1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
|
// @strict: true
// @declaration: true
// Repro from #17456
type StringContains<S extends string, L extends string> = ({ [K in S]: 'true' } & { [key: string]: 'false'})[L];
type ObjectHasKey<O, L extends string> = StringContains<Extract<keyof O, string>, L>;
type A<T> = ObjectHasKey<T, '0'>;
type B = ObjectHasKey<[string, number], '1'>; // "true"
type C = ObjectHasKey<[string, number], '2'>; // "false"
type D = A<[string]>; // "true"
// Error, "false" not handled
type E<T> = { true: 'true' }[ObjectHasKey<T, '1'>];
type Juxtapose<T> = ({ true: 'otherwise' } & { [k: string]: 'true' })[ObjectHasKey<T, '1'>];
// Error, "otherwise" is missing
type DeepError<T> = { true: 'true' }[Juxtapose<T>];
type DeepOK<T> = { true: 'true', otherwise: 'false' }[Juxtapose<T>];
|