Doesn't support TypeScript 4's labeled tuple syntax

[cakoose]

Prettier v2.1.1 reports a syntax error in the following code.

type X = [a: string, b: string];  // SyntaxError: Unexpected token, expected "," (1:12)

Prettier playground: link

TypeScript playground: link

TypeScript added this syntax in v4: "labeled tuple elements" in the release notes

There was an earlier bug and apparently also a fix: #8646 (comment). Maybe I'm missing something?

[cakoose]

Oh hmm, looks like the original fix (#8885) had a caveat:

Current typescript-estree cannot parse labeled tuple types. So we should put this in /tests/misc/typescript-babel-only for now.

That was on Aug 3. A week later @typescript-eslint/typescript-estree 3.9 was released and claims to support labeled tuple types: ChangeLog v3.9. And Prettier's current @typescript-eslint/typescript-estree dependency is v3.10.1.

[sosukesuzuki]

You seem to be using a babel parser. please use the typescript parser or the babel-ts parser.

Prettier 2.1.1
Playground link

--parser typescript

Input:

type X = [a: string, b: string];

Output:

type X = [a: string, b: string];

[cakoose]

Thanks!

The default parser seems to accept many TypeScript constructs, which I guess confused me a bit...