diff --git a/clang-tools-extra/clangd/Hover.cpp b/clang-tools-extra/clangd/Hover.cpp
index 2ec0994e846e94..de103e011c7085 100644
--- a/clang-tools-extra/clangd/Hover.cpp
+++ b/clang-tools-extra/clangd/Hover.cpp
@@ -262,7 +262,8 @@ fetchTemplateParameters(const TemplateParameterList *Params,
       if (NTTP->hasDefaultArgument()) {
         P.Default.emplace();
         llvm::raw_string_ostream Out(*P.Default);
-        NTTP->getDefaultArgument()->printPretty(Out, nullptr, PP);
+        NTTP->getDefaultArgument().getArgument().print(PP, Out,
+                                                       /*IncludeType=*/false);
       }
     } else if (const auto *TTPD = dyn_cast<TemplateTemplateParmDecl>(Param)) {
       P.Type = printType(TTPD, PP);
diff --git a/clang/include/clang/AST/ASTNodeTraverser.h b/clang/include/clang/AST/ASTNodeTraverser.h
index 98db1cb5789909..616f92691ec323 100644
--- a/clang/include/clang/AST/ASTNodeTraverser.h
+++ b/clang/include/clang/AST/ASTNodeTraverser.h
@@ -704,9 +704,9 @@ class ASTNodeTraverser
     if (const auto *E = D->getPlaceholderTypeConstraint())
       Visit(E);
     if (D->hasDefaultArgument())
-      Visit(D->getDefaultArgument(), SourceRange(),
-            D->getDefaultArgStorage().getInheritedFrom(),
-            D->defaultArgumentWasInherited() ? "inherited from" : "previous");
+      dumpTemplateArgumentLoc(
+          D->getDefaultArgument(), D->getDefaultArgStorage().getInheritedFrom(),
+          D->defaultArgumentWasInherited() ? "inherited from" : "previous");
   }
 
   void VisitTemplateTemplateParmDecl(const TemplateTemplateParmDecl *D) {
diff --git a/clang/include/clang/AST/DeclTemplate.h b/clang/include/clang/AST/DeclTemplate.h
index 07b08b5ed43ca4..5b6a6b40b28ef8 100644
--- a/clang/include/clang/AST/DeclTemplate.h
+++ b/clang/include/clang/AST/DeclTemplate.h
@@ -1360,7 +1360,8 @@ class NonTypeTemplateParmDecl final
 
   /// The default template argument, if any, and whether or not
   /// it was inherited.
-  using DefArgStorage = DefaultArgStorage<NonTypeTemplateParmDecl, Expr *>;
+  using DefArgStorage =
+      DefaultArgStorage<NonTypeTemplateParmDecl, TemplateArgumentLoc *>;
   DefArgStorage DefaultArgument;
 
   // FIXME: Collapse this into TemplateParamPosition; or, just move depth/index
@@ -1430,7 +1431,10 @@ class NonTypeTemplateParmDecl final
   bool hasDefaultArgument() const { return DefaultArgument.isSet(); }
 
   /// Retrieve the default argument, if any.
-  Expr *getDefaultArgument() const { return DefaultArgument.get(); }
+  const TemplateArgumentLoc &getDefaultArgument() const {
+    static const TemplateArgumentLoc NoneLoc;
+    return DefaultArgument.isSet() ? *DefaultArgument.get() : NoneLoc;
+  }
 
   /// Retrieve the location of the default argument, if any.
   SourceLocation getDefaultArgumentLoc() const;
@@ -1444,7 +1448,8 @@ class NonTypeTemplateParmDecl final
   /// Set the default argument for this template parameter, and
   /// whether that default argument was inherited from another
   /// declaration.
-  void setDefaultArgument(Expr *DefArg) { DefaultArgument.set(DefArg); }
+  void setDefaultArgument(const ASTContext &C,
+                          const TemplateArgumentLoc &DefArg);
   void setInheritedDefaultArgument(const ASTContext &C,
                                    NonTypeTemplateParmDecl *Parm) {
     DefaultArgument.setInherited(C, Parm);
diff --git a/clang/include/clang/AST/RecursiveASTVisitor.h b/clang/include/clang/AST/RecursiveASTVisitor.h
index 659e4cdd1037b1..a4b8d6ef61d564 100644
--- a/clang/include/clang/AST/RecursiveASTVisitor.h
+++ b/clang/include/clang/AST/RecursiveASTVisitor.h
@@ -2320,7 +2320,7 @@ DEF_TRAVERSE_DECL(NonTypeTemplateParmDecl, {
   // A non-type template parameter, e.g. "S" in template<int S> class Foo ...
   TRY_TO(TraverseDeclaratorHelper(D));
   if (D->hasDefaultArgument() && !D->defaultArgumentWasInherited())
-    TRY_TO(TraverseStmt(D->getDefaultArgument()));
+    TRY_TO(TraverseTemplateArgumentLoc(D->getDefaultArgument()));
 })
 
 DEF_TRAVERSE_DECL(ParmVarDecl, {
diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index f9902a978aa34a..a2398fef623ea2 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -6503,8 +6503,10 @@ bool ASTContext::isSameDefaultTemplateArgument(const NamedDecl *X,
     if (!NTTPX->hasDefaultArgument() || !NTTPY->hasDefaultArgument())
       return false;
 
