π Search Terms
silent never leak reverse mapped types nested calls return type inference
π Version & Regression Information
- This is the behavior in every version I tried
β― Playground Link
https://www.typescriptlang.org/play/?noEmit=true&ts=6.0.0-dev.20251202#code/C4TwDgpgBAaghgGwK4QM4B4AqA+KBeKTAbQGsIQB7AM0IF0BuAKEdEigFk4BjACwEsAdhADCFAcAgAPYPigAlCFwoAnACbpUwZYIDmAGihwBIbE0aCJyqt2gAFOMrgBbCJb4AvCKoDyAIwBWijIA3oxQUKwQAFxQmtoCOkzhYA7OqAD8MUgCJAIUAO4CTAC+zJFQAIJcwHxiAGLZ1bUC6GGEouJSMl0QAqqoHNz8Qh0S0nptmPaOTgM9fQPTzq4Q2p4+AUFEAEQpM6jbtFAAPlDZqhBUgl4T4ZhVNWJQ8-1QSy5u636B1RO4BKFwgAKaqSGKYUZdAx7NLg96oACUMQAbhQ+KoklAAPoUJDALH3JpiTKEB7NEpmcqYCjvFZrLzfIKtO60z5eThgZ7SXqvBRKNTM8KxLS6W5C1mrDwMzbVHYw2aHE5nPqXa6qNrYP6yeDINDoQFQIgAaSggigZEoNCmqQ+kvWHKgADJhfEdLQYgbwpEYkbMckbag4Ta6VLVBzjQw2sUSqYyuBoKIEAggmSxBhJpDpFyJAtBrxrpngGLrftszzFsG2RsfsA5QHFadzqqhKotQQgW1PVAlJ1xm1wr0AI4oFBi4oe-vdsRjYDgwt+54CYcQFAxIHcR4CNcI-C4VHond4PdojFRsXywOEeETQ-H9FmC5cBAOaBURqbxfLlCpgTpu6Fstc04fMRmnKFJnhQDXglelqy2XZ6yORsVSuFtix-KCKxmEMvhlGQCBg0NGV+RhsA7cIlCTIIYkTZNqh-DAITA8YrwDTVGCRSoiQEBoBG4rBCwMEs0iEn9Y0YR9n2UV932aWJXCQMBBSY3tum5IChgLZii0mBjMPkRQVHUSc4lFSdCNwms632BtlQuVCvA1WRgmKP4gQNSJUDFDdmi8xhxygDz4wyD0p1UkkVJnKBozaHy0xJLtjVNARzXIahSW41B3S4zdeP4yd-20sUhQyzdUAjYqhWpCzpRrLAGOwSdY3CGLik4-dT0YVAFLAdzYsyicStUCgAGVgCQKgqBiIcRwgBigSBLFoQDGIBCQJxfFWW9ArascJjasxuvG3qDTi39BqFYaxomqbP1m+bFuW-ZVvWzblG2lyEUq4bvGAHhVmuya1yWqALxiUyEg+1yz38hFDp6vrwjOy8uyu8agbulc5syhaQbBqA1o2rbdx2r7Jx+v6AfR27FpiIwQCe2EXV0KG9thpggA
π» Code
type Values<T> = T[keyof T];
type MachineContext = Record<string, any>;
interface ParameterizedObject {
type: string;
params?: unknown;
}
type ActionFunction<
TContext extends MachineContext,
TParams extends ParameterizedObject["params"] | undefined,
TAction extends ParameterizedObject,
> = {
(ctx: TContext, params: TParams): void;
_out_TAction?: TAction;
};
type ToParameterizedObject<
TParameterizedMap extends Record<
string,
ParameterizedObject["params"] | undefined
>,
> = Values<{
[K in keyof TParameterizedMap & string]: {
type: K;
params: TParameterizedMap[K];
};
}>;
type CollectActions<
TContext extends MachineContext,
TParams extends ParameterizedObject["params"] | undefined,
> = (
{
context,
enqueue,
}: {
context: TContext;
enqueue: (action: () => void) => void;
},
params: TParams,
) => void;
declare function enqueueActions<
TContext extends MachineContext,
TParams extends ParameterizedObject["params"] | undefined,
TAction extends ParameterizedObject = ParameterizedObject,
>(
collect: CollectActions<TContext, TParams>,
): ActionFunction<TContext, TParams, TAction>;
declare function setup<
TContext extends MachineContext,
TActions extends Record<
string,
ParameterizedObject["params"] | undefined
> = {},
>({
types,
actions,
}: {
types?: { context?: TContext };
actions?: {
[K in keyof TActions]: ActionFunction<
TContext,
TActions[K],
ToParameterizedObject<TActions>
>;
};
}): void;
setup({
actions: {
doStuff: enqueueActions((_, params: number) => {}),
},
});
setup({
actions: {
doStuff: enqueueActions((_, params: number) => {}),
doOtherStuff: (_, params: string) => {},
},
});
setup({
actions: {
doStuff: enqueueActions((_, params: number) => {}),
doOtherStuff: (_: any, params: string) => {},
},
});π Actual behavior
First 2 calls mention such a relationship check failure in the error message:
Type 'ActionFunction<MachineContext, number, { type: string; params: never; }>' is not assignable to type 'ActionFunction<MachineContext, number, { type: "doStuff"; params: number; }>'.
