1+ // Widening vs. non-widening literal types
2+
3+ function f1 ( ) {
4+ const c1 = "hello" ; // Widening type "hello"
5+ let v1 = c1 ; // Type string
6+ const c2 = c1 ; // Widening type "hello"
7+ let v2 = c2 ; // Type string
8+ const c3 : "hello" = "hello" ; // Type "hello"
9+ let v3 = c3 ; // Type "hello"
10+ const c4 : "hello" = c1 ; // Type "hello"
11+ let v4 = c4 ; // Type "hello"
12+ }
13+
14+ function f2 ( cond : boolean ) {
15+ const c1 = cond ? "foo" : "bar" ; // widening "foo" | widening "bar"
16+ const c2 : "foo" | "bar" = c1 ; // "foo" | "bar"
17+ const c3 = cond ? c1 : c2 ; // "foo" | "bar"
18+ const c4 = cond ? c3 : "baz" ; // "foo" | "bar" | widening "baz"
19+ const c5 : "foo" | "bar" | "baz" = c4 ; // "foo" | "bar" | "baz"
20+ let v1 = c1 ; // string
21+ let v2 = c2 ; // "foo" | "bar"
22+ let v3 = c3 ; // "foo" | "bar"
23+ let v4 = c4 ; // string
24+ let v5 = c5 ; // "foo" | "bar" | "baz"
25+ }
26+
27+ function f3 ( ) {
28+ const c1 = 123 ; // Widening type 123
29+ let v1 = c1 ; // Type number
30+ const c2 = c1 ; // Widening type 123
31+ let v2 = c2 ; // Type number
32+ const c3 : 123 = 123 ; // Type 123
33+ let v3 = c3 ; // Type 123
34+ const c4 : 123 = c1 ; // Type 123
35+ let v4 = c4 ; // Type 123
36+ }
37+
38+ function f4 ( cond : boolean ) {
39+ const c1 = cond ? 123 : 456 ; // widening 123 | widening 456
40+ const c2 : 123 | 456 = c1 ; // 123 | 456
41+ const c3 = cond ? c1 : c2 ; // 123 | 456
42+ const c4 = cond ? c3 : 789 ; // 123 | 456 | widening 789
43+ const c5 : 123 | 456 | 789 = c4 ; // 123 | 456 | 789
44+ let v1 = c1 ; // number
45+ let v2 = c2 ; // 123 | 456
46+ let v3 = c3 ; // 123 | 456
47+ let v4 = c4 ; // number
48+ let v5 = c5 ; // 123 | 456 | 789
49+ }
50+
51+ function f5 ( ) {
52+ const c1 = "foo" ;
53+ let v1 = c1 ;
54+ const c2 : "foo" = "foo" ;
55+ let v2 = c2 ;
56+ const c3 = "foo" as "foo" ;
57+ let v3 = c3 ;
58+ const c4 = < "foo" > "foo" ;
59+ let v4 = c4 ;
60+ }
61+
62+ // Repro from #10898
63+
64+ type FAILURE = "FAILURE" ;
65+ const FAILURE = "FAILURE" ;
66+
67+ type Result < T > = T | FAILURE ;
68+
69+ function doWork < T > ( ) : Result < T > {
70+ return FAILURE ;
71+ }
72+
73+ function isSuccess < T > ( result : Result < T > ) : result is T {
74+ return ! isFailure ( result ) ;
75+ }
76+
77+ function isFailure < T > ( result : Result < T > ) : result is FAILURE {
78+ return result === FAILURE ;
79+ }
80+
81+ function increment ( x : number ) : number {
82+ return x + 1 ;
83+ }
84+
85+ let result = doWork < number > ( ) ;
86+
87+ if ( isSuccess ( result ) ) {
88+ increment ( result ) ;
89+ }
90+
91+ // Repro from #10898
92+
93+ type TestEvent = "onmouseover" | "onmouseout" ;
94+
95+ function onMouseOver ( ) : TestEvent { return "onmouseover" ; }
96+
97+ let x = onMouseOver ( ) ;
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