noUselessSpread rule

[mirelon]

Rule type: suggestion / suspicious code

Description:
Prevent spreading array literals into function or constructor calls when the spread is unnecessary or misleading.

Example:

new Set(...['aa']) // looks like Set will contain 'aa', but actually contains 'a'

This happens because ['aa'] spreads into "aa", and Set treats a string as an iterable of characters. This is almost always unintended.

Valid code:

new Set(['aa'])

Invalid code:

new Set(...['aa'])
new Map(...[entries])
someFn(...['arg']) // instead of someFn('arg') or someFn(['arg'])

Motivation:

• This pattern is legal in JS, so TypeScript doesn’t complain.
• It’s easy to write accidentally (especially when refactoring).
• It produces very surprising runtime behavior.
• This is similar to ESLint Unicorn’s no-useless-spread, but for a different case (new Set(...['aa']) instead of new Set([...iterable])). To avoid confusion, we can call it noConfusingSpread or noArgumentSpreadArray.

Suggested category:
suspicious (since it’s very likely a bug)

Autofix:
Replace fn(...[expr]) with fn(expr) or fn([expr]) depending on context.