public void enterRule(ParserRuleContext localctx, int state, int ruleIndex) {
		setState(state);
		_ctx = localctx;
		_ctx.start = _input.LT(1);
		if (_buildParseTrees) addContextToParseTree();
        if ( _parseListeners != null) triggerEnterRuleEvent();
	}
Always called by generated parsers upon entry to a rule. Access field
{@link #_ctx} get the current context.
runtime/Java/src/org/antlr/v4/runtime/Parser.java