CODEWITHSUNDEEP
antlrxtext
alexp82539
alexp82539

Reputation: 77

XText Turn on Backtracking Correctly

I've got a large grammar in X-Text, and it's got some ambiguities. I'm fully aware of the problems this will cause, but I'd like to be able to test the grammar before I look at optimising it.

I've been trying to turn on backtrack in the X-Text workflow, and can't seem to manage it. I've got the following code in my mwe2 file, under the main project:

language = StandardLanguage {
        fragment=parser.antlr.XtextAntlrGeneratorFragment2 auto-inject{
            options = {
                backtrack= true
            }
        }
        fragment=idea.parser.antlr.XtextAntlrIDEAGeneratorFragment auto-inject{
            options={
                backtrack=true
            }
        }
...

But I still get errors in the form:

error(211): ../org.xtext.example.CSPTest/src-gen/org/xtext/example/mydsl/parser/antlr/internal/InternalMyDsl.g:1183:2: [fatal] rule ruleAny has non-LL(*) decision due to recursive rule invocations reachable from alts 1,2.  Resolve by left-factoring or using syntactic predicates or using backtrack=true option.

How can I correctly turn on backtrack in order to prevent this?

Upvotes: 4

Views: 1245

Answers (1)

Sven Efftinge
Sven Efftinge

Reputation: 3095

For the new generator the correct setting is :

parserGenerator = {
  options = {
    backtrack = true
  }
}

Upvotes: 10

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