Combined syntax compliance

[GrahamCampbell]

We currently fail on the following upstream compliance tests:

  {
    "comment": "Combined syntax",
    "given": [],
    "cases": [
        {
          "expression": "*||*|*|*",
          "result": null
        },
        {
          "expression": "*[]||[*]",
          "result": []
        },
        {
          "expression": "[*.*]",
          "result": [null]
        }
    ]
  }

The first and last case are incorrect, but we handle the middle case correctly at the moment.