Move all sources from the llvm project into contrib/llvm-project.

This uses the new layout of the upstream repository, which was recently
migrated to GitHub, and converted into a "monorepo".  That is, most of
the earlier separate sub-projects with their own branches and tags were
consolidated into one top-level directory, and are now branched and
tagged together.

Updating the vendor area to match this layout is next.

1 files changed, 3065 insertions, 0 deletions

diff --git a/contrib/llvm-project/clang/lib/Sema/SemaTemplateInstantiate.cpp b/contrib/llvm-project/clang/lib/Sema/SemaTemplateInstantiate.cpp
new file mode 100644
index 000000000000..973f564d3058
--- /dev/null
+++ b/contrib/llvm-project/clang/lib/Sema/SemaTemplateInstantiate.cpp
@@ -0,0 +1,3065 @@
+//===------- SemaTemplateInstantiate.cpp - C++ Template Instantiation ------===/
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//===----------------------------------------------------------------------===/
+//
+//  This file implements C++ template instantiation.
+//
+//===----------------------------------------------------------------------===/
+
+#include "clang/Sema/SemaInternal.h"
+#include "TreeTransform.h"
+#include "clang/AST/ASTConsumer.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/ASTLambda.h"
+#include "clang/AST/ASTMutationListener.h"
+#include "clang/AST/DeclTemplate.h"
+#include "clang/AST/Expr.h"
+#include "clang/AST/PrettyDeclStackTrace.h"
+#include "clang/Basic/LangOptions.h"
+#include "clang/Sema/DeclSpec.h"
+#include "clang/Sema/Initialization.h"
+#include "clang/Sema/Lookup.h"
+#include "clang/Sema/Template.h"
+#include "clang/Sema/TemplateDeduction.h"
+#include "clang/Sema/TemplateInstCallback.h"
+#include "llvm/Support/TimeProfiler.h"
+
+using namespace clang;
+using namespace sema;
+
+//===----------------------------------------------------------------------===/
+// Template Instantiation Support
+//===----------------------------------------------------------------------===/
+
+/// Retrieve the template argument list(s) that should be used to
+/// instantiate the definition of the given declaration.
+///
+/// \param D the declaration for which we are computing template instantiation
+/// arguments.
+///
+/// \param Innermost if non-NULL, the innermost template argument list.
+///
+/// \param RelativeToPrimary true if we should get the template
+/// arguments relative to the primary template, even when we're
+/// dealing with a specialization. This is only relevant for function
+/// template specializations.
+///
+/// \param Pattern If non-NULL, indicates the pattern from which we will be
+/// instantiating the definition of the given declaration, \p D. This is
+/// used to determine the proper set of template instantiation arguments for
+/// friend function template specializations.
+MultiLevelTemplateArgumentList
+Sema::getTemplateInstantiationArgs(NamedDecl *D,
+                                   const TemplateArgumentList *Innermost,
+                                   bool RelativeToPrimary,
+                                   const FunctionDecl *Pattern) {
+  // Accumulate the set of template argument lists in this structure.
+  MultiLevelTemplateArgumentList Result;
+
+  if (Innermost)
+    Result.addOuterTemplateArguments(Innermost);
+
+  DeclContext *Ctx = dyn_cast<DeclContext>(D);
+  if (!Ctx) {
+    Ctx = D->getDeclContext();
+
+    // Add template arguments from a variable template instantiation. For a
+    // class-scope explicit specialization, there are no template arguments
+    // at this level, but there may be enclosing template arguments.
+    VarTemplateSpecializationDecl *Spec =
+        dyn_cast<VarTemplateSpecializationDecl>(D);
+    if (Spec && !Spec->isClassScopeExplicitSpecialization()) {
+      // We're done when we hit an explicit specialization.
+      if (Spec->getSpecializationKind() == TSK_ExplicitSpecialization &&
+          !isa<VarTemplatePartialSpecializationDecl>(Spec))
+        return Result;
+
+      Result.addOuterTemplateArguments(&Spec->getTemplateInstantiationArgs());
+
+      // If this variable template specialization was instantiated from a
+      // specialized member that is a variable template, we're done.
+      assert(Spec->getSpecializedTemplate() && "No variable template?");
+      llvm::PointerUnion<VarTemplateDecl*,
+                         VarTemplatePartialSpecializationDecl*> Specialized
+                             = Spec->getSpecializedTemplateOrPartial();
+      if (VarTemplatePartialSpecializationDecl *Partial =
+              Specialized.dyn_cast<VarTemplatePartialSpecializationDecl *>()) {
+        if (Partial->isMemberSpecialization())
+          return Result;
+      } else {
+        VarTemplateDecl *Tmpl = Specialized.get<VarTemplateDecl *>();
+        if (Tmpl->isMemberSpecialization())
+          return Result;
+      }
+    }
+
+    // If we have a template template parameter with translation unit context,
+    // then we're performing substitution into a default template argument of
+    // this template template parameter before we've constructed the template
+    // that will own this template template parameter. In this case, we
+    // use empty template parameter lists for all of the outer templates
+    // to avoid performing any substitutions.
+    if (Ctx->isTranslationUnit()) {
+      if (TemplateTemplateParmDecl *TTP
+                                      = dyn_cast<TemplateTemplateParmDecl>(D)) {
+        for (unsigned I = 0, N = TTP->getDepth() + 1; I != N; ++I)
+          Result.addOuterTemplateArguments(None);
+        return Result;
+      }
+    }
+  }
+
+  while (!Ctx->isFileContext()) {
+    // Add template arguments from a class template instantiation.
+    ClassTemplateSpecializationDecl *Spec
+          = dyn_cast<ClassTemplateSpecializationDecl>(Ctx);
+    if (Spec && !Spec->isClassScopeExplicitSpecialization()) {
+      // We're done when we hit an explicit specialization.
+      if (Spec->getSpecializationKind() == TSK_ExplicitSpecialization &&
+          !isa<ClassTemplatePartialSpecializationDecl>(Spec))
+        break;
+
+      Result.addOuterTemplateArguments(&Spec->getTemplateInstantiationArgs());
+
+      // If this class template specialization was instantiated from a
+      // specialized member that is a class template, we're done.
+      assert(Spec->getSpecializedTemplate() && "No class template?");
+      if (Spec->getSpecializedTemplate()->isMemberSpecialization())
+        break;
+    }
+    // Add template arguments from a function template specialization.
+    else if (FunctionDecl *Function = dyn_cast<FunctionDecl>(Ctx)) {
+      if (!RelativeToPrimary &&
+          Function->getTemplateSpecializationKindForInstantiation() ==
+              TSK_ExplicitSpecialization)
+        break;
+
+      if (const TemplateArgumentList *TemplateArgs
+            = Function->getTemplateSpecializationArgs()) {
+        // Add the template arguments for this specialization.
+        Result.addOuterTemplateArguments(TemplateArgs);
+
+        // If this function was instantiated from a specialized member that is
+        // a function template, we're done.
+        assert(Function->getPrimaryTemplate() && "No function template?");
+        if (Function->getPrimaryTemplate()->isMemberSpecialization())
+          break;
+
+        // If this function is a generic lambda specialization, we are done.
+        if (isGenericLambdaCallOperatorSpecialization(Function))
+          break;
+
+      } else if (FunctionTemplateDecl *FunTmpl
+                                   = Function->getDescribedFunctionTemplate()) {
+        // Add the "injected" template arguments.
+        Result.addOuterTemplateArguments(FunTmpl->getInjectedTemplateArgs());
+      }
+
+      // If this is a friend declaration and it declares an entity at
+      // namespace scope, take arguments from its lexical parent
+      // instead of its semantic parent, unless of course the pattern we're
+      // instantiating actually comes from the file's context!
+      if (Function->getFriendObjectKind() &&
+          Function->getDeclContext()->isFileContext() &&
+          (!Pattern || !Pattern->getLexicalDeclContext()->isFileContext())) {
+        Ctx = Function->getLexicalDeclContext();
+        RelativeToPrimary = false;
+        continue;
+      }
+    } else if (CXXRecordDecl *Rec = dyn_cast<CXXRecordDecl>(Ctx)) {
+      if (ClassTemplateDecl *ClassTemplate = Rec->getDescribedClassTemplate()) {
+        QualType T = ClassTemplate->getInjectedClassNameSpecialization();
+        const TemplateSpecializationType *TST =
+            cast<TemplateSpecializationType>(Context.getCanonicalType(T));
+        Result.addOuterTemplateArguments(
+            llvm::makeArrayRef(TST->getArgs(), TST->getNumArgs()));
+        if (ClassTemplate->isMemberSpecialization())
+          break;
+      }
+    }
+
+    Ctx = Ctx->getParent();
+    RelativeToPrimary = false;
+  }
+
+  return Result;
+}
+
+bool Sema::CodeSynthesisContext::isInstantiationRecord() const {
+  switch (Kind) {
+  case TemplateInstantiation:
+  case ExceptionSpecInstantiation:
+  case DefaultTemplateArgumentInstantiation:
+  case DefaultFunctionArgumentInstantiation:
+  case ExplicitTemplateArgumentSubstitution:
+  case DeducedTemplateArgumentSubstitution:
+  case PriorTemplateArgumentSubstitution:
+    return true;
+
+  case DefaultTemplateArgumentChecking:
+  case DeclaringSpecialMember:
+  case DefiningSynthesizedFunction:
+  case ExceptionSpecEvaluation:
+    return false;
+
+  // This function should never be called when Kind's value is Memoization.
+  case Memoization:
+    break;
+  }
+
+  llvm_unreachable("Invalid SynthesisKind!");
+}
+
+Sema::InstantiatingTemplate::InstantiatingTemplate(
+    Sema &SemaRef, CodeSynthesisContext::SynthesisKind Kind,
+    SourceLocation PointOfInstantiation, SourceRange InstantiationRange,
+    Decl *Entity, NamedDecl *Template, ArrayRef<TemplateArgument> TemplateArgs,
+    sema::TemplateDeductionInfo *DeductionInfo)
+    : SemaRef(SemaRef) {
+  // Don't allow further instantiation if a fatal error and an uncompilable
+  // error have occurred. Any diagnostics we might have raised will not be
+  // visible, and we do not need to construct a correct AST.