-    Expr *DefaultArgumentX = NTTPX->getDefaultArgument()->IgnoreImpCasts();
-    Expr *DefaultArgumentY = NTTPY->getDefaultArgument()->IgnoreImpCasts();
+    Expr *DefaultArgumentX =
+        NTTPX->getDefaultArgument().getArgument().getAsExpr()->IgnoreImpCasts();
+    Expr *DefaultArgumentY =
+        NTTPY->getDefaultArgument().getArgument().getAsExpr()->IgnoreImpCasts();
     llvm::FoldingSetNodeID XID, YID;
     DefaultArgumentX->Profile(XID, *this, /*Canonical=*/true);
     DefaultArgumentY->Profile(YID, *this, /*Canonical=*/true);
diff --git a/clang/lib/AST/ASTDiagnostic.cpp b/clang/lib/AST/ASTDiagnostic.cpp
index 7b0d5f9cc1a93d..91bc1b22acfc7f 100644
--- a/clang/lib/AST/ASTDiagnostic.cpp
+++ b/clang/lib/AST/ASTDiagnostic.cpp
@@ -1238,7 +1238,7 @@ class TemplateDiff {
           E = Iter->getAsExpr();
       }
     } else if (!Default->isParameterPack()) {
-      E = Default->getDefaultArgument();
+      E = Default->getDefaultArgument().getArgument().getAsExpr();
     }
 
     if (!Iter.hasDesugaredTA()) return;
diff --git a/clang/lib/AST/ASTImporter.cpp b/clang/lib/AST/ASTImporter.cpp
index a47dd72a5679cd..cab5ee60479564 100644
--- a/clang/lib/AST/ASTImporter.cpp
+++ b/clang/lib/AST/ASTImporter.cpp
@@ -5949,10 +5949,11 @@ ASTNodeImporter::VisitNonTypeTemplateParmDecl(NonTypeTemplateParmDecl *D) {
     return ToD;
 
   if (D->hasDefaultArgument()) {
-    ExpectedExpr ToDefaultArgOrErr = import(D->getDefaultArgument());
+    Expected<TemplateArgumentLoc> ToDefaultArgOrErr =
+        import(D->getDefaultArgument());
     if (!ToDefaultArgOrErr)
       return ToDefaultArgOrErr.takeError();
-    ToD->setDefaultArgument(*ToDefaultArgOrErr);
+    ToD->setDefaultArgument(Importer.getToContext(), *ToDefaultArgOrErr);
   }
 
   return ToD;
diff --git a/clang/lib/AST/DeclPrinter.cpp b/clang/lib/AST/DeclPrinter.cpp
index bf32aafc3d0af4..0cf4e64f83b8df 100644
--- a/clang/lib/AST/DeclPrinter.cpp
+++ b/clang/lib/AST/DeclPrinter.cpp
@@ -1898,7 +1898,7 @@ void DeclPrinter::VisitNonTypeTemplateParmDecl(
 
   if (NTTP->hasDefaultArgument()) {
     Out << " = ";
-    NTTP->getDefaultArgument()->printPretty(Out, nullptr, Policy, Indentation,
-                                            "\n", &Context);
+    NTTP->getDefaultArgument().getArgument().print(Policy, Out,
+                                                   /*IncludeType=*/false);
   }
 }
diff --git a/clang/lib/AST/DeclTemplate.cpp b/clang/lib/AST/DeclTemplate.cpp
index 46bb3e8e51389f..95ffd4784641fc 100644
--- a/clang/lib/AST/DeclTemplate.cpp
+++ b/clang/lib/AST/DeclTemplate.cpp
@@ -795,14 +795,21 @@ NonTypeTemplateParmDecl::CreateDeserialized(ASTContext &C, GlobalDeclID ID,
 SourceRange NonTypeTemplateParmDecl::getSourceRange() const {
   if (hasDefaultArgument() && !defaultArgumentWasInherited())
     return SourceRange(getOuterLocStart(),
-                       getDefaultArgument()->getSourceRange().getEnd());
+                       getDefaultArgument().getSourceRange().getEnd());
   return DeclaratorDecl::getSourceRange();
 }
 
 SourceLocation NonTypeTemplateParmDecl::getDefaultArgumentLoc() const {
-  return hasDefaultArgument()
-    ? getDefaultArgument()->getSourceRange().getBegin()
-    : SourceLocation();
+  return hasDefaultArgument() ? getDefaultArgument().getSourceRange().getBegin()
+                              : SourceLocation();
+}
+
+void NonTypeTemplateParmDecl::setDefaultArgument(
+    const ASTContext &C, const TemplateArgumentLoc &DefArg) {
+  if (DefArg.getArgument().isNull())
+    DefaultArgument.set(nullptr);
+  else
+    DefaultArgument.set(new (C) TemplateArgumentLoc(DefArg));
 }
 
