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
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
|
=== tests/cases/conformance/expressions/typeGuards/typeGuardsDefeat.ts ===
// Also note that it is possible to defeat a type guard by calling a function that changes the
// type of the guarded variable.
function foo(x: number | string) {
>foo : (x: number | string) => number
>x : string | number
function f() {
>f : () => void
x = 10;
>x = 10 : 10
>x : string | number
>10 : 10
}
if (typeof x === "string") {
>typeof x === "string" : boolean
>typeof x : "string" | "number" | "bigint" | "boolean" | "symbol" | "undefined" | "object" | "function"
>x : string | number
>"string" : "string"
f();
>f() : void
>f : () => void
return x.length; // string
>x.length : number
>x : string
>length : number
}
else {
return x++; // number
>x++ : number
>x : number
}
}
function foo2(x: number | string) {
>foo2 : (x: number | string) => number
>x : string | number
if (typeof x === "string") {
>typeof x === "string" : boolean
>typeof x : "string" | "number" | "bigint" | "boolean" | "symbol" | "undefined" | "object" | "function"
>x : string | number
>"string" : "string"
return x.length; // string
>x.length : number
>x : string
>length : number
}
else {
var f = function () {
>f : () => number
>function () { return x * x; } : () => number
return x * x;
>x * x : number
>x : string | number
>x : string | number
};
}
x = "hello";
>x = "hello" : "hello"
>x : string | number
>"hello" : "hello"
f();
>f() : number
>f : () => number
}
function foo3(x: number | string) {
>foo3 : (x: number | string) => number
>x : string | number
if (typeof x === "string") {
>typeof x === "string" : boolean
>typeof x : "string" | "number" | "bigint" | "boolean" | "symbol" | "undefined" | "object" | "function"
>x : string | number
>"string" : "string"
return x.length; // string
>x.length : number
>x : string
>length : number
}
else {
var f = () => x * x;
>f : () => number
>() => x * x : () => number
>x * x : number
>x : string | number
>x : string | number
}
x = "hello";
>x = "hello" : "hello"
>x : string | number
>"hello" : "hello"
f();
>f() : number
>f : () => number
}
|
