打字稿错误地推论元组为数组 [英] Typescript inferring Tuple as Array Incorrectly

问题描述

先为我的英语道歉.

我有一个像 function func():[string，string []] 这样的函数，它返回一个元组.但是，当我实现return语句

I have a function like function func(): [string, string[]] which returns a Tuple. However, when I implement the return statement like

var test = ['text', ['foo', 'bar']];
return test;

Typescript推断我的返回类型为(string | string [])[] ，而不是 [string，string []] .

Typescript inferred my return type as (string | string[])[] instead of [string, string[]].

我是否错过了某些东西，还是应该每次都像 return< [string，string []]> ['text'，['foo'，'bar']一样将返回对象显式转换为元组] .如果是，那会不会很烦人?

Did I missed something or should I need to cast the return object as Tuple explicitly everytime like return <[string, string[]]>['text', ['foo', 'bar']]. If yes then isn't it quite annoying?

提供的完整功能如下:

function func(): [string, string[]] {
    var test= ['text', ['foo', 'bar']];

    return test;
}

错误:类型'((string | string [])[]'缺少类型'[string，string []]'的以下属性:0，1ts(2739)

推荐答案

如果您想将 ['text'，['foo'，'bar']] 用作数组或

TS cannot differentiate, if you want ['text', ['foo', 'bar']] to be an array or a tuple - the expression is the same! It will default to an array for the test variable type, if nothing else specified.

如果要使用元组，请执行以下一项操作:

If you want a tuple, do one of the following:

• 使用 const断言
• 赋予 test 一个明确的元组类型

• use a const assertion
• give test an explicit tuple type

function func(): [string, string[]] {
    const test = ['text', ['foo', 'bar']];
    const test2 = ['text', ['foo', 'bar']] as const;
    const test3: [string, string[]] = ['text', ['foo', 'bar']];
    // return test;   // error, was inferred as array
    // return test2; // works
    return test3; // works
}

使用作为常量，您不必重复输入类型，但是必须使用 readonly 修饰符注释函数返回类型: readonly [string，只读[string，string]] .

With as const you don't have to repeat your type, but you will have to annotate the function return type with readonly modifiers: readonly [string, readonly [string, string]].

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