@NotNull
  private VarargCheckResult checkVarargInSuperFunctions(
      @NotNull ValueParameterDescriptor originalParam) {
    boolean someSupersVararg = false;
    boolean someSupersNotVararg = false;
    for (FunctionDescriptor superFunction : superFunctions) {
      if (superFunction.getValueParameters().get(originalParam.getIndex()).getVarargElementType()
          != null) {
        someSupersVararg = true;
      } else {
        someSupersNotVararg = true;
      }
    }

    JetType originalVarargElementType = originalParam.getVarargElementType();
    JetType originalType = originalParam.getType();

    if (someSupersVararg && someSupersNotVararg) {
      reportError("Incompatible super methods: some have vararg parameter, some have not");
      return new VarargCheckResult(originalType, originalVarargElementType != null);
    }

    KotlinBuiltIns builtIns = KotlinBuiltIns.getInstance();
    if (someSupersVararg && originalVarargElementType == null) {
      // convert to vararg

      assert isArrayType(originalType);

      if (builtIns.isPrimitiveArray(originalType)) {
        // replace IntArray? with IntArray
        return new VarargCheckResult(TypeUtils.makeNotNullable(originalType), true);
      }

      // replace Array<out Foo>? with Array<Foo>
      JetType varargElementType = builtIns.getArrayElementType(originalType);
      return new VarargCheckResult(builtIns.getArrayType(INVARIANT, varargElementType), true);
    } else if (someSupersNotVararg && originalVarargElementType != null) {
      // convert to non-vararg

      assert isArrayType(originalType);

      if (builtIns.isPrimitiveArray(originalType)) {
        // replace IntArray with IntArray?
        return new VarargCheckResult(TypeUtils.makeNullable(originalType), false);
      }

      // replace Array<Foo> with Array<out Foo>?
      return new VarargCheckResult(
          TypeUtils.makeNullable(
              builtIns.getArrayType(Variance.OUT_VARIANCE, originalVarargElementType)),
          false);
    }

    return new VarargCheckResult(originalType, originalVarargElementType != null);
  }
  @NotNull
  private static Multimap<FqName, Pair<FunctionDescriptor, PsiMethod>>
      getSuperclassToFunctionsMultimap(
          @NotNull PsiMethodWrapper method,
          @NotNull BindingContext bindingContext,
          @NotNull ClassDescriptor containingClass) {
    Multimap<FqName, Pair<FunctionDescriptor, PsiMethod>> result = HashMultimap.create();

    Name functionName = Name.identifier(method.getName());
    int parameterCount = method.getParameters().size();

    for (JetType supertype : TypeUtils.getAllSupertypes(containingClass.getDefaultType())) {
      ClassifierDescriptor klass = supertype.getConstructor().getDeclarationDescriptor();
      assert klass != null;
      FqName fqName = DescriptorUtils.getFQName(klass).toSafe();

      for (FunctionDescriptor fun :
          klass.getDefaultType().getMemberScope().getFunctions(functionName)) {
        if (fun.getKind().isReal() && fun.getValueParameters().size() == parameterCount) {
          PsiElement declaration = BindingContextUtils.descriptorToDeclaration(bindingContext, fun);
          if (declaration instanceof PsiMethod) {
            result.put(fqName, Pair.create(fun, (PsiMethod) declaration));
          } // else declaration is null or JetNamedFunction: both cases are processed later
        }
      }
    }
    return result;
  }
  // Returns list with type arguments info from supertypes
  // Example:
  //     - Foo<A, B> is a subtype of Bar<A, List<B>>, Baz<Boolean, A>
  //     - input: klass = Foo, typesFromSuper = [Bar<String, List<Int>>, Baz<Boolean, CharSequence>]
  //     - output[0] = [String, CharSequence], output[1] = []
  private static List<List<TypeProjectionAndVariance>> calculateTypeArgumentsFromSuper(
      @NotNull ClassDescriptor klass, @NotNull Collection<TypeAndVariance> typesFromSuper) {
    // For each superclass of klass and its parameters, hold their mapping to klass' parameters
    // #0 of Bar ->  A
    // #1 of Bar ->  List<B>
    // #0 of Baz ->  Boolean
    // #1 of Baz ->  A
    // #0 of Foo ->  A (mapped to itself)
    // #1 of Foo ->  B (mapped to itself)
    Multimap<TypeConstructor, TypeProjection> substitution =
        SubstitutionUtils.buildDeepSubstitutionMultimap(
            TypeUtils.makeUnsubstitutedType(klass, JetScope.EMPTY));

    // for each parameter of klass, hold arguments in corresponding supertypes
    List<List<TypeProjectionAndVariance>> parameterToArgumentsFromSuper = Lists.newArrayList();
    for (TypeParameterDescriptor ignored : klass.getTypeConstructor().getParameters()) {
      parameterToArgumentsFromSuper.add(new ArrayList<TypeProjectionAndVariance>());
    }

    // Enumerate all types from super and all its parameters
    for (TypeAndVariance typeFromSuper : typesFromSuper) {
      for (TypeParameterDescriptor parameter :
          typeFromSuper.type.getConstructor().getParameters()) {
        TypeProjection argument = typeFromSuper.type.getArguments().get(parameter.getIndex());

        // for given example, this block is executed four times:
        // 1. typeFromSuper = Bar<String, List<Int>>,      parameter = "#0 of Bar",  argument =
        // String
        // 2. typeFromSuper = Bar<String, List<Int>>,      parameter = "#1 of Bar",  argument =
        // List<Int>
        // 3. typeFromSuper = Baz<Boolean, CharSequence>,  parameter = "#0 of Baz",  argument =
        // Boolean
        // 4. typeFromSuper = Baz<Boolean, CharSequence>,  parameter = "#1 of Baz",  argument =
        // CharSequence

        // if it is mapped to klass' parameter, then store it into map
        for (TypeProjection projection : substitution.get(parameter.getTypeConstructor())) {
          // 1. projection = A
          // 2. projection = List<B>
          // 3. projection = Boolean
          // 4. projection = A
          ClassifierDescriptor classifier =
              projection.getType().getConstructor().getDeclarationDescriptor();

          // this condition is true for 1 and 4, false for 2 and 3
          if (classifier instanceof TypeParameterDescriptor
              && classifier.getContainingDeclaration() == klass) {
            int parameterIndex = ((TypeParameterDescriptor) classifier).getIndex();
            Variance effectiveVariance =
                parameter.getVariance().superpose(typeFromSuper.varianceOfPosition);
            parameterToArgumentsFromSuper
                .get(parameterIndex)
                .add(new TypeProjectionAndVariance(argument, effectiveVariance));
          }
        }
      }
    }
    return parameterToArgumentsFromSuper;
  }
 private static Map<ClassDescriptor, JetType> getSuperclassToSupertypeMap(
     ClassDescriptor containingClass) {
   Map<ClassDescriptor, JetType> superclassToSupertype = Maps.newHashMap();
   for (JetType supertype : TypeUtils.getAllSupertypes(containingClass.getDefaultType())) {
     ClassifierDescriptor superclass = supertype.getConstructor().getDeclarationDescriptor();
     assert superclass instanceof ClassDescriptor;
     superclassToSupertype.put((ClassDescriptor) superclass, supertype);
   }
   return superclassToSupertype;
 }