Index: clang/lib/Sema/SemaTemplateInstantiate.cpp
===================================================================
--- clang/lib/Sema/SemaTemplateInstantiate.cpp
+++ clang/lib/Sema/SemaTemplateInstantiate.cpp
@@ -2846,8 +2846,6 @@
   SavedContext.pop();
 
   if (!Instantiation->isInvalidDecl()) {
-    Consumer.HandleTagDeclDefinition(Instantiation);
-
     // Always emit the vtable for an explicit instantiation definition
     // of a polymorphic class template specialization. Otherwise, eagerly
     // instantiate only constexpr virtual functions in preparation for their use
@@ -2859,6 +2857,8 @@
                                    /*ConstexprOnly*/ true);
   }
 
+  Consumer.HandleTagDeclDefinition(Instantiation);
+
   return Instantiation->isInvalidDecl();
 }