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
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
|
=== tests/cases/conformance/expressions/functionCalls/overloadResolution.ts ===
class SomeBase {
>SomeBase : SomeBase
private n;
>n : any
public s: string;
>s : string
}
class SomeDerived1 extends SomeBase {
>SomeDerived1 : SomeDerived1
>SomeBase : SomeBase
private m;
>m : any
}
class SomeDerived2 extends SomeBase {
>SomeDerived2 : SomeDerived2
>SomeBase : SomeBase
private m;
>m : any
}
class SomeDerived3 extends SomeBase {
>SomeDerived3 : SomeDerived3
>SomeBase : SomeBase
private m;
>m : any
}
// Ambiguous call picks the first overload in declaration order
function fn1(s: string): string;
>fn1 : { (s: string): string; (s: number): number; }
>s : string
function fn1(s: number): number;
>fn1 : { (s: string): string; (s: number): number; }
>s : number
function fn1() { return null; }
>fn1 : { (s: string): string; (s: number): number; }
>null : null
var s = fn1(undefined);
>s : string
>fn1(undefined) : string
>fn1 : { (s: string): string; (s: number): number; }
>undefined : undefined
var s: string;
>s : string
// No candidate overloads found
fn1({}); // Error
>fn1({}) : never
>fn1 : { (s: string): string; (s: number): number; }
>{} : {}
// Generic and non - generic overload where generic overload is the only candidate when called with type arguments
function fn2(s: string, n: number): number;
>fn2 : { (s: string, n: number): number; <T>(n: number, t: T): T; }
>s : string
>n : number
function fn2<T>(n: number, t: T): T;
>fn2 : { (s: string, n: number): number; <T>(n: number, t: T): T; }
>n : number
>t : T
function fn2() { return undefined; }
>fn2 : { (s: string, n: number): number; <T>(n: number, t: T): T; }
>undefined : undefined
var d = fn2<Date>(0, undefined);
>d : Date
>fn2<Date>(0, undefined) : Date
>fn2 : { (s: string, n: number): number; <T>(n: number, t: T): T; }
>0 : 0
>undefined : undefined
var d: Date;
>d : Date
// Generic and non - generic overload where generic overload is the only candidate when called without type arguments
var s = fn2(0, '');
>s : string
>fn2(0, '') : ""
>fn2 : { (s: string, n: number): number; <T>(n: number, t: T): T; }
>0 : 0
>'' : ""
// Generic and non - generic overload where non - generic overload is the only candidate when called with type arguments
fn2<Date>('', 0); // Error
>fn2<Date>('', 0) : number
>fn2 : { (s: string, n: number): number; <T>(n: number, t: T): T; }
>'' : ""
>0 : 0
// Generic and non - generic overload where non - generic overload is the only candidate when called without type arguments
fn2('', 0); // OK
>fn2('', 0) : number
>fn2 : { (s: string, n: number): number; <T>(n: number, t: T): T; }
>'' : ""
>0 : 0
// Generic overloads with differing arity called without type arguments
function fn3<T>(n: T): string;
>fn3 : { <T>(n: T): string; <T, U>(s: string, t: T, u: U): U; <T, U, V>(v: V, u: U, t: T): number; }
>n : T
function fn3<T, U>(s: string, t: T, u: U): U;
>fn3 : { <T>(n: T): string; <T, U>(s: string, t: T, u: U): U; <T, U, V>(v: V, u: U, t: T): number; }
>s : string
>t : T
>u : U
function fn3<T, U, V>(v: V, u: U, t: T): number;
>fn3 : { <T>(n: T): string; <T, U>(s: string, t: T, u: U): U; <T, U, V>(v: V, u: U, t: T): number; }
>v : V
>u : U
>t : T
function fn3() { return null; }
>fn3 : { <T>(n: T): string; <T, U>(s: string, t: T, u: U): U; <T, U, V>(v: V, u: U, t: T): number; }
>null : null
var s = fn3(3);
>s : string
>fn3(3) : string
>fn3 : { <T>(n: T): string; <T, U>(s: string, t: T, u: U): U; <T, U, V>(v: V, u: U, t: T): number; }
>3 : 3
var s = fn3('', 3, '');
>s : string
>fn3('', 3, '') : ""
>fn3 : { <T>(n: T): string; <T, U>(s: string, t: T, u: U): U; <T, U, V>(v: V, u: U, t: T): number; }
>'' : ""
>3 : 3
>'' : ""
var n = fn3(5, 5, 5);
>n : number
>fn3(5, 5, 5) : number
>fn3 : { <T>(n: T): string; <T, U>(s: string, t: T, u: U): U; <T, U, V>(v: V, u: U, t: T): number; }
>5 : 5
>5 : 5
>5 : 5
var n: number;
>n : number
// Generic overloads with differing arity called with type arguments matching each overload type parameter count
var s = fn3<number>(4);
>s : string
>fn3<number>(4) : string
>fn3 : { <T>(n: T): string; <T, U>(s: string, t: T, u: U): U; <T, U, V>(v: V, u: U, t: T): number; }
>4 : 4
var s = fn3<string, string>('', '', '');
>s : string
>fn3<string, string>('', '', '') : string
>fn3 : { <T>(n: T): string; <T, U>(s: string, t: T, u: U): U; <T, U, V>(v: V, u: U, t: T): number; }
>'' : ""
>'' : ""
>'' : ""
var n = fn3<number, string, string>('', '', 3);
>n : number
>fn3<number, string, string>('', '', 3) : number
>fn3 : { <T>(n: T): string; <T, U>(s: string, t: T, u: U): U; <T, U, V>(v: V, u: U, t: T): number; }
