TypeScript 奇怪的运行时缓存错误，涉及const和const T泛型

rryofs0p 于 6个月前发布在 TypeScript

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🔎 搜索词

is:issue runtime caching as const

🕗 版本与回归信息

这是类型检查器运行时不一致的情况
自引入const泛型以来，这是我在每个版本中尝试的行为

⏯ Playground链接

https://www.typescriptlang.org/play/?target=99#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

💻 代码

type ObjectFromEntries<T> = T extends readonly [infer Key extends string | number | symbol, infer Value][]
  ? { [key in Key]: Value }
  : never;

type KeyValuePairs<T> = {
  [K in keyof T]: [K, T[K]];
}[keyof T];

export function mapObjectEntries<
  const T extends object,
  const TMapped extends [string | number | symbol, unknown],
>(
  obj: T,
  mapper: ([a, b]: KeyValuePairs<T>) => TMapped,
): ObjectFromEntries<TMapped[]> {
  //@ts-expect-error Already properly typed through the signature
  return Object.fromEntries(Object.entries(obj).map(mapper));
}

const test = mapObjectEntries({ a: 1, b: 2 }, ([x, y]) => [x, y]);

这里有一个屏幕录制，说明了这个问题：
vivaldi_gWZYW9aEDa.mp4

🙁 实际行为

类型检查器是上下文敏感的。当我在表达式后面添加一个 as const(参见屏幕录制),即使我再次删除 as const,它也能正常编译。

🙂 预期行为

一致性

关于此问题的其他信息

无响应*

typescript

来源：https://github.com/microsoft/TypeScript/issues/58351

1条答案

按热度按时间

xlpyo6sf1#

基于报告的问题准备的失败的测试用例：

/// <reference path="fourslash.ts" />

// @strict: true
// @target: esnext
// @lib: esnext

//// type ObjectFromEntries<T> = T extends readonly [
////   infer Key extends string | number | symbol,
////   infer Value,
//// ][]
////   ? { [key in Key]: Value }
////   : never;
////
//// type KeyValuePairs<T> = {
////   [K in keyof T]: [K, T[K]];
//// }[keyof T];
////
//// declare function mapObjectEntries<
////   const T extends object,
////   const TMapped extends [string | number | symbol, unknown],
//// >(
////   obj: T,
////   mapper: ([a, b]: KeyValuePairs<T>) => TMapped,
//// ): ObjectFromEntries<TMapped[]>;
////
//// mapObjectEntries({ a: 1, b: 2 }, ([x, y]) => ["a/*1*/", y]);

verify.completions({
    marker: "1",
    exact: ["a"],
});
verify.getSemanticDiagnostics([]);

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