+  if (SemaRef.Diags.hasFatalErrorOccurred() &&
+      SemaRef.Diags.hasUncompilableErrorOccurred()) {
+    Invalid = true;
+    return;
+  }
+  Invalid = CheckInstantiationDepth(PointOfInstantiation, InstantiationRange);
+  if (!Invalid) {
+    CodeSynthesisContext Inst;
+    Inst.Kind = Kind;
+    Inst.PointOfInstantiation = PointOfInstantiation;
+    Inst.Entity = Entity;
+    Inst.Template = Template;
+    Inst.TemplateArgs = TemplateArgs.data();
+    Inst.NumTemplateArgs = TemplateArgs.size();
+    Inst.DeductionInfo = DeductionInfo;
+    Inst.InstantiationRange = InstantiationRange;
+    SemaRef.pushCodeSynthesisContext(Inst);
+
+    AlreadyInstantiating =
+        !SemaRef.InstantiatingSpecializations
+             .insert(std::make_pair(Inst.Entity->getCanonicalDecl(), Inst.Kind))
+             .second;
+    atTemplateBegin(SemaRef.TemplateInstCallbacks, SemaRef, Inst);
+  }
+}
+
+Sema::InstantiatingTemplate::InstantiatingTemplate(
+    Sema &SemaRef, SourceLocation PointOfInstantiation, Decl *Entity,
+    SourceRange InstantiationRange)
+    : InstantiatingTemplate(SemaRef,
+                            CodeSynthesisContext::TemplateInstantiation,
+                            PointOfInstantiation, InstantiationRange, Entity) {}
+
+Sema::InstantiatingTemplate::InstantiatingTemplate(
+    Sema &SemaRef, SourceLocation PointOfInstantiation, FunctionDecl *Entity,
+    ExceptionSpecification, SourceRange InstantiationRange)
+    : InstantiatingTemplate(
+          SemaRef, CodeSynthesisContext::ExceptionSpecInstantiation,
+          PointOfInstantiation, InstantiationRange, Entity) {}
+
+Sema::InstantiatingTemplate::InstantiatingTemplate(
+    Sema &SemaRef, SourceLocation PointOfInstantiation, TemplateParameter Param,
+    TemplateDecl *Template, ArrayRef<TemplateArgument> TemplateArgs,
+    SourceRange InstantiationRange)
+    : InstantiatingTemplate(
+          SemaRef,
+          CodeSynthesisContext::DefaultTemplateArgumentInstantiation,
+          PointOfInstantiation, InstantiationRange, getAsNamedDecl(Param),
+          Template, TemplateArgs) {}
+
+Sema::InstantiatingTemplate::InstantiatingTemplate(
+    Sema &SemaRef, SourceLocation PointOfInstantiation,
+    FunctionTemplateDecl *FunctionTemplate,
+    ArrayRef<TemplateArgument> TemplateArgs,
+    CodeSynthesisContext::SynthesisKind Kind,
+    sema::TemplateDeductionInfo &DeductionInfo, SourceRange InstantiationRange)
+    : InstantiatingTemplate(SemaRef, Kind, PointOfInstantiation,
+                            InstantiationRange, FunctionTemplate, nullptr,
+                            TemplateArgs, &DeductionInfo) {
+  assert(
+    Kind == CodeSynthesisContext::ExplicitTemplateArgumentSubstitution ||
+    Kind == CodeSynthesisContext::DeducedTemplateArgumentSubstitution);
+}
+
+Sema::InstantiatingTemplate::InstantiatingTemplate(
+    Sema &SemaRef, SourceLocation PointOfInstantiation,
+    TemplateDecl *Template,
+    ArrayRef<TemplateArgument> TemplateArgs,
+    sema::TemplateDeductionInfo &DeductionInfo, SourceRange InstantiationRange)
+    : InstantiatingTemplate(
+          SemaRef,
+          CodeSynthesisContext::DeducedTemplateArgumentSubstitution,
+          PointOfInstantiation, InstantiationRange, Template, nullptr,
+          TemplateArgs, &DeductionInfo) {}
+
+Sema::InstantiatingTemplate::InstantiatingTemplate(
+    Sema &SemaRef, SourceLocation PointOfInstantiation,
+    ClassTemplatePartialSpecializationDecl *PartialSpec,
+    ArrayRef<TemplateArgument> TemplateArgs,
+    sema::TemplateDeductionInfo &DeductionInfo, SourceRange InstantiationRange)
+    : InstantiatingTemplate(
+          SemaRef,
+          CodeSynthesisContext::DeducedTemplateArgumentSubstitution,
+          PointOfInstantiation, InstantiationRange, PartialSpec, nullptr,
+          TemplateArgs, &DeductionInfo) {}
+
+Sema::InstantiatingTemplate::InstantiatingTemplate(
+    Sema &SemaRef, SourceLocation PointOfInstantiation,
+    VarTemplatePartialSpecializationDecl *PartialSpec,
+    ArrayRef<TemplateArgument> TemplateArgs,
+    sema::TemplateDeductionInfo &DeductionInfo, SourceRange InstantiationRange)
+    : InstantiatingTemplate(
+          SemaRef,
+          CodeSynthesisContext::DeducedTemplateArgumentSubstitution,
+          PointOfInstantiation, InstantiationRange, PartialSpec, nullptr,
+          TemplateArgs, &DeductionInfo) {}
+
+Sema::InstantiatingTemplate::InstantiatingTemplate(
+    Sema &SemaRef, SourceLocation PointOfInstantiation, ParmVarDecl *Param,
+    ArrayRef<TemplateArgument> TemplateArgs, SourceRange InstantiationRange)
+    : InstantiatingTemplate(
+          SemaRef,
+          CodeSynthesisContext::DefaultFunctionArgumentInstantiation,
+          PointOfInstantiation, InstantiationRange, Param, nullptr,
+          TemplateArgs) {}
+
+Sema::InstantiatingTemplate::InstantiatingTemplate(
+    Sema &SemaRef, SourceLocation PointOfInstantiation, NamedDecl *Template,
+    NonTypeTemplateParmDecl *Param, ArrayRef<TemplateArgument> TemplateArgs,
+    SourceRange InstantiationRange)
+    : InstantiatingTemplate(
+          SemaRef,
+          CodeSynthesisContext::PriorTemplateArgumentSubstitution,
+          PointOfInstantiation, InstantiationRange, Param, Template,
+          TemplateArgs) {}
+
+Sema::InstantiatingTemplate::InstantiatingTemplate(
+    Sema &SemaRef, SourceLocation PointOfInstantiation, NamedDecl *Template,
+    TemplateTemplateParmDecl *Param, ArrayRef<TemplateArgument> TemplateArgs,
+    SourceRange InstantiationRange)
+    : InstantiatingTemplate(
+          SemaRef,
+          CodeSynthesisContext::PriorTemplateArgumentSubstitution,
+          PointOfInstantiation, InstantiationRange, Param, Template,
+          TemplateArgs) {}
+
+Sema::InstantiatingTemplate::InstantiatingTemplate(
+    Sema &SemaRef, SourceLocation PointOfInstantiation, TemplateDecl *Template,
+    NamedDecl *Param, ArrayRef<TemplateArgument> TemplateArgs,
+    SourceRange InstantiationRange)
+    : InstantiatingTemplate(
+          SemaRef, CodeSynthesisContext::DefaultTemplateArgumentChecking,
+          PointOfInstantiation, InstantiationRange, Param, Template,
+          TemplateArgs) {}
+
+void Sema::pushCodeSynthesisContext(CodeSynthesisContext Ctx) {
+  Ctx.SavedInNonInstantiationSFINAEContext = InNonInstantiationSFINAEContext;
+  InNonInstantiationSFINAEContext = false;
+
+  CodeSynthesisContexts.push_back(Ctx);
+
+  if (!Ctx.isInstantiationRecord())
+    ++NonInstantiationEntries;
+}
+
+void Sema::popCodeSynthesisContext() {
+  auto &Active = CodeSynthesisContexts.back();
+  if (!Active.isInstantiationRecord()) {
+    assert(NonInstantiationEntries > 0);
+    --NonInstantiationEntries;
+  }
+
+  InNonInstantiationSFINAEContext = Active.SavedInNonInstantiationSFINAEContext;
+
+  // Name lookup no longer looks in this template's defining module.
+  assert(CodeSynthesisContexts.size() >=
+             CodeSynthesisContextLookupModules.size() &&
+         "forgot to remove a lookup module for a template instantiation");
+  if (CodeSynthesisContexts.size() ==
+      CodeSynthesisContextLookupModules.size()) {
+    if (Module *M = CodeSynthesisContextLookupModules.back())
+      LookupModulesCache.erase(M);
+    CodeSynthesisContextLookupModules.pop_back();
+  }
+
+  // If we've left the code synthesis context for the current context stack,
+  // stop remembering that we've emitted that stack.
+  if (CodeSynthesisContexts.size() ==
+      LastEmittedCodeSynthesisContextDepth)
+    LastEmittedCodeSynthesisContextDepth = 0;
+
+  CodeSynthesisContexts.pop_back();
+}
+
+void Sema::InstantiatingTemplate::Clear() {
+  if (!Invalid) {
+    if (!AlreadyInstantiating) {
+      auto &Active = SemaRef.CodeSynthesisContexts.back();
+      SemaRef.InstantiatingSpecializations.erase(
+          std::make_pair(Active.Entity, Active.Kind));
+    }
+
+    atTemplateEnd(SemaRef.TemplateInstCallbacks, SemaRef,
+                  SemaRef.CodeSynthesisContexts.back());
+
+    SemaRef.popCodeSynthesisContext();
+    Invalid = true;
+  }
+}
+
+bool Sema::InstantiatingTemplate::CheckInstantiationDepth(
+                                        SourceLocation PointOfInstantiation,
+                                           SourceRange InstantiationRange) {
+  assert(SemaRef.NonInstantiationEntries <=
+         SemaRef.CodeSynthesisContexts.size());
+  if ((SemaRef.CodeSynthesisContexts.size() -
+          SemaRef.NonInstantiationEntries)
+        <= SemaRef.getLangOpts().InstantiationDepth)
+    return false;
+
+  SemaRef.Diag(PointOfInstantiation,
+               diag::err_template_recursion_depth_exceeded)
+    << SemaRef.getLangOpts().InstantiationDepth
+    << InstantiationRange;
+  SemaRef.Diag(PointOfInstantiation, diag::note_template_recursion_depth)
+    << SemaRef.getLangOpts().InstantiationDepth;
+  return true;
+}
+
+/// Prints the current instantiation stack through a series of
+/// notes.
+void Sema::PrintInstantiationStack() {
+  // Determine which template instantiations to skip, if any.
+  unsigned SkipStart = CodeSynthesisContexts.size(), SkipEnd = SkipStart;
+  unsigned Limit = Diags.getTemplateBacktraceLimit();
+  if (Limit && Limit < CodeSynthesisContexts.size()) {
+    SkipStart = Limit / 2 + Limit % 2;
+    SkipEnd = CodeSynthesisContexts.size() - Limit / 2;
+  }
+
+  // FIXME: In all of these cases, we need to show the template arguments
+  unsigned InstantiationIdx = 0;
+  for (SmallVectorImpl<CodeSynthesisContext>::reverse_iterator
+         Active = CodeSynthesisContexts.rbegin(),
+         ActiveEnd = CodeSynthesisContexts.rend();
+       Active != ActiveEnd;
+       ++Active, ++InstantiationIdx) {
+    // Skip this instantiation?
+    if (InstantiationIdx >= SkipStart && InstantiationIdx < SkipEnd) {
+      if (InstantiationIdx == SkipStart) {
+        // Note that we're skipping instantiations.
+        Diags.Report(Active->PointOfInstantiation,
+                     diag::note_instantiation_contexts_suppressed)
+          << unsigned(CodeSynthesisContexts.size() - Limit);
+      }
+      continue;
+    }
+
+    switch (Active->Kind) {
+    case CodeSynthesisContext::TemplateInstantiation: {
+      Decl *D = Active->Entity;
+      if (CXXRecordDecl *Record = dyn_cast<CXXRecordDecl>(D)) {
+        unsigned DiagID = diag::note_template_member_class_here;
+        if (isa<ClassTemplateSpecializationDecl>(Record))
+          DiagID = diag::note_template_class_instantiation_here;
+        Diags.Report(Active->PointOfInstantiation, DiagID)
+          << Record << Active->InstantiationRange;
+      } else if (FunctionDecl *Function = dyn_cast<FunctionDecl>(D)) {
+        unsigned DiagID;
+        if (Function->getPrimaryTemplate())
+          DiagID = diag::note_function_template_spec_here;
+        else
+          DiagID = diag::note_template_member_function_here;
+        Diags.Report(Active->PointOfInstantiation, DiagID)
+          << Function
+          << Active->InstantiationRange;
+      } else if (VarDecl *VD = dyn_cast<VarDecl>(D)) {
+        Diags.Report(Active->PointOfInstantiation,
+                     VD->isStaticDataMember()?
