为什么'let'声明符号将在TypeScript中转换为字符串索引签名？

Question

使用IDS将符号声明为对象的键时，例如：

dfb

let s = Symbol()的类型将自动变为let a = { [s]:1 } ，而在尝试像a这样建立索引时会出错：

  

类型'symbol'不能用作索引类型（2538）

在使用{[x:string]:number}声明的同时，a[s]也可以正常工作。

Answer 1

这是一个非常老的问题。参见https://github.com/microsoft/TypeScript/issues/1863和https://github.com/Microsoft/TypeScript/issues/24587。

对后者的一个奇怪的评论是

  

we forbid symbols as indexers because we have no symbol index signatures (this was a hole we patched in 2.9 - previously it would assume the string indexer type, which was very incorrect), however unique symbols - a type associated with exactly one symbol are fine, since they refer to exactly one property.

在我看来，您似乎发现了一个案例，他们没有在2.9版中修复或从那时起恢复原状...