 //===----------------------------------------------------------------------===//
diff --git a/clang/lib/AST/JSONNodeDumper.cpp b/clang/lib/AST/JSONNodeDumper.cpp
index efd3a639d746b3..3bbb3a905e9b91 100644
--- a/clang/lib/AST/JSONNodeDumper.cpp
+++ b/clang/lib/AST/JSONNodeDumper.cpp
@@ -1044,7 +1044,7 @@ void JSONNodeDumper::VisitNonTypeTemplateParmDecl(
 
   if (D->hasDefaultArgument())
     JOS.attributeObject("defaultArg", [=] {
-      Visit(D->getDefaultArgument(), SourceRange(),
+      Visit(D->getDefaultArgument().getArgument(), SourceRange(),
             D->getDefaultArgStorage().getInheritedFrom(),
             D->defaultArgumentWasInherited() ? "inherited from" : "previous");
     });
diff --git a/clang/lib/AST/ODRDiagsEmitter.cpp b/clang/lib/AST/ODRDiagsEmitter.cpp
index 97b6c14d9ede61..37f0f68c92355f 100644
--- a/clang/lib/AST/ODRDiagsEmitter.cpp
+++ b/clang/lib/AST/ODRDiagsEmitter.cpp
@@ -1523,8 +1523,11 @@ bool ODRDiagsEmitter::diagnoseMismatch(
         }
 
         if (HasFirstDefaultArgument && HasSecondDefaultArgument) {
-          Expr *FirstDefaultArgument = FirstNTTPD->getDefaultArgument();
-          Expr *SecondDefaultArgument = SecondNTTPD->getDefaultArgument();
+          TemplateArgument FirstDefaultArgument =
+              FirstNTTPD->getDefaultArgument().getArgument();
+          TemplateArgument SecondDefaultArgument =
+              SecondNTTPD->getDefaultArgument().getArgument();
+
           if (computeODRHash(FirstDefaultArgument) !=
               computeODRHash(SecondDefaultArgument)) {
             DiagTemplateError(FunctionTemplateParameterDifferentDefaultArgument)
diff --git a/clang/lib/AST/ODRHash.cpp b/clang/lib/AST/ODRHash.cpp
index 18b1e17e0fee5d..246e56231539ae 100644
--- a/clang/lib/AST/ODRHash.cpp
+++ b/clang/lib/AST/ODRHash.cpp
@@ -480,7 +480,7 @@ class ODRDeclVisitor : public ConstDeclVisitor<ODRDeclVisitor> {
         D->hasDefaultArgument() && !D->defaultArgumentWasInherited();
     Hash.AddBoolean(hasDefaultArgument);
     if (hasDefaultArgument) {
-      AddStmt(D->getDefaultArgument());
+      AddTemplateArgument(D->getDefaultArgument().getArgument());
     }
     Hash.AddBoolean(D->isParameterPack());
 
diff --git a/clang/lib/AST/TypePrinter.cpp b/clang/lib/AST/TypePrinter.cpp
index 981f09410401b0..5ed56b367a46a7 100644
--- a/clang/lib/AST/TypePrinter.cpp
+++ b/clang/lib/AST/TypePrinter.cpp
@@ -2281,8 +2281,9 @@ bool clang::isSubstitutedDefaultArgument(ASTContext &Ctx, TemplateArgument Arg,
                Ctx, Arg, TTPD->getDefaultArgument().getArgument(), Args, Depth);
   } else if (auto *NTTPD = dyn_cast<NonTypeTemplateParmDecl>(Param)) {
     return NTTPD->hasDefaultArgument() &&
-           isSubstitutedTemplateArgument(Ctx, Arg, NTTPD->getDefaultArgument(),
-                                         Args, Depth);
+           isSubstitutedTemplateArgument(
+               Ctx, Arg, NTTPD->getDefaultArgument().getArgument(), Args,
+               Depth);
   }
   return false;
 }
diff --git a/clang/lib/ExtractAPI/DeclarationFragments.cpp b/clang/lib/ExtractAPI/DeclarationFragments.cpp
index d88e4e0df8ef89..904b9315f26ef4 100644
--- a/clang/lib/ExtractAPI/DeclarationFragments.cpp
+++ b/clang/lib/ExtractAPI/DeclarationFragments.cpp
@@ -1023,8 +1023,9 @@ DeclarationFragmentsBuilder::getFragmentsForTemplateParameters(
       if (NTP->hasDefaultArgument()) {
         SmallString<8> ExprStr;
         raw_svector_ostream Output(ExprStr);
-        NTP->getDefaultArgument()->printPretty(
-            Output, nullptr, NTP->getASTContext().getPrintingPolicy());
+        NTP->getDefaultArgument().getArgument().print(
+            NTP->getASTContext().getPrintingPolicy(), Output,
+            /*IncludeType=*/false);
         Fragments.append(" = ", DeclarationFragments::FragmentKind::Text)
             .append(ExprStr, DeclarationFragments::FragmentKind::Text);
       }
diff --git a/clang/lib/Index/IndexDecl.cpp b/clang/lib/Index/IndexDecl.cpp
index 058f4aef918a8f..a7fa6c5e6898ec 100644
--- a/clang/lib/Index/IndexDecl.cpp
+++ b/clang/lib/Index/IndexDecl.cpp
@@ -711,7 +711,8 @@ class IndexingDeclVisitor : public ConstDeclVisitor<IndexingDeclVisitor, bool> {
       } else if (const auto *NTTP = dyn_cast<NonTypeTemplateParmDecl>(TP)) {
         IndexCtx.indexTypeSourceInfo(NTTP->getTypeSourceInfo(), Parent);
         if (NTTP->hasDefaultArgument())
-          IndexCtx.indexBody(NTTP->getDefaultArgument(), Parent);
+          handleTemplateArgumentLoc(NTTP->getDefaultArgument(), Parent,
+                                    TP->getLexicalDeclContext());
       } else if (const auto *TTPD = dyn_cast<TemplateTemplateParmDecl>(TP)) {
         if (TTPD->hasDefaultArgument())
           handleTemplateArgumentLoc(TTPD->getDefaultArgument(), Parent,
diff --git a/clang/lib/Sema/HLSLExternalSemaSource.cpp b/clang/lib/Sema/HLSLExternalSemaSource.cpp
index fa8c852ea9e9f2..a2b29a7bdf505c 100644
--- a/clang/lib/Sema/HLSLExternalSemaSource.cpp
+++ b/clang/lib/Sema/HLSLExternalSemaSource.cpp
@@ -442,10 +442,12 @@ void HLSLExternalSemaSource::defineHLSLVectorAlias() {
       AST, HLSLNamespace, SourceLocation(), SourceLocation(), 0, 1,
       &AST.Idents.get("element_count", tok::TokenKind::identifier), AST.IntTy,
       false, AST.getTrivialTypeSourceInfo(AST.IntTy));
-  Expr *LiteralExpr =
-      IntegerLiteral::Create(AST, llvm::APInt(AST.getIntWidth(AST.IntTy), 4),
-                             AST.IntTy, SourceLocation());
-  SizeParam->setDefaultArgument(LiteralExpr);
+  llvm::APInt Val(AST.getIntWidth(AST.IntTy), 4);
+  TemplateArgument Default(AST, llvm::APSInt(std::move(Val)), AST.IntTy,
+                           /*IsDefaulted=*/true);
+  SizeParam->setDefaultArgument(
+      AST, SemaPtr->getTrivialTemplateArgumentLoc(Default, AST.IntTy,
+                                                  SourceLocation(), SizeParam));
   TemplateParams.emplace_back(SizeParam);
 
