diff --git a/clang-tools-extra/clang-tidy/modernize/UseTransparentFunctorsCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseTransparentFunctorsCheck.cpp
index 02b602ea1a0f7..58bd9e76eaf76 100644
--- a/clang-tools-extra/clang-tidy/modernize/UseTransparentFunctorsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseTransparentFunctorsCheck.cpp
@@ -96,8 +96,9 @@ void UseTransparentFunctorsCheck::check(
   unsigned ArgNum = 0;
   const auto *FunctorParentType =
       FunctorParentLoc.getType()->castAs<TemplateSpecializationType>();
-  for (; ArgNum < FunctorParentType->getNumArgs(); ++ArgNum) {
-    const TemplateArgument &Arg = FunctorParentType->getArg(ArgNum);
+  for (; ArgNum < FunctorParentType->template_arguments().size(); ++ArgNum) {
+    const TemplateArgument &Arg =
+        FunctorParentType->template_arguments()[ArgNum];
     if (Arg.getKind() != TemplateArgument::Type)
       continue;
     QualType ParentArgType = Arg.getAsType();
@@ -107,7 +108,7 @@ void UseTransparentFunctorsCheck::check(
       break;
   }
   // Functor is a default template argument.
-  if (ArgNum == FunctorParentType->getNumArgs())
+  if (ArgNum == FunctorParentType->template_arguments().size())
     return;
   TemplateArgumentLoc FunctorLoc = FunctorParentLoc.getArgLoc(ArgNum);
   auto FunctorTypeLoc = getInnerTypeLocAs<TemplateSpecializationTypeLoc>(
diff --git a/clang-tools-extra/clang-tidy/mpi/TypeMismatchCheck.cpp b/clang-tools-extra/clang-tidy/mpi/TypeMismatchCheck.cpp
index a050a0ded574e..6f7bfe69c54eb 100644
--- a/clang-tools-extra/clang-tidy/mpi/TypeMismatchCheck.cpp
+++ b/clang-tools-extra/clang-tidy/mpi/TypeMismatchCheck.cpp
@@ -183,8 +183,10 @@ isCXXComplexTypeMatching(const TemplateSpecializationType *const Template,
   if (Template->getAsCXXRecordDecl()->getName() != "complex")
     return true;
 
-  const auto *Builtin =
-      Template->getArg(0).getAsType().getTypePtr()->getAs<BuiltinType>();
+  const auto *Builtin = Template->template_arguments()[0]
+                            .getAsType()
+                            .getTypePtr()
+                            ->getAs<BuiltinType>();
 
   if (Builtin &&
       !isMPITypeMatching(ComplexCXXMatches, Builtin->getKind(), MPIDatatype)) {
diff --git a/clang-tools-extra/clangd/HeuristicResolver.cpp b/clang-tools-extra/clangd/HeuristicResolver.cpp
index 1a09cbe45a859..460b9be592baa 100644
--- a/clang-tools-extra/clangd/HeuristicResolver.cpp
+++ b/clang-tools-extra/clangd/HeuristicResolver.cpp
@@ -80,9 +80,9 @@ const Type *HeuristicResolver::getPointeeType(const Type *T) const {
   auto *TST = T->getAs<TemplateSpecializationType>();
   if (!TST)
     return nullptr;
-  if (TST->getNumArgs() == 0)
+  if (TST->template_arguments().size() == 0)
     return nullptr;
-  const TemplateArgument &FirstArg = TST->getArg(0);
+  const TemplateArgument &FirstArg = TST->template_arguments()[0];
   if (FirstArg.getKind() != TemplateArgument::Type)
     return nullptr;
   return FirstArg.getAsType().getTypePtrOrNull();
diff --git a/clang-tools-extra/modularize/Modularize.cpp b/clang-tools-extra/modularize/Modularize.cpp
index 4b95711813d9e..b3da2ffb11c4a 100644
--- a/clang-tools-extra/modularize/Modularize.cpp
+++ b/clang-tools-extra/modularize/Modularize.cpp
@@ -561,10 +561,7 @@ class CollectEntitiesVisitor
   bool TraverseTemplateArgumentLoc(const TemplateArgumentLoc &ArgLoc) {
     return true;
   }
-  bool TraverseTemplateArguments(const TemplateArgument *Args,
-                                 unsigned NumArgs) {
-    return true;
-  }
+  bool TraverseTemplateArguments(ArrayRef<TemplateArgument>) { return true; }
   bool TraverseConstructorInitializer(CXXCtorInitializer *Init) { return true; }
   bool TraverseLambdaCapture(LambdaExpr *LE, const LambdaCapture *C,
                              Expr *Init) {
@@ -750,10 +747,7 @@ class CompileCheckVisitor
   bool TraverseTemplateArgumentLoc(const TemplateArgumentLoc &ArgLoc) {
     return true;
   }
-  bool TraverseTemplateArguments(const TemplateArgument *Args,
-    unsigned NumArgs) {
-    return true;
-  }
+  bool TraverseTemplateArguments(ArrayRef<TemplateArgument>) { return true; }
   bool TraverseConstructorInitializer(CXXCtorInitializer *Init) { return true; }
   bool TraverseLambdaCapture(LambdaExpr *LE, const LambdaCapture *C,
                              Expr *Init) {
diff --git a/clang/include/clang/AST/ASTContext.h b/clang/include/clang/AST/ASTContext.h
index bd47744261ce2..a6b3301f2a73a 100644
--- a/clang/include/clang/AST/ASTContext.h
+++ b/clang/include/clang/AST/ASTContext.h
@@ -1659,10 +1659,9 @@ class ASTContext : public RefCountedBase<ASTContext> {
                                 const IdentifierInfo *Name,
                                 QualType Canon = QualType()) const;
 
-  QualType getDependentTemplateSpecializationType(ElaboratedTypeKeyword Keyword,
-                                                  NestedNameSpecifier *NNS,
-                                                  const IdentifierInfo *Name,
-                                    const TemplateArgumentListInfo &Args) const;
+  QualType getDependentTemplateSpecializationType(
+      ElaboratedTypeKeyword Keyword, NestedNameSpecifier *NNS,
+      const IdentifierInfo *Name, ArrayRef<TemplateArgumentLoc> Args) const;
   QualType getDependentTemplateSpecializationType(
       ElaboratedTypeKeyword Keyword, NestedNameSpecifier *NNS,
       const IdentifierInfo *Name, ArrayRef<TemplateArgument> Args) const;
diff --git a/clang/include/clang/AST/ASTNodeTraverser.h b/clang/include/clang/AST/ASTNodeTraverser.h
index 6df3a83b6404a..b24c7c1508376 100644
--- a/clang/include/clang/AST/ASTNodeTraverser.h
+++ b/clang/include/clang/AST/ASTNodeTraverser.h
@@ -395,7 +395,7 @@ class ASTNodeTraverser
     Visit(T->getArgumentPack());
   }
   void VisitTemplateSpecializationType(const TemplateSpecializationType *T) {
-    for (const auto &Arg : *T)
+    for (const auto &Arg : T->template_arguments())
       Visit(Arg);
   }
   void VisitObjCObjectPointerType(const ObjCObjectPointerType *T) {
diff --git a/clang/include/clang/AST/RecursiveASTVisitor.h b/clang/include/clang/AST/RecursiveASTVisitor.h
index 8c5412648bcd4..5eb8e0353ffd8 100644
--- a/clang/include/clang/AST/RecursiveASTVisitor.h
+++ b/clang/include/clang/AST/RecursiveASTVisitor.h
@@ -276,8 +276,7 @@ template <typename Derived> class RecursiveASTVisitor {
   ///
   /// \returns false if the visitation was terminated early, true otherwise.
   // FIXME: take a TemplateArgumentLoc* (or TemplateArgumentListInfo) instead.
-  bool TraverseTemplateArguments(const TemplateArgument *Args,
-                                 unsigned NumArgs);
+  bool TraverseTemplateArguments(ArrayRef<TemplateArgument> Args);
 
