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
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
|
=== tests/cases/compiler/keyofDoesntContainSymbols.ts ===
const sym = Symbol();
>sym : unique symbol
>Symbol() : unique symbol
>Symbol : SymbolConstructor
const num = 0;
>num : 0
>0 : 0
const obj = { num: 0, str: 's', [num]: num as 0, [sym]: sym };
>obj : { num: number; str: string; [num]: 0; [sym]: symbol; }
>{ num: 0, str: 's', [num]: num as 0, [sym]: sym } : { num: number; str: string; [num]: 0; [sym]: symbol; }
>num : number
>0 : 0
>str : string
>'s' : "s"
>[num] : 0
>num : 0
>num as 0 : 0
>num : 0
>[sym] : symbol
>sym : unique symbol
>sym : unique symbol
function set <T extends object, K extends keyof T> (obj: T, key: K, value: T[K]): T[K] {
>set : <T extends object, K extends keyof T>(obj: T, key: K, value: T[K]) => T[K]
>obj : T
>key : K
>value : T[K]
return obj[key] = value;
>obj[key] = value : T[K]
>obj[key] : T[K]
>obj : T
>key : K
>value : T[K]
}
const val = set(obj, 'str', '');
>val : string
>set(obj, 'str', '') : string
>set : <T extends object, K extends keyof T>(obj: T, key: K, value: T[K]) => T[K]
>obj : { num: number; str: string; [num]: 0; [sym]: symbol; }
>'str' : "str"
>'' : ""
// string
const valB = set(obj, 'num', '');
>valB : any
>set(obj, 'num', '') : any
>set : <T extends object, K extends keyof T>(obj: T, key: K, value: T[K]) => T[K]
>obj : { num: number; str: string; [num]: 0; [sym]: symbol; }
>'num' : "num"
>'' : ""
// Expect type error
// Argument of type '""' is not assignable to parameter of type 'number'.
const valC = set(obj, sym, sym);
>valC : any
>set(obj, sym, sym) : any
>set : <T extends object, K extends keyof T>(obj: T, key: K, value: T[K]) => T[K]
>obj : { num: number; str: string; [num]: 0; [sym]: symbol; }
>sym : unique symbol
>sym : unique symbol
// Expect type error
// Argument of type 'unique symbol' is not assignable to parameter of type "str" | "num"
const valD = set(obj, num, num);
>valD : any
>set(obj, num, num) : any
>set : <T extends object, K extends keyof T>(obj: T, key: K, value: T[K]) => T[K]
>obj : { num: number; str: string; [num]: 0; [sym]: symbol; }
>num : 0
>num : 0
// Expect type error
// Argument of type '0' is not assignable to parameter of type "str" | "num"
type KeyofObj = keyof typeof obj;
>KeyofObj : "str" | "num"
>obj : { num: number; str: string; [num]: 0; [sym]: symbol; }
// "str" | "num"
type Values<T> = T[keyof T];
>Values : T[keyof T]
type ValuesOfObj = Values<typeof obj>;
>ValuesOfObj : string | number
>obj : { num: number; str: string; [num]: 0; [sym]: symbol; }
|
