40 columns                              |
>>> Unsplit.
var list = [  ...  a,...b,  ...
c];
<<<
var list = [...a, ...b, ...c];
>>> Don't split after `...`.
var list = [...comicallyLongIdentifierThatOverflows];
<<<
var list = [
  ...comicallyLongIdentifierThatOverflows,
];
>>> Null-aware.
var list = [  ...?  a,...?b,  ...?
c];
<<<
var list = [...?a, ...?b, ...?c];
>>> Don't split after `...?`.
var list = [...?comicallyLongIdentifierThatOverflows];
<<<
var list = [
  ...?comicallyLongIdentifierThatOverflows,
];
>>> Split inside spread expression.
var list = [1, ...some + very + long + spread + expression, 3];
<<<
var list = [
  1,
  ...some +
      very +
      long +
      spread +
      expression,
  3,
];
>>> Spread function expression.
var list = [1, ...() { body; }, 4];
<<<
var list = [
  1,
  ...() {
    body;
  },
  4,
];
>>> Spread immediately invoked function expression.
var list = [1, ...() sync* { yield thing; }(), 4];
<<<
var list = [
  1,
  ...() sync* {
    yield thing;
  }(),
  4,
];
>>> Spread cascade.
var list = [1, ...thing..cascade()..another(), 4];
<<<
var list = [
  1,
  ...thing
    ..cascade()
    ..another(),
  4,
];