@Nullable
  private static JetType computeUnsafeReturnType(
      @NotNull JetFunctionLiteralExpression expression,
      @NotNull ExpressionTypingContext context,
      @NotNull SimpleFunctionDescriptorImpl functionDescriptor,
      @Nullable JetType expectedReturnType) {
    JetFunctionLiteral functionLiteral = expression.getFunctionLiteral();
    JetBlockExpression bodyExpression = functionLiteral.getBodyExpression();
    assert bodyExpression != null;

    JetScope functionInnerScope =
        FunctionDescriptorUtil.getFunctionInnerScope(
            context.scope, functionDescriptor, context.trace);
    JetTypeReference returnTypeRef = functionLiteral.getReturnTypeRef();
    JetType declaredReturnType = null;
    if (returnTypeRef != null) {
      declaredReturnType =
          context
              .expressionTypingServices
              .getTypeResolver()
              .resolveType(context.scope, returnTypeRef, context.trace, true);
      // This is needed for ControlStructureTypingVisitor#visitReturnExpression() to properly
      // type-check returned expressions
      functionDescriptor.setReturnType(declaredReturnType);
      if (expectedReturnType != null) {
        if (!JetTypeChecker.INSTANCE.isSubtypeOf(declaredReturnType, expectedReturnType)) {
          context.trace.report(EXPECTED_RETURN_TYPE_MISMATCH.on(returnTypeRef, expectedReturnType));
        }
      }
    }

    // Type-check the body
    ExpressionTypingContext newContext =
        context
            .replaceScope(functionInnerScope)
            .replaceExpectedType(
                declaredReturnType != null
                    ? declaredReturnType
                    : (expectedReturnType != null ? expectedReturnType : NO_EXPECTED_TYPE));

    JetType typeOfBodyExpression =
        context
            .expressionTypingServices
            .getBlockReturnedType(bodyExpression, COERCION_TO_UNIT, newContext)
            .getType();

    List<JetType> returnedExpressionTypes =
        Lists.newArrayList(
            getTypesOfLocallyReturnedExpressions(
                functionLiteral, context.trace, collectReturns(bodyExpression)));
    ContainerUtil.addIfNotNull(returnedExpressionTypes, typeOfBodyExpression);

    if (declaredReturnType != null) return declaredReturnType;
    if (returnedExpressionTypes.isEmpty()) return null;
    return CommonSupertypes.commonSupertype(returnedExpressionTypes);
  }
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  public static SimpleFunctionDescriptor createInvoke(FunctionDescriptor fd) {
    int arity = fd.getValueParameters().size();
    SimpleFunctionDescriptorImpl invokeDescriptor =
        new SimpleFunctionDescriptorImpl(
            fd.getExpectedThisObject().exists()
                ? JetStandardClasses.getReceiverFunction(arity)
                : JetStandardClasses.getFunction(arity),
            Collections.<AnnotationDescriptor>emptyList(),
            Name.identifier("invoke"),
            CallableMemberDescriptor.Kind.DECLARATION);

    invokeDescriptor.initialize(
        fd.getReceiverParameter().exists() ? fd.getReceiverParameter().getType() : null,
        fd.getExpectedThisObject(),
        Collections.<TypeParameterDescriptorImpl>emptyList(),
        fd.getValueParameters(),
        fd.getReturnType(),
        Modality.FINAL,
        Visibilities.PUBLIC,
        /*isInline = */ false);
    return invokeDescriptor;
  }