{
  "expression": [
    "match",
    "x",
    ["string", ["get", "y"]],
    "thing one",
    "thing two"
  ],
  "expected": {
    "compiled": {
      "result": "error",
      "errors": [
        {"key": "[2]", "error": "Branch labels must be numbers or strings."}
      ]
    }
  }
}