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
|
=== tests/cases/compiler/contextualSignatureInstantiation3.ts ===
function map<T, U>(items: T[], f: (x: T) => U): U[]{
>map : <T, U>(items: T[], f: (x: T) => U) => U[]
>items : T[]
>f : (x: T) => U
>x : T
return items.map(f);
>items.map(f) : U[]
>items.map : <U>(callbackfn: (value: T, index: number, array: T[]) => U, thisArg?: any) => U[]
>items : T[]
>map : <U>(callbackfn: (value: T, index: number, array: T[]) => U, thisArg?: any) => U[]
>f : (x: T) => U
}
function identity<T>(x: T) {
>identity : <T>(x: T) => T
>x : T
return x;
>x : T
}
function singleton<T>(x: T) {
>singleton : <T>(x: T) => T[]
>x : T
return [x];
>[x] : T[]
>x : T
}
var xs = [1, 2, 3];
>xs : number[]
>[1, 2, 3] : number[]
>1 : 1
>2 : 2
>3 : 3
// Have compiler check that we get the correct types
var v1: number[];
>v1 : number[]
var v1 = xs.map(identity); // Error if not number[]
>v1 : number[]
>xs.map(identity) : number[]
>xs.map : <U>(callbackfn: (value: number, index: number, array: number[]) => U, thisArg?: any) => U[]
>xs : number[]
>map : <U>(callbackfn: (value: number, index: number, array: number[]) => U, thisArg?: any) => U[]
>identity : <T>(x: T) => T
var v1 = map(xs, identity); // Error if not number[]
>v1 : number[]
>map(xs, identity) : number[]
>map : <T, U>(items: T[], f: (x: T) => U) => U[]
>xs : number[]
>identity : <T>(x: T) => T
var v2: number[][];
>v2 : number[][]
var v2 = xs.map(singleton); // Error if not number[][]
>v2 : number[][]
>xs.map(singleton) : number[][]
>xs.map : <U>(callbackfn: (value: number, index: number, array: number[]) => U, thisArg?: any) => U[]
>xs : number[]
>map : <U>(callbackfn: (value: number, index: number, array: number[]) => U, thisArg?: any) => U[]
>singleton : <T>(x: T) => T[]
var v2 = map(xs, singleton); // Error if not number[][]
>v2 : number[][]
>map(xs, singleton) : number[][]
>map : <T, U>(items: T[], f: (x: T) => U) => U[]
>xs : number[]
>singleton : <T>(x: T) => T[]
|
