Support TypeScript 4.5

[sosukesuzuki]

• TypeScript 4.5 Iteration Plan microsoft/TypeScript#45418
• https://devblogs.microsoft.com/typescript/announcing-typescript-4-5-beta/

Private fields in-in

• babel-ts: already supported
• typescript: TypeScript 4.5 Support typescript-eslint/typescript-eslint#3950

class Person {
    #name: string;
    constructor(name: string) {
        this.#name = name;
    }

    equals(other: unknown) {
        return other &&
            typeof other === "object" &&
            #name in other && // <- this is new!
            this.#name === other.#name;
    }
}

Import Assertions

• babel-ts: already supported
• typescript: TypeScript 4.5 Support typescript-eslint/typescript-eslint#3950

import obj from "./something.json" assert { type: "json" };

Type-only import/export specifiers

• babel-ts: Support TypeScript 4.5 type-only import/export specifiers babel/babel#13802
• typescript: TypeScript 4.5 Support typescript-eslint/typescript-eslint#3950

import { someFunc, type BaseType } from "./some-module.js";

Handle .mts and .cts file extensions.

https://devblogs.microsoft.com/typescript/announcing-typescript-4-5-beta/#type-in-packagejson-and-new-extensions

[kachkaev]

📖 Prettier 2.5 blog post 🎉