How about forcing the looped expression to be one of:

• a variable (x)
• a property access (x.a.b)
• a single function call with no arguments (x(), x.a.b())
• one of built-in function calls commonly used for iteration (Object.keys(x)/Object.values(x)/Object.entries(x))

Otherwise force the user to define a variable before the loop (may be possible to auto-fix, the iteratee variable name could be the pluralized name of the element variable).

Originally from #846 (comment)

Fail

for (const x of xs.filter(x => shouldKeep(x))) {
	console.log(x)
}

Pass

const filteredXs = xs.filter(x => shouldKeep(x))

for (const x of filteredXs) {
	console.log(x)
}

for (const x of Object.values(xs)) {
	console.log(x)
}