   auto *ParamList =
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index f930bd8651d51d..268f079980a6c3 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -1599,7 +1599,9 @@ NamedDecl *Sema::ActOnNonTypeTemplateParameter(Scope *S, Declarator &D,
     if (DiagnoseUnexpandedParameterPack(Default, UPPC_DefaultArgument))
       return Param;
 
-    Param->setDefaultArgument(Default);
+    Param->setDefaultArgument(
+        Context, getTrivialTemplateArgumentLoc(TemplateArgument(Default),
+                                               QualType(), SourceLocation()));
   }
 
   return Param;
@@ -1805,6 +1807,8 @@ static void SetNestedNameSpecifier(Sema &S, TagDecl *T,
 // Returns the template parameter list with all default template argument
 // information.
 static TemplateParameterList *GetTemplateParameterList(TemplateDecl *TD) {
+  if (TD->isImplicit())
+    return TD->getTemplateParameters();
   // Make sure we get the template parameter list from the most
   // recent declaration, since that is the only one that is guaranteed to
   // have all the default template argument information.
@@ -1825,7 +1829,8 @@ static TemplateParameterList *GetTemplateParameterList(TemplateDecl *TD) {
   //    template <class = void> friend struct C;
   //  };
   //  template struct S<int>;
-  while (D->getFriendObjectKind() != Decl::FriendObjectKind::FOK_None &&
+  while ((D->isImplicit() ||
+          D->getFriendObjectKind() != Decl::FriendObjectKind::FOK_None) &&
          D->getPreviousDecl())
     D = D->getPreviousDecl();
   return cast<TemplateDecl>(D)->getTemplateParameters();
@@ -3630,9 +3635,9 @@ bool Sema::CheckTemplateParameterList(TemplateParameterList *NewParams,
 
       // Check the presence of a default argument here.
       if (NewNonTypeParm->hasDefaultArgument() &&
-          DiagnoseDefaultTemplateArgument(*this, TPC,
-                                          NewNonTypeParm->getLocation(),
-                    NewNonTypeParm->getDefaultArgument()->getSourceRange())) {
+          DiagnoseDefaultTemplateArgument(
+              *this, TPC, NewNonTypeParm->getLocation(),
+              NewNonTypeParm->getDefaultArgument().getSourceRange())) {
         NewNonTypeParm->removeDefaultArgument();
       }
 
@@ -6107,16 +6112,17 @@ static bool SubstDefaultTemplateArgument(
 /// parameters that precede \p Param in the template parameter list.
 ///
 /// \returns the substituted template argument, or NULL if an error occurred.
-static ExprResult SubstDefaultTemplateArgument(
+static bool SubstDefaultTemplateArgument(
     Sema &SemaRef, TemplateDecl *Template, SourceLocation TemplateLoc,
     SourceLocation RAngleLoc, NonTypeTemplateParmDecl *Param,
     ArrayRef<TemplateArgument> SugaredConverted,
-    ArrayRef<TemplateArgument> CanonicalConverted) {
+    ArrayRef<TemplateArgument> CanonicalConverted,
+    TemplateArgumentLoc &Output) {
   Sema::InstantiatingTemplate Inst(SemaRef, TemplateLoc, Param, Template,
                                    SugaredConverted,
                                    SourceRange(TemplateLoc, RAngleLoc));
   if (Inst.isInvalid())
-    return ExprError();
+    return true;
 