Notice never there. This is quite weird an unexpected as there is no never in sight here. It turns out this is a silentNeverType that leaked through.
π Expected behavior
At the very least, I would expect it to error with consistent error messages mentioning unknown instead of never. Even better, if it could behave closer to a very similar version of this code: TS playground. In there the third error still errors but the first two infers nicely.
Additional information about the issue
No response
π Search Terms
silent never leak reverse mapped types nested calls return type inference
π Version & Regression Information
β― Playground Link
https://www.typescriptlang.org/play/?noEmit=true&ts=6.0.0-dev.20251202#code/C4TwDgpgBAaghgGwK4QM4B4AqA+KBeKTAbQGsIQB7AM0IF0BuAKEdEigFk4BjACwEsAdhADCFAcAgAPYPigAlCFwoAnACbpUwZYIDmAGihwBIbE0aCJyqt2gAFOMrgBbCJb4AvCKoDyAIwBWijIA3oxQUKwQAFxQmtoCOkzhYA7OqAD8MUgCJAIUAO4CTAC+zJFQAIJcwHxiAGLZ1bUC6GGEouJSMl0QAqqoHNz8Qh0S0nptmPaOTgM9fQPTzq4Q2p4+AUFEAEQpM6jbtFAAPlDZqhBUgl4T4ZhVNWJQ8-1QSy5u636B1RO4BKFwgAKaqSGKYUZdAx7NLg96oACUMQAbhQ+KoklAAPoUJDALH3JpiTKEB7NEpmcqYCjvFZrLzfIKtO60z5eThgZ7SXqvBRKNTM8KxLS6W5C1mrDwMzbVHYw2aHE5nPqXa6qNrYP6yeDINDoQFQIgAaSggigZEoNCmqQ+kvWHKgADJhfEdLQYgbwpEYkbMckbag4Ta6VLVBzjQw2sUSqYyuBoKIEAggmSxBhJpDpFyJAtBrxrpngGLrftszzFsG2RsfsA5QHFadzqqhKotQQgW1PVAlJ1xm1wr0AI4oFBi4oe-vdsRjYDgwt+54CYcQFAxIHcR4CNcI-C4VHond4PdojFRsXywOEeETQ-H9FmC5cBAOaBURqbxfLlCpgTpu6Fstc04fMRmnKFJnhQDXglelqy2XZ6yORsVSuFtix-KCKxmEMvhlGQCBg0NGV+RhsA7cIlCTIIYkTZNqh-DAITA8YrwDTVGCRSoiQEBoBG4rBCwMEs0iEn9Y0YR9n2UV932aWJXCQMBBSY3tum5IChgLZii0mBjMPkRQVHUSc4lFSdCNwms632BtlQuVCvA1WRgmKP4gQNSJUDFDdmi8xhxygDz4wyD0p1UkkVJnKBozaHy0xJLtjVNARzXIahSW41B3S4zdeP4yd-20sUhQyzdUAjYqhWpCzpRrLAGOwSdY3CGLik4-dT0YVAFLAdzYsyicStUCgAGVgCQKgqBiIcRwgBigSBLFoQDGIBCQJxfFWW9ArascJjasxuvG3qDTi39BqFYaxomqbP1m+bFuW-ZVvWzblG2lyEUq4bvGAHhVmuya1yWqALxiUyEg+1yz38hFDp6vrwjOy8uyu8agbulc5syhaQbBqA1o2rbdx2r7Jx+v6AfR27FpiIwQCe2EXV0KG9thpggA
π» Code
π Actual behavior
First 2 calls mention such a relationship check failure in the error message:
Notice never there. This is quite weird an unexpected as there is no
neverin sight here. It turns out this is asilentNeverTypethat leaked through.π Expected behavior
At the very least, I would expect it to error with consistent error messages mentioning
unknowninstead ofnever. Even better, if it could behave closer to a very similar version of this code: TS playground. In there the third error still errors but the first two infers nicely.Additional information about the issue
No response