antlr/antlr4 · critical · Exception

The specified state type

Error message

The specified state type {} is not valid.

What it means

Symmetric to the transition factory: stateFactory() maps state-type codes (basic, rule start/stop, block start/end, loop variants, tokens start) to constructors. An out-of-table code raises this Exception, again indicating the serialized stream does not match what this runtime knows how to read.

Solutions

1. Match ANTLR tool and Python runtime versions and regenerate everything.
2. Purge old generated artifacts (*.py, *.tokens, *.interp) and regenerate from scratch.
3. Vendor generated files per-version in separate directories so mixed imports cannot occur.

try:
    parser = MyParser(tokens)
except Exception as e:
    if 'state type' in str(e):
        raise RuntimeError('serialized ATN format not supported by this runtime: align ANTLR tool and runtime versions')
    raise

When it happens

Trigger: deserialize() encountering a state type code not in the runtime's stateFactories table — misaligned data stream from version mismatch or corrupted generated file.

Common situations: Tool/runtime version skew (state kinds were added/renumbered across serialized format revisions); stale or hand-edited generated files; importing generated code from a project built with a different ANTLR release.

Related errors

• Could not deserialize ATN with version
• The specified transition type
• Couldn't identify final state of the precedence rule prefix…
• IllegalState
• The specified lexer action type

AI-assisted analysis of antlr/antlr4@7d5770395b (2026-08-14). Data as JSON: /api/errors/719d956a80972d5f. Report an issue: GitHub.

Appendix: source

Thrown at runtime/Python3/src/antlr4/atn/ATNDeserializer.py:415

    stateFactories = [  lambda : None,
                        lambda : BasicState(),
                        lambda : RuleStartState(),
                        lambda : BasicBlockStartState(),
                        lambda : PlusBlockStartState(),
                        lambda : StarBlockStartState(),
                        lambda : TokensStartState(),
                        lambda : RuleStopState(),
                        lambda : BlockEndState(),
                        lambda : StarLoopbackState(),
                        lambda : StarLoopEntryState(),
                        lambda : PlusLoopbackState(),
                        lambda : LoopEndState()
                    ]

    def stateFactory(self, type:int, ruleIndex:int):
        if type> len(self.stateFactories) or self.stateFactories[type] is None:
            raise Exception("The specified state type " + str(type) + " is not valid.")
        else:
            s = self.stateFactories[type]()
            if s is not None:
                s.ruleIndex = ruleIndex
        return s

    CHANNEL = 0     #The type of a {@link LexerChannelAction} action.
    CUSTOM = 1      #The type of a {@link LexerCustomAction} action.
    MODE = 2        #The type of a {@link LexerModeAction} action.
    MORE = 3        #The type of a {@link LexerMoreAction} action.
    POP_MODE = 4    #The type of a {@link LexerPopModeAction} action.
    PUSH_MODE = 5   #The type of a {@link LexerPushModeAction} action.
    SKIP = 6        #The type of a {@link LexerSkipAction} action.
    TYPE = 7        #The type of a {@link LexerTypeAction} action.

    actionFactories = [ lambda data1, data2: LexerChannelAction(data1),
                        lambda data1, data2: LexerCustomAction(data1, data2),
                        lambda data1, data2: LexerModeAction(data1),

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