   // Only substitute for the innermost template argument list.
   MultiLevelTemplateArgumentList TemplateArgLists(Template, SugaredConverted,
@@ -6127,7 +6133,8 @@ static ExprResult SubstDefaultTemplateArgument(
   Sema::ContextRAII SavedContext(SemaRef, Template->getDeclContext());
   EnterExpressionEvaluationContext ConstantEvaluated(
       SemaRef, Sema::ExpressionEvaluationContext::ConstantEvaluated);
-  return SemaRef.SubstExpr(Param->getDefaultArgument(), TemplateArgLists);
+  return SemaRef.SubstTemplateArgument(Param->getDefaultArgument(),
+                                       TemplateArgLists, Output);
 }
 
 /// Substitute template arguments into the default template argument for
@@ -6219,14 +6226,12 @@ TemplateArgumentLoc Sema::SubstDefaultTemplateArgumentIfAvailable(
       return TemplateArgumentLoc();
 
     HasDefaultArg = true;
-    ExprResult Arg = SubstDefaultTemplateArgument(
-        *this, Template, TemplateLoc, RAngleLoc, NonTypeParm, SugaredConverted,
-        CanonicalConverted);
-    if (Arg.isInvalid())
+    TemplateArgumentLoc Output;
+    if (SubstDefaultTemplateArgument(*this, Template, TemplateLoc, RAngleLoc,
+                                     NonTypeParm, SugaredConverted,
+                                     CanonicalConverted, Output))
       return TemplateArgumentLoc();
-
-    Expr *ArgE = Arg.getAs<Expr>();
-    return TemplateArgumentLoc(TemplateArgument(ArgE), ArgE);
+    return Output;
   }
 
   TemplateTemplateParmDecl *TempTempParm
@@ -6803,14 +6808,10 @@ bool Sema::CheckTemplateArgumentList(
         return diagnoseMissingArgument(*this, TemplateLoc, Template, NTTP,
                                        NewArgs);
 
-      ExprResult E = SubstDefaultTemplateArgument(
-          *this, Template, TemplateLoc, RAngleLoc, NTTP, SugaredConverted,
-          CanonicalConverted);
-      if (E.isInvalid())
+      if (SubstDefaultTemplateArgument(*this, Template, TemplateLoc, RAngleLoc,
+                                       NTTP, SugaredConverted,
+                                       CanonicalConverted, Arg))
         return true;
-
-      Expr *Ex = E.getAs<Expr>();
-      Arg = TemplateArgumentLoc(TemplateArgument(Ex), Ex);
     } else {
       TemplateTemplateParmDecl *TempParm
         = cast<TemplateTemplateParmDecl>(*Param);
@@ -9523,10 +9524,10 @@ DeclResult Sema::ActOnClassTemplateSpecialization(
         }
       } else if (NonTypeTemplateParmDecl *NTTP
                    = dyn_cast<NonTypeTemplateParmDecl>(Param)) {
-        if (Expr *DefArg = NTTP->getDefaultArgument()) {
+        if (NTTP->hasDefaultArgument()) {
           Diag(NTTP->getDefaultArgumentLoc(),
                diag::err_default_arg_in_partial_spec)
-            << DefArg->getSourceRange();
+              << NTTP->getDefaultArgument().getSourceRange();
           NTTP->removeDefaultArgument();
         }
       } else {
diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp b/clang/lib/Sema/SemaTemplateDeduction.cpp
index 0c348633576d64..76f47e9cb2560d 100644
--- a/clang/lib/Sema/SemaTemplateDeduction.cpp
+++ b/clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -527,8 +527,8 @@ static NamedDecl *getTemplateParameterWithDefault(Sema &S, NamedDecl *A,
     R->setDefaultArgument(
         S.Context,
         S.getTrivialTemplateArgumentLoc(Default, QualType(), SourceLocation()));
-    if (R->hasTypeConstraint()) {
-      auto *C = R->getTypeConstraint();
+    if (T->hasTypeConstraint()) {
+      auto *C = T->getTypeConstraint();
       R->setTypeConstraint(C->getConceptReference(),
                            C->getImmediatelyDeclaredConstraint());
     }
@@ -536,14 +536,14 @@ static NamedDecl *getTemplateParameterWithDefault(Sema &S, NamedDecl *A,
   }
   case Decl::NonTypeTemplateParm: {
     auto *T = cast<NonTypeTemplateParmDecl>(A);
-    // FIXME: Ditto, as above for TemplateTypeParm case.
-    if (T->isParameterPack())
-      return A;
     auto *R = NonTypeTemplateParmDecl::Create(
         S.Context, A->getDeclContext(), SourceLocation(), SourceLocation(),
         T->getDepth(), T->getIndex(), T->getIdentifier(), T->getType(),
-        /*ParameterPack=*/false, T->getTypeSourceInfo());
-    R->setDefaultArgument(Default.getAsExpr());
+        T->isParameterPack(), T->getTypeSourceInfo());
+    R->setDefaultArgument(S.Context,
+                          S.getTrivialTemplateArgumentLoc(
+                              Default, Default.getNonTypeTemplateArgumentType(),
+                              SourceLocation()));
     if (auto *PTC = T->getPlaceholderTypeConstraint())
       R->setPlaceholderTypeConstraint(PTC);
     return R;
@@ -583,37 +583,53 @@ DeduceTemplateArguments(Sema &S, TemplateParameterList *TemplateParams,
       return TemplateDeductionResult::Success;
 