   /// Recursively visit a base specifier. This can be overridden by a
   /// subclass.
@@ -873,8 +872,7 @@ bool RecursiveASTVisitor<Derived>::TraverseTemplateArgument(
     return getDerived().TraverseStmt(Arg.getAsExpr());
 
   case TemplateArgument::Pack:
-    return getDerived().TraverseTemplateArguments(Arg.pack_begin(),
-                                                  Arg.pack_size());
+    return getDerived().TraverseTemplateArguments(Arg.pack_elements());
   }
 
   return true;
@@ -914,8 +912,7 @@ bool RecursiveASTVisitor<Derived>::TraverseTemplateArgumentLoc(
     return getDerived().TraverseStmt(ArgLoc.getSourceExpression());
 
   case TemplateArgument::Pack:
-    return getDerived().TraverseTemplateArguments(Arg.pack_begin(),
-                                                  Arg.pack_size());
+    return getDerived().TraverseTemplateArguments(Arg.pack_elements());
   }
 
   return true;
@@ -923,10 +920,9 @@ bool RecursiveASTVisitor<Derived>::TraverseTemplateArgumentLoc(
 
 template <typename Derived>
 bool RecursiveASTVisitor<Derived>::TraverseTemplateArguments(
-    const TemplateArgument *Args, unsigned NumArgs) {
-  for (unsigned I = 0; I != NumArgs; ++I) {
-    TRY_TO(TraverseTemplateArgument(Args[I]));
-  }
+    ArrayRef<TemplateArgument> Args) {
+  for (const TemplateArgument &Arg : Args)
+    TRY_TO(TraverseTemplateArgument(Arg));
 
   return true;
 }
@@ -1083,7 +1079,7 @@ DEF_TRAVERSE_TYPE(UnaryTransformType, {
 DEF_TRAVERSE_TYPE(AutoType, {
   TRY_TO(TraverseType(T->getDeducedType()));
   if (T->isConstrained()) {
-    TRY_TO(TraverseTemplateArguments(T->getArgs(), T->getNumArgs()));
+    TRY_TO(TraverseTemplateArguments(T->getTypeConstraintArguments()));
   }
 })
 DEF_TRAVERSE_TYPE(DeducedTemplateSpecializationType, {
@@ -1103,7 +1099,7 @@ DEF_TRAVERSE_TYPE(SubstTemplateTypeParmPackType, {
 
 DEF_TRAVERSE_TYPE(TemplateSpecializationType, {
   TRY_TO(TraverseTemplateName(T->getTemplateName()));
-  TRY_TO(TraverseTemplateArguments(T->getArgs(), T->getNumArgs()));
+  TRY_TO(TraverseTemplateArguments(T->template_arguments()));
 })
 
 DEF_TRAVERSE_TYPE(InjectedClassNameType, {})
@@ -1131,7 +1127,7 @@ DEF_TRAVERSE_TYPE(DependentNameType,
 
 DEF_TRAVERSE_TYPE(DependentTemplateSpecializationType, {
   TRY_TO(TraverseNestedNameSpecifier(T->getQualifier()));
-  TRY_TO(TraverseTemplateArguments(T->getArgs(), T->getNumArgs()));
+  TRY_TO(TraverseTemplateArguments(T->template_arguments()));
 })
 
 DEF_TRAVERSE_TYPE(PackExpansionType, { TRY_TO(TraverseType(T->getPattern())); })
@@ -2305,8 +2301,7 @@ DEF_TRAVERSE_DECL(ParmVarDecl, {
 DEF_TRAVERSE_DECL(RequiresExprBodyDecl, {})
 
 DEF_TRAVERSE_DECL(ImplicitConceptSpecializationDecl, {
-  TRY_TO(TraverseTemplateArguments(D->getTemplateArguments().data(),
-                                   D->getTemplateArguments().size()));
+  TRY_TO(TraverseTemplateArguments(D->getTemplateArguments()));
 })
 
 #undef DEF_TRAVERSE_DECL
diff --git a/clang/include/clang/AST/TemplateBase.h b/clang/include/clang/AST/TemplateBase.h
index 3ac755ef74a17..3aef26f326a79 100644
--- a/clang/include/clang/AST/TemplateBase.h
+++ b/clang/include/clang/AST/TemplateBase.h
@@ -698,33 +698,6 @@ struct alignas(void *) ASTTemplateKWAndArgsInfo {
 const StreamingDiagnostic &operator<<(const StreamingDiagnostic &DB,
                                       const TemplateArgument &Arg);
 
-inline TemplateSpecializationType::iterator
-    TemplateSpecializationType::end() const {
-  return getArgs() + getNumArgs();
-}
-
-inline DependentTemplateSpecializationType::iterator
-    DependentTemplateSpecializationType::end() const {
-  return getArgs() + getNumArgs();
-}
-
-inline const TemplateArgument &
-    TemplateSpecializationType::getArg(unsigned Idx) const {
-  assert(Idx < getNumArgs() && "Template argument out of range");
-  return getArgs()[Idx];
-}
-
-inline const TemplateArgument &
-    DependentTemplateSpecializationType::getArg(unsigned Idx) const {
-  assert(Idx < getNumArgs() && "Template argument out of range");
-  return getArgs()[Idx];
-}
-
-inline const TemplateArgument &AutoType::getArg(unsigned Idx) const {
-  assert(Idx < getNumArgs() && "Template argument out of range");
-  return getArgs()[Idx];
-}
-
 } // namespace clang
 
 #endif // LLVM_CLANG_AST_TEMPLATEBASE_H
diff --git a/clang/include/clang/AST/Type.h b/clang/include/clang/AST/Type.h
index ec980700a626a..a288241fe99ba 100644
--- a/clang/include/clang/AST/Type.h
+++ b/clang/include/clang/AST/Type.h
@@ -5248,29 +5248,10 @@ class alignas(8) AutoType : public DeducedType, public llvm::FoldingSetNode {
            TypeDependence ExtraDependence, QualType Canon, ConceptDecl *CD,
            ArrayRef<TemplateArgument> TypeConstraintArgs);
 
-  const TemplateArgument *getArgBuffer() const {
-    return reinterpret_cast<const TemplateArgument*>(this+1);
-  }
-
-  TemplateArgument *getArgBuffer() {
-    return reinterpret_cast<TemplateArgument*>(this+1);
-  }
-
 public:
-  /// Retrieve the template arguments.
-  const TemplateArgument *getArgs() const {
-    return getArgBuffer();
-  }
-
-  /// Retrieve the number of template arguments.
-  unsigned getNumArgs() const {
-    return AutoTypeBits.NumArgs;
-  }
-
-  const TemplateArgument &getArg(unsigned Idx) const; // in TemplateBase.h
-
   ArrayRef<TemplateArgument> getTypeConstraintArguments() const {
-    return {getArgs(), getNumArgs()};
+    return {reinterpret_cast<const TemplateArgument *>(this + 1),
+            AutoTypeBits.NumArgs};
   }
 
   ConceptDecl *getTypeConstraintConcept() const {
@@ -5293,11 +5274,7 @@ class alignas(8) AutoType : public DeducedType, public llvm::FoldingSetNode {
     return (AutoTypeKeyword)AutoTypeBits.Keyword;
   }
 
-  void Profile(llvm::FoldingSetNodeID &ID, const ASTContext &Context) {
-    Profile(ID, Context, getDeducedType(), getKeyword(), isDependentType(),
-            getTypeConstraintConcept(), getTypeConstraintArguments());
-  }
-
+  void Profile(llvm::FoldingSetNodeID &ID, const ASTContext &Context);
   static void Profile(llvm::FoldingSetNodeID &ID, const ASTContext &Context,
                       QualType Deduced, AutoTypeKeyword Keyword,
                       bool IsDependent, ConceptDecl *CD,
@@ -5435,35 +5412,14 @@ class alignas(8) TemplateSpecializationType
 
   /// Get the aliased type, if this is a specialization of a type alias
   /// template.
-  QualType getAliasedType() const {
-    assert(isTypeAlias() && "not a type alias template specialization");
-    return *reinterpret_cast<const QualType*>(end());
-  }
-
-  using iterator = const TemplateArgument *;
-
-  iterator begin() const { return getArgs(); }
-  iterator end() const; // defined inline in TemplateBase.h
+  QualType getAliasedType() const;
 
   /// Retrieve the name of the template that we are specializing.
   TemplateName getTemplateName() const { return Template; }
 
-  /// Retrieve the template arguments.
-  const TemplateArgument *getArgs() const {
-    return reinterpret_cast<const TemplateArgument *>(this + 1);
-  }
-
-  /// Retrieve the number of template arguments.
-  unsigned getNumArgs() const {
-    return TemplateSpecializationTypeBits.NumArgs;
-  }
-
-  /// Retrieve a specific template argument as a type.
-  /// \pre \c isArgType(Arg)
-  const TemplateArgument &getArg(unsigned Idx) const; // in TemplateBase.h
-
   ArrayRef<TemplateArgument> template_arguments() const {
-    return {getArgs(), getNumArgs()};
+    return {reinterpret_cast<const TemplateArgument *>(this + 1),
+            TemplateSpecializationTypeBits.NumArgs};
   }
 
   bool isSugared() const {
@@ -5474,12 +5430,7 @@ class alignas(8) TemplateSpecializationType
     return isTypeAlias() ? getAliasedType() : getCanonicalTypeInternal();
   }
 
-  void Profile(llvm::FoldingSetNodeID &ID, const ASTContext &Ctx) {
-    Profile(ID, Template, template_arguments(), Ctx);
-    if (isTypeAlias())
-      getAliasedType().Profile(ID);
-  }
-
+  void Profile(llvm::FoldingSetNodeID &ID, const ASTContext &Ctx);
   static void Profile(llvm::FoldingSetNodeID &ID, TemplateName T,
                       ArrayRef<TemplateArgument> Args,
                       const ASTContext &Context);
@@ -5822,44 +5773,20 @@ class alignas(8) DependentTemplateSpecializationType
                                       ArrayRef<TemplateArgument> Args,
                                       QualType Canon);
 
