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
|
// @strict: true
// @declaration: true
// Repro from #17456
type StringContains<S extends string, L extends string> = (
{ [K in S]: 'true' } &
{ [key: string]: 'false' }
)[L]
type ObjectHasKey<O, L extends string> = StringContains<Extract<keyof O, string>, L>
type First<T> = ObjectHasKey<T, '0'>; // Should be deferred
type T1 = ObjectHasKey<{ a: string }, 'a'>; // 'true'
type T2 = ObjectHasKey<{ a: string }, 'b'>; // 'false'
// Verify that mapped type isn't eagerly resolved in type-to-string operation
declare function f1<A extends string, B extends string>(a: A, b: B): { [P in A | B]: any };
function f2<A extends string>(a: A) {
return f1(a, 'x');
}
function f3(x: 'a' | 'b') {
return f2(x);
}
|