     auto NewDeduced = DeducedTemplateArgument(Arg);
-    // Provisional resolution for CWG2398: If Arg is also a template template
-    // param, and it names a template specialization, then we deduce a
-    // synthesized template template parameter based on A, but using the TS's
-    // arguments as defaults.
-    if (auto *TempArg = dyn_cast_or_null<TemplateTemplateParmDecl>(
-            Arg.getAsTemplateDecl())) {
+    // Provisional resolution for CWG2398: If Arg names a template
+    // specialization, then we deduce a synthesized template template parameter
+    // based on A, but using the TS's arguments as defaults.
+    if (DefaultArguments.size() != 0) {
       assert(Arg.getKind() == TemplateName::Template);
-      assert(!TempArg->isExpandedParameterPack());
-
+      TemplateDecl *TempArg = Arg.getAsTemplateDecl();
       TemplateParameterList *As = TempArg->getTemplateParameters();
-      if (DefaultArguments.size() != 0) {
-        assert(DefaultArguments.size() <= As->size());
-        SmallVector<NamedDecl *, 4> Params(As->size());
-        for (unsigned I = 0; I < DefaultArguments.size(); ++I)
-          Params[I] = getTemplateParameterWithDefault(S, As->getParam(I),
-                                                      DefaultArguments[I]);
-        for (unsigned I = DefaultArguments.size(); I < As->size(); ++I)
-          Params[I] = As->getParam(I);
-        // FIXME: We could unique these, and also the parameters, but we don't
-        // expect programs to contain a large enough amount of these deductions
-        // for that to be worthwhile.
-        auto *TPL = TemplateParameterList::Create(
-            S.Context, SourceLocation(), SourceLocation(), Params,
-            SourceLocation(), As->getRequiresClause());
-        NewDeduced = DeducedTemplateArgument(
-            TemplateName(TemplateTemplateParmDecl::Create(
-                S.Context, TempArg->getDeclContext(), SourceLocation(),
-                TempArg->getDepth(), TempArg->getPosition(),
-                TempArg->isParameterPack(), TempArg->getIdentifier(),
-                TempArg->wasDeclaredWithTypename(), TPL)));
+      assert(DefaultArguments.size() <= As->size());
+
+      SmallVector<NamedDecl *, 4> Params(As->size());
+      for (unsigned I = 0; I < DefaultArguments.size(); ++I)
+        Params[I] = getTemplateParameterWithDefault(S, As->getParam(I),
+                                                    DefaultArguments[I]);
+      for (unsigned I = DefaultArguments.size(); I < As->size(); ++I)
+        Params[I] = As->getParam(I);
+      // FIXME: We could unique these, and also the parameters, but we don't
+      // expect programs to contain a large enough amount of these deductions
+      // for that to be worthwhile.
+      auto *TPL = TemplateParameterList::Create(
+          S.Context, SourceLocation(), SourceLocation(), Params,
+          SourceLocation(), As->getRequiresClause());
+
+      TemplateDecl *TD;
+      switch (TempArg->getKind()) {
+      case Decl::TemplateTemplateParm: {
+        auto *A = cast<TemplateTemplateParmDecl>(TempArg);
+        assert(!A->isExpandedParameterPack());
+        TD = TemplateTemplateParmDecl::Create(
+            S.Context, A->getDeclContext(), SourceLocation(), A->getDepth(),
+            A->getPosition(), A->isParameterPack(), A->getIdentifier(),
+            A->wasDeclaredWithTypename(), TPL);
+        break;
+      }
+      case Decl::ClassTemplate: {
+        auto *A = cast<ClassTemplateDecl>(TempArg);
+        auto *CT = ClassTemplateDecl::Create(S.Context, A->getDeclContext(),
+                                             SourceLocation(), A->getDeclName(),
+                                             TPL, A->getTemplatedDecl());
+        CT->setPreviousDecl(A);
+        TD = CT;
+        break;
+      }
+      default:
+        llvm_unreachable("Unexpected Template Kind");
       }
+      TD->setImplicit(true);
+      NewDeduced = DeducedTemplateArgument(TemplateName(TD));
     }
 
     DeducedTemplateArgument Result = checkDeducedTemplateArguments(S.Context,
diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index 38a300332068fa..09812946bd3833 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -3123,9 +3123,10 @@ Decl *TemplateDeclInstantiator::VisitNonTypeTemplateParmDecl(
   if (D->hasDefaultArgument() && !D->defaultArgumentWasInherited()) {
     EnterExpressionEvaluationContext ConstantEvaluated(
         SemaRef, Sema::ExpressionEvaluationContext::ConstantEvaluated);
-    ExprResult Value = SemaRef.SubstExpr(D->getDefaultArgument(), TemplateArgs);
-    if (!Value.isInvalid())
-      Param->setDefaultArgument(Value.get());
+    TemplateArgumentLoc Result;
+    if (!SemaRef.SubstTemplateArgument(D->getDefaultArgument(), TemplateArgs,
+                                       Result))
+      Param->setDefaultArgument(SemaRef.Context, Result);
   }
 