+                       diag::note_template_static_data_member_def_here
+                     : diag::note_template_variable_def_here)
+          << VD
+          << Active->InstantiationRange;
+      } else if (EnumDecl *ED = dyn_cast<EnumDecl>(D)) {
+        Diags.Report(Active->PointOfInstantiation,
+                     diag::note_template_enum_def_here)
+          << ED
+          << Active->InstantiationRange;
+      } else if (FieldDecl *FD = dyn_cast<FieldDecl>(D)) {
+        Diags.Report(Active->PointOfInstantiation,
+                     diag::note_template_nsdmi_here)
+            << FD << Active->InstantiationRange;
+      } else {
+        Diags.Report(Active->PointOfInstantiation,
+                     diag::note_template_type_alias_instantiation_here)
+          << cast<TypeAliasTemplateDecl>(D)
+          << Active->InstantiationRange;
+      }
+      break;
+    }
+
+    case CodeSynthesisContext::DefaultTemplateArgumentInstantiation: {
+      TemplateDecl *Template = cast<TemplateDecl>(Active->Template);
+      SmallVector<char, 128> TemplateArgsStr;
+      llvm::raw_svector_ostream OS(TemplateArgsStr);
+      Template->printName(OS);
+      printTemplateArgumentList(OS, Active->template_arguments(),
+                                getPrintingPolicy());
+      Diags.Report(Active->PointOfInstantiation,
+                   diag::note_default_arg_instantiation_here)
+        << OS.str()
+        << Active->InstantiationRange;
+      break;
+    }
+
+    case CodeSynthesisContext::ExplicitTemplateArgumentSubstitution: {
+      FunctionTemplateDecl *FnTmpl = cast<FunctionTemplateDecl>(Active->Entity);
+      Diags.Report(Active->PointOfInstantiation,
+                   diag::note_explicit_template_arg_substitution_here)
+        << FnTmpl
+        << getTemplateArgumentBindingsText(FnTmpl->getTemplateParameters(),
+                                           Active->TemplateArgs,
+                                           Active->NumTemplateArgs)
+        << Active->InstantiationRange;
+      break;
+    }
+
+    case CodeSynthesisContext::DeducedTemplateArgumentSubstitution: {
+      if (FunctionTemplateDecl *FnTmpl =
+              dyn_cast<FunctionTemplateDecl>(Active->Entity)) {
+        Diags.Report(Active->PointOfInstantiation,
+                     diag::note_function_template_deduction_instantiation_here)
+          << FnTmpl
+          << getTemplateArgumentBindingsText(FnTmpl->getTemplateParameters(),
+                                             Active->TemplateArgs,
+                                             Active->NumTemplateArgs)
+          << Active->InstantiationRange;
+      } else {
+        bool IsVar = isa<VarTemplateDecl>(Active->Entity) ||
+                     isa<VarTemplateSpecializationDecl>(Active->Entity);
+        bool IsTemplate = false;
+        TemplateParameterList *Params;
+        if (auto *D = dyn_cast<TemplateDecl>(Active->Entity)) {
+          IsTemplate = true;
+          Params = D->getTemplateParameters();
+        } else if (auto *D = dyn_cast<ClassTemplatePartialSpecializationDecl>(
+                       Active->Entity)) {
+          Params = D->getTemplateParameters();
+        } else if (auto *D = dyn_cast<VarTemplatePartialSpecializationDecl>(
+                       Active->Entity)) {
+          Params = D->getTemplateParameters();
+        } else {
+          llvm_unreachable("unexpected template kind");
+        }
+
+        Diags.Report(Active->PointOfInstantiation,
+                     diag::note_deduced_template_arg_substitution_here)
+          << IsVar << IsTemplate << cast<NamedDecl>(Active->Entity)
+          << getTemplateArgumentBindingsText(Params, Active->TemplateArgs,
+                                             Active->NumTemplateArgs)
+          << Active->InstantiationRange;
+      }
+      break;
+    }
+
+    case CodeSynthesisContext::DefaultFunctionArgumentInstantiation: {
+      ParmVarDecl *Param = cast<ParmVarDecl>(Active->Entity);
+      FunctionDecl *FD = cast<FunctionDecl>(Param->getDeclContext());
+
+      SmallVector<char, 128> TemplateArgsStr;
+      llvm::raw_svector_ostream OS(TemplateArgsStr);
+      FD->printName(OS);
+      printTemplateArgumentList(OS, Active->template_arguments(),
+                                getPrintingPolicy());
+      Diags.Report(Active->PointOfInstantiation,
+                   diag::note_default_function_arg_instantiation_here)
+        << OS.str()
+        << Active->InstantiationRange;
+      break;
+    }
+
+    case CodeSynthesisContext::PriorTemplateArgumentSubstitution: {
+      NamedDecl *Parm = cast<NamedDecl>(Active->Entity);
+      std::string Name;
+      if (!Parm->getName().empty())
+        Name = std::string(" '") + Parm->getName().str() + "'";
+
+      TemplateParameterList *TemplateParams = nullptr;
+      if (TemplateDecl *Template = dyn_cast<TemplateDecl>(Active->Template))
+        TemplateParams = Template->getTemplateParameters();
+      else
+        TemplateParams =
+          cast<ClassTemplatePartialSpecializationDecl>(Active->Template)
+                                                      ->getTemplateParameters();
+      Diags.Report(Active->PointOfInstantiation,
+                   diag::note_prior_template_arg_substitution)
+        << isa<TemplateTemplateParmDecl>(Parm)
+        << Name
+        << getTemplateArgumentBindingsText(TemplateParams,
+                                           Active->TemplateArgs,
+                                           Active->NumTemplateArgs)
+        << Active->InstantiationRange;
+      break;
+    }
+
+    case CodeSynthesisContext::DefaultTemplateArgumentChecking: {
+      TemplateParameterList *TemplateParams = nullptr;
+      if (TemplateDecl *Template = dyn_cast<TemplateDecl>(Active->Template))
+        TemplateParams = Template->getTemplateParameters();
+      else
+        TemplateParams =
+          cast<ClassTemplatePartialSpecializationDecl>(Active->Template)
+                                                      ->getTemplateParameters();
+
+      Diags.Report(Active->PointOfInstantiation,
+                   diag::note_template_default_arg_checking)
+        << getTemplateArgumentBindingsText(TemplateParams,
+                                           Active->TemplateArgs,
+                                           Active->NumTemplateArgs)
+        << Active->InstantiationRange;
+      break;
+    }
+
+    case CodeSynthesisContext::ExceptionSpecEvaluation:
+      Diags.Report(Active->PointOfInstantiation,
+                   diag::note_evaluating_exception_spec_here)
+          << cast<FunctionDecl>(Active->Entity);
+      break;
+
+    case CodeSynthesisContext::ExceptionSpecInstantiation:
+      Diags.Report(Active->PointOfInstantiation,
+                   diag::note_template_exception_spec_instantiation_here)
+        << cast<FunctionDecl>(Active->Entity)
+        << Active->InstantiationRange;
+      break;
+
+    case CodeSynthesisContext::DeclaringSpecialMember:
+      Diags.Report(Active->PointOfInstantiation,
+                   diag::note_in_declaration_of_implicit_special_member)
+        << cast<CXXRecordDecl>(Active->Entity) << Active->SpecialMember;
+      break;
+
+    case CodeSynthesisContext::DefiningSynthesizedFunction: {
+      // FIXME: For synthesized members other than special members, produce a note.
+      auto *MD = dyn_cast<CXXMethodDecl>(Active->Entity);
+      auto CSM = MD ? getSpecialMember(MD) : CXXInvalid;
+      if (CSM != CXXInvalid) {
+        Diags.Report(Active->PointOfInstantiation,
+                     diag::note_member_synthesized_at)
+          << CSM << Context.getTagDeclType(MD->getParent());
+      }
+      break;
+    }
+
+    case CodeSynthesisContext::Memoization:
+      break;
+    }
+  }
+}
+
+Optional<TemplateDeductionInfo *> Sema::isSFINAEContext() const {
+  if (InNonInstantiationSFINAEContext)
+    return Optional<TemplateDeductionInfo *>(nullptr);
+
+  for (SmallVectorImpl<CodeSynthesisContext>::const_reverse_iterator
+         Active = CodeSynthesisContexts.rbegin(),
+         ActiveEnd = CodeSynthesisContexts.rend();
+       Active != ActiveEnd;
+       ++Active)
+  {
+    switch (Active->Kind) {
+    case CodeSynthesisContext::TemplateInstantiation:
+      // An instantiation of an alias template may or may not be a SFINAE
+      // context, depending on what else is on the stack.
+      if (isa<TypeAliasTemplateDecl>(Active->Entity))
+        break;
+      LLVM_FALLTHROUGH;
+    case CodeSynthesisContext::DefaultFunctionArgumentInstantiation:
+    case CodeSynthesisContext::ExceptionSpecInstantiation:
+      // This is a template instantiation, so there is no SFINAE.
+      return None;
+
+    case CodeSynthesisContext::DefaultTemplateArgumentInstantiation:
+    case CodeSynthesisContext::PriorTemplateArgumentSubstitution:
+    case CodeSynthesisContext::DefaultTemplateArgumentChecking:
+      // A default template argument instantiation and substitution into
+      // template parameters with arguments for prior parameters may or may
+      // not be a SFINAE context; look further up the stack.
+      break;
+
+    case CodeSynthesisContext::ExplicitTemplateArgumentSubstitution:
+    case CodeSynthesisContext::DeducedTemplateArgumentSubstitution:
+      // We're either substitution explicitly-specified template arguments
+      // or deduced template arguments, so SFINAE applies.
+      assert(Active->DeductionInfo && "Missing deduction info pointer");
+      return Active->DeductionInfo;
+
+    case CodeSynthesisContext::DeclaringSpecialMember:
+    case CodeSynthesisContext::DefiningSynthesizedFunction:
+      // This happens in a context unrelated to template instantiation, so
+      // there is no SFINAE.
+      return None;
+
+    case CodeSynthesisContext::ExceptionSpecEvaluation:
+      // FIXME: This should not be treated as a SFINAE context, because
+      // we will cache an incorrect exception specification. However, clang
+      // bootstrap relies this! See PR31692.
+      break;
+
+    case CodeSynthesisContext::Memoization:
+      break;
+    }
+
+    // The inner context was transparent for SFINAE. If it occurred within a
+    // non-instantiation SFINAE context, then SFINAE applies.
+    if (Active->SavedInNonInstantiationSFINAEContext)
+      return Optional<TemplateDeductionInfo *>(nullptr);
+  }
+
+  return None;
+}
+
+//===----------------------------------------------------------------------===/
+// Template Instantiation for Types
+//===----------------------------------------------------------------------===/
+namespace {
+  class TemplateInstantiator : public TreeTransform<TemplateInstantiator> {
+    const MultiLevelTemplateArgumentList &TemplateArgs;
+    SourceLocation Loc;
+    DeclarationName Entity;
+
+  public:
+    typedef TreeTransform<TemplateInstantiator> inherited;
+
+    TemplateInstantiator(Sema &SemaRef,
+                         const MultiLevelTemplateArgumentList &TemplateArgs,
+                         SourceLocation Loc,
+                         DeclarationName Entity)
+      : inherited(SemaRef), TemplateArgs(TemplateArgs), Loc(Loc),
+        Entity(Entity) { }
+
+    /// Determine whether the given type \p T has already been
+    /// transformed.
+    ///
+    /// For the purposes of template instantiation, a type has already been
+    /// transformed if it is NULL or if it is not dependent.
+    bool AlreadyTransformed(QualType T);
+
+    /// Returns the location of the entity being instantiated, if known.
+    SourceLocation getBaseLocation() { return Loc; }
+
+    /// Returns the name of the entity being instantiated, if any.
+    DeclarationName getBaseEntity() { return Entity; }
+
+    /// Sets the "base" location and entity when that
+    /// information is known based on another transformation.