-  const TemplateArgument *getArgBuffer() const {
-    return reinterpret_cast<const TemplateArgument*>(this+1);
-  }
-
-  TemplateArgument *getArgBuffer() {
-    return reinterpret_cast<TemplateArgument*>(this+1);
-  }
-
 public:
   NestedNameSpecifier *getQualifier() const { return NNS; }
   const IdentifierInfo *getIdentifier() const { return Name; }
 
-  /// Retrieve the template arguments.
-  const TemplateArgument *getArgs() const {
-    return getArgBuffer();
-  }
-
-  /// Retrieve the number of template arguments.
-  unsigned getNumArgs() const {
-    return DependentTemplateSpecializationTypeBits.NumArgs;
-  }
-
-  const TemplateArgument &getArg(unsigned Idx) const; // in TemplateBase.h
-
   ArrayRef<TemplateArgument> template_arguments() const {
-    return {getArgs(), getNumArgs()};
+    return {reinterpret_cast<const TemplateArgument *>(this + 1),
+            DependentTemplateSpecializationTypeBits.NumArgs};
   }
 
-  using iterator = const TemplateArgument *;
-
-  iterator begin() const { return getArgs(); }
-  iterator end() const; // inline in TemplateBase.h
-
   bool isSugared() const { return false; }
   QualType desugar() const { return QualType(this, 0); }
 
   void Profile(llvm::FoldingSetNodeID &ID, const ASTContext &Context) {
-    Profile(ID, Context, getKeyword(), NNS, Name, {getArgs(), getNumArgs()});
+    Profile(ID, Context, getKeyword(), NNS, Name, template_arguments());
   }
 
   static void Profile(llvm::FoldingSetNodeID &ID,
diff --git a/clang/include/clang/AST/TypeLoc.h b/clang/include/clang/AST/TypeLoc.h
index cdd8fb52089eb..ce2ddca830b71 100644
--- a/clang/include/clang/AST/TypeLoc.h
+++ b/clang/include/clang/AST/TypeLoc.h
@@ -1634,7 +1634,7 @@ class TemplateSpecializationTypeLoc :
   }
 
   unsigned getNumArgs() const {
-    return getTypePtr()->getNumArgs();
+    return getTypePtr()->template_arguments().size();
   }
 
   void setArgLocInfo(unsigned i, TemplateArgumentLocInfo AI) {
@@ -1646,7 +1646,8 @@ class TemplateSpecializationTypeLoc :
   }
 
   TemplateArgumentLoc getArgLoc(unsigned i) const {
-    return TemplateArgumentLoc(getTypePtr()->getArg(i), getArgLocInfo(i));
+    return TemplateArgumentLoc(getTypePtr()->template_arguments()[i],
+                               getArgLocInfo(i));
   }
 
   SourceLocation getTemplateNameLoc() const {
@@ -1681,12 +1682,12 @@ class TemplateSpecializationTypeLoc :
     setTemplateNameLoc(Loc);
     setLAngleLoc(Loc);
     setRAngleLoc(Loc);
-    initializeArgLocs(Context, getNumArgs(), getTypePtr()->getArgs(),
+    initializeArgLocs(Context, getTypePtr()->template_arguments(),
                       getArgInfos(), Loc);
   }
 
-  static void initializeArgLocs(ASTContext &Context, unsigned NumArgs,
-                                const TemplateArgument *Args,
+  static void initializeArgLocs(ASTContext &Context,
+                                ArrayRef<TemplateArgument> Args,
                                 TemplateArgumentLocInfo *ArgInfos,
                                 SourceLocation Loc);
 
@@ -2188,7 +2189,7 @@ class AutoTypeLoc
   }
 
   unsigned getNumArgs() const {
-    return getTypePtr()->getNumArgs();
+    return getTypePtr()->getTypeConstraintArguments().size();
   }
 
   void setArgLocInfo(unsigned i, TemplateArgumentLocInfo AI) {
@@ -2464,7 +2465,7 @@ class DependentTemplateSpecializationTypeLoc :
   }
 
   unsigned getNumArgs() const {
-    return getTypePtr()->getNumArgs();
+    return getTypePtr()->template_arguments().size();
   }
 
   void setArgLocInfo(unsigned i, TemplateArgumentLocInfo AI) {
@@ -2476,7 +2477,8 @@ class DependentTemplateSpecializationTypeLoc :
   }
 
   TemplateArgumentLoc getArgLoc(unsigned i) const {
-    return TemplateArgumentLoc(getTypePtr()->getArg(i), getArgLocInfo(i));
+    return TemplateArgumentLoc(getTypePtr()->template_arguments()[i],
+                               getArgLocInfo(i));
   }
 
   SourceRange getLocalSourceRange() const {
diff --git a/clang/include/clang/ASTMatchers/ASTMatchersInternal.h b/clang/include/clang/ASTMatchers/ASTMatchersInternal.h
index 12bc593b785ae..32316e26a4c2e 100644
--- a/clang/include/clang/ASTMatchers/ASTMatchersInternal.h
+++ b/clang/include/clang/ASTMatchers/ASTMatchersInternal.h
@@ -1942,7 +1942,7 @@ getTemplateSpecializationArgs(const ClassTemplateSpecializationDecl &D) {
 
 inline ArrayRef<TemplateArgument>
 getTemplateSpecializationArgs(const TemplateSpecializationType &T) {
-  return llvm::makeArrayRef(T.getArgs(), T.getNumArgs());
+  return T.template_arguments();
 }
 
 inline ArrayRef<TemplateArgument>
diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index 08cbe2a9a5811..e8a9c7efa3964 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -5150,12 +5150,9 @@ QualType ASTContext::getDependentNameType(ElaboratedTypeKeyword Keyword,
   return QualType(T, 0);
 }
 
-QualType
-ASTContext::getDependentTemplateSpecializationType(
-                                 ElaboratedTypeKeyword Keyword,
-                                 NestedNameSpecifier *NNS,
-                                 const IdentifierInfo *Name,
-                                 const TemplateArgumentListInfo &Args) const {
+QualType ASTContext::getDependentTemplateSpecializationType(
+    ElaboratedTypeKeyword Keyword, NestedNameSpecifier *NNS,
+    const IdentifierInfo *Name, ArrayRef<TemplateArgumentLoc> Args) const {
   // TODO: avoid this copy
   SmallVector<TemplateArgument, 16> ArgCopy;
   for (unsigned I = 0, E = Args.size(); I != E; ++I)
diff --git a/clang/lib/AST/ASTDiagnostic.cpp b/clang/lib/AST/ASTDiagnostic.cpp
index 079fd268f4d37..4cf557c1485a4 100644
--- a/clang/lib/AST/ASTDiagnostic.cpp
+++ b/clang/lib/AST/ASTDiagnostic.cpp
@@ -118,8 +118,7 @@ QualType clang::desugarForDiagnostic(ASTContext &Context, QualType QT,
       if (!TST->isTypeAlias()) {
         bool DesugarArgument = false;
         SmallVector<TemplateArgument, 4> Args;
-        for (unsigned I = 0, N = TST->getNumArgs(); I != N; ++I) {
-          const TemplateArgument &Arg = TST->getArg(I);
+        for (const TemplateArgument &Arg : TST->template_arguments()) {
           if (Arg.getKind() == TemplateArgument::Type)
             Args.push_back(desugarForDiagnostic(Context, Arg.getAsType(),
                                                 DesugarArgument));
@@ -986,7 +985,7 @@ class TemplateDiff {
         if (isEnd()) return;
 
         // Set to first template argument.  If not a parameter pack, done.
-        TemplateArgument TA = TST->getArg(0);
+        TemplateArgument TA = TST->template_arguments()[0];
         if (TA.getKind() != TemplateArgument::Pack) return;
 
         // Start looking into the parameter pack.
@@ -1007,7 +1006,7 @@ class TemplateDiff {
       /// isEnd - Returns true if the iterator is one past the end.
       bool isEnd() const {
         assert(TST && "InternalIterator is invalid with a null TST.");
-        return Index >= TST->getNumArgs();
+        return Index >= TST->template_arguments().size();
       }
 
       /// &operator++ - Increment the iterator to the next template argument.
@@ -1027,11 +1026,11 @@ class TemplateDiff {
         // Loop until a template argument is found, or the end is reached.
         while (true) {
           // Advance to the next template argument.  Break if reached the end.
-          if (++Index == TST->getNumArgs())
+          if (++Index == TST->template_arguments().size())
             break;
 
           // If the TemplateArgument is not a parameter pack, done.
-          TemplateArgument TA = TST->getArg(Index);
+          TemplateArgument TA = TST->template_arguments()[Index];
           if (TA.getKind() != TemplateArgument::Pack)
             break;
 
