1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
|
// @lib: es6
// @keyofStringsOnly: true
const sym = Symbol();
const num = 0;
const obj = { num: 0, str: 's', [num]: num as 0, [sym]: sym };
function set <T extends object, K extends keyof T> (obj: T, key: K, value: T[K]): T[K] {
return obj[key] = value;
}
const val = set(obj, 'str', '');
// string
const valB = set(obj, 'num', '');
// Expect type error
// Argument of type '""' is not assignable to parameter of type 'number'.
const valC = set(obj, sym, sym);
// Expect type error
// Argument of type 'unique symbol' is not assignable to parameter of type "str" | "num"
const valD = set(obj, num, num);
// Expect type error
// Argument of type '0' is not assignable to parameter of type "str" | "num"
type KeyofObj = keyof typeof obj;
// "str" | "num"
type Values<T> = T[keyof T];
type ValuesOfObj = Values<typeof obj>;
|