New rule: Prefer short-circuiting assignment operators (TS 4+)

[glen-84]

Info:

• https://github.com/tc39/proposal-logical-assignment/
• https://devblogs.microsoft.com/typescript/announcing-typescript-4-0-beta/

Bad:

opts.foo = opts.foo ?? 'bar'

Good:

opts.foo ??= 'bar'

(same for ||= and &&=)

Optional extras:

Bad:

if (!a) {
  a = 'foo';
}

Good:

a ||= 'foo';

Bad:

opts.baz ?? (opts.baz = 'qux');

Good:

opts.baz ??= 'qux';

[bradzacher]

Will require #2260

[JoshuaKGoldberg]

Looks like this one is unblocked - I'll take it on! 🙌

[JoshuaKGoldberg]

Actually, on second thought, this really isn't a TypeScript-specific rule, as the operators are general JavaScript syntax. Should this be moved to ESLint core @bradzacher?

[bradzacher]

Probably could do yeah. They have support for the new logical operators!

[glen-84]

I'll move this issue (probably on Sunday or Monday).

[glen-84]

Closing in favour of eslint/eslint#13689.