@@ -1051,7 +1050,7 @@ class TemplateDiff {
         assert(TST && "InternalIterator is invalid with a null TST.");
         assert(!isEnd() && "Index exceeds number of arguments.");
         if (CurrentTA == EndTA)
-          return TST->getArg(Index);
+          return TST->template_arguments()[Index];
         else
           return *CurrentTA;
       }
diff --git a/clang/lib/AST/ASTImporter.cpp b/clang/lib/AST/ASTImporter.cpp
index 4dcc92f97cfdb..0606c5ca0785c 100644
--- a/clang/lib/AST/ASTImporter.cpp
+++ b/clang/lib/AST/ASTImporter.cpp
@@ -471,9 +471,8 @@ namespace clang {
     Error ImportDefinition(
         ObjCProtocolDecl *From, ObjCProtocolDecl *To,
         ImportDefinitionKind Kind = IDK_Default);
-    Error ImportTemplateArguments(
-        const TemplateArgument *FromArgs, unsigned NumFromArgs,
-        SmallVectorImpl<TemplateArgument> &ToArgs);
+    Error ImportTemplateArguments(ArrayRef<TemplateArgument> FromArgs,
+                                  SmallVectorImpl<TemplateArgument> &ToArgs);
     Expected<TemplateArgument>
     ImportTemplateArgument(const TemplateArgument &From);
 
@@ -791,9 +790,8 @@ ASTNodeImporter::ImportFunctionTemplateWithTemplateArgsFromSpecialization(
     return std::move(Err);
 
   // Import template arguments.
-  auto TemplArgs = FTSInfo->TemplateArguments->asArray();
-  if (Error Err = ImportTemplateArguments(TemplArgs.data(), TemplArgs.size(),
-      std::get<1>(Result)))
+  if (Error Err = ImportTemplateArguments(FTSInfo->TemplateArguments->asArray(),
+                                          std::get<1>(Result)))
     return std::move(Err);
 
   return Result;
@@ -894,8 +892,7 @@ ASTNodeImporter::import(const TemplateArgument &From) {
   case TemplateArgument::Pack: {
     SmallVector<TemplateArgument, 2> ToPack;
     ToPack.reserve(From.pack_size());
-    if (Error Err = ImportTemplateArguments(
-        From.pack_begin(), From.pack_size(), ToPack))
+    if (Error Err = ImportTemplateArguments(From.pack_elements(), ToPack))
       return std::move(Err);
 
     return TemplateArgument(
@@ -1435,9 +1432,7 @@ ExpectedType ASTNodeImporter::VisitAutoType(const AutoType *T) {
     return ToTypeConstraintConcept.takeError();
 
   SmallVector<TemplateArgument, 2> ToTemplateArgs;
-  ArrayRef<TemplateArgument> FromTemplateArgs = T->getTypeConstraintArguments();
-  if (Error Err = ImportTemplateArguments(FromTemplateArgs.data(),
-                                          FromTemplateArgs.size(),
+  if (Error Err = ImportTemplateArguments(T->getTypeConstraintArguments(),
                                           ToTemplateArgs))
     return std::move(Err);
 
@@ -1557,8 +1552,8 @@ ExpectedType ASTNodeImporter::VisitTemplateSpecializationType(
     return ToTemplateOrErr.takeError();
 
   SmallVector<TemplateArgument, 2> ToTemplateArgs;
-  if (Error Err = ImportTemplateArguments(
-      T->getArgs(), T->getNumArgs(), ToTemplateArgs))
+  if (Error Err =
+          ImportTemplateArguments(T->template_arguments(), ToTemplateArgs))
     return std::move(Err);
 
   QualType ToCanonType;
@@ -1615,9 +1610,8 @@ ExpectedType ASTNodeImporter::VisitDependentTemplateSpecializationType(
   IdentifierInfo *ToName = Importer.Import(T->getIdentifier());
 
   SmallVector<TemplateArgument, 2> ToPack;
-  ToPack.reserve(T->getNumArgs());
-  if (Error Err = ImportTemplateArguments(
-      T->getArgs(), T->getNumArgs(), ToPack))
+  ToPack.reserve(T->template_arguments().size());
+  if (Error Err = ImportTemplateArguments(T->template_arguments(), ToPack))
     return std::move(Err);
 
   return Importer.getToContext().getDependentTemplateSpecializationType(
@@ -2188,10 +2182,10 @@ Error ASTNodeImporter::ImportDefinition(
 }
 
 Error ASTNodeImporter::ImportTemplateArguments(
-    const TemplateArgument *FromArgs, unsigned NumFromArgs,
+    ArrayRef<TemplateArgument> FromArgs,
     SmallVectorImpl<TemplateArgument> &ToArgs) {
-  for (unsigned I = 0; I != NumFromArgs; ++I) {
-    if (auto ToOrErr = import(FromArgs[I]))
+  for (const auto &Arg : FromArgs) {
+    if (auto ToOrErr = import(Arg))
       ToArgs.push_back(*ToOrErr);
     else
       return ToOrErr.takeError();
@@ -5838,8 +5832,8 @@ ExpectedDecl ASTNodeImporter::VisitClassTemplateSpecializationDecl(
 
   // Import template arguments.
   SmallVector<TemplateArgument, 2> TemplateArgs;
-  if (Error Err = ImportTemplateArguments(
-      D->getTemplateArgs().data(), D->getTemplateArgs().size(), TemplateArgs))
+  if (Error Err =
+          ImportTemplateArguments(D->getTemplateArgs().asArray(), TemplateArgs))
     return std::move(Err);
   // Try to find an existing specialization with these template arguments and
   // template parameter list.
@@ -6160,8 +6154,8 @@ ExpectedDecl ASTNodeImporter::VisitVarTemplateSpecializationDecl(
 
   // Import template arguments.
   SmallVector<TemplateArgument, 2> TemplateArgs;
-  if (Error Err = ImportTemplateArguments(
-      D->getTemplateArgs().data(), D->getTemplateArgs().size(), TemplateArgs))
+  if (Error Err =
+          ImportTemplateArguments(D->getTemplateArgs().asArray(), TemplateArgs))
     return std::move(Err);
 
   // Try to find an existing specialization with these template arguments.
@@ -7817,10 +7811,8 @@ ExpectedStmt ASTNodeImporter::VisitSizeOfPackExpr(SizeOfPackExpr *E) {
 
   SmallVector<TemplateArgument, 8> ToPartialArguments;
   if (E->isPartiallySubstituted()) {
-    if (Error Err = ImportTemplateArguments(
-        E->getPartialArguments().data(),
-        E->getPartialArguments().size(),
-        ToPartialArguments))
+    if (Error Err = ImportTemplateArguments(E->getPartialArguments(),
+                                            ToPartialArguments))
       return std::move(Err);
   }
 
diff --git a/clang/lib/AST/ASTStructuralEquivalence.cpp b/clang/lib/AST/ASTStructuralEquivalence.cpp
index 71c32d3f80e72..73d1aded05abe 100644
--- a/clang/lib/AST/ASTStructuralEquivalence.cpp
+++ b/clang/lib/AST/ASTStructuralEquivalence.cpp
@@ -533,6 +533,10 @@ static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
   return true;
 }
 
+static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
+                                     ArrayRef<TemplateArgument> Args1,
+                                     ArrayRef<TemplateArgument> Args2);
+
 /// Determine whether two template arguments are equivalent.
 static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
                                      const TemplateArgument &Arg1,
@@ -575,20 +579,26 @@ static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
                                     Arg2.getAsExpr());
 
   case TemplateArgument::Pack:
-    if (Arg1.pack_size() != Arg2.pack_size())
-      return false;
-
-    for (unsigned I = 0, N = Arg1.pack_size(); I != N; ++I)
-      if (!IsStructurallyEquivalent(Context, Arg1.pack_begin()[I],
-                                    Arg2.pack_begin()[I]))
-        return false;
-
-    return true;
+    return IsStructurallyEquivalent(Context, Arg1.pack_elements(),
+                                    Arg2.pack_elements());
   }
 