   // Introduce this template parameter's instantiation into the instantiation
diff --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
index d7a9e31b477f88..61cc99d4df6871 100644
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -2717,7 +2717,8 @@ void ASTDeclReader::VisitNonTypeTemplateParmDecl(NonTypeTemplateParmDecl *D) {
     // Rest of NonTypeTemplateParmDecl.
     D->ParameterPack = Record.readInt();
     if (Record.readInt())
-      D->setDefaultArgument(Record.readExpr());
+      D->setDefaultArgument(Reader.getContext(),
+                            Record.readTemplateArgumentLoc());
   }
 }
 
diff --git a/clang/lib/Serialization/ASTWriterDecl.cpp b/clang/lib/Serialization/ASTWriterDecl.cpp
index b2a214e935aadd..bbd16dbdb8ffff 100644
--- a/clang/lib/Serialization/ASTWriterDecl.cpp
+++ b/clang/lib/Serialization/ASTWriterDecl.cpp
@@ -1941,7 +1941,7 @@ void ASTDeclWriter::VisitNonTypeTemplateParmDecl(NonTypeTemplateParmDecl *D) {
                           !D->defaultArgumentWasInherited();
     Record.push_back(OwnsDefaultArg);
     if (OwnsDefaultArg)
-      Record.AddStmt(D->getDefaultArgument());
+      Record.AddTemplateArgumentLoc(D->getDefaultArgument());
     Code = serialization::DECL_NON_TYPE_TEMPLATE_PARM;
   }
 }
diff --git a/clang/test/AST/ast-dump-decl.cpp b/clang/test/AST/ast-dump-decl.cpp
index 554cdcf83fcdfc..e062d4f068a403 100644
--- a/clang/test/AST/ast-dump-decl.cpp
+++ b/clang/test/AST/ast-dump-decl.cpp
@@ -459,7 +459,7 @@ namespace testClassTemplateDecl {
 
 // CHECK:       ClassTemplateDecl 0x{{.+}} <{{.+}}:[[@LINE-148]]:3, col:31> col:31 TestTemplateDefaultNonType{{$}}
 // CHECK-NEXT:  |-NonTypeTemplateParmDecl 0x{{.+}} <col:12, col:20> col:16 'int' depth 0 index 0 I{{$}}
-// CHECK-NEXT:  | `-TemplateArgument expr{{$}}
+// CHECK-NEXT:  | `-TemplateArgument <col:20> expr{{$}}
 // CHECK-NEXT:  |   `-IntegerLiteral 0x{{.+}} <col:20> 'int' 42{{$}}
 // CHECK-NEXT:  `-CXXRecordDecl 0x{{.+}} <col:24, col:31> col:31 struct TestTemplateDefaultNonType{{$}}
 
@@ -671,7 +671,7 @@ namespace TestNonTypeTemplateParmDecl {
 // CHECK:      NamespaceDecl{{.*}} TestNonTypeTemplateParmDecl
 // CHECK-NEXT:   FunctionTemplateDecl
 // CHECK-NEXT:     NonTypeTemplateParmDecl{{.*}} 'int' depth 0 index 0 I
-// CHECK-NEXT:       TemplateArgument expr
+// CHECK-NEXT:       TemplateArgument {{.*}} expr
 // CHECK-NEXT:         IntegerLiteral{{.*}} 'int' 1
 // CHECK-NEXT:     NonTypeTemplateParmDecl{{.*}} 'int' depth 0 index 1 ... J
 
diff --git a/clang/test/CXX/temp/temp.decls/temp.alias/p2.cpp b/clang/test/CXX/temp/temp.decls/temp.alias/p2.cpp
index a5b39fe5c51f70..bc39431253880c 100644
--- a/clang/test/CXX/temp/temp.decls/temp.alias/p2.cpp
+++ b/clang/test/CXX/temp/temp.decls/temp.alias/p2.cpp
@@ -28,13 +28,14 @@ namespace StdExample {
     { /* ... */ }
 
   template<template<class> class TT>
-    void f(TT<int>); // expected-note {{candidate template ignored}}
+    void f(TT<int>);
 
   template<template<class,class> class TT>
     void g(TT<int, Alloc<int>>);
 
   int h() {
-    f(v); // expected-error {{no matching function for call to 'f'}}
+    f(v); // OK: TT = vector, Alloc<int> is used as the default argument for the
+          // second parameter.
     g(v); // OK: TT = vector
   }
 
diff --git a/clang/test/SemaTemplate/cwg2398.cpp b/clang/test/SemaTemplate/cwg2398.cpp
index e3b5e575374d3f..4cc946735a1e27 100644
--- a/clang/test/SemaTemplate/cwg2398.cpp
+++ b/clang/test/SemaTemplate/cwg2398.cpp
@@ -65,13 +65,10 @@ namespace class_template {
   template <class T3> struct B;
 
   template <template <class T4> class TT1, class T5> struct B<TT1<T5>>;
-  // new-note@-1 {{partial specialization matches}}
 
