Q125495: BUG: Enum in Function Template Causes C2065 Compiler Error

Article: Q125495
Product(s): Microsoft C Compiler
Version(s): 2.0,2.1
Operating System(s): 
Keyword(s): kbCompiler kbCPPonly kbVCkbbuglist
Last Modified: 29-NOV-2001

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft Visual C++, versions 2.0, 2.1 
-------------------------------------------------------------------------------

SYMPTOMS
========

When an enum type is used as a return type of a function template, the compiler
generates the following error as the function template is instantiated:

  Error C2065 : 'FunctionName' : undeclared identifier
  Error C2064 : term does not evaluate to a function

This error happens only when the function template takes arguments that involve a
user-defined class template. For more information, please see the "Sample Code"
section in this article.

RESOLUTION
==========

To work around the problem, use a typedef to define the enum type, and use it as
the return type for the function template.

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article. We are researching this problem and will post new
information here in the Microsoft Knowledge Base as it becomes available.

MORE INFORMATION
================

The sample code below can be used to demonstrate both the problem and its
solution.

Sample Code
-----------

  /* Compile options needed: none
     Use /DFIX to work around the problem
  */ 

  template <class Type>
  class TestClass
  {
    Type t;
  };

  enum EnumType { E1, E2, E3 };

  #ifndef FIX        // Used to reproduce the problem

     template <class Type>
     EnumType EnumReturnDoesntWork( const TestClass<Type> &a )
     {
       return E1;
     }

  #else              // Used to work around the problem

     typedef EnumType MyType;

     template <class Type>
     MyType EnumReturnDoesntWork( const TestClass<Type> &a )
     {
       return E1;
     }

  #endif

  void main(void)
  {
     TestClass<int> a;

     EnumReturnDoesntWork( a );   // C2065
  }

Additional query words: 2.00 2.10 9.00 9.10 noupdate

======================================================================
Keywords          : kbCompiler kbCPPonly kbVC kbbuglist
Technology        : kbVCsearch kbAudDeveloper kbVC200 kbVC210
Version           : :2.0,2.1
Issue type        : kbbug

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 1986-2002.