+    void setBase(SourceLocation Loc, DeclarationName Entity) {
+      this->Loc = Loc;
+      this->Entity = Entity;
+    }
+
+    bool TryExpandParameterPacks(SourceLocation EllipsisLoc,
+                                 SourceRange PatternRange,
+                                 ArrayRef<UnexpandedParameterPack> Unexpanded,
+                                 bool &ShouldExpand, bool &RetainExpansion,
+                                 Optional<unsigned> &NumExpansions) {
+      return getSema().CheckParameterPacksForExpansion(EllipsisLoc,
+                                                       PatternRange, Unexpanded,
+                                                       TemplateArgs,
+                                                       ShouldExpand,
+                                                       RetainExpansion,
+                                                       NumExpansions);
+    }
+
+    void ExpandingFunctionParameterPack(ParmVarDecl *Pack) {
+      SemaRef.CurrentInstantiationScope->MakeInstantiatedLocalArgPack(Pack);
+    }
+
+    TemplateArgument ForgetPartiallySubstitutedPack() {
+      TemplateArgument Result;
+      if (NamedDecl *PartialPack
+            = SemaRef.CurrentInstantiationScope->getPartiallySubstitutedPack()){
+        MultiLevelTemplateArgumentList &TemplateArgs
+          = const_cast<MultiLevelTemplateArgumentList &>(this->TemplateArgs);
+        unsigned Depth, Index;
+        std::tie(Depth, Index) = getDepthAndIndex(PartialPack);
+        if (TemplateArgs.hasTemplateArgument(Depth, Index)) {
+          Result = TemplateArgs(Depth, Index);
+          TemplateArgs.setArgument(Depth, Index, TemplateArgument());
+        }
+      }
+
+      return Result;
+    }
+
+    void RememberPartiallySubstitutedPack(TemplateArgument Arg) {
+      if (Arg.isNull())
+        return;
+
+      if (NamedDecl *PartialPack
+            = SemaRef.CurrentInstantiationScope->getPartiallySubstitutedPack()){
+        MultiLevelTemplateArgumentList &TemplateArgs
+        = const_cast<MultiLevelTemplateArgumentList &>(this->TemplateArgs);
+        unsigned Depth, Index;
+        std::tie(Depth, Index) = getDepthAndIndex(PartialPack);
+        TemplateArgs.setArgument(Depth, Index, Arg);
+      }
+    }
+
+    /// Transform the given declaration by instantiating a reference to
+    /// this declaration.
+    Decl *TransformDecl(SourceLocation Loc, Decl *D);
+
+    void transformAttrs(Decl *Old, Decl *New) {
+      SemaRef.InstantiateAttrs(TemplateArgs, Old, New);
+    }
+
+    void transformedLocalDecl(Decl *Old, ArrayRef<Decl *> NewDecls) {
+      if (Old->isParameterPack()) {
+        SemaRef.CurrentInstantiationScope->MakeInstantiatedLocalArgPack(Old);
+        for (auto *New : NewDecls)
+          SemaRef.CurrentInstantiationScope->InstantiatedLocalPackArg(
+              Old, cast<VarDecl>(New));
+        return;
+      }
+
+      assert(NewDecls.size() == 1 &&
+             "should only have multiple expansions for a pack");
+      Decl *New = NewDecls.front();
+
+      // If we've instantiated the call operator of a lambda or the call
+      // operator template of a generic lambda, update the "instantiation of"
+      // information.
+      auto *NewMD = dyn_cast<CXXMethodDecl>(New);
+      if (NewMD && isLambdaCallOperator(NewMD)) {
+        auto *OldMD = dyn_cast<CXXMethodDecl>(Old);
+        if (auto *NewTD = NewMD->getDescribedFunctionTemplate())
+          NewTD->setInstantiatedFromMemberTemplate(
+              OldMD->getDescribedFunctionTemplate());
+        else
+          NewMD->setInstantiationOfMemberFunction(OldMD,
+                                                  TSK_ImplicitInstantiation);
+      }
+
+      SemaRef.CurrentInstantiationScope->InstantiatedLocal(Old, New);
+
+      // We recreated a local declaration, but not by instantiating it. There
+      // may be pending dependent diagnostics to produce.
+      if (auto *DC = dyn_cast<DeclContext>(Old))
+        SemaRef.PerformDependentDiagnostics(DC, TemplateArgs);
+    }
+
+    /// Transform the definition of the given declaration by
+    /// instantiating it.
+    Decl *TransformDefinition(SourceLocation Loc, Decl *D);
+
+    /// Transform the first qualifier within a scope by instantiating the
+    /// declaration.
+    NamedDecl *TransformFirstQualifierInScope(NamedDecl *D, SourceLocation Loc);
+
+    /// Rebuild the exception declaration and register the declaration
+    /// as an instantiated local.
+    VarDecl *RebuildExceptionDecl(VarDecl *ExceptionDecl,
+                                  TypeSourceInfo *Declarator,
+                                  SourceLocation StartLoc,
+                                  SourceLocation NameLoc,
+                                  IdentifierInfo *Name);
+
+    /// Rebuild the Objective-C exception declaration and register the
+    /// declaration as an instantiated local.
+    VarDecl *RebuildObjCExceptionDecl(VarDecl *ExceptionDecl,
+                                      TypeSourceInfo *TSInfo, QualType T);
+
+    /// Check for tag mismatches when instantiating an
+    /// elaborated type.
+    QualType RebuildElaboratedType(SourceLocation KeywordLoc,
+                                   ElaboratedTypeKeyword Keyword,
+                                   NestedNameSpecifierLoc QualifierLoc,
+                                   QualType T);
+
+    TemplateName
+    TransformTemplateName(CXXScopeSpec &SS, TemplateName Name,
+                          SourceLocation NameLoc,
+                          QualType ObjectType = QualType(),
+                          NamedDecl *FirstQualifierInScope = nullptr,
+                          bool AllowInjectedClassName = false);
+
+    const LoopHintAttr *TransformLoopHintAttr(const LoopHintAttr *LH);
+
+    ExprResult TransformPredefinedExpr(PredefinedExpr *E);
+    ExprResult TransformDeclRefExpr(DeclRefExpr *E);
+    ExprResult TransformCXXDefaultArgExpr(CXXDefaultArgExpr *E);
+
+    ExprResult TransformTemplateParmRefExpr(DeclRefExpr *E,
+                                            NonTypeTemplateParmDecl *D);
+    ExprResult TransformSubstNonTypeTemplateParmPackExpr(
+                                           SubstNonTypeTemplateParmPackExpr *E);
+
+    /// Rebuild a DeclRefExpr for a VarDecl reference.
+    ExprResult RebuildVarDeclRefExpr(VarDecl *PD, SourceLocation Loc);
+
+    /// Transform a reference to a function or init-capture parameter pack.
+    ExprResult TransformFunctionParmPackRefExpr(DeclRefExpr *E, VarDecl *PD);
+
+    /// Transform a FunctionParmPackExpr which was built when we couldn't
+    /// expand a function parameter pack reference which refers to an expanded
+    /// pack.
+    ExprResult TransformFunctionParmPackExpr(FunctionParmPackExpr *E);
+
+    QualType TransformFunctionProtoType(TypeLocBuilder &TLB,
+                                        FunctionProtoTypeLoc TL) {
+      // Call the base version; it will forward to our overridden version below.
+      return inherited::TransformFunctionProtoType(TLB, TL);
+    }
+
+    template<typename Fn>
+    QualType TransformFunctionProtoType(TypeLocBuilder &TLB,
+                                        FunctionProtoTypeLoc TL,
+                                        CXXRecordDecl *ThisContext,
+                                        Qualifiers ThisTypeQuals,
+                                        Fn TransformExceptionSpec);
+
+    ParmVarDecl *TransformFunctionTypeParam(ParmVarDecl *OldParm,
+                                            int indexAdjustment,
+                                            Optional<unsigned> NumExpansions,
+                                            bool ExpectParameterPack);
+
+    /// Transforms a template type parameter type by performing
+    /// substitution of the corresponding template type argument.
+    QualType TransformTemplateTypeParmType(TypeLocBuilder &TLB,
+                                           TemplateTypeParmTypeLoc TL);
+
+    /// Transforms an already-substituted template type parameter pack
+    /// into either itself (if we aren't substituting into its pack expansion)
+    /// or the appropriate substituted argument.
+    QualType TransformSubstTemplateTypeParmPackType(TypeLocBuilder &TLB,
+                                           SubstTemplateTypeParmPackTypeLoc TL);
+
+    ExprResult TransformLambdaExpr(LambdaExpr *E) {
+      LocalInstantiationScope Scope(SemaRef, /*CombineWithOuterScope=*/true);
+      return TreeTransform<TemplateInstantiator>::TransformLambdaExpr(E);
+    }
+
+    TemplateParameterList *TransformTemplateParameterList(
+                              TemplateParameterList *OrigTPL)  {
+      if (!OrigTPL || !OrigTPL->size()) return OrigTPL;
+
+      DeclContext *Owner = OrigTPL->getParam(0)->getDeclContext();
+      TemplateDeclInstantiator  DeclInstantiator(getSema(),
+                        /* DeclContext *Owner */ Owner, TemplateArgs);
+      return DeclInstantiator.SubstTemplateParams(OrigTPL);
+    }
+  private:
+    ExprResult transformNonTypeTemplateParmRef(NonTypeTemplateParmDecl *parm,
+                                               SourceLocation loc,
+                                               TemplateArgument arg);
+  };
+}
+
+bool TemplateInstantiator::AlreadyTransformed(QualType T) {
+  if (T.isNull())
+    return true;
+
+  if (T->isInstantiationDependentType() || T->isVariablyModifiedType())
+    return false;
+
+  getSema().MarkDeclarationsReferencedInType(Loc, T);
+  return true;
+}
+
+static TemplateArgument
+getPackSubstitutedTemplateArgument(Sema &S, TemplateArgument Arg) {
+  assert(S.ArgumentPackSubstitutionIndex >= 0);
+  assert(S.ArgumentPackSubstitutionIndex < (int)Arg.pack_size());
+  Arg = Arg.pack_begin()[S.ArgumentPackSubstitutionIndex];
+  if (Arg.isPackExpansion())
+    Arg = Arg.getPackExpansionPattern();
+  return Arg;
+}
+
+Decl *TemplateInstantiator::TransformDecl(SourceLocation Loc, Decl *D) {
+  if (!D)
+    return nullptr;
+
+  if (TemplateTemplateParmDecl *TTP = dyn_cast<TemplateTemplateParmDecl>(D)) {
+    if (TTP->getDepth() < TemplateArgs.getNumLevels()) {
+      // If the corresponding template argument is NULL or non-existent, it's
+      // because we are performing instantiation from explicitly-specified
+      // template arguments in a function template, but there were some
+      // arguments left unspecified.
+      if (!TemplateArgs.hasTemplateArgument(TTP->getDepth(),
+                                            TTP->getPosition()))
+        return D;
+
+      TemplateArgument Arg = TemplateArgs(TTP->getDepth(), TTP->getPosition());
+
+      if (TTP->isParameterPack()) {
+        assert(Arg.getKind() == TemplateArgument::Pack &&
+               "Missing argument pack");
+        Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
+      }
+
+      TemplateName Template = Arg.getAsTemplate().getNameToSubstitute();
+      assert(!Template.isNull() && Template.getAsTemplateDecl() &&
+             "Wrong kind of template template argument");
+      return Template.getAsTemplateDecl();
+    }
+
+    // Fall through to find the instantiated declaration for this template
+    // template parameter.
+  }
+
+  return SemaRef.FindInstantiatedDecl(Loc, cast<NamedDecl>(D), TemplateArgs);
+}
+
+Decl *TemplateInstantiator::TransformDefinition(SourceLocation Loc, Decl *D) {
+  Decl *Inst = getSema().SubstDecl(D, getSema().CurContext, TemplateArgs);
+  if (!Inst)
+    return nullptr;
+
+  getSema().CurrentInstantiationScope->InstantiatedLocal(D, Inst);
+  return Inst;
+}
+
+NamedDecl *
+TemplateInstantiator::TransformFirstQualifierInScope(NamedDecl *D,
+                                                     SourceLocation Loc) {
+  // If the first part of the nested-name-specifier was a template type
+  // parameter, instantiate that type parameter down to a tag type.
+  if (TemplateTypeParmDecl *TTPD = dyn_cast_or_null<TemplateTypeParmDecl>(D)) {
+    const TemplateTypeParmType *TTP
+      = cast<TemplateTypeParmType>(getSema().Context.getTypeDeclType(TTPD));
+
+    if (TTP->getDepth() < TemplateArgs.getNumLevels()) {
+      // FIXME: This needs testing w/ member access expressions.
