Nested conditional generic types yields boolean not assignable to true | false | undefined. #22630
Description
TypeScript Version: 2.8RC
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Code
End of friday, so I don't have enough time to make a proper repro, hopefully this will be enough to go by:
type RecursivePartial<T> = { [param in keyof T]?: T[param] extends object ? RecursivePartial<T[param]> : T[param] }; interface UpdateValue<T> { $set: T extends object? RecursivePartial<T>: T; } interface ArrayUpdate<T> { $wildcard: WriteQuery<T>; } export type TypeWriteQuery<T> = T extends Array<infer U> ? Partial<ArrayUpdate<U>> : T extends object ? WriteQuery<T> : Partial<UpdateValue<T>> ; export type WriteQuery<T> = { [param in keyof T]?: TypeWriteQuery<T[param]> }; ///----- Erroring code: interface Approved { approved: boolean; } var check = <WriteQuery<Approved>>{ approved: { $set: true } };Expected behavior:
Works fine (unless I've made another mistake).
Actual behavior:
Errors that boolean isn't assignable to true | false | undefined because boolean isn't assignable to false.