   llvm_unreachable("Invalid template argument kind");
 }
 
+/// Determine structural equivalence of two template argument lists.
+static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
+                                     ArrayRef<TemplateArgument> Args1,
+                                     ArrayRef<TemplateArgument> Args2) {
+  if (Args1.size() != Args2.size())
+    return false;
+  for (unsigned I = 0, N = Args1.size(); I != N; ++I) {
+    if (!IsStructurallyEquivalent(Context, Args1[I], Args2[I]))
+      return false;
+  }
+  return true;
+}
+
 /// Determine structural equivalence for the common part of array
 /// types.
 static bool IsArrayStructurallyEquivalent(StructuralEquivalenceContext &Context,
@@ -1018,16 +1028,10 @@ static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
       if (Auto1->getTypeConstraintConcept() !=
           Auto2->getTypeConstraintConcept())
         return false;
-      ArrayRef<TemplateArgument> Auto1Args =
-          Auto1->getTypeConstraintArguments();
-      ArrayRef<TemplateArgument> Auto2Args =
-          Auto2->getTypeConstraintArguments();
-      if (Auto1Args.size() != Auto2Args.size())
+      if (!IsStructurallyEquivalent(Context,
+                                    Auto1->getTypeConstraintArguments(),
+                                    Auto2->getTypeConstraintArguments()))
         return false;
-      for (unsigned I = 0, N = Auto1Args.size(); I != N; ++I) {
-        if (!IsStructurallyEquivalent(Context, Auto1Args[I], Auto2Args[I]))
-          return false;
-      }
     }
     break;
   }
@@ -1101,13 +1105,9 @@ static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
     if (!IsStructurallyEquivalent(Context, Spec1->getTemplateName(),
                                   Spec2->getTemplateName()))
       return false;
-    if (Spec1->getNumArgs() != Spec2->getNumArgs())
+    if (!IsStructurallyEquivalent(Context, Spec1->template_arguments(),
+                                  Spec2->template_arguments()))
       return false;
-    for (unsigned I = 0, N = Spec1->getNumArgs(); I != N; ++I) {
-      if (!IsStructurallyEquivalent(Context, Spec1->getArg(I),
-                                    Spec2->getArg(I)))
-        return false;
-    }
     break;
   }
 
@@ -1158,13 +1158,9 @@ static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
     if (!IsStructurallyEquivalent(Spec1->getIdentifier(),
                                   Spec2->getIdentifier()))
       return false;
-    if (Spec1->getNumArgs() != Spec2->getNumArgs())
+    if (!IsStructurallyEquivalent(Context, Spec1->template_arguments(),
+                                  Spec2->template_arguments()))
       return false;
-    for (unsigned I = 0, N = Spec1->getNumArgs(); I != N; ++I) {
-      if (!IsStructurallyEquivalent(Context, Spec1->getArg(I),
-                                    Spec2->getArg(I)))
-        return false;
-    }
     break;
   }
 
diff --git a/clang/lib/AST/ItaniumMangle.cpp b/clang/lib/AST/ItaniumMangle.cpp
index dbd9bb518d8b9..c95ca68397430 100644
--- a/clang/lib/AST/ItaniumMangle.cpp
+++ b/clang/lib/AST/ItaniumMangle.cpp
@@ -484,8 +484,7 @@ class CXXNameMangler {
                              const AbiTagList *AdditionalAbiTags);
   void mangleModuleName(const NamedDecl *ND);
   void mangleTemplateName(const TemplateDecl *TD,
-                          const TemplateArgument *TemplateArgs,
-                          unsigned NumTemplateArgs);
+                          ArrayRef<TemplateArgument> Args);
   void mangleUnqualifiedName(GlobalDecl GD, const DeclContext *DC,
                              const AbiTagList *AdditionalAbiTags) {
     mangleUnqualifiedName(GD, cast<NamedDecl>(GD.getDecl())->getDeclName(), DC,
@@ -513,8 +512,7 @@ class CXXNameMangler {
                         const AbiTagList *AdditionalAbiTags,
                         bool NoFunction=false);
   void mangleNestedName(const TemplateDecl *TD,
-                        const TemplateArgument *TemplateArgs,
-                        unsigned NumTemplateArgs);
+                        ArrayRef<TemplateArgument> Args);
   void mangleNestedNameWithClosurePrefix(GlobalDecl GD,
                                          const NamedDecl *PrefixND,
                                          const AbiTagList *AdditionalAbiTags);
@@ -578,8 +576,7 @@ class CXXNameMangler {
   void mangleTemplateArgs(TemplateName TN,
                           const TemplateArgumentLoc *TemplateArgs,
                           unsigned NumTemplateArgs);
-  void mangleTemplateArgs(TemplateName TN, const TemplateArgument *TemplateArgs,
-                          unsigned NumTemplateArgs);
+  void mangleTemplateArgs(TemplateName TN, ArrayRef<TemplateArgument> Args);
   void mangleTemplateArgs(TemplateName TN, const TemplateArgumentList &AL);
   void mangleTemplateArg(TemplateArgument A, bool NeedExactType);
   void mangleTemplateArgExpr(const Expr *E);
@@ -1087,15 +1084,14 @@ void CXXNameMangler::mangleModuleNamePrefix(StringRef Name, bool IsPartition) {
 }
 
 void CXXNameMangler::mangleTemplateName(const TemplateDecl *TD,
-                                        const TemplateArgument *TemplateArgs,
-                                        unsigned NumTemplateArgs) {
+                                        ArrayRef<TemplateArgument> Args) {
   const DeclContext *DC = Context.getEffectiveDeclContext(TD);
 
   if (DC->isTranslationUnit() || isStdNamespace(DC)) {
     mangleUnscopedTemplateName(TD, DC, nullptr);
-    mangleTemplateArgs(asTemplateName(TD), TemplateArgs, NumTemplateArgs);
+    mangleTemplateArgs(asTemplateName(TD), Args);
   } else {
-    mangleNestedName(TD, TemplateArgs, NumTemplateArgs);
+    mangleNestedName(TD, Args);
   }
 }
 
@@ -1244,8 +1240,7 @@ void CXXNameMangler::manglePrefix(QualType type) {
       // FIXME: GCC does not appear to mangle the template arguments when
       // the template in question is a dependent template name. Should we
       // emulate that badness?
-      mangleTemplateArgs(TST->getTemplateName(), TST->getArgs(),
-                         TST->getNumArgs());
+      mangleTemplateArgs(TST->getTemplateName(), TST->template_arguments());
       addSubstitution(QualType(TST, 0));
     }
   } else if (const auto *DTST =
@@ -1258,7 +1253,7 @@ void CXXNameMangler::manglePrefix(QualType type) {
       // FIXME: GCC does not appear to mangle the template arguments when
       // the template in question is a dependent template name. Should we
       // emulate that badness?
-      mangleTemplateArgs(Template, DTST->getArgs(), DTST->getNumArgs());
+      mangleTemplateArgs(Template, DTST->template_arguments());
       addSubstitution(QualType(DTST, 0));
     }
   } else {
@@ -1732,14 +1727,13 @@ void CXXNameMangler::mangleNestedName(GlobalDecl GD,
   Out << 'E';
 }
 void CXXNameMangler::mangleNestedName(const TemplateDecl *TD,
-                                      const TemplateArgument *TemplateArgs,
-                                      unsigned NumTemplateArgs) {
+                                      ArrayRef<TemplateArgument> Args) {
   // <nested-name> ::= N [<CV-qualifiers>] <template-prefix> <template-args> E
 
   Out << 'N';
 
   mangleTemplatePrefix(TD);
-  mangleTemplateArgs(asTemplateName(TD), TemplateArgs, NumTemplateArgs);
+  mangleTemplateArgs(asTemplateName(TD), Args);
 
   Out << 'E';
 }
@@ -2418,7 +2412,7 @@ bool CXXNameMangler::mangleUnresolvedTypeOrSimpleId(QualType Ty,
     // conversions to the corresponding template parameter.
     // FIXME: Other compilers mangle partially-resolved template arguments in
     // unresolved-qualifier-levels.
-    mangleTemplateArgs(TemplateName(), TST->getArgs(), TST->getNumArgs());
+    mangleTemplateArgs(TemplateName(), TST->template_arguments());
     break;
   }
 
@@ -2437,7 +2431,7 @@ bool CXXNameMangler::mangleUnresolvedTypeOrSimpleId(QualType Ty,
     TemplateName Template = getASTContext().getDependentTemplateName(
         DTST->getQualifier(), DTST->getIdentifier());
     mangleSourceName(DTST->getIdentifier());
-    mangleTemplateArgs(Template, DTST->getArgs(), DTST->getNumArgs());
+    mangleTemplateArgs(Template, DTST->template_arguments());
     break;
   }
 
@@ -3876,7 +3870,7 @@ void CXXNameMangler::mangleType(const InjectedClassNameType *T) {
 
 void CXXNameMangler::mangleType(const TemplateSpecializationType *T) {
   if (TemplateDecl *TD = T->getTemplateName().getAsTemplateDecl()) {
-    mangleTemplateName(TD, T->getArgs(), T->getNumArgs());
+    mangleTemplateName(TD, T->template_arguments());
   } else {
     if (mangleSubstitution(QualType(T, 0)))
       return;
@@ -3886,7 +3880,7 @@ void CXXNameMangler::mangleType(const TemplateSpecializationType *T) {
     // FIXME: GCC does not appear to mangle the template arguments when
     // the template in question is a dependent template name. Should we
     // emulate that badness?
-    mangleTemplateArgs(T->getTemplateName(), T->getArgs(), T->getNumArgs());
+    mangleTemplateArgs(T->getTemplateName(), T->template_arguments());
     addSubstitution(QualType(T, 0));
   }
 }
@@ -3938,7 +3932,7 @@ void CXXNameMangler::mangleType(const DependentTemplateSpecializationType *T) {
   // FIXME: GCC does not appear to mangle the template arguments when
   // the template in question is a dependent template name. Should we
   // emulate that badness?
-  mangleTemplateArgs(Prefix, T->getArgs(), T->getNumArgs());
+  mangleTemplateArgs(Prefix, T->template_arguments());
   Out << 'E';
 }
 
