Local token matched even though starting token is not present

[pe.affenzeller]

hi marijn!

yet another question, this time related to local token groups.
what I have is the following:

@top Filter { expression* }

expression { FilterGroup | FilterStatement | space }

FilterGroup { OpeningBracket (FilterStatement | FilterGroup | space)* ClosingBracket }
FilterStatement { FilterKey space+ ComparisonOperator space+ FilterSimpleValue }

FilterKey { Identifier | String }
FilterSimpleValue[@isGroup=FilterValue] { Identifier | String }

@skip {} {
  String { DoubleQuotes (StringContent | EscapedStringCharacter)* StringEnd }
}

@local tokens {
  StringEnd[@name='DoubleQuotes'] { '"' }
  EscapedStringCharacter { "\\" _ }
  @else StringContent
}

@tokens {
  space { @whitespace }
  newLine { '\n'}
  escapedCharacter { "\\" _ }

  DoubleQuotes[closedBy="DoubleQuotes"] { "\"" }
  OpeningBracket[closedBy="ClosingBracket"] { "(" }
  ClosingBracket { ")" }

  ComparisonOperator { '=' | '!=' | '<' | '<=' | '>' | '>=' }
  Identifier { ((![ *,\\()] (newLine | std.eof)?) | escapedCharacter )+ }

  @precedence { space, OpeningBracket, ClosingBracket, DoubleQuotes, ComparisonOperator, Identifier }
}

with input a = (b) , I get the following tree as expected

as soon as I add another character after the space (a = (b) c), the tree switches to

even though there are no double quotes anywhere in the input and those should be required to start matching the local tokens if I understood correctly.

how is it possible that the String is still matching here?

I would have expected that I still get a statement with an error node (a =), a group (including a statement with an error node, (b)), and then another statement with an error node (c).

[marijn]

It looks like the parser inserted the opening quote token as part of its error recovery because it didn’t find any matching tokens at that position.

[pe.affenzeller]

what’s interesting, though, is that if I remove the closing bracket of the group, it does detect the opening bracket.

but as soon as I add the closing, it “merges” everything into a string.
maybe I can work around that issue by adding something like an IncompleteStatement to make it more predictable, unless you have another idea?