[cfe-commits] PR12937 - explicitly deleting an explicit template specialization

[Douglas Gregor]

On Jun 21, 2012, at 3:14 PM, David Blaikie wrote:

> As per PR12937 Clang rejects valid code that attempts to explicitly
> delete an explicit template specialization.
> 
> This is due to the way Clang represents explicit template
> specializations as redeclarations of an implicit specialization of the
> original function template.
> 
> The fix is a pretty vague workaround - I'm open to suggestions of how
> to more deliberately test for the "magic" implicit declaration for an
> explicit specialization but I couldn't find one - so for now I just
> assume it's the first (getPreviousDecl() == nullptr) declaration of
> any explicit specialization.

diff --git lib/Sema/SemaDeclCXX.cpp lib/Sema/SemaDeclCXX.cpp
index 8280835..dab2d4d 100644
--- lib/Sema/SemaDeclCXX.cpp
+++ lib/Sema/SemaDeclCXX.cpp
@@ -10316,8 +10316,13 @@ void Sema::SetDeclDeleted(Decl *Dcl, SourceLocation DelLoc) {
     return;
   }
   if (const FunctionDecl *Prev = Fn->getPreviousDecl()) {
-    Diag(DelLoc, diag::err_deleted_decl_not_first);
-    Diag(Prev->getLocation(), diag::note_previous_declaration);
+    // Don't consider the implicit declaration we generate for explicit
+    // specializations. FIXME: Do not generate these implicit declarations.
+    if (Prev->getTemplateSpecializationKind() != TSK_ExplicitSpecialization
+        || Prev->getPreviousDecl()) {
+      Diag(DelLoc, diag::err_deleted_decl_not_first);
+      Diag(Prev->getLocation(), diag::note_previous_declaration);
+    }
     // If the declaration wasn't the first, we delete the function anyway for
     // recovery.
   }

I suggest checking that Prev->getTemplateSpecializationKind() == TSK_ImplicitInstantiation. The others (explicit instantiations) should still, presumably, cause us to complain. Otherwise, this looks good!

> At some point it would be nice to clean up the AST to more accurately
> represent the C++ semantics here so we don't have to do such hurdles.
> <pr12937.diff>


Yes, that would be a wonderful cleanup to our handling of template argument deduction.

	- Doug