+      TemplateArgument Arg = TemplateArgs(TTP->getDepth(), TTP->getIndex());
+
+      if (TTP->isParameterPack()) {
+        assert(Arg.getKind() == TemplateArgument::Pack &&
+               "Missing argument pack");
+
+        if (getSema().ArgumentPackSubstitutionIndex == -1)
+          return nullptr;
+
+        Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
+      }
+
+      QualType T = Arg.getAsType();
+      if (T.isNull())
+        return cast_or_null<NamedDecl>(TransformDecl(Loc, D));
+
+      if (const TagType *Tag = T->getAs<TagType>())
+        return Tag->getDecl();
+
+      // The resulting type is not a tag; complain.
+      getSema().Diag(Loc, diag::err_nested_name_spec_non_tag) << T;
+      return nullptr;
+    }
+  }
+
+  return cast_or_null<NamedDecl>(TransformDecl(Loc, D));
+}
+
+VarDecl *
+TemplateInstantiator::RebuildExceptionDecl(VarDecl *ExceptionDecl,
+                                           TypeSourceInfo *Declarator,
+                                           SourceLocation StartLoc,
+                                           SourceLocation NameLoc,
+                                           IdentifierInfo *Name) {
+  VarDecl *Var = inherited::RebuildExceptionDecl(ExceptionDecl, Declarator,
+                                                 StartLoc, NameLoc, Name);
+  if (Var)
+    getSema().CurrentInstantiationScope->InstantiatedLocal(ExceptionDecl, Var);
+  return Var;
+}
+
+VarDecl *TemplateInstantiator::RebuildObjCExceptionDecl(VarDecl *ExceptionDecl,
+                                                        TypeSourceInfo *TSInfo,
+                                                        QualType T) {
+  VarDecl *Var = inherited::RebuildObjCExceptionDecl(ExceptionDecl, TSInfo, T);
+  if (Var)
+    getSema().CurrentInstantiationScope->InstantiatedLocal(ExceptionDecl, Var);
+  return Var;
+}
+
+QualType
+TemplateInstantiator::RebuildElaboratedType(SourceLocation KeywordLoc,
+                                            ElaboratedTypeKeyword Keyword,
+                                            NestedNameSpecifierLoc QualifierLoc,
+                                            QualType T) {
+  if (const TagType *TT = T->getAs<TagType>()) {
+    TagDecl* TD = TT->getDecl();
+
+    SourceLocation TagLocation = KeywordLoc;
+
+    IdentifierInfo *Id = TD->getIdentifier();
+
+    // TODO: should we even warn on struct/class mismatches for this?  Seems
+    // like it's likely to produce a lot of spurious errors.
+    if (Id && Keyword != ETK_None && Keyword != ETK_Typename) {
+      TagTypeKind Kind = TypeWithKeyword::getTagTypeKindForKeyword(Keyword);
+      if (!SemaRef.isAcceptableTagRedeclaration(TD, Kind, /*isDefinition*/false,
+                                                TagLocation, Id)) {
+        SemaRef.Diag(TagLocation, diag::err_use_with_wrong_tag)
+          << Id
+          << FixItHint::CreateReplacement(SourceRange(TagLocation),
+                                          TD->getKindName());
+        SemaRef.Diag(TD->getLocation(), diag::note_previous_use);
+      }
+    }
+  }
+
+  return TreeTransform<TemplateInstantiator>::RebuildElaboratedType(KeywordLoc,
+                                                                    Keyword,
+                                                                  QualifierLoc,
+                                                                    T);
+}
+
+TemplateName TemplateInstantiator::TransformTemplateName(
+    CXXScopeSpec &SS, TemplateName Name, SourceLocation NameLoc,
+    QualType ObjectType, NamedDecl *FirstQualifierInScope,
+    bool AllowInjectedClassName) {
+  if (TemplateTemplateParmDecl *TTP
+       = dyn_cast_or_null<TemplateTemplateParmDecl>(Name.getAsTemplateDecl())) {
+    if (TTP->getDepth() < TemplateArgs.getNumLevels()) {
+      // If the corresponding template argument is NULL or non-existent, it's
+      // because we are performing instantiation from explicitly-specified
+      // template arguments in a function template, but there were some
+      // arguments left unspecified.
+      if (!TemplateArgs.hasTemplateArgument(TTP->getDepth(),
+                                            TTP->getPosition()))
+        return Name;
+
+      TemplateArgument Arg = TemplateArgs(TTP->getDepth(), TTP->getPosition());
+
+      if (TTP->isParameterPack()) {
+        assert(Arg.getKind() == TemplateArgument::Pack &&
+               "Missing argument pack");
+
+        if (getSema().ArgumentPackSubstitutionIndex == -1) {
+          // We have the template argument pack to substitute, but we're not
+          // actually expanding the enclosing pack expansion yet. So, just
+          // keep the entire argument pack.
+          return getSema().Context.getSubstTemplateTemplateParmPack(TTP, Arg);
+        }
+
+        Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
+      }
+
+      TemplateName Template = Arg.getAsTemplate().getNameToSubstitute();
+      assert(!Template.isNull() && "Null template template argument");
+      assert(!Template.getAsQualifiedTemplateName() &&
+             "template decl to substitute is qualified?");
+
+      Template = getSema().Context.getSubstTemplateTemplateParm(TTP, Template);
+      return Template;
+    }
+  }
+
+  if (SubstTemplateTemplateParmPackStorage *SubstPack
+      = Name.getAsSubstTemplateTemplateParmPack()) {
+    if (getSema().ArgumentPackSubstitutionIndex == -1)
+      return Name;
+
+    TemplateArgument Arg = SubstPack->getArgumentPack();
+    Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
+    return Arg.getAsTemplate().getNameToSubstitute();
+  }
+
+  return inherited::TransformTemplateName(SS, Name, NameLoc, ObjectType,
+                                          FirstQualifierInScope,
+                                          AllowInjectedClassName);
+}
+
+ExprResult
+TemplateInstantiator::TransformPredefinedExpr(PredefinedExpr *E) {
+  if (!E->isTypeDependent())
+    return E;
+
+  return getSema().BuildPredefinedExpr(E->getLocation(), E->getIdentKind());
+}
+
+ExprResult
+TemplateInstantiator::TransformTemplateParmRefExpr(DeclRefExpr *E,
+                                               NonTypeTemplateParmDecl *NTTP) {
+  // If the corresponding template argument is NULL or non-existent, it's
+  // because we are performing instantiation from explicitly-specified
+  // template arguments in a function template, but there were some
+  // arguments left unspecified.
+  if (!TemplateArgs.hasTemplateArgument(NTTP->getDepth(),
+                                        NTTP->getPosition()))
+    return E;
+
+  TemplateArgument Arg = TemplateArgs(NTTP->getDepth(), NTTP->getPosition());
+
+  if (TemplateArgs.getNumLevels() != TemplateArgs.getNumSubstitutedLevels()) {
+    // We're performing a partial substitution, so the substituted argument
+    // could be dependent. As a result we can't create a SubstNonType*Expr
+    // node now, since that represents a fully-substituted argument.
+    // FIXME: We should have some AST representation for this.
+    if (Arg.getKind() == TemplateArgument::Pack) {
+      // FIXME: This won't work for alias templates.
+      assert(Arg.pack_size() == 1 && Arg.pack_begin()->isPackExpansion() &&
+             "unexpected pack arguments in partial substitution");
+      Arg = Arg.pack_begin()->getPackExpansionPattern();
+    }
+    assert(Arg.getKind() == TemplateArgument::Expression &&
+           "unexpected nontype template argument kind in partial substitution");
+    return Arg.getAsExpr();
+  }
+
+  if (NTTP->isParameterPack()) {
+    assert(Arg.getKind() == TemplateArgument::Pack &&
+           "Missing argument pack");
+
+    if (getSema().ArgumentPackSubstitutionIndex == -1) {
+      // We have an argument pack, but we can't select a particular argument
+      // out of it yet. Therefore, we'll build an expression to hold on to that
+      // argument pack.
+      QualType TargetType = SemaRef.SubstType(NTTP->getType(), TemplateArgs,
+                                              E->getLocation(),
+                                              NTTP->getDeclName());
+      if (TargetType.isNull())
+        return ExprError();
+
+      return new (SemaRef.Context) SubstNonTypeTemplateParmPackExpr(
+          TargetType.getNonLValueExprType(SemaRef.Context),
+          TargetType->isReferenceType() ? VK_LValue : VK_RValue, NTTP,
+          E->getLocation(), Arg);
+    }
+
+    Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
+  }
+
+  return transformNonTypeTemplateParmRef(NTTP, E->getLocation(), Arg);
+}
+
+const LoopHintAttr *
+TemplateInstantiator::TransformLoopHintAttr(const LoopHintAttr *LH) {
+  Expr *TransformedExpr = getDerived().TransformExpr(LH->getValue()).get();
+
+  if (TransformedExpr == LH->getValue())
+    return LH;
+
+  // Generate error if there is a problem with the value.
+  if (getSema().CheckLoopHintExpr(TransformedExpr, LH->getLocation()))
+    return LH;
+
+  // Create new LoopHintValueAttr with integral expression in place of the
+  // non-type template parameter.
+  return LoopHintAttr::CreateImplicit(
+      getSema().Context, LH->getSemanticSpelling(), LH->getOption(),
+      LH->getState(), TransformedExpr, LH->getRange());
+}
+
+ExprResult TemplateInstantiator::transformNonTypeTemplateParmRef(
+                                                 NonTypeTemplateParmDecl *parm,
+                                                 SourceLocation loc,
+                                                 TemplateArgument arg) {
+  ExprResult result;
+  QualType type;
+
+  // The template argument itself might be an expression, in which
+  // case we just return that expression.
+  if (arg.getKind() == TemplateArgument::Expression) {
+    Expr *argExpr = arg.getAsExpr();
+    result = argExpr;
+    type = argExpr->getType();
+
+  } else if (arg.getKind() == TemplateArgument::Declaration ||
+             arg.getKind() == TemplateArgument::NullPtr) {
+    ValueDecl *VD;
+    if (arg.getKind() == TemplateArgument::Declaration) {
+      VD = arg.getAsDecl();
+
+      // Find the instantiation of the template argument.  This is
+      // required for nested templates.
+      VD = cast_or_null<ValueDecl>(
+             getSema().FindInstantiatedDecl(loc, VD, TemplateArgs));
+      if (!VD)
+        return ExprError();
+    } else {
+      // Propagate NULL template argument.
+      VD = nullptr;
+    }
+
+    // Derive the type we want the substituted decl to have.  This had
+    // better be non-dependent, or these checks will have serious problems.
+    if (parm->isExpandedParameterPack()) {
+      type = parm->getExpansionType(SemaRef.ArgumentPackSubstitutionIndex);
+    } else if (parm->isParameterPack() &&
+               isa<PackExpansionType>(parm->getType())) {
+      type = SemaRef.SubstType(
+                        cast<PackExpansionType>(parm->getType())->getPattern(),
+                                     TemplateArgs, loc, parm->getDeclName());
+    } else {
+      type = SemaRef.SubstType(VD ? arg.getParamTypeForDecl() : arg.getNullPtrType(),
+                               TemplateArgs, loc, parm->getDeclName());
+    }
+    assert(!type.isNull() && "type substitution failed for param type");
+    assert(!type->isDependentType() && "param type still dependent");
+    result = SemaRef.BuildExpressionFromDeclTemplateArgument(arg, type, loc);
+
+    if (!result.isInvalid()) type = result.get()->getType();
+  } else {
+    result = SemaRef.BuildExpressionFromIntegralTemplateArgument(arg, loc);
+
+    // Note that this type can be different from the type of 'result',
+    // e.g. if it's an enum type.
+    type = arg.getIntegralType();
+  }
+  if (result.isInvalid()) return ExprError();
+
+  Expr *resultExpr = result.get();
+  return new (SemaRef.Context) SubstNonTypeTemplateParmExpr(
+      type, resultExpr->getValueKind(), loc, parm, resultExpr);
+}
+
+ExprResult
+TemplateInstantiator::TransformSubstNonTypeTemplateParmPackExpr(
+                                          SubstNonTypeTemplateParmPackExpr *E) {
+  if (getSema().ArgumentPackSubstitutionIndex == -1) {
+    // We aren't expanding the parameter pack, so just return ourselves.
