code: private void visit(VariableRestrictionDescr descr) {
  
          PatternVariable patternVariable = (PatternVariable) data.getVariableByRuleAndVariableName(pattern.getRuleName(),
                  descr.getIdentifier());
          VariableRestriction restriction = new VariableRestriction(pattern);
  
          restriction.setPatternIsNot(pattern.isPatternNot());
          restriction.setFieldPath(field.getPath());
          restriction.setOperator(Operator.determineOperator(descr.getEvaluator(),
                  descr.isNegated()));
          restriction.setVariable(patternVariable);
          restriction.setOrderNumber(orderNumber);
          restriction.setParentPath(pattern.getPath());
          restriction.setParentType(pattern.getVerifierComponentType());
  
          // Set field value, if it is unset.
          field.setFieldType(Field.VARIABLE);
  
          data.add(restriction);
          solvers.addPatternComponent(restriction);
      }
docs: End
  <p/>
  Foo( bar == $bar )<br>
  $bar is a VariableRestrictionDescr
  
  @param descr