我在一个typescript文件中有以下函数：

export function buildEnvTests<T extends ReadonlyArray<string>>(environments: T) {
    const r = {} as {[K in T[number] as `is${K}`]: () => boolean};
    for (let e of environments) {
        r[`is${e}`] = () => '' === e;
    }
    return r;
}

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如果我要将此函数导入到TS文件中，VS Code中的Intellisense会在返回值中正确报告派生的键。例如：

import { buildEnvTests } from "./test.js";
const x = ['A', 'B', 'C'] as const;
const r = buildEnvTests(x);
r. // Here, properties named isA, isB and isC show up as expected.

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但是，如果我在JavaScript文件中执行相同的操作，则不会得到任何建议：

import { buildEnvTests } from "./test.js";
const x = ['A', 'B', 'C'];
const r = buildEnvTests(x);
r. // Here:  No Intellisense.

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