+    return E;
+  }
+
+  TemplateArgument Arg = E->getArgumentPack();
+  Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
+  return transformNonTypeTemplateParmRef(E->getParameterPack(),
+                                         E->getParameterPackLocation(),
+                                         Arg);
+}
+
+ExprResult TemplateInstantiator::RebuildVarDeclRefExpr(VarDecl *PD,
+                                                       SourceLocation Loc) {
+  DeclarationNameInfo NameInfo(PD->getDeclName(), Loc);
+  return getSema().BuildDeclarationNameExpr(CXXScopeSpec(), NameInfo, PD);
+}
+
+ExprResult
+TemplateInstantiator::TransformFunctionParmPackExpr(FunctionParmPackExpr *E) {
+  if (getSema().ArgumentPackSubstitutionIndex != -1) {
+    // We can expand this parameter pack now.
+    VarDecl *D = E->getExpansion(getSema().ArgumentPackSubstitutionIndex);
+    VarDecl *VD = cast_or_null<VarDecl>(TransformDecl(E->getExprLoc(), D));
+    if (!VD)
+      return ExprError();
+    return RebuildVarDeclRefExpr(VD, E->getExprLoc());
+  }
+
+  QualType T = TransformType(E->getType());
+  if (T.isNull())
+    return ExprError();
+
+  // Transform each of the parameter expansions into the corresponding
+  // parameters in the instantiation of the function decl.
+  SmallVector<VarDecl *, 8> Vars;
+  Vars.reserve(E->getNumExpansions());
+  for (FunctionParmPackExpr::iterator I = E->begin(), End = E->end();
+       I != End; ++I) {
+    VarDecl *D = cast_or_null<VarDecl>(TransformDecl(E->getExprLoc(), *I));
+    if (!D)
+      return ExprError();
+    Vars.push_back(D);
+  }
+
+  auto *PackExpr =
+      FunctionParmPackExpr::Create(getSema().Context, T, E->getParameterPack(),
+                                   E->getParameterPackLocation(), Vars);
+  getSema().MarkFunctionParmPackReferenced(PackExpr);
+  return PackExpr;
+}
+
+ExprResult
+TemplateInstantiator::TransformFunctionParmPackRefExpr(DeclRefExpr *E,
+                                                       VarDecl *PD) {
+  typedef LocalInstantiationScope::DeclArgumentPack DeclArgumentPack;
+  llvm::PointerUnion<Decl *, DeclArgumentPack *> *Found
+    = getSema().CurrentInstantiationScope->findInstantiationOf(PD);
+  assert(Found && "no instantiation for parameter pack");
+
+  Decl *TransformedDecl;
+  if (DeclArgumentPack *Pack = Found->dyn_cast<DeclArgumentPack *>()) {
+    // If this is a reference to a function parameter pack which we can
+    // substitute but can't yet expand, build a FunctionParmPackExpr for it.
+    if (getSema().ArgumentPackSubstitutionIndex == -1) {
+      QualType T = TransformType(E->getType());
+      if (T.isNull())
+        return ExprError();
+      auto *PackExpr = FunctionParmPackExpr::Create(getSema().Context, T, PD,
+                                                    E->getExprLoc(), *Pack);
+      getSema().MarkFunctionParmPackReferenced(PackExpr);
+      return PackExpr;
+    }
+
+    TransformedDecl = (*Pack)[getSema().ArgumentPackSubstitutionIndex];
+  } else {
+    TransformedDecl = Found->get<Decl*>();
+  }
+
+  // We have either an unexpanded pack or a specific expansion.
+  return RebuildVarDeclRefExpr(cast<VarDecl>(TransformedDecl), E->getExprLoc());
+}
+
+ExprResult
+TemplateInstantiator::TransformDeclRefExpr(DeclRefExpr *E) {
+  NamedDecl *D = E->getDecl();
+
+  // Handle references to non-type template parameters and non-type template
+  // parameter packs.
+  if (NonTypeTemplateParmDecl *NTTP = dyn_cast<NonTypeTemplateParmDecl>(D)) {
+    if (NTTP->getDepth() < TemplateArgs.getNumLevels())
+      return TransformTemplateParmRefExpr(E, NTTP);
+
+    // We have a non-type template parameter that isn't fully substituted;
+    // FindInstantiatedDecl will find it in the local instantiation scope.
+  }
+
+  // Handle references to function parameter packs.
+  if (VarDecl *PD = dyn_cast<VarDecl>(D))
+    if (PD->isParameterPack())
+      return TransformFunctionParmPackRefExpr(E, PD);
+
+  return TreeTransform<TemplateInstantiator>::TransformDeclRefExpr(E);
+}
+
+ExprResult TemplateInstantiator::TransformCXXDefaultArgExpr(
+    CXXDefaultArgExpr *E) {
+  assert(!cast<FunctionDecl>(E->getParam()->getDeclContext())->
+             getDescribedFunctionTemplate() &&
+         "Default arg expressions are never formed in dependent cases.");
+  return SemaRef.BuildCXXDefaultArgExpr(E->getUsedLocation(),
+                           cast<FunctionDecl>(E->getParam()->getDeclContext()),
+                                        E->getParam());
+}
+
+template<typename Fn>
+QualType TemplateInstantiator::TransformFunctionProtoType(TypeLocBuilder &TLB,
+                                 FunctionProtoTypeLoc TL,
+                                 CXXRecordDecl *ThisContext,
+                                 Qualifiers ThisTypeQuals,
+                                 Fn TransformExceptionSpec) {
+  // We need a local instantiation scope for this function prototype.
+  LocalInstantiationScope Scope(SemaRef, /*CombineWithOuterScope=*/true);
+  return inherited::TransformFunctionProtoType(
+      TLB, TL, ThisContext, ThisTypeQuals, TransformExceptionSpec);
+}
+
+ParmVarDecl *
+TemplateInstantiator::TransformFunctionTypeParam(ParmVarDecl *OldParm,
+                                                 int indexAdjustment,
+                                               Optional<unsigned> NumExpansions,
+                                                 bool ExpectParameterPack) {
+  return SemaRef.SubstParmVarDecl(OldParm, TemplateArgs, indexAdjustment,
+                                  NumExpansions, ExpectParameterPack);
+}
+
+QualType
+TemplateInstantiator::TransformTemplateTypeParmType(TypeLocBuilder &TLB,
+                                                TemplateTypeParmTypeLoc TL) {
+  const TemplateTypeParmType *T = TL.getTypePtr();
+  if (T->getDepth() < TemplateArgs.getNumLevels()) {
+    // Replace the template type parameter with its corresponding
+    // template argument.
+
+    // If the corresponding template argument is NULL or doesn't exist, it's
+    // because we are performing instantiation from explicitly-specified
+    // template arguments in a function template class, but there were some
+    // arguments left unspecified.
+    if (!TemplateArgs.hasTemplateArgument(T->getDepth(), T->getIndex())) {
+      TemplateTypeParmTypeLoc NewTL
+        = TLB.push<TemplateTypeParmTypeLoc>(TL.getType());
+      NewTL.setNameLoc(TL.getNameLoc());
+      return TL.getType();
+    }
+
+    TemplateArgument Arg = TemplateArgs(T->getDepth(), T->getIndex());
+
+    if (T->isParameterPack()) {
+      assert(Arg.getKind() == TemplateArgument::Pack &&
+             "Missing argument pack");
+
+      if (getSema().ArgumentPackSubstitutionIndex == -1) {
+        // We have the template argument pack, but we're not expanding the
+        // enclosing pack expansion yet. Just save the template argument
+        // pack for later substitution.
+        QualType Result
+          = getSema().Context.getSubstTemplateTypeParmPackType(T, Arg);
+        SubstTemplateTypeParmPackTypeLoc NewTL
+          = TLB.push<SubstTemplateTypeParmPackTypeLoc>(Result);
+        NewTL.setNameLoc(TL.getNameLoc());
+        return Result;
+      }
+
+      Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
+    }
+
+    assert(Arg.getKind() == TemplateArgument::Type &&
+           "Template argument kind mismatch");
+
+    QualType Replacement = Arg.getAsType();
+
+    // TODO: only do this uniquing once, at the start of instantiation.
+    QualType Result
+      = getSema().Context.getSubstTemplateTypeParmType(T, Replacement);
+    SubstTemplateTypeParmTypeLoc NewTL
+      = TLB.push<SubstTemplateTypeParmTypeLoc>(Result);
+    NewTL.setNameLoc(TL.getNameLoc());
+    return Result;
+  }
+
+  // The template type parameter comes from an inner template (e.g.,
+  // the template parameter list of a member template inside the
+  // template we are instantiating). Create a new template type
+  // parameter with the template "level" reduced by one.
+  TemplateTypeParmDecl *NewTTPDecl = nullptr;
+  if (TemplateTypeParmDecl *OldTTPDecl = T->getDecl())
+    NewTTPDecl = cast_or_null<TemplateTypeParmDecl>(
+                                  TransformDecl(TL.getNameLoc(), OldTTPDecl));
+
+  QualType Result = getSema().Context.getTemplateTypeParmType(
+      T->getDepth() - TemplateArgs.getNumSubstitutedLevels(), T->getIndex(),
+      T->isParameterPack(), NewTTPDecl);
+  TemplateTypeParmTypeLoc NewTL = TLB.push<TemplateTypeParmTypeLoc>(Result);
+  NewTL.setNameLoc(TL.getNameLoc());
+  return Result;
+}
+
+QualType
+TemplateInstantiator::TransformSubstTemplateTypeParmPackType(
+                                                            TypeLocBuilder &TLB,
+                                         SubstTemplateTypeParmPackTypeLoc TL) {
+  if (getSema().ArgumentPackSubstitutionIndex == -1) {
+    // We aren't expanding the parameter pack, so just return ourselves.
+    SubstTemplateTypeParmPackTypeLoc NewTL
+      = TLB.push<SubstTemplateTypeParmPackTypeLoc>(TL.getType());
+    NewTL.setNameLoc(TL.getNameLoc());
+    return TL.getType();
+  }
+
+  TemplateArgument Arg = TL.getTypePtr()->getArgumentPack();
+  Arg = getPackSubstitutedTemplateArgument(getSema(), Arg);
+  QualType Result = Arg.getAsType();
+
+  Result = getSema().Context.getSubstTemplateTypeParmType(
+                                      TL.getTypePtr()->getReplacedParameter(),
+                                                          Result);
+  SubstTemplateTypeParmTypeLoc NewTL
+    = TLB.push<SubstTemplateTypeParmTypeLoc>(Result);
+  NewTL.setNameLoc(TL.getNameLoc());
+  return Result;
+}
+
+/// Perform substitution on the type T with a given set of template
+/// arguments.
+///
+/// This routine substitutes the given template arguments into the
+/// type T and produces the instantiated type.
+///
+/// \param T the type into which the template arguments will be
+/// substituted. If this type is not dependent, it will be returned
+/// immediately.
+///
+/// \param Args the template arguments that will be
+/// substituted for the top-level template parameters within T.
+///
+/// \param Loc the location in the source code where this substitution
+/// is being performed. It will typically be the location of the
+/// declarator (if we're instantiating the type of some declaration)
+/// or the location of the type in the source code (if, e.g., we're
+/// instantiating the type of a cast expression).
+///
+/// \param Entity the name of the entity associated with a declaration
+/// being instantiated (if any). May be empty to indicate that there
+/// is no such entity (if, e.g., this is a type that occurs as part of
+/// a cast expression) or that the entity has no name (e.g., an
+/// unnamed function parameter).
+///
+/// \param AllowDeducedTST Whether a DeducedTemplateSpecializationType is
+/// acceptable as the top level type of the result.
+///
+/// \returns If the instantiation succeeds, the instantiated
+/// type. Otherwise, produces diagnostics and returns a NULL type.