>'' : ""
>'' : ""
>3 : 3
// Generic overloads with differing arity called with type argument count that doesn't match any overload
fn3<number, number, number, number>(); // Error
>fn3<number, number, number, number>() : string
>fn3 : { <T>(n: T): string; <T, U>(s: string, t: T, u: U): U; <T, U, V>(v: V, u: U, t: T): number; }
// Generic overloads with constraints called with type arguments that satisfy the constraints
function fn4<T extends string, U extends number>(n: T, m: U);
>fn4 : { <T extends string, U extends number>(n: T, m: U): any; <T extends number, U extends string>(n: T, m: U): any; }
>n : T
>m : U
function fn4<T extends number, U extends string>(n: T, m: U);
>fn4 : { <T extends string, U extends number>(n: T, m: U): any; <T extends number, U extends string>(n: T, m: U): any; }
>n : T
>m : U
function fn4() { }
>fn4 : { <T extends string, U extends number>(n: T, m: U): any; <T extends number, U extends string>(n: T, m: U): any; }
fn4<string, number>('', 3);
>fn4<string, number>('', 3) : any
>fn4 : { <T extends string, U extends number>(n: T, m: U): any; <T extends number, U extends string>(n: T, m: U): any; }
>'' : ""
>3 : 3
fn4<string, number>(3, ''); // Error
>fn4<string, number>(3, '') : any
>fn4 : { <T extends string, U extends number>(n: T, m: U): any; <T extends number, U extends string>(n: T, m: U): any; }
>3 : 3
>'' : ""
fn4<number, string>('', 3); // Error
>fn4<number, string>('', 3) : any
>fn4 : { <T extends string, U extends number>(n: T, m: U): any; <T extends number, U extends string>(n: T, m: U): any; }
>'' : ""
>3 : 3
fn4<number, string>(3, '');
>fn4<number, string>(3, '') : any
>fn4 : { <T extends string, U extends number>(n: T, m: U): any; <T extends number, U extends string>(n: T, m: U): any; }
>3 : 3
>'' : ""
// Generic overloads with constraints called without type arguments but with types that satisfy the constraints
fn4('', 3);
>fn4('', 3) : any
>fn4 : { <T extends string, U extends number>(n: T, m: U): any; <T extends number, U extends string>(n: T, m: U): any; }
>'' : ""
>3 : 3
fn4(3, '');
>fn4(3, '') : any
>fn4 : { <T extends string, U extends number>(n: T, m: U): any; <T extends number, U extends string>(n: T, m: U): any; }
>3 : 3
>'' : ""
fn4(3, undefined);
>fn4(3, undefined) : any
>fn4 : { <T extends string, U extends number>(n: T, m: U): any; <T extends number, U extends string>(n: T, m: U): any; }
>3 : 3
>undefined : undefined
fn4('', null);
>fn4('', null) : any
>fn4 : { <T extends string, U extends number>(n: T, m: U): any; <T extends number, U extends string>(n: T, m: U): any; }
>'' : ""
>null : null
// Generic overloads with constraints called with type arguments that do not satisfy the constraints
fn4<boolean, Date>(null, null); // Error
>fn4<boolean, Date>(null, null) : any
>fn4 : { <T extends string, U extends number>(n: T, m: U): any; <T extends number, U extends string>(n: T, m: U): any; }
>null : null
>null : null
// Generic overloads with constraints called without type arguments but with types that do not satisfy the constraints
fn4(true, null); // Error
>fn4(true, null) : any
>fn4 : { <T extends string, U extends number>(n: T, m: U): any; <T extends number, U extends string>(n: T, m: U): any; }
>true : true
>null : null
fn4(null, true); // Error
>fn4(null, true) : any
>fn4 : { <T extends string, U extends number>(n: T, m: U): any; <T extends number, U extends string>(n: T, m: U): any; }
>null : null
>true : true
// Non - generic overloads where contextual typing of function arguments has errors
function fn5(f: (n: string) => void): string;
>fn5 : { (f: (n: string) => void): string; (f: (n: number) => void): number; }
>f : (n: string) => void
>n : string
function fn5(f: (n: number) => void): number;
>fn5 : { (f: (n: string) => void): string; (f: (n: number) => void): number; }
>f : (n: number) => void
>n : number
function fn5() { return undefined; }
>fn5 : { (f: (n: string) => void): string; (f: (n: number) => void): number; }
>undefined : undefined
var n = fn5((n) => n.toFixed());
>n : number
>fn5((n) => n.toFixed()) : string
>fn5 : { (f: (n: string) => void): string; (f: (n: number) => void): number; }
>(n) => n.toFixed() : (n: string) => any
>n : string
>n.toFixed() : any
>n.toFixed : any
>n : string
>toFixed : any
var s = fn5((n) => n.substr(0));
>s : string
>fn5((n) => n.substr(0)) : string
>fn5 : { (f: (n: string) => void): string; (f: (n: number) => void): number; }
>(n) => n.substr(0) : (n: string) => string
>n : string
>n.substr(0) : string
>n.substr : (from: number, length?: number) => string
>n : string
>substr : (from: number, length?: number) => string
>0 : 0
|
