code: protected VarRefAssignExpress parseAssingInExp(AssignGeneralInExpContext agc) {
  
  		VarRefAssignExpress vas = null;
  		ExpressionContext expCtx = agc.generalAssignExp().expression();
  		Expression exp = parseExpress(expCtx);
  		VarRefContext varRefCtx = agc.generalAssignExp().varRef();		
  		VarRef ref = this.parseVarRefInLeftExpression(varRefCtx);
  		vas = new VarRefAssignExpress(exp,ref);
  		
  		if (ref.attributes.length==0) {
  			// 变量定义:
  			Token token = varRefCtx.Identifier().getSymbol();
  			if (pbCtx.hasDefined(token.getText()) != null) {
  				registerVar(vas);
  				return vas;
  			} else {
  				BeetlException ex = new BeetlException(BeetlException.VAR_NOT_DEFINED);
  				ex.pushToken(this.getBTToken(token));
  				throw ex;
  			}
  
  		} 
  		return vas;
  		
  
  	}
docs: 赋值变量
  @param agc
  @return