[PATCH] Fix crash-on-invalid bug in template instantiation.

[Richard Smith]

================
Comment at: lib/Sema/SemaTemplateInstantiate.cpp:2273-2297
@@ -2272,27 +2274,27 @@
 
   // Check whether we have already instantiated or specialized this class
   // template specialization.
   if (ClassTemplateSpec->getSpecializationKind() != TSK_Undeclared) {
     if (ClassTemplateSpec->getSpecializationKind() == 
           TSK_ExplicitInstantiationDeclaration &&
         TSK == TSK_ExplicitInstantiationDefinition) {
       // An explicit instantiation definition follows an explicit instantiation
       // declaration (C++0x [temp.explicit]p10); go ahead and perform the
       // explicit instantiation.
       ClassTemplateSpec->setSpecializationKind(TSK);
       
       // If this is an explicit instantiation definition, mark the
       // vtable as used.
       if (TSK == TSK_ExplicitInstantiationDefinition &&
           !ClassTemplateSpec->isInvalidDecl())
         MarkVTableUsed(PointOfInstantiation, ClassTemplateSpec, true);
 
       return false;
     }
     
     // We can only instantiate something that hasn't already been
     // instantiated or specialized. Fail without any diagnostics: our
     // caller will provide an error message.    
     return true;
   }
 
----------------
Better solution: just delete all of this code.

http://reviews.llvm.org/D10622

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