{"record":{"id":"1459c85c9d6edd43","repo":"antlr/antlr4","slug":"unrecognized-atn-transition-type-1459c8","errorCode":null,"errorMessage":"Unrecognized ATN transition type.","messagePattern":"Unrecognized ATN transition type\\.","errorType":"exception","errorClass":"NotSupportedException","httpStatus":null,"severity":"error","filePath":"runtime/CSharp/src/ParserInterpreter.cs","lineNumber":277,"sourceCode":"                case TransitionType.ACTION:\n                {\n                    ActionTransition actionTransition = (ActionTransition)transition;\n\t\t\t\t\tAction(RuleContext, actionTransition.ruleIndex, actionTransition.actionIndex);\n                    break;\n                }\n\n                case TransitionType.PRECEDENCE:\n                {\n\t\t\t\t\tif (!Precpred(RuleContext, ((PrecedencePredicateTransition)transition).precedence))\n                    {\n                        throw new FailedPredicateException(this, string.Format(\"precpred(_ctx, {0})\", ((PrecedencePredicateTransition)transition).precedence));\n                    }\n                    break;\n                }\n\n                default:\n                {\n                    throw new NotSupportedException(\"Unrecognized ATN transition type.\");\n                }\n            }\n            State = transition.target.stateNumber;\n        }\n\n        protected internal virtual void VisitRuleStopState(ATNState p)\n        {\n            RuleStartState ruleStartState = _atn.ruleToStartState[p.ruleIndex];\n            if (ruleStartState.isPrecedenceRule)\n            {\n                Tuple<ParserRuleContext, int> parentContext = _parentContextStack.Pop();\n                UnrollRecursionContexts(parentContext.Item1);\n                State = parentContext.Item2;\n            }\n            else\n            {\n                ExitRule();\n            }","sourceCodeStart":259,"sourceCodeEnd":295,"githubUrl":"https://github.com/antlr/antlr4/blob/7d5770395bb7b02eb56e7c62662cb1d7c08f42a3/runtime/CSharp/src/ParserInterpreter.cs#L259-L295","documentation":"Error \"Unrecognized ATN transition type.\" thrown in antlr/antlr4.","triggerScenarios":"ParserInterpreter encounters a transition type it does not recognize while visiting the ATN.","commonSituations":"Verify the serialized ATN matches the runtime version; regenerated corrupted or mismatched ATNs cause this.","solutions":["The serialized ATN was produced by an incompatible tool version; regenerate the parser with an ANTLR tool whose version matches the runtime.","Do not hand-edit generated .interp/serialized ATN data."],"exampleFix":"// match Antlr4.Runtime.Standard package version with the ANTLR generator version","handlingStrategy":null,"validationCode":null,"typeGuard":null,"tryCatchPattern":null,"preventionTips":[],"tags":[],"backgroundTag":null,"analyzedSha":"7d5770395bb7b02eb56e7c62662cb1d7c08f42a3","analyzedAt":"2026-08-14T14:47:56.354Z","schemaVersion":2},"datasetVersion":"2026-08-15T22:17:37.221Z"}