Omit<SharedGestureState & DragState, "event">
// ^? (parameter) state: Omit<SharedGestureState & DragState, "event">
type StateKeys = keyof typeof state;
// ^? type StateKeys = "dragging"
console.log(state.movement); // Property 'movement' does not exist on type 'Omit<SharedGestureState & DragState, "event">'.(2339)
};π Actual behavior
We can observe a type error in the doesntWork function and the keyof reporting incorrect result there for the given parameter type.
π Expected behavior
There should be no error as the type for the state parameter in both functions is the same.
Activity
typescript-bot commentedon Oct 27, 2022
The change between release-4.6 and main occurred at 51b346d.
ahejlsberg commentedon Dec 2, 2023
The core issue here is the normalization we perform on index types. Specifically, we generally normalize
keyof (A & B)intokeyof A | keyof B. Turns out that doesn't always hold whenAandBare generic types:Above,
keyof Foo | keyof Baris just"y", whereaskeyof (Foo & Bar)is"x" | "y"becauseFoo & Baris reduced to just{ x: string} & { y: string }, thus eliminating theundefinedtype.We already have logic in place to defer types like
keyof (T & {}), but it looks like we need to defer allkeyof (T & U)where one or both of the types are generic. We can then simplify the type tokeyof T | keyof Uwhere appropriate. I'm going to put together a PR and we'll see what the effects are.pkudryashov commentedon Jul 3, 2024
I have similar issue in 5.4.x and 5.5.x
Output
Compiler Options
{ "compilerOptions": { "strict": true, "noImplicitAny": true, "strictNullChecks": true, "strictFunctionTypes": true, "strictPropertyInitialization": true, "strictBindCallApply": true, "noImplicitThis": true, "noImplicitReturns": true, "alwaysStrict": true, "esModuleInterop": true, "declaration": true, "target": "ES2017", "jsx": "react", "module": "ESNext", "moduleResolution": "node" } }Playground Link: Provided
Is this the same bug?