mutable syntax issue

[a10k]

The below .ojs markup works perfectly on observable, the parser library is able to parse it correctly as a block cell too, but in the new interpreter this fails.

mutable x = []
{
  mutable x.push(1);
  mutable x = mutable x;
}

Console error when it fails

VM130:3 Uncaught (in promise) SyntaxError: Invalid or unexpected token
    at new Function (<anonymous>)
    at createRegularCellDefinition (index.js:formatted:7648)
    at Interpreter.cell (index.js:formatted:7737)
    at Interpreter.module (index.js:formatted:7694)
    at HTMLDivElement.eval (observablehq-214:8)
    at worker.8767064650b2824c13f8f3e3a6bb3bd4accb75c98d9277e71e09afe4bedf282d.js:2

[asg017]

Yup, can confirm this is a bug with this compiler, thanks for the report! It's super hard to catch edge cases like these.

Pretty sure it's got to do with this part of the codebase, will take a closer look

[mootari]

Parser AST for the example (without the first line):

{
  "type": "Cell",
  "start": 0,
  "end": 49,
  "id": null,
  "body": {
    "type": "BlockStatement",
    "start": 0,
    "end": 49,
    "body": [
      {
        "type": "ExpressionStatement",
        "start": 4,
        "end": 22,
        "expression": {
          "type": "CallExpression",
          "start": 4,
          "end": 21,
          "callee": {
            "type": "MemberExpression",
            "start": 4,
            "end": 18,
            "object": {
              "type": "MutableExpression",
              "start": 4,
              "end": 13,
              "id": {
                "type": "Identifier",
                "start": 12,
                "end": 13,
                "name": "x"
              }
            },
            "property": {
              "type": "Identifier",
              "start": 14,
              "end": 18,
              "name": "push"
            },
            "computed": false,
            "optional": false
          },
          "arguments": [
            {
              "type": "Literal",
              "start": 19,
              "end": 20,
              "value": 1,
              "raw": "1"
            }
          ],
          "optional": false
        }
      },
      {
        "type": "ExpressionStatement",
        "start": 25,
        "end": 47,
        "expression": {
          "type": "AssignmentExpression",
          "start": 25,
          "end": 46,
          "operator": "=",
          "left": {
            "type": "MutableExpression",
            "start": 25,
            "end": 34,
            "id": {
              "type": "Identifier",
              "start": 33,
              "end": 34,
              "name": "x"
            }
          },
          "right": {
            "type": "MutableExpression",
            "start": 37,
            "end": 46,
            "id": {
              "type": "Identifier",
              "start": 45,
              "end": 46,
              "name": "x"
            }
          }
        }
      }
    ]
  },
  "async": false,
  "generator": false,
  "references": [
    {
      "type": "MutableExpression",
      "start": 4,
      "end": 13,
      "id": {
        "type": "Identifier",
        "start": 12,
        "end": 13,
        "name": "x"
      }
    },
    {
      "type": "MutableExpression",
      "start": 25,
      "end": 34,
      "id": {
        "type": "Identifier",
        "start": 33,
        "end": 34,
        "name": "x"
      }
    },
    {
      "type": "MutableExpression",
      "start": 37,
      "end": 46,
      "id": {
        "type": "Identifier",
        "start": 45,
        "end": 46,
        "name": "x"
      }
    }
  ],
  "fileAttachments": {},
  "databaseClients": {},
  "secrets": {}
}