@@ -4894,9 +4888,7 @@ void CXXNameMangler::mangleExpression(const Expr *E, unsigned Arity,
     //  <expr-primary> ::= L <mangled-name> E # external name
     Out << "L_Z";
     auto *CSE = cast<ConceptSpecializationExpr>(E);
-    mangleTemplateName(CSE->getNamedConcept(),
-                       CSE->getTemplateArguments().data(),
-                       CSE->getTemplateArguments().size());
+    mangleTemplateName(CSE->getNamedConcept(), CSE->getTemplateArguments());
     Out << 'E';
     break;
   }
@@ -5353,13 +5345,12 @@ void CXXNameMangler::mangleTemplateArgs(TemplateName TN,
 }
 
 void CXXNameMangler::mangleTemplateArgs(TemplateName TN,
-                                        const TemplateArgument *TemplateArgs,
-                                        unsigned NumTemplateArgs) {
+                                        ArrayRef<TemplateArgument> Args) {
   // <template-args> ::= I <template-arg>+ E
   Out << 'I';
   TemplateArgManglingInfo Info(TN);
-  for (unsigned i = 0; i != NumTemplateArgs; ++i)
-    mangleTemplateArg(TemplateArgs[i], Info.needExactType(i, TemplateArgs[i]));
+  for (unsigned i = 0; i != Args.size(); ++i)
+    mangleTemplateArg(Args[i], Info.needExactType(i, Args[i]));
   Out << 'E';
 }
 
diff --git a/clang/lib/AST/ODRHash.cpp b/clang/lib/AST/ODRHash.cpp
index d07a0afd1b423..384259c72d810 100644
--- a/clang/lib/AST/ODRHash.cpp
+++ b/clang/lib/AST/ODRHash.cpp
@@ -948,7 +948,7 @@ class ODRTypeVisitor : public TypeVisitor<ODRTypeVisitor> {
     ID.AddInteger(T->isConstrained());
     if (T->isConstrained()) {
       AddDecl(T->getTypeConstraintConcept());
-      ID.AddInteger(T->getNumArgs());
+      ID.AddInteger(T->getTypeConstraintArguments().size());
       for (const auto &TA : T->getTypeConstraintArguments())
         Hash.AddTemplateArgument(TA);
     }
@@ -1102,7 +1102,7 @@ class ODRTypeVisitor : public TypeVisitor<ODRTypeVisitor> {
   void VisitEnumType(const EnumType *T) { VisitTagType(T); }
 
   void VisitTemplateSpecializationType(const TemplateSpecializationType *T) {
-    ID.AddInteger(T->getNumArgs());
+    ID.AddInteger(T->template_arguments().size());
     for (const auto &TA : T->template_arguments()) {
       Hash.AddTemplateArgument(TA);
     }
@@ -1167,7 +1167,7 @@ class ODRTypeVisitor : public TypeVisitor<ODRTypeVisitor> {
       const DependentTemplateSpecializationType *T) {
     AddIdentifierInfo(T->getIdentifier());
     AddNestedNameSpecifier(T->getQualifier());
-    ID.AddInteger(T->getNumArgs());
+    ID.AddInteger(T->template_arguments().size());
     for (const auto &TA : T->template_arguments()) {
       Hash.AddTemplateArgument(TA);
     }
diff --git a/clang/lib/AST/QualTypeNames.cpp b/clang/lib/AST/QualTypeNames.cpp
index 1bfe9996e44c3..7557336f0aafa 100644
--- a/clang/lib/AST/QualTypeNames.cpp
+++ b/clang/lib/AST/QualTypeNames.cpp
@@ -129,11 +129,9 @@ static const Type *getFullyQualifiedTemplateType(const ASTContext &Ctx,
   if (const auto *TST = dyn_cast<const TemplateSpecializationType>(TypePtr)) {
     bool MightHaveChanged = false;
     SmallVector<TemplateArgument, 4> FQArgs;
-    for (TemplateSpecializationType::iterator I = TST->begin(), E = TST->end();
-         I != E; ++I) {
-      // Cheap to copy and potentially modified by
-      // getFullyQualifedTemplateArgument.
-      TemplateArgument Arg(*I);
+    // Cheap to copy and potentially modified by
+    // getFullyQualifedTemplateArgument.
+    for (TemplateArgument Arg : TST->template_arguments()) {
       MightHaveChanged |= getFullyQualifiedTemplateArgument(
           Ctx, Arg, WithGlobalNsPrefix);
       FQArgs.push_back(Arg);
diff --git a/clang/lib/AST/Type.cpp b/clang/lib/AST/Type.cpp
index 4c1ea0fb8f7f4..e27ef7bfab390 100644
--- a/clang/lib/AST/Type.cpp
+++ b/clang/lib/AST/Type.cpp
@@ -2896,7 +2896,7 @@ DependentTemplateSpecializationType::DependentTemplateSpecializationType(
   DependentTemplateSpecializationTypeBits.NumArgs = Args.size();
   assert((!NNS || NNS->isDependent()) &&
          "DependentTemplateSpecializatonType requires dependent qualifier");
-  TemplateArgument *ArgBuffer = getArgBuffer();
+  auto *ArgBuffer = const_cast<TemplateArgument *>(template_arguments().data());
   for (const TemplateArgument &Arg : Args) {
     addDependence(toTypeDependence(Arg.getDependence() &
                                    TemplateArgumentDependence::UnexpandedPack));
@@ -3769,10 +3769,22 @@ TemplateSpecializationType::TemplateSpecializationType(
   // Store the aliased type if this is a type alias template specialization.
   if (isTypeAlias()) {
     auto *Begin = reinterpret_cast<TemplateArgument *>(this + 1);
-    *reinterpret_cast<QualType*>(Begin + getNumArgs()) = AliasedType;
+    *reinterpret_cast<QualType *>(Begin + Args.size()) = AliasedType;
   }
 }
 
+QualType TemplateSpecializationType::getAliasedType() const {
+  assert(isTypeAlias() && "not a type alias template specialization");
+  return *reinterpret_cast<const QualType *>(template_arguments().end());
+}
+
+void TemplateSpecializationType::Profile(llvm::FoldingSetNodeID &ID,
+                                         const ASTContext &Ctx) {
+  Profile(ID, Template, template_arguments(), Ctx);
+  if (isTypeAlias())
+    getAliasedType().Profile(ID);
+}
+
 void
 TemplateSpecializationType::Profile(llvm::FoldingSetNodeID &ID,
                                     TemplateName T,
@@ -4487,7 +4499,8 @@ AutoType::AutoType(QualType DeducedAsType, AutoTypeKeyword Keyword,
   AutoTypeBits.NumArgs = TypeConstraintArgs.size();
   this->TypeConstraintConcept = TypeConstraintConcept;
   if (TypeConstraintConcept) {
-    TemplateArgument *ArgBuffer = getArgBuffer();
+    auto *ArgBuffer =
+        const_cast<TemplateArgument *>(getTypeConstraintArguments().data());
     for (const TemplateArgument &Arg : TypeConstraintArgs) {
       addDependence(
           toSyntacticDependence(toTypeDependence(Arg.getDependence())));
@@ -4508,3 +4521,8 @@ void AutoType::Profile(llvm::FoldingSetNodeID &ID, const ASTContext &Context,
   for (const TemplateArgument &Arg : Arguments)
     Arg.Profile(ID, Context);
 }
+
+void AutoType::Profile(llvm::FoldingSetNodeID &ID, const ASTContext &Context) {
+  Profile(ID, Context, getDeducedType(), getKeyword(), isDependentType(),
+          getTypeConstraintConcept(), getTypeConstraintArguments());
+}
diff --git a/clang/lib/AST/TypeLoc.cpp b/clang/lib/AST/TypeLoc.cpp
index 99566b4ce68b0..bcc5a223e6f73 100644
--- a/clang/lib/AST/TypeLoc.cpp
+++ b/clang/lib/AST/TypeLoc.cpp
@@ -568,17 +568,14 @@ DependentTemplateSpecializationTypeLoc::initializeLocal(ASTContext &Context,
   setTemplateNameLoc(Loc);
   setLAngleLoc(Loc);
   setRAngleLoc(Loc);
-  TemplateSpecializationTypeLoc::initializeArgLocs(Context, getNumArgs(),
-                                                   getTypePtr()->getArgs(),
-                                                   getArgInfos(), Loc);
+  TemplateSpecializationTypeLoc::initializeArgLocs(
+      Context, getTypePtr()->template_arguments(), getArgInfos(), Loc);
 }
 
