如何覆盖 TypeScript 类型别名的 VSCode 工具提示？

Question

The following code doesn't work:

type char = 'a' | 'b' | 'c' | 'd' | 'e' | 'f';
const s: string = 'foo';
const [c]: char = s;
// [ERROR]: Type 'string' is not assignable to type 'char'.

I could do this instead:

type char = 'a' | 'b' | 'c' | 'd' | 'e' | 'f' | string;

But that causes 2 problems:

1. When I hover over a char variable, the tooltip says it's type string not char (I'm in VSCode). I know I don't have the 'a' | 'b' | 'c' 'a' | 'b' | 'c' 'a' | 'b' | 'c' etc... in the screenshot, but pretend I do, because tooltip is the same.

   

2. I won't get warned if I try to do something like const letter: char = 'notachar' ;

Answer 1

How to override VSCode tooltip for TypeScript type alias?

When you have a union that resolves to something simpler, TypeScript will always show the simpler version

Example:

type char = 'a' | 'b' | 'c' | 'd' | 'e' | 'f' | string;
// resolves to the following simpler type so that is what TypeScript will show. 
type char = string;