public void visitAssignmentExpression(GrAssignmentExpression expression) {
   GrExpression rValue = expression.getRValue();
   GrExpression lValue = expression.getLValue();
   if (myExpression.equals(rValue)) {
     PsiType lType = lValue.getNominalType();
     if (lType != null) {
       myResult = new TypeConstraint[] {SubtypeConstraint.create(lType)};
     } else if (lValue instanceof GrReferenceExpression) {
       GroovyResolveResult result = ((GrReferenceExpression) lValue).advancedResolve();
       PsiElement resolved = result.getElement();
       if (resolved instanceof GrVariable) {
         PsiType type = ((GrVariable) resolved).getTypeGroovy();
         if (type != null) {
           myResult =
               new TypeConstraint[] {
                 SubtypeConstraint.create(result.getSubstitutor().substitute(type))
               };
         }
       }
     }
   } else if (myExpression.equals(lValue)) {
     if (rValue != null) {
       PsiType rType = rValue.getType();
       if (rType != null) {
         myResult = new TypeConstraint[] {SupertypeConstraint.create(rType)};
       }
     }
   }
 }
    @Override
    public void visitBinaryExpression(GrBinaryExpression expression) {
      final IElementType type = expression.getOperationTokenType();
      final GrExpression left = expression.getLeftOperand();
      final GrExpression right = expression.getRightOperand();

      if (type == mREGEX_FIND || type == mREGEX_MATCH) {
        final PsiClassType string =
            TypesUtil.createType(CommonClassNames.JAVA_LANG_STRING, expression);
        myResult = createSimpleSubTypeResult(string);
        return;
      }

      final GrExpression other = myExpression == left ? right : left;
      final PsiType otherType = other != null ? other.getType() : null;

      if (otherType == null) return;

      if (type == mPLUS && otherType.equalsToText(CommonClassNames.JAVA_LANG_STRING)) {
        final PsiClassType obj = TypesUtil.getJavaLangObject(expression);
        myResult = createSimpleSubTypeResult(obj);
        return;
      }

      myResult = createSimpleSubTypeResult(otherType);
    }
 @Nullable
 private static PsiType getNominalTypeNoRecursion(@NotNull final GrExpression expression) {
   if (expression instanceof GrNewExpression) {
     return expression.getType();
   } else if (expression instanceof GrReferenceExpression
       && ((GrReferenceExpression) expression).getQualifier() == null) {
     return getTypeByRef((GrReferenceExpression) expression);
   }
   return null;
 }
    @Override
    public void visitCaseLabel(GrCaseLabel caseLabel) {
      final PsiElement parent = caseLabel.getParent().getParent();
      assert parent instanceof GrSwitchStatement : parent + " of class " + parent.getClass();
      final GrExpression condition = ((GrSwitchStatement) parent).getCondition();
      if (condition == null) return;

      final PsiType type = condition.getType();
      if (type == null) return;

      myResult = new TypeConstraint[] {SubtypeConstraint.create(type)};
    }
    @Override
    public void visitSwitchStatement(GrSwitchStatement switchStatement) {
      final GrCaseSection[] sections = switchStatement.getCaseSections();
      List<PsiType> types = new ArrayList<PsiType>(sections.length);
      for (GrCaseSection section : sections) {
        final GrExpression value = section.getCaseLabel().getValue();
        final PsiType type = value != null ? value.getType() : null;
        if (type != null) types.add(type);
      }

      final PsiType upperBoundNullable =
          TypesUtil.getLeastUpperBoundNullable(types, switchStatement.getManager());
      if (upperBoundNullable == null) return;

      myResult = new TypeConstraint[] {SubtypeConstraint.create(upperBoundNullable)};
    }