Support TypeScript 4.2

[sosukesuzuki]

TypeScript 4.2 beta has been announced.

• TypeScript 4.2 Iteration Plan

We should consider to support new syntax:

Leading/Middle Rest Elements in Tuple Types

Prettier already can format leading/middle rest elements. We should add more tests.

let bar: [boolean, ...string[], boolean];
let StealersWheel: [...Clown[], "me", ...Joker[]];

abstract constructor signatures

let Ctor: abstract new () => HasArea = Shape;

namespaced JSX elements and attributes

const foo = <n:a n:v />;

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Anything else?

[remcohaszing]

I doubt this requires any changes in Prettier, but TypeScript 4.2 also supports namespaced JSX elements and attributes.

[Gerrit0]

TypeScript 4.2 is out! Is there anything I can do to make support happen sooner? Abstract constructor types are the one thing that's getting in my way.

[leops]

I think Prettier uses @typescript-eslint/typescript-estree to parse TypeScript, and support of TypeScript 4.2 was added in version 4.16.0 of that library so unless some special handling of the new nodes is required in Prettier, the only thing needed to support the new syntax would be upgrading the typescript-eslint dependency ?

[thorn0]

Turns out this issue was closed too early. See typescript-eslint/typescript-eslint#3183

[dora-gt]

Has this been shipped already?
I use prettier 2.2.1 and it warns abstract constructor like the following.

[sosukesuzuki]

No, TypeScript 4.2 supports have not been released yet.