-void TemplateSpecializationTypeLoc::initializeArgLocs(ASTContext &Context,
-                                                      unsigned NumArgs,
-                                                  const TemplateArgument *Args,
-                                              TemplateArgumentLocInfo *ArgInfos,
-                                                      SourceLocation Loc) {
-  for (unsigned i = 0, e = NumArgs; i != e; ++i) {
+void TemplateSpecializationTypeLoc::initializeArgLocs(
+    ASTContext &Context, ArrayRef<TemplateArgument> Args,
+    TemplateArgumentLocInfo *ArgInfos, SourceLocation Loc) {
+  for (unsigned i = 0, e = Args.size(); i != e; ++i) {
     switch (Args[i].getKind()) {
     case TemplateArgument::Null:
       llvm_unreachable("Impossible TemplateArgument");
@@ -635,9 +632,8 @@ void AutoTypeLoc::initializeLocal(ASTContext &Context, SourceLocation Loc) {
   setRAngleLoc(Loc);
   setLAngleLoc(Loc);
   setRParenLoc(Loc);
-  TemplateSpecializationTypeLoc::initializeArgLocs(Context, getNumArgs(),
-                                                   getTypePtr()->getArgs(),
-                                                   getArgInfos(), Loc);
+  TemplateSpecializationTypeLoc::initializeArgLocs(
+      Context, getTypePtr()->getTypeConstraintArguments(), getArgInfos(), Loc);
   setNameLoc(Loc);
 }
 
diff --git a/clang/lib/AST/TypePrinter.cpp b/clang/lib/AST/TypePrinter.cpp
index 463db3332adf0..f6e67a805f740 100644
--- a/clang/lib/AST/TypePrinter.cpp
+++ b/clang/lib/AST/TypePrinter.cpp
@@ -2000,11 +2000,11 @@ static bool isSubstitutedType(ASTContext &Ctx, QualType T, QualType Pattern,
     if (!isSubstitutedTemplateArgument(Ctx, Template, PTST->getTemplateName(),
                                        Args, Depth))
       return false;
-    if (TemplateArgs.size() != PTST->getNumArgs())
+    if (TemplateArgs.size() != PTST->template_arguments().size())
       return false;
     for (unsigned I = 0, N = TemplateArgs.size(); I != N; ++I)
-      if (!isSubstitutedTemplateArgument(Ctx, TemplateArgs[I], PTST->getArg(I),
-                                         Args, Depth))
+      if (!isSubstitutedTemplateArgument(
+              Ctx, TemplateArgs[I], PTST->template_arguments()[I], Args, Depth))
         return false;
     return true;
   }
diff --git a/clang/lib/Index/USRGeneration.cpp b/clang/lib/Index/USRGeneration.cpp
index e804abe2de50f..19b8ff9d51207 100644
--- a/clang/lib/Index/USRGeneration.cpp
+++ b/clang/lib/Index/USRGeneration.cpp
@@ -856,9 +856,9 @@ void USRGenerator::VisitType(QualType T) {
                                     = T->getAs<TemplateSpecializationType>()) {
       Out << '>';
       VisitTemplateName(Spec->getTemplateName());
-      Out << Spec->getNumArgs();
-      for (unsigned I = 0, N = Spec->getNumArgs(); I != N; ++I)
-        VisitTemplateArgument(Spec->getArg(I));
+      Out << Spec->template_arguments().size();
+      for (const auto &Arg : Spec->template_arguments())
+        VisitTemplateArgument(Arg);
       return;
     }
     if (const DependentNameType *DNT = T->getAs<DependentNameType>()) {
diff --git a/clang/lib/Sema/SemaCXXScopeSpec.cpp b/clang/lib/Sema/SemaCXXScopeSpec.cpp
index 3f8fedda7174e..daa61ba45e8e3 100644
--- a/clang/lib/Sema/SemaCXXScopeSpec.cpp
+++ b/clang/lib/Sema/SemaCXXScopeSpec.cpp
@@ -931,10 +931,9 @@ bool Sema::ActOnCXXNestedNameSpecifier(Scope *S,
     // Handle a dependent template specialization for which we cannot resolve
     // the template name.
     assert(DTN->getQualifier() == SS.getScopeRep());
-    QualType T = Context.getDependentTemplateSpecializationType(ETK_None,
-                                                          DTN->getQualifier(),
-                                                          DTN->getIdentifier(),
-                                                                TemplateArgs);
+    QualType T = Context.getDependentTemplateSpecializationType(
+        ETK_None, DTN->getQualifier(), DTN->getIdentifier(),
+        TemplateArgs.arguments());
 
     // Create source-location information for this type.
     TypeLocBuilder Builder;
diff --git a/clang/lib/Sema/SemaCodeComplete.cpp b/clang/lib/Sema/SemaCodeComplete.cpp
index efa78ace8d376..2da588011b7fe 100644
--- a/clang/lib/Sema/SemaCodeComplete.cpp
+++ b/clang/lib/Sema/SemaCodeComplete.cpp
@@ -4666,9 +4666,9 @@ static const FunctionProtoType *TryDeconstructFunctionLike(QualType T) {
   // Note we only handle the sugared types, they closely match what users wrote.
   // We explicitly choose to not handle ClassTemplateSpecializationDecl.
   if (auto *Specialization = T->getAs<TemplateSpecializationType>()) {
-    if (Specialization->getNumArgs() != 1)
+    if (Specialization->template_arguments().size() != 1)
       return nullptr;
-    const TemplateArgument &Argument = Specialization->getArg(0);
+    const TemplateArgument &Argument = Specialization->template_arguments()[0];
     if (Argument.getKind() != TemplateArgument::Type)
       return nullptr;
     return Argument.getAsType()->getAs<FunctionProtoType>();
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index 5fe6f82fe3d08..1e5a56a14fba4 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -11525,7 +11525,7 @@ bool Sema::isStdInitializerList(QualType Ty, QualType *Element) {
                  Ty->getAs<TemplateSpecializationType>()) {
     Template = dyn_cast_or_null<ClassTemplateDecl>(
         TST->getTemplateName().getAsTemplateDecl());
-    Arguments = TST->getArgs();
+    Arguments = TST->template_arguments().begin();
   }
   if (!Template)
     return false;
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index d81ed15f979f1..7a30a736bff9f 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -3819,10 +3819,9 @@ QualType Sema::CheckTemplateIdType(TemplateName Name,
     // assume the template is a type template. Either our assumption is
     // correct, or the code is ill-formed and will be diagnosed when the
     // dependent name is substituted.
-    return Context.getDependentTemplateSpecializationType(ETK_None,
-                                                          DTN->getQualifier(),
-                                                          DTN->getIdentifier(),
-                                                          TemplateArgs);
+    return Context.getDependentTemplateSpecializationType(
+        ETK_None, DTN->getQualifier(), DTN->getIdentifier(),
+        TemplateArgs.arguments());
 
   if (Name.getAsAssumedTemplateName() &&
       resolveAssumedTemplateNameAsType(/*Scope*/nullptr, Name, TemplateLoc))
@@ -4133,11 +4132,10 @@ TypeResult Sema::ActOnTemplateIdType(
   translateTemplateArguments(TemplateArgsIn, TemplateArgs);
 
   if (DependentTemplateName *DTN = Template.getAsDependentTemplateName()) {
-    QualType T
-      = Context.getDependentTemplateSpecializationType(ETK_None,
-                                                       DTN->getQualifier(),
-                                                       DTN->getIdentifier(),
-                                                       TemplateArgs);
+    assert(SS.getScopeRep() == DTN->getQualifier());
+    QualType T = Context.getDependentTemplateSpecializationType(
+        ETK_None, DTN->getQualifier(), DTN->getIdentifier(),
+        TemplateArgs.arguments());
     // Build type-source information.
     TypeLocBuilder TLB;
     DependentTemplateSpecializationTypeLoc SpecTL
@@ -4203,10 +4201,10 @@ TypeResult Sema::ActOnTagTemplateIdType(TagUseKind TUK,
     = TypeWithKeyword::getKeywordForTagTypeKind(TagKind);
 
   if (DependentTemplateName *DTN = Template.getAsDependentTemplateName()) {
-    QualType T = Context.getDependentTemplateSpecializationType(Keyword,
-                                                          DTN->getQualifier(),
-                                                          DTN->getIdentifier(),
-                                                                TemplateArgs);
+    assert(SS.getScopeRep() == DTN->getQualifier());
+    QualType T = Context.getDependentTemplateSpecializationType(
+        Keyword, DTN->getQualifier(), DTN->getIdentifier(),
+        TemplateArgs.arguments());
 
