--downlevelIteration errors should mention using later targets

[DanielRosenwasser]

// @ts-check
class Foo {
  constructor(...args) {}
}
function makeFoo() {
  return new Foo(...arguments)
}

Actual

Type 'IArguments' is not an array type. Use compiler option '--downlevelIteration' to allow iterating of iterators.

Expected

Type 'IArguments' is not an array type. Either use the '--downlevelIteration' compiler option to allow iterating on iterators, or set the '--target' option to 'es2015' or above.

[kschiang19]

Hi, can I work on this issue?

[DanielRosenwasser]

Go for it - update diagnosticMessages.json, run the test suite, accept the baselines, and send us a PR.

[DanielRosenwasser]

Thanks @a-tarasyuk!