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12.ts
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12.ts
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import { Expect, Equal } from "type-testing";
type WithIndex<Tuple extends any[], Output extends any[] = []> = Tuple extends [
infer First,
...infer Rest,
]
? WithIndex<Rest, [...Output, [First, Output["length"]]]>
: Output;
type DoFind<Tuple extends any[]> = Tuple extends [infer First, ...infer Rest]
? First extends ["🎅🏼", infer Count]
? Count
: DoFind<Rest>
: never;
type FindSanta<Tuple extends any[]> = DoFind<WithIndex<Tuple>>;
type Forest0 = ["🎅🏼", "🎄", "🎄", "🎄"];
type test_0_actual = FindSanta<Forest0>;
// ^?
type test_0_expected = 0;
type test_0 = Expect<Equal<test_0_expected, test_0_actual>>;
type Forest1 = ["🎄", "🎅🏼", "🎄", "🎄", "🎄", "🎄"];
type test_1_actual = FindSanta<Forest1>;
// ^?
type test_1_expected = 1;
type test_1 = Expect<Equal<test_1_expected, test_1_actual>>;
type Forest2 = ["🎄", "🎄", "🎅🏼", "🎄"];
type test_2_actual = FindSanta<Forest2>;
// ^?
type test_2_expected = 2;
type test_2 = Expect<Equal<test_2_expected, test_2_actual>>;
type Forest3 = ["🎄", "🎄", "🎄", "🎅🏼", "🎄"];
type test_3_actual = FindSanta<Forest3>;
// ^?
type test_3_expected = 3;
type test_3 = Expect<Equal<test_3_expected, test_3_actual>>;
type Forest4 = ["🎄", "🎄", "🎄", "🎄"];
type test_4_actual = FindSanta<Forest4>;
// ^?
type test_4_expected = never;
type test_4 = Expect<Equal<test_4_expected, test_4_actual>>;