+TypeSourceInfo *Sema::SubstType(TypeSourceInfo *T,
+                                const MultiLevelTemplateArgumentList &Args,
+                                SourceLocation Loc,
+                                DeclarationName Entity,
+                                bool AllowDeducedTST) {
+  assert(!CodeSynthesisContexts.empty() &&
+         "Cannot perform an instantiation without some context on the "
+         "instantiation stack");
+
+  if (!T->getType()->isInstantiationDependentType() &&
+      !T->getType()->isVariablyModifiedType())
+    return T;
+
+  TemplateInstantiator Instantiator(*this, Args, Loc, Entity);
+  return AllowDeducedTST ? Instantiator.TransformTypeWithDeducedTST(T)
+                         : Instantiator.TransformType(T);
+}
+
+TypeSourceInfo *Sema::SubstType(TypeLoc TL,
+                                const MultiLevelTemplateArgumentList &Args,
+                                SourceLocation Loc,
+                                DeclarationName Entity) {
+  assert(!CodeSynthesisContexts.empty() &&
+         "Cannot perform an instantiation without some context on the "
+         "instantiation stack");
+
+  if (TL.getType().isNull())
+    return nullptr;
+
+  if (!TL.getType()->isInstantiationDependentType() &&
+      !TL.getType()->isVariablyModifiedType()) {
+    // FIXME: Make a copy of the TypeLoc data here, so that we can
+    // return a new TypeSourceInfo. Inefficient!
+    TypeLocBuilder TLB;
+    TLB.pushFullCopy(TL);
+    return TLB.getTypeSourceInfo(Context, TL.getType());
+  }
+
+  TemplateInstantiator Instantiator(*this, Args, Loc, Entity);
+  TypeLocBuilder TLB;
+  TLB.reserve(TL.getFullDataSize());
+  QualType Result = Instantiator.TransformType(TLB, TL);
+  if (Result.isNull())
+    return nullptr;
+
+  return TLB.getTypeSourceInfo(Context, Result);
+}
+
+/// Deprecated form of the above.
+QualType Sema::SubstType(QualType T,
+                         const MultiLevelTemplateArgumentList &TemplateArgs,
+                         SourceLocation Loc, DeclarationName Entity) {
+  assert(!CodeSynthesisContexts.empty() &&
+         "Cannot perform an instantiation without some context on the "
+         "instantiation stack");
+
+  // If T is not a dependent type or a variably-modified type, there
+  // is nothing to do.
+  if (!T->isInstantiationDependentType() && !T->isVariablyModifiedType())
+    return T;
+
+  TemplateInstantiator Instantiator(*this, TemplateArgs, Loc, Entity);
+  return Instantiator.TransformType(T);
+}
+
+static bool NeedsInstantiationAsFunctionType(TypeSourceInfo *T) {
+  if (T->getType()->isInstantiationDependentType() ||
+      T->getType()->isVariablyModifiedType())
+    return true;
+
+  TypeLoc TL = T->getTypeLoc().IgnoreParens();
+  if (!TL.getAs<FunctionProtoTypeLoc>())
+    return false;
+
+  FunctionProtoTypeLoc FP = TL.castAs<FunctionProtoTypeLoc>();
+  for (ParmVarDecl *P : FP.getParams()) {
+    // This must be synthesized from a typedef.
+    if (!P) continue;
+
+    // If there are any parameters, a new TypeSourceInfo that refers to the
+    // instantiated parameters must be built.
+    return true;
+  }
+
+  return false;
+}
+
+/// A form of SubstType intended specifically for instantiating the
+/// type of a FunctionDecl.  Its purpose is solely to force the
+/// instantiation of default-argument expressions and to avoid
+/// instantiating an exception-specification.
+TypeSourceInfo *Sema::SubstFunctionDeclType(TypeSourceInfo *T,
+                                const MultiLevelTemplateArgumentList &Args,
+                                SourceLocation Loc,
+                                DeclarationName Entity,
+                                CXXRecordDecl *ThisContext,
+                                Qualifiers ThisTypeQuals) {
+  assert(!CodeSynthesisContexts.empty() &&
+         "Cannot perform an instantiation without some context on the "
+         "instantiation stack");
+
+  if (!NeedsInstantiationAsFunctionType(T))
+    return T;
+
+  TemplateInstantiator Instantiator(*this, Args, Loc, Entity);
+
+  TypeLocBuilder TLB;
+
+  TypeLoc TL = T->getTypeLoc();
+  TLB.reserve(TL.getFullDataSize());
+
+  QualType Result;
+
+  if (FunctionProtoTypeLoc Proto =
+          TL.IgnoreParens().getAs<FunctionProtoTypeLoc>()) {
+    // Instantiate the type, other than its exception specification. The
+    // exception specification is instantiated in InitFunctionInstantiation
+    // once we've built the FunctionDecl.
+    // FIXME: Set the exception specification to EST_Uninstantiated here,
+    // instead of rebuilding the function type again later.
+    Result = Instantiator.TransformFunctionProtoType(
+        TLB, Proto, ThisContext, ThisTypeQuals,
+        [](FunctionProtoType::ExceptionSpecInfo &ESI,
+           bool &Changed) { return false; });
+  } else {
+    Result = Instantiator.TransformType(TLB, TL);
+  }
+  if (Result.isNull())
+    return nullptr;
+
+  return TLB.getTypeSourceInfo(Context, Result);
+}
+
+bool Sema::SubstExceptionSpec(SourceLocation Loc,
+                              FunctionProtoType::ExceptionSpecInfo &ESI,
+                              SmallVectorImpl<QualType> &ExceptionStorage,
+                              const MultiLevelTemplateArgumentList &Args) {
+  assert(ESI.Type != EST_Uninstantiated);
+
+  bool Changed = false;
+  TemplateInstantiator Instantiator(*this, Args, Loc, DeclarationName());
+  return Instantiator.TransformExceptionSpec(Loc, ESI, ExceptionStorage,
+                                             Changed);
+}
+
+void Sema::SubstExceptionSpec(FunctionDecl *New, const FunctionProtoType *Proto,
+                              const MultiLevelTemplateArgumentList &Args) {
+  FunctionProtoType::ExceptionSpecInfo ESI =
+      Proto->getExtProtoInfo().ExceptionSpec;
+
+  SmallVector<QualType, 4> ExceptionStorage;
+  if (SubstExceptionSpec(New->getTypeSourceInfo()->getTypeLoc().getEndLoc(),
+                         ESI, ExceptionStorage, Args))
+    // On error, recover by dropping the exception specification.
+    ESI.Type = EST_None;
+
+  UpdateExceptionSpec(New, ESI);
+}
+
+ParmVarDecl *Sema::SubstParmVarDecl(ParmVarDecl *OldParm,
+                            const MultiLevelTemplateArgumentList &TemplateArgs,
+                                    int indexAdjustment,
+                                    Optional<unsigned> NumExpansions,
+                                    bool ExpectParameterPack) {
+  TypeSourceInfo *OldDI = OldParm->getTypeSourceInfo();
+  TypeSourceInfo *NewDI = nullptr;
+
+  TypeLoc OldTL = OldDI->getTypeLoc();
+  if (PackExpansionTypeLoc ExpansionTL = OldTL.getAs<PackExpansionTypeLoc>()) {
+
+    // We have a function parameter pack. Substitute into the pattern of the
+    // expansion.
+    NewDI = SubstType(ExpansionTL.getPatternLoc(), TemplateArgs,
+                      OldParm->getLocation(), OldParm->getDeclName());
+    if (!NewDI)
+      return nullptr;
+
+    if (NewDI->getType()->containsUnexpandedParameterPack()) {
+      // We still have unexpanded parameter packs, which means that
+      // our function parameter is still a function parameter pack.
+      // Therefore, make its type a pack expansion type.
+      NewDI = CheckPackExpansion(NewDI, ExpansionTL.getEllipsisLoc(),
+                                 NumExpansions);
+    } else if (ExpectParameterPack) {
+      // We expected to get a parameter pack but didn't (because the type
+      // itself is not a pack expansion type), so complain. This can occur when
+      // the substitution goes through an alias template that "loses" the
+      // pack expansion.
+      Diag(OldParm->getLocation(),
+           diag::err_function_parameter_pack_without_parameter_packs)
+        << NewDI->getType();
+      return nullptr;
+    }
+  } else {
+    NewDI = SubstType(OldDI, TemplateArgs, OldParm->getLocation(),
+                      OldParm->getDeclName());
+  }
+
+  if (!NewDI)
+    return nullptr;
+
+  if (NewDI->getType()->isVoidType()) {
+    Diag(OldParm->getLocation(), diag::err_param_with_void_type);
+    return nullptr;
+  }
+
+  ParmVarDecl *NewParm = CheckParameter(Context.getTranslationUnitDecl(),
+                                        OldParm->getInnerLocStart(),
+                                        OldParm->getLocation(),
+                                        OldParm->getIdentifier(),
+                                        NewDI->getType(), NewDI,
+                                        OldParm->getStorageClass());
+  if (!NewParm)
+    return nullptr;
+
+  // Mark the (new) default argument as uninstantiated (if any).
+  if (OldParm->hasUninstantiatedDefaultArg()) {
+    Expr *Arg = OldParm->getUninstantiatedDefaultArg();
+    NewParm->setUninstantiatedDefaultArg(Arg);
+  } else if (OldParm->hasUnparsedDefaultArg()) {
+    NewParm->setUnparsedDefaultArg();
+    UnparsedDefaultArgInstantiations[OldParm].push_back(NewParm);
+  } else if (Expr *Arg = OldParm->getDefaultArg()) {
+    FunctionDecl *OwningFunc = cast<FunctionDecl>(OldParm->getDeclContext());
+    if (OwningFunc->isLexicallyWithinFunctionOrMethod()) {
+      // Instantiate default arguments for methods of local classes (DR1484)
+      // and non-defining declarations.
+      Sema::ContextRAII SavedContext(*this, OwningFunc);
+      LocalInstantiationScope Local(*this, true);
+      ExprResult NewArg = SubstExpr(Arg, TemplateArgs);
+      if (NewArg.isUsable()) {
+        // It would be nice if we still had this.
+        SourceLocation EqualLoc = NewArg.get()->getBeginLoc();
+        SetParamDefaultArgument(NewParm, NewArg.get(), EqualLoc);
+      }
+    } else {
+      // FIXME: if we non-lazily instantiated non-dependent default args for
+      // non-dependent parameter types we could remove a bunch of duplicate
+      // conversion warnings for such arguments.
+      NewParm->setUninstantiatedDefaultArg(Arg);
+    }
+  }
+
+  NewParm->setHasInheritedDefaultArg(OldParm->hasInheritedDefaultArg());
+
+  if (OldParm->isParameterPack() && !NewParm->isParameterPack()) {
+    // Add the new parameter to the instantiated parameter pack.
+    CurrentInstantiationScope->InstantiatedLocalPackArg(OldParm, NewParm);
+  } else {
+    // Introduce an Old -> New mapping
+    CurrentInstantiationScope->InstantiatedLocal(OldParm, NewParm);
+  }
+
+  // FIXME: OldParm may come from a FunctionProtoType, in which case CurContext
+  // can be anything, is this right ?
+  NewParm->setDeclContext(CurContext);
+
+  NewParm->setScopeInfo(OldParm->getFunctionScopeDepth(),
+                        OldParm->getFunctionScopeIndex() + indexAdjustment);
+
+  InstantiateAttrs(TemplateArgs, OldParm, NewParm);
+
+  return NewParm;
+}
+
+/// Substitute the given template arguments into the given set of
+/// parameters, producing the set of parameter types that would be generated
+/// from such a substitution.
+bool Sema::SubstParmTypes(
+    SourceLocation Loc, ArrayRef<ParmVarDecl *> Params,
+    const FunctionProtoType::ExtParameterInfo *ExtParamInfos,
+    const MultiLevelTemplateArgumentList &TemplateArgs,
+    SmallVectorImpl<QualType> &ParamTypes,
+    SmallVectorImpl<ParmVarDecl *> *OutParams,
+    ExtParameterInfoBuilder &ParamInfos) {
+  assert(!CodeSynthesisContexts.empty() &&
+         "Cannot perform an instantiation without some context on the "
+         "instantiation stack");
+
+  TemplateInstantiator Instantiator(*this, TemplateArgs, Loc,
+                                    DeclarationName());
+  return Instantiator.TransformFunctionTypeParams(
+      Loc, Params, nullptr, ExtParamInfos, ParamTypes, OutParams, ParamInfos);
+}
+
+/// Perform substitution on the base class specifiers of the
+/// given class template specialization.
