http://d.puremagic.com/issues/show_bug.cgi?id=1918

           Summary: __traits(getVirtualFunctions) returns final functions
           Product: D
           Version: 2.012
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Keywords: spec
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: bugzilla@digitalmars.com
        ReportedBy: dhasenan@gmail.com


static assert(__traits(getVirtualFunctions, Object, "notifyRegister").length ==
0);

That should succeed; Object.notifyRegister is final and therefore not virtual.

Clearer example:
class C
{
   final void foo(){}
}
static assert(__traits(getVirtualFunctions, C, "foo").length == 0);

That also fails.


-- 

http://d.puremagic.com/issues/show_bug.cgi?id=1918





------- Comment #1 from dhasenan@gmail.com  2008-11-16 08:22 -------
Okay, I've worked out how all this works.

__traits (getVirtualFunctions) gets all non-static methods.

__traits (isVirtualFunction) returns true iff the argument is a non-static
method.

__traits (isFinalFunction) returns true iff __traits (isVirtualFunction)
returns true and the function is not marked final.

This is consistent, and 'fixing' the issues by changing features would result in a loss of functionality.

This is not consistent with the expected meaning of "virtual function". I request that the documentation for __traits be updated to include a definition for "virtual function".

I also request that the keywords be changed to "getInstanceMethods" and "isInstanceMethod" or something like that, for clarity.


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http://d.puremagic.com/issues/show_bug.cgi?id=1918



--- Comment #2 from github-bugzilla@puremagic.com 2012-01-21 21:55:30 PST ---
Commit pushed to https://github.com/D-Programming-Language/d-programming-language.org

https://github.com/D-Programming-Language/d-programming-language.org/commit/d096698029399aaf2e2f62527173d80e8ef24cb4 fix Issue 1918 - __traits(getVirtualFunctions) returns final functions

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Walter Bright <bugzilla@digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |bugzilla@digitalmars.com
         Resolution|                            |FIXED


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Andrei Alexandrescu <andrei@metalanguage.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
                 CC|                            |andrei@metalanguage.com
         Resolution|FIXED                       |


--- Comment #3 from Andrei Alexandrescu <andrei@metalanguage.com> 2012-01-21 22:17:45 PST ---
Could you please explain how a final function that doesn't override anything is ever supposed to be virtual?

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Andrei Alexandrescu <andrei@metalanguage.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement


--- Comment #4 from Andrei Alexandrescu <andrei@metalanguage.com> 2012-01-21 22:58:29 PST ---
Documenting the agreement reached with Walter:

We'll define __traits(getVirtualMethods) to do the "right" thing, i.e. only
include final methods that actually override something, and put
__traits(getVirtualFunctions) on the slow deprecation path.

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yebblies <yebblies@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |yebblies@gmail.com


--- Comment #5 from yebblies <yebblies@gmail.com> 2012-01-22 19:01:55 EST ---
(In reply to comment #3)
> Could you please explain how a final function that doesn't override anything is ever supposed to be virtual?

Final functions can be seen as the end of a chain of overridden functions - even if the functions is also the first in the chain and therefore never uses virtual dispatch.  Either definition could be useful so having both available is probably the best solution.

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Jonathan M Davis <jmdavisProg@gmx.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jmdavisProg@gmx.com


--- Comment #6 from Jonathan M Davis <jmdavisProg@gmx.com> 2012-01-22 00:14:21 PST ---
Why would it be useful to have a non-virtual function listed as a virtual function? Because that's what you're doing when mark a function which doesn't override anything final. It's _not_ in any kind of override chain.

Imagine for a moment that private functions become virtual by default like TDPL says (which I still hopes doesn't happen, since it'll be a major blow to the efficiency of the language) and final functions which didn't override anything were listed as virtual functions, pretty much _every_ function would then be returned by getVirtualFunctions.

If you're using getVirtualFunctions or getVirtualMethods or whatever, then you want the _virtual_ functions. As such, I see _zero_ reason to be returning final functions which don't override anything, and so I see no reason to keep getVirtualFunctions around.

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--- Comment #7 from github-bugzilla@puremagic.com 2012-01-22 00:36:01 PST ---
Commit pushed to https://github.com/D-Programming-Language/dmd

https://github.com/D-Programming-Language/dmd/commit/adb62254d26ab0b29f543f2562a55b331f4ef297 fix Issue 1918 - __traits(getVirtualFunctions) returns final functions

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--- Comment #8 from github-bugzilla@puremagic.com 2012-01-22 00:43:05 PST ---
Commit pushed to https://github.com/D-Programming-Language/d-programming-language.org

https://github.com/D-Programming-Language/d-programming-language.org/commit/89f321f5ee0d0c3eeed478a70ef1cd79116c6736 fix Issue 1918 - __traits(getVirtualFunctions) returns final functions

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