   template <class T6, class T7> struct B<A<T6, T7>> {};
-  // new-note@-1 {{partial specialization matches}}
 
   template struct B<A<int>>;
-  // new-error@-1 {{ambiguous partial specialization}}
 } // namespace class_template
 
 namespace type_pack1 {
diff --git a/clang/test/SemaTemplate/deduction-guide.cpp b/clang/test/SemaTemplate/deduction-guide.cpp
index a91ab5ec7bcc5f..0eaeb49e6b32de 100644
--- a/clang/test/SemaTemplate/deduction-guide.cpp
+++ b/clang/test/SemaTemplate/deduction-guide.cpp
@@ -100,7 +100,7 @@ using CT = C<int>;
 // CHECK: | `-NonTypeTemplateParmDecl {{.*}} 'X' depth 1 index 1
 // CHECK: |-TemplateTypeParmDecl {{.*}} typename depth 0 index 2 U
 // CHECK: |-NonTypeTemplateParmDecl {{.*}} 'type-parameter-0-2' depth 0 index 3 V
-// CHECK: | `-TemplateArgument expr
+// CHECK: | `-TemplateArgument {{.*}} expr
 // CHECK: |   `-IntegerLiteral {{.*}} 'int' 0
 // CHECK: |-CXXDeductionGuideDecl {{.*}} 'auto (A, Y<>, type-parameter-0-2) -> C<A>'
 // CHECK: | |-ParmVarDecl {{.*}} 'A'
@@ -139,7 +139,7 @@ using DT = D<int, int>;
 // CHECK: |-TemplateTypeParmDecl {{.*}} typename depth 0 index 0 ... T
 // CHECK: |-TemplateTypeParmDecl {{.*}} typename depth 0 index 1 U1
 // CHECK: |-TemplateTypeParmDecl {{.*}} typename depth 0 index 2 U2
-// CHECK: `-CXXDeductionGuideDecl {{.*}} 'auto (B<type-parameter-0-1, type-parameter-0-2> *) -> D<T...>'  
+// CHECK: `-CXXDeductionGuideDecl {{.*}} 'auto (B<type-parameter-0-1, type-parameter-0-2> *) -> D<T...>'
 // CHECK:   `-ParmVarDecl {{.*}} 'B<type-parameter-0-1, type-parameter-0-2> *'
 // CHECK: FunctionProtoType {{.*}} 'auto (B<type-parameter-0-1, type-parameter-0-2> *) -> D<T...>' dependent trailing_return
 // CHECK: |-InjectedClassNameType {{.*}} 'D<T...>' dependent
@@ -222,7 +222,7 @@ F s(0);
 // CHECK-LABEL: Dumping <deduction guide for F>:
 // CHECK: FunctionTemplateDecl
 // CHECK: |-NonTypeTemplateParmDecl {{.*}} 'char' depth 0 index 0
-// CHECK:   `-TemplateArgument expr
+// CHECK:   `-TemplateArgument {{.*}} expr
 // CHECK: |   |-inherited from NonTypeTemplateParm {{.*}} '' 'char'
 // CHECK: |   `-CharacterLiteral {{.*}} 'char' 120
 // CHECK: |-TemplateTypeParmDecl {{.*}} typename depth 0 index 1 U
diff --git a/clang/tools/libclang/CIndex.cpp b/clang/tools/libclang/CIndex.cpp
index d0d654568d8475..49ed60d990ca69 100644
--- a/clang/tools/libclang/CIndex.cpp
+++ b/clang/tools/libclang/CIndex.cpp
@@ -945,8 +945,9 @@ bool CursorVisitor::VisitNonTypeTemplateParmDecl(NonTypeTemplateParmDecl *D) {
     return true;
 
   if (D->hasDefaultArgument() && !D->defaultArgumentWasInherited())
-    if (Expr *DefArg = D->getDefaultArgument())
-      return Visit(MakeCXCursor(DefArg, StmtParent, TU, RegionOfInterest));
+    if (D->hasDefaultArgument() &&
+        VisitTemplateArgumentLoc(D->getDefaultArgument()))
+      return true;
 
   return false;
 }
diff --git a/clang/unittests/AST/ASTImporterTest.cpp b/clang/unittests/AST/ASTImporterTest.cpp
index ba630002c055a3..3dc1c336365d12 100644
--- a/clang/unittests/AST/ASTImporterTest.cpp
+++ b/clang/unittests/AST/ASTImporterTest.cpp
@@ -1260,7 +1260,7 @@ TEST_P(ASTImporterOptionSpecificTestBase, NonTypeTemplateParmDeclDefaultArg) {
       FromTU, nonTypeTemplateParmDecl(hasName("S")));
   NonTypeTemplateParmDecl *To = Import(From, Lang_CXX03);
   ASSERT_TRUE(To->hasDefaultArgument());
-  Stmt *ToArg = To->getDefaultArgument();
+  Stmt *ToArg = To->getDefaultArgument().getArgument().getAsExpr();
   ASSERT_TRUE(isa<IntegerLiteral>(ToArg));
   ASSERT_EQ(cast<IntegerLiteral>(ToArg)->getValue().getLimitedValue(), 1U);
 }