Validating nested loops

[alecmolloy]

An issue as old as time, but still is wreaking havoc on some cool challenges i've been trying to do.

This validates totally fine:

{
    "id": "pattern",
    "title": "Pattern",
    "description": "Learn about color interactions and how shapes can affect our perception of color",
    "code": "",
    "startAt": 2,
    "steps": [
        {
            "hint": "",
            "solution": "for r in [0 .. 350] by 50"
        },
        {
            "hint": "",
            "solution": "    offset = random 0, 1, true"
        },
        {
            "hint": "",
            "solution": "    for i in [0 ... 2] by .1"
        },
        {
            "hint": "",
            "solution": "        arc r, i, i - .05",
        }
    ],
    "completion_text": "",
    "cover": "ozwaldboateng/pattern.png"
}

This does not:

{
    "id": "pattern",
    "title": "Pattern",
    "description": "Learn about color interactions and how shapes can affect our perception of color",
    "code": "",
    "startAt": 2,
    "steps": [
        {
            "hint": "",
            "solution": "for r in [0 .. 350] by 50"
        },
        {
            "hint": "",
            "solution": "    offset = random 0, 1, true"
        },
        {
            "hint": "",
            "solution": "    for i in [0 ... 2] by .1"
        },
        {
            "hint": "",
            "solution": "        arc r, i + offset, i - .05 + offset"
        }
    ],
    "completion_text": "",
    "cover": "ozwaldboateng/pattern.png"
}

The only difference between the two above JSON files is the inclusion of extra binary operators in the second example (adding an offset). Doing so in a nested loop reliably breaks validation for no clear reason.