[Bug] closure() function can cause Maximum call stack size exceeded

[matthew-dean]

I'm getting a Maximum call stack size exceeded in the closure() function. I'm attempting to investigate, and no doubt there's a problem in my grammar; but I thought it would be worth reporting that there is apparently a grammar problem that can trigger this.

[matthew-dean]

Oh okay, apparently it was this rule:

$.RULE('expression', () => {
    $.SUBRULE($.expressionValue, { LABEL: 'L' })
    $.MANY(() => {
      $.OR([
        {
          ALT: () => {
            $.OR2([
              { ALT: () => $.CONSUME(T.Plus) },
              { ALT: () => $.CONSUME(T.Minus) },
              { ALT: () => $.CONSUME(T.Star) },
              { ALT: () => $.CONSUME(T.Divide) }
            ])
            $.SUBRULE2($.expressionValue, { LABEL: 'R' })
          }
        },
        {
          GATE: $.noSep,
          ALT: () => {
            /** This will be interpreted by Less as a complete expression */
            $.CONSUME(T.Signed)
          }
        },
        // The existence of this causes an infinite loop in this package.
        { ALT: EMPTY_ALT() }
      ])
    })
  })

[msujew]

Have you disabled the validator for your parser? A MANY wrapping an empty element should throw an error during validation.

[matthew-dean]

Nope, I had't disabled the validator.

[msujew]

I see. I'm on vacation until next week, but I'll look into these issues and see what I can do once I'm back.