+///
+/// Produces a diagnostic and returns true on error, returns false and
+/// attaches the instantiated base classes to the class template
+/// specialization if successful.
+bool
+Sema::SubstBaseSpecifiers(CXXRecordDecl *Instantiation,
+                          CXXRecordDecl *Pattern,
+                          const MultiLevelTemplateArgumentList &TemplateArgs) {
+  bool Invalid = false;
+  SmallVector<CXXBaseSpecifier*, 4> InstantiatedBases;
+  for (const auto &Base : Pattern->bases()) {
+    if (!Base.getType()->isDependentType()) {
+      if (const CXXRecordDecl *RD = Base.getType()->getAsCXXRecordDecl()) {
+        if (RD->isInvalidDecl())
+          Instantiation->setInvalidDecl();
+      }
+      InstantiatedBases.push_back(new (Context) CXXBaseSpecifier(Base));
+      continue;
+    }
+
+    SourceLocation EllipsisLoc;
+    TypeSourceInfo *BaseTypeLoc;
+    if (Base.isPackExpansion()) {
+      // This is a pack expansion. See whether we should expand it now, or
+      // wait until later.
+      SmallVector<UnexpandedParameterPack, 2> Unexpanded;
+      collectUnexpandedParameterPacks(Base.getTypeSourceInfo()->getTypeLoc(),
+                                      Unexpanded);
+      bool ShouldExpand = false;
+      bool RetainExpansion = false;
+      Optional<unsigned> NumExpansions;
+      if (CheckParameterPacksForExpansion(Base.getEllipsisLoc(),
+                                          Base.getSourceRange(),
+                                          Unexpanded,
+                                          TemplateArgs, ShouldExpand,
+                                          RetainExpansion,
+                                          NumExpansions)) {
+        Invalid = true;
+        continue;
+      }
+
+      // If we should expand this pack expansion now, do so.
+      if (ShouldExpand) {
+        for (unsigned I = 0; I != *NumExpansions; ++I) {
+            Sema::ArgumentPackSubstitutionIndexRAII SubstIndex(*this, I);
+
+          TypeSourceInfo *BaseTypeLoc = SubstType(Base.getTypeSourceInfo(),
+                                                  TemplateArgs,
+                                              Base.getSourceRange().getBegin(),
+                                                  DeclarationName());
+          if (!BaseTypeLoc) {
+            Invalid = true;
+            continue;
+          }
+
+          if (CXXBaseSpecifier *InstantiatedBase
+                = CheckBaseSpecifier(Instantiation,
+                                     Base.getSourceRange(),
+                                     Base.isVirtual(),
+                                     Base.getAccessSpecifierAsWritten(),
+                                     BaseTypeLoc,
+                                     SourceLocation()))
+            InstantiatedBases.push_back(InstantiatedBase);
+          else
+            Invalid = true;
+        }
+
+        continue;
+      }
+
+      // The resulting base specifier will (still) be a pack expansion.
+      EllipsisLoc = Base.getEllipsisLoc();
+      Sema::ArgumentPackSubstitutionIndexRAII SubstIndex(*this, -1);
+      BaseTypeLoc = SubstType(Base.getTypeSourceInfo(),
+                              TemplateArgs,
+                              Base.getSourceRange().getBegin(),
+                              DeclarationName());
+    } else {
+      BaseTypeLoc = SubstType(Base.getTypeSourceInfo(),
+                              TemplateArgs,
+                              Base.getSourceRange().getBegin(),
+                              DeclarationName());
+    }
+
+    if (!BaseTypeLoc) {
+      Invalid = true;
+      continue;
+    }
+
+    if (CXXBaseSpecifier *InstantiatedBase
+          = CheckBaseSpecifier(Instantiation,
+                               Base.getSourceRange(),
+                               Base.isVirtual(),
+                               Base.getAccessSpecifierAsWritten(),
+                               BaseTypeLoc,
+                               EllipsisLoc))
+      InstantiatedBases.push_back(InstantiatedBase);
+    else
+      Invalid = true;
+  }
+
+  if (!Invalid && AttachBaseSpecifiers(Instantiation, InstantiatedBases))
+    Invalid = true;
+
+  return Invalid;
+}
+
+// Defined via #include from SemaTemplateInstantiateDecl.cpp
+namespace clang {
+  namespace sema {
+    Attr *instantiateTemplateAttribute(const Attr *At, ASTContext &C, Sema &S,
+                            const MultiLevelTemplateArgumentList &TemplateArgs);
+    Attr *instantiateTemplateAttributeForDecl(
+        const Attr *At, ASTContext &C, Sema &S,
+        const MultiLevelTemplateArgumentList &TemplateArgs);
+  }
+}
+
+/// Instantiate the definition of a class from a given pattern.
+///
+/// \param PointOfInstantiation The point of instantiation within the
+/// source code.
+///
+/// \param Instantiation is the declaration whose definition is being
+/// instantiated. This will be either a class template specialization
+/// or a member class of a class template specialization.
+///
+/// \param Pattern is the pattern from which the instantiation
+/// occurs. This will be either the declaration of a class template or
+/// the declaration of a member class of a class template.
+///
+/// \param TemplateArgs The template arguments to be substituted into
+/// the pattern.
+///
+/// \param TSK the kind of implicit or explicit instantiation to perform.
+///
+/// \param Complain whether to complain if the class cannot be instantiated due
+/// to the lack of a definition.
+///
+/// \returns true if an error occurred, false otherwise.
+bool
+Sema::InstantiateClass(SourceLocation PointOfInstantiation,
+                       CXXRecordDecl *Instantiation, CXXRecordDecl *Pattern,
+                       const MultiLevelTemplateArgumentList &TemplateArgs,
+                       TemplateSpecializationKind TSK,
+                       bool Complain) {
+  CXXRecordDecl *PatternDef
+    = cast_or_null<CXXRecordDecl>(Pattern->getDefinition());
+  if (DiagnoseUninstantiableTemplate(PointOfInstantiation, Instantiation,
+                                Instantiation->getInstantiatedFromMemberClass(),
+                                     Pattern, PatternDef, TSK, Complain))
+    return true;
+
+  llvm::TimeTraceScope TimeScope("InstantiateClass", [&]() {
+    std::string Name;
+    llvm::raw_string_ostream OS(Name);
+    Instantiation->getNameForDiagnostic(OS, getPrintingPolicy(),
+                                        /*Qualified=*/true);
+    return Name;
+  });
+
+  Pattern = PatternDef;
+
+  // Record the point of instantiation.
+  if (MemberSpecializationInfo *MSInfo
+        = Instantiation->getMemberSpecializationInfo()) {
+    MSInfo->setTemplateSpecializationKind(TSK);
+    MSInfo->setPointOfInstantiation(PointOfInstantiation);
+  } else if (ClassTemplateSpecializationDecl *Spec
+        = dyn_cast<ClassTemplateSpecializationDecl>(Instantiation)) {
+    Spec->setTemplateSpecializationKind(TSK);
+    Spec->setPointOfInstantiation(PointOfInstantiation);
+  }
+
+  InstantiatingTemplate Inst(*this, PointOfInstantiation, Instantiation);
+  if (Inst.isInvalid())
+    return true;
+  assert(!Inst.isAlreadyInstantiating() && "should have been caught by caller");
+  PrettyDeclStackTraceEntry CrashInfo(Context, Instantiation, SourceLocation(),
+                                      "instantiating class definition");
+
+  // Enter the scope of this instantiation. We don't use
+  // PushDeclContext because we don't have a scope.
+  ContextRAII SavedContext(*this, Instantiation);
+  EnterExpressionEvaluationContext EvalContext(
+      *this, Sema::ExpressionEvaluationContext::PotentiallyEvaluated);
+
+  // If this is an instantiation of a local class, merge this local
+  // instantiation scope with the enclosing scope. Otherwise, every
+  // instantiation of a class has its own local instantiation scope.
+  bool MergeWithParentScope = !Instantiation->isDefinedOutsideFunctionOrMethod();
+  LocalInstantiationScope Scope(*this, MergeWithParentScope);
+
+  // Some class state isn't processed immediately but delayed till class
+  // instantiation completes. We may not be ready to handle any delayed state
+  // already on the stack as it might correspond to a different class, so save
+  // it now and put it back later.
+  SavePendingParsedClassStateRAII SavedPendingParsedClassState(*this);
+
+  // Pull attributes from the pattern onto the instantiation.
+  InstantiateAttrs(TemplateArgs, Pattern, Instantiation);
+
+  // Start the definition of this instantiation.
+  Instantiation->startDefinition();
+
+  // The instantiation is visible here, even if it was first declared in an
+  // unimported module.
+  Instantiation->setVisibleDespiteOwningModule();
+
+  // FIXME: This loses the as-written tag kind for an explicit instantiation.
+  Instantiation->setTagKind(Pattern->getTagKind());
+
+  // Do substitution on the base class specifiers.
+  if (SubstBaseSpecifiers(Instantiation, Pattern, TemplateArgs))
+    Instantiation->setInvalidDecl();
+
+  TemplateDeclInstantiator Instantiator(*this, Instantiation, TemplateArgs);
+  SmallVector<Decl*, 4> Fields;
+  // Delay instantiation of late parsed attributes.
+  LateInstantiatedAttrVec LateAttrs;
+  Instantiator.enableLateAttributeInstantiation(&LateAttrs);
+
+  bool MightHaveConstexprVirtualFunctions = false;
+  for (auto *Member : Pattern->decls()) {
+    // Don't instantiate members not belonging in this semantic context.
+    // e.g. for:
+    // @code
+    //    template <int i> class A {
+    //      class B *g;
+    //    };
+    // @endcode
+    // 'class B' has the template as lexical context but semantically it is
+    // introduced in namespace scope.
+    if (Member->getDeclContext() != Pattern)
+      continue;
+
+    // BlockDecls can appear in a default-member-initializer. They must be the
+    // child of a BlockExpr, so we only know how to instantiate them from there.
+    if (isa<BlockDecl>(Member))
+      continue;
+
+    if (Member->isInvalidDecl()) {
+      Instantiation->setInvalidDecl();
+      continue;
+    }
+
+    Decl *NewMember = Instantiator.Visit(Member);
+    if (NewMember) {
+      if (FieldDecl *Field = dyn_cast<FieldDecl>(NewMember)) {
+        Fields.push_back(Field);
+      } else if (EnumDecl *Enum = dyn_cast<EnumDecl>(NewMember)) {
+        // C++11 [temp.inst]p1: The implicit instantiation of a class template
+        // specialization causes the implicit instantiation of the definitions
+        // of unscoped member enumerations.
+        // Record a point of instantiation for this implicit instantiation.
+        if (TSK == TSK_ImplicitInstantiation && !Enum->isScoped() &&
+            Enum->isCompleteDefinition()) {
+          MemberSpecializationInfo *MSInfo =Enum->getMemberSpecializationInfo();
+          assert(MSInfo && "no spec info for member enum specialization");
+          MSInfo->setTemplateSpecializationKind(TSK_ImplicitInstantiation);
+          MSInfo->setPointOfInstantiation(PointOfInstantiation);
+        }
+      } else if (StaticAssertDecl *SA = dyn_cast<StaticAssertDecl>(NewMember)) {
+        if (SA->isFailed()) {
+          // A static_assert failed. Bail out; instantiating this
+          // class is probably not meaningful.
+          Instantiation->setInvalidDecl();
+          break;
+        }
+      } else if (CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(NewMember)) {
+        if (MD->isConstexpr() && !MD->getFriendObjectKind() &&
+            (MD->isVirtualAsWritten() || Instantiation->getNumBases()))
+          MightHaveConstexprVirtualFunctions = true