```
interface PathArray<T, L> extends Array<string | number> {
["0"]?: keyof T;
["1"]?: L extends {
["0"]: infer K0;
}
? K0 extends keyof T
? keyof T[K0]
: never
: never;
["2"]?: L extends {
["0"]: infer K0;
["1"]: infer K1;
}
? K0 extends keyof T
? K1 extends keyof T[K0]
? keyof T[K0][K1]
: never
: never
: never;
["3"]?: L extends {
["0"]: infer K0;
["1"]: infer K1;
["2"]: infer K2;
}
? K0 extends keyof T
? K1 extends keyof T[K0]
? K2 extends keyof T[K0][K1]
? keyof T[K0][K1][K2]
: never
: never
: never
: never;
["4"]?: L extends {
["0"]: infer K0;
["1"]: infer K1;
["2"]: infer K2;
["3"]: infer K3;
}
? K0 extends keyof T
? K1 extends keyof T[K0]
? K2 extends keyof T[K0][K1]
? K3 extends keyof T[K0][K1][K2]
? keyof T[K0][K1][K2][K3]
: never
: never
: never
: never
: never;
["5"]?: L extends {
["0"]: infer K0;
["1"]: infer K1;
["2"]: infer K2;
["3"]: infer K3;
["4"]: infer K4;
}
? K0 extends keyof T
? K1 extends keyof T[K0]
? K2 extends keyof T[K0][K1]
? K3 extends keyof T[K0][K1][K2]
? K4 extends keyof T[K0][K1][K2][K3]
? keyof T[K0][K1][K2][K3][K4]
: never
: never
: never
: never
: never
: never;
["6"]?: L extends {
["0"]: infer K0;
["1"]: infer K1;
["2"]: infer K2;
["3"]: infer K3;
["4"]: infer K4;
["5"]: infer K5;
}
? K0 extends keyof T
? K1 extends keyof T[K0]
? K2 extends keyof T[K0][K1]
? K3 extends keyof T[K0][K1][K2]
? K4 extends keyof T[K0][K1][K2][K3]
? K5 extends keyof T[K0][K1][K2][K3][K4]
? keyof T[K0][K1][K2][K3][K4][K5]
: never
: never
: never
: never
: never
: never
: never;
}
type ArrayHasIndex<MinLenght extends number> = { [K in MinLenght]: any };
export type PathArrayValue<
T,
L extends PathArray<T, L>
> = L extends ArrayHasIndex<0 | 1 | 2 | 3 | 4 | 5 | 6 | 7>
? any
: L extends ArrayHasIndex<0 | 1 | 2 | 3 | 4 | 5 | 6>
? T[L[0]][L[1]][L[2]][L[3]][L[4]][L[5]][L[6]]
: L extends ArrayHasIndex<0 | 1 | 2 | 3 | 4 | 5>
? T[L[0]][L[1]][L[2]][L[3]][L[4]][L[5]]
: L extends ArrayHasIndex<0 | 1 | 2 | 3 | 4>
? T[L[0]][L[1]][L[2]][L[3]][L[4]]
: L extends ArrayHasIndex<0 | 1 | 2 | 3>
? T[L[0]][L[1]][L[2]][L[3]]
: L extends ArrayHasIndex<0 | 1 | 2>
? T[L[0]][L[1]][L[2]]
: L extends ArrayHasIndex<0 | 1>
? T[L[0]][L[1]]
: L extends ArrayHasIndex<0>
? T[L[0]]
: never;
export type Path<T, L> = PathArray<T, L> | keyof T;
export type PathValue<T, L extends Path<T, L>> = L extends PathArray<T, L>
? PathArrayValue<T, L>
: L extends keyof T
? T[L]
: any;
declare function path<T, L extends Path<T, L>>(
object: T,
params: L
): PathValue<T, L>;
const obj = {
v: {
w: { x: { y: { z: { a: { b: { c: 2 } } } } } },
ouch: true,
foo: [{ bar: 2 }, { bar: 3 }]
}
};
const output: number = path(obj, ["v", "w", "x"]); // 💥
const output2: object = path(obj, ["v", "w", "x"]); // ✔️
const output4: { c: string } = path(obj, ["v", "w", "x", "y", "z", "a", "b"]); // 💥
const output3: { c: number } = path(obj, ["v", "w", "x", "y", "z", "a", "b"]); // ✔️
const output5: "wrong" = path(obj, ["v", "w", "x", "y", "z", "a", "b", "c"]); // ✔️ since after 7 levels there is no typechecking
const x = path(obj, ["v", "ouch", "x"]); // 💥
const y = path(obj, ["v", "ouch", "y"]); // 💥
const z = path(obj, ["v", "ouch", "somethingCompletelyDifferent"]); // 💥
path(obj, "!"); // 💥
path(obj, ["!"]); // 💥
path(obj, ["v", "!"]); // 💥
path(obj, ["v", "w", "!"]); // 💥
path(obj, ["v", "w", "x", "!"]); // 💥
path(obj, ["v", "w", "x", "y", "!"]); // 💥
path(obj, ["v", "w", "x", "y", "z", "!"]); // 💥
path(obj, ["v", "w", "x", "y", "z", "a", "!"]); // 💥
path(obj, ["v", "w", "x", "y", "z", "a", "b", "!"]); // ✔️ since after 7 levels there is no typechecking
path(obj, "v"); // ✔️
path(obj, ["v"]); // ✔️
path(obj, ["v", "w"]); // ✔️
path(obj, ["v", "w", "x"]); // ✔️
path(obj, ["v", "w", "x", "y"]); // ✔️
path(obj, ["v", "w", "x", "y", "z"]); // ✔️
path(obj, ["v", "w", "x", "y", "z", "a"]); // ✔️
path(obj, ["v", "w", "x", "y", "z", "a", "b"]); // ✔️
path(obj, ["v", "w", "x", "y", "z", "a", "b", "c"]); // ✔️
```
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