3 files changed, 38 insertions, 9 deletions
diff --git a/clang/lib/AST/DeclBase.cpp b/clang/lib/AST/DeclBase.cpp
index 57149af3c10..aec3b7cd3bd 100644
--- a/clang/lib/AST/DeclBase.cpp
+++ b/clang/lib/AST/DeclBase.cpp
@@ -196,6 +196,17 @@ bool Decl::isTemplateDecl() const {
   return isa<TemplateDecl>(this);
 }
 
+TemplateDecl *Decl::getDescribedTemplate() const {
+  if (auto *FD = dyn_cast<FunctionDecl>(this))
+    return FD->getDescribedFunctionTemplate();
+  else if (auto *RD = dyn_cast<CXXRecordDecl>(this))
+    return RD->getDescribedClassTemplate();
+  else if (auto *VD = dyn_cast<VarDecl>(this))
+    return VD->getDescribedVarTemplate();
+
+  return nullptr;
+}
+
 const DeclContext *Decl::getParentFunctionOrMethod() const {
   for (const DeclContext *DC = getDeclContext();
        DC && !DC->isTranslationUnit() && !DC->isNamespace(); 
diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index 034b090fdf3..405a66f3b23 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -9324,11 +9324,8 @@ static void DiagnoseArityMismatch(Sema &S, OverloadCandidate *Cand,
 }
 
 static TemplateDecl *getDescribedTemplate(Decl *Templated) {
-  if (FunctionDecl *FD = dyn_cast<FunctionDecl>(Templated))
-    return FD->getDescribedFunctionTemplate();
-  else if (CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(Templated))
-    return RD->getDescribedClassTemplate();
-
+  if (TemplateDecl *TD = Templated->getDescribedTemplate())
+    return TD;
   llvm_unreachable("Unsupported: Getting the described template declaration"
                    " for bad deduction diagnosis");
 }
diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index 307d804a4ca..8e42be0ee2e 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -3530,7 +3530,8 @@ TemplateDeclInstantiator::InitMethodInstantiation(CXXMethodDecl *New,
 void Sema::InstantiateFunctionDefinition(SourceLocation PointOfInstantiation,
                                          FunctionDecl *Function,
                                          bool Recursive,
-                                         bool DefinitionRequired) {
+                                         bool DefinitionRequired,
+                                         bool AtEndOfTU) {
   if (Function->isInvalidDecl() || Function->isDefined())
     return;
 
@@ -3604,6 +3605,16 @@ void Sema::InstantiateFunctionDefinition(SourceLocation PointOfInstantiation,
       assert(!Recursive);
       PendingInstantiations.push_back(
         std::make_pair(Function, PointOfInstantiation));
+    } else if (Function->getTemplateSpecializationKind()
+                 == TSK_ImplicitInstantiation) {
+      if (AtEndOfTU && !getDiagnostics().hasErrorOccurred()) {
+        Diag(PointOfInstantiation, diag::warn_func_template_missing)
+          << Function;
+        Diag(PatternDecl->getLocation(), diag::note_forward_template_decl);
+        if (getLangOpts().CPlusPlus11)
+          Diag(PointOfInstantiation, diag::note_inst_declaration_hint)
+            << Function;
+      }
     }
 
     return;
@@ -3951,7 +3962,7 @@ void Sema::InstantiateStaticDataMemberDefinition(
 
 void Sema::InstantiateVariableDefinition(SourceLocation PointOfInstantiation,
                                          VarDecl *Var, bool Recursive,
-                                         bool DefinitionRequired) {
+                                      bool DefinitionRequired, bool AtEndOfTU) {
   if (Var->isInvalidDecl())
     return;
 
@@ -4083,6 +4094,16 @@ void Sema::InstantiateVariableDefinition(SourceLocation PointOfInstantiation,
                  == TSK_ExplicitInstantiationDefinition) {
       PendingInstantiations.push_back(
         std::make_pair(Var, PointOfInstantiation));
+    } else if (Var->getTemplateSpecializationKind()
+                 == TSK_ImplicitInstantiation) {
+      // Warn about missing definition at the end of translation unit.
+      if (AtEndOfTU && !getDiagnostics().hasErrorOccurred()) {
+        Diag(PointOfInstantiation, diag::warn_var_template_missing)
+          << Var;
+        Diag(PatternDecl->getLocation(), diag::note_forward_template_decl);
+        if (getLangOpts().CPlusPlus11)
+          Diag(PointOfInstantiation, diag::note_inst_declaration_hint) << Var;
+      }
     }
 
     return;
@@ -4852,7 +4873,7 @@ void Sema::PerformPendingInstantiations(bool LocalOnly) {
       bool DefinitionRequired = Function->getTemplateSpecializationKind() ==
                                 TSK_ExplicitInstantiationDefinition;
       InstantiateFunctionDefinition(/*FIXME:*/Inst.second, Function, true,
-                                    DefinitionRequired);
+                                    DefinitionRequired, true);
       continue;
     }
 
@@ -4893,7 +4914,7 @@ void Sema::PerformPendingInstantiations(bool LocalOnly) {
     // Instantiate static data member definitions or variable template
     // specializations.
     InstantiateVariableDefinition(/*FIXME:*/ Inst.second, Var, true,
-                                  DefinitionRequired);
+                                  DefinitionRequired, true);
   }
 }