     // Build type-source information.
     TypeLocBuilder TLB;
@@ -10730,10 +10728,9 @@ Sema::ActOnTypenameType(Scope *S,
     // Construct a dependent template specialization type.
     assert(DTN && "dependent template has non-dependent name?");
     assert(DTN->getQualifier() == SS.getScopeRep());
-    QualType T = Context.getDependentTemplateSpecializationType(ETK_Typename,
-                                                          DTN->getQualifier(),
-                                                          DTN->getIdentifier(),
-                                                                TemplateArgs);
+    QualType T = Context.getDependentTemplateSpecializationType(
+        ETK_Typename, DTN->getQualifier(), DTN->getIdentifier(),
+        TemplateArgs.arguments());
 
     // Create source-location information for this type.
     TypeLocBuilder Builder;
diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp b/clang/lib/Sema/SemaTemplateDeduction.cpp
index a731ff674f882..7bc743044b740 100644
--- a/clang/lib/Sema/SemaTemplateDeduction.cpp
+++ b/clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -5224,7 +5224,8 @@ FunctionTemplateDecl *Sema::getMoreSpecializedTemplate(
         continue;
       const TemplateArgument &TA1 = TST1->template_arguments().back();
       if (TA1.getKind() == TemplateArgument::Pack) {
-        assert(TST1->getNumArgs() == TST2->getNumArgs());
+        assert(TST1->template_arguments().size() ==
+               TST2->template_arguments().size());
         const TemplateArgument &TA2 = TST2->template_arguments().back();
         assert(TA2.getKind() == TemplateArgument::Pack);
         unsigned PackSize1 = TA1.pack_size();
@@ -5461,7 +5462,7 @@ static bool isAtLeastAsSpecializedAs(Sema &S, QualType T1, QualType T2,
   if (Inst.isInvalid())
     return false;
 
-  auto *TST1 = T1->castAs<TemplateSpecializationType>();
+  const auto *TST1 = cast<TemplateSpecializationType>(T1);
   bool AtLeastAsSpecialized;
   S.runWithSufficientStackSpace(Info.getLocation(), [&] {
     AtLeastAsSpecialized = !FinishTemplateArgumentDeduction(
@@ -5591,7 +5592,8 @@ getMoreSpecialized(Sema &S, QualType T1, QualType T2, TemplateLikeDecl *P1,
     auto *TST2 = cast<TemplateSpecializationType>(T2);
     const TemplateArgument &TA1 = TST1->template_arguments().back();
     if (TA1.getKind() == TemplateArgument::Pack) {
-      assert(TST1->getNumArgs() == TST2->getNumArgs());
+      assert(TST1->template_arguments().size() ==
+             TST2->template_arguments().size());
       const TemplateArgument &TA2 = TST2->template_arguments().back();
       assert(TA2.getKind() == TemplateArgument::Pack);
       unsigned PackSize1 = TA1.pack_size();
@@ -6074,9 +6076,8 @@ MarkUsedTemplateParameters(ASTContext &Ctx, QualType T,
         hasPackExpansionBeforeEnd(Spec->template_arguments()))
       break;
 
-    for (unsigned I = 0, N = Spec->getNumArgs(); I != N; ++I)
-      MarkUsedTemplateParameters(Ctx, Spec->getArg(I), OnlyDeduced, Depth,
-                                 Used);
+    for (const auto &Arg : Spec->template_arguments())
+      MarkUsedTemplateParameters(Ctx, Arg, OnlyDeduced, Depth, Used);
     break;
   }
 
@@ -6120,9 +6121,8 @@ MarkUsedTemplateParameters(ASTContext &Ctx, QualType T,
     MarkUsedTemplateParameters(Ctx, Spec->getQualifier(),
                                OnlyDeduced, Depth, Used);
 
-    for (unsigned I = 0, N = Spec->getNumArgs(); I != N; ++I)
-      MarkUsedTemplateParameters(Ctx, Spec->getArg(I), OnlyDeduced, Depth,
-                                 Used);
+    for (const auto &Arg : Spec->template_arguments())
+      MarkUsedTemplateParameters(Ctx, Arg, OnlyDeduced, Depth, Used);
     break;
   }
 
diff --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h
index ebb83f12b6566..031856ceb56a1 100644
--- a/clang/lib/Sema/TreeTransform.h
+++ b/clang/lib/Sema/TreeTransform.h
@@ -1098,10 +1098,9 @@ class TreeTransform {
 
     // If it's still dependent, make a dependent specialization.
     if (InstName.getAsDependentTemplateName())
-      return SemaRef.Context.getDependentTemplateSpecializationType(Keyword,
-                                          QualifierLoc.getNestedNameSpecifier(),
-                                                                    Name,
-                                                                    Args);
+      return SemaRef.Context.getDependentTemplateSpecializationType(
+          Keyword, QualifierLoc.getNestedNameSpecifier(), Name,
+          Args.arguments());
 
     // Otherwise, make an elaborated type wrapping a non-dependent
     // specialization.
@@ -6778,12 +6777,9 @@ QualType TreeTransform<Derived>::TransformDependentTemplateSpecializationType(
   // FIXME: maybe don't rebuild if all the template arguments are the same.
 
   if (DependentTemplateName *DTN = Template.getAsDependentTemplateName()) {
-    QualType Result
-      = getSema().Context.getDependentTemplateSpecializationType(
-                                                TL.getTypePtr()->getKeyword(),
-                                                         DTN->getQualifier(),
-                                                         DTN->getIdentifier(),
-                                                               NewTemplateArgs);
+    QualType Result = getSema().Context.getDependentTemplateSpecializationType(
+        TL.getTypePtr()->getKeyword(), DTN->getQualifier(),
+        DTN->getIdentifier(), NewTemplateArgs.arguments());
 
     DependentTemplateSpecializationTypeLoc NewTL
       = TLB.push<DependentTemplateSpecializationTypeLoc>(Result);
diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index ad979d5497f23..b2ab6b84aebb3 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -6690,8 +6690,9 @@ void TypeLocReader::VisitAutoTypeLoc(AutoTypeLoc TL) {
     TL.setLAngleLoc(readSourceLocation());
     TL.setRAngleLoc(readSourceLocation());
     for (unsigned i = 0, e = TL.getNumArgs(); i != e; ++i)
-      TL.setArgLocInfo(i, Reader.readTemplateArgumentLocInfo(
-                              TL.getTypePtr()->getArg(i).getKind()));
+      TL.setArgLocInfo(
+          i, Reader.readTemplateArgumentLocInfo(
+                 TL.getTypePtr()->getTypeConstraintArguments()[i].getKind()));
   }
   if (Reader.readBool())
     TL.setRParenLoc(readSourceLocation());
@@ -6739,10 +6740,9 @@ void TypeLocReader::VisitTemplateSpecializationTypeLoc(
   TL.setLAngleLoc(readSourceLocation());
   TL.setRAngleLoc(readSourceLocation());
   for (unsigned i = 0, e = TL.getNumArgs(); i != e; ++i)
-    TL.setArgLocInfo(
-        i,
-        Reader.readTemplateArgumentLocInfo(
-          TL.getTypePtr()->getArg(i).getKind()));
+    TL.setArgLocInfo(i,
+                     Reader.readTemplateArgumentLocInfo(
+                         TL.getTypePtr()->template_arguments()[i].getKind()));
 }
 
 void TypeLocReader::VisitParenTypeLoc(ParenTypeLoc TL) {
@@ -6774,10 +6774,9 @@ void TypeLocReader::VisitDependentTemplateSpecializationTypeLoc(
   TL.setLAngleLoc(readSourceLocation());
   TL.setRAngleLoc(readSourceLocation());
   for (unsigned I = 0, E = TL.getNumArgs(); I != E; ++I)
-    TL.setArgLocInfo(
-        I,
-        Reader.readTemplateArgumentLocInfo(
-            TL.getTypePtr()->getArg(I).getKind()));
+    TL.setArgLocInfo(I,
+                     Reader.readTemplateArgumentLocInfo(
+                         TL.getTypePtr()->template_arguments()[I].getKind()));
 }
 
 void TypeLocReader::VisitPackExpansionTypeLoc(PackExpansionTypeLoc TL) {
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 4dcc5ee0a1c86..b019b6f48a63a 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -463,8 +463,9 @@ void TypeLocWriter::VisitAutoTypeLoc(AutoTypeLoc TL) {
     addSourceLocation(TL.getLAngleLoc());
     addSourceLocation(TL.getRAngleLoc());
     for (unsigned I = 0; I < TL.getNumArgs(); ++I)
-      Record.AddTemplateArgumentLocInfo(TL.getTypePtr()->getArg(I).getKind(),
-                                        TL.getArgLocInfo(I));
+      Record.AddTemplateArgumentLocInfo(
+          TL.getTypePtr()->getTypeConstraintArguments()[I].getKind(),
+          TL.getArgLocInfo(I));
   }
   Record.push_back(TL.isDecltypeAuto());
   if (TL.isDecltypeAuto())