[cfe-commits] [patch] rejects-valid: explicit specialization of redeclaration of a deleted function template

[David Blaikie]

Ping.

On Tue, Jun 26, 2012 at 11:37 AM, David Blaikie <dblaikie at gmail.com> wrote:
> The following code is (incorrectly) rejected:
>
> template<typename> void foo() = delete;
> template<typename> void foo(); // remove this line & the error is not produced
> template void foo<int>(); // "explicit instantiation of undefined
> function template 'foo'"
>
> There's a few ways to fix this & I'm not sure which one is preferred:
>
> 1) Correct the first 3 lines of
> TemplateDeclInstantiator::InitFunctionInstantiation:
>
>   if (Tmpl->isDeletedAsWritten())
>     New->setDeletedAsWritten()
>
> to
>
>   if (Tmpl->isDeleted())
>     New->setDeletedAsWritten()
>
> In this way, the implicit specialization will always correctly reflect
> the fact that it's deleted and intervening redeclarations won't
> confuse/break this invariant.
>
> 2) Remove the first 3 lines of
> TemplateDeclInstantiator::InitFunctionInstantiator. Since we're only
> instantiating the declaration, one could argue that it shouldn't be
> prematurely turned into a definition just because it's deleted
> (conversely: = delete has to be the first declaration, so having a
> declaration that isn't an = delete definition is also a bit
> questionable). In this case we'd need to also fix line
> SemaTemplateInstantiateDecl:2572 (SemaInstantiateFunctionDefinition)
> to test "IsDefined()" not just "IsDefaulted()". If that's the way
> we're going to deal with deleted templates, we could go & change
> SemaTemplateInstantiateDecl.cpp:1537 for member functions to match
> this too (hmm, actually removing the setDefaulted/setDeleted calls
> does cause at least one test to fail, so I'd have to poke around more
> if I was going to do that)
>
> Any thoughts/preferences?
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 2-remove.diff
Type: application/octet-stream
Size: 2389 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20120702/4f14ddfd/attachment.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 1-modify.diff
Type: application/octet-stream
Size: 1371 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20120702/4f14ddfd/attachment-0001.obj>