$ cat object-spread-effects.js
let result = "FAIL";
const unused = ({
    ...{
        get prop() {
            result = "PASS";
        }
    }
});
console.log(result);

$ cat object-spread-effects.js | node
PASS

$ cat object-spread-effects.js | rollup --silent | node
FAIL

$ cat object-spread-effects.js | rollup --silent
let result = "FAIL";
console.log(result);