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// https://github.com/microsoft/TypeScript/issues/41984
interface TestCase<T extends string | number> {
readonly val1: T | ReadonlyArray<T>;
readonly val2: ReadonlyArray<T>;
}
interface MultiCaseFixture<T> {
cases: T[];
}
function subDataFunc(): TestCase<string | number>[] {
return [
{ val1: "a", val2: ["a", "b", "c"] },
{ val1: 2, val2: [1, 2, 3] },
{ val1: ["a", "z"], val2: ["x", "y", "z"] },
{ val1: [5, 10], val2: [10, 100, 1000] },
];
}
function dataFunc<T>(subFunc: () => T[]): MultiCaseFixture<T> {
return { cases: subFunc() };
}
function testFunc() {
const fixture = dataFunc<TestCase<string | number>>(subDataFunc);
fixture.cases.forEach(({ val1, val2 }) => {
if (Array.isArray(val1)) {
// This should retain val1 as being an array
const reversedVal1 = val1.slice().reverse();
console.log(reversedVal1);
} else {
console.log(val1);
}
console.log(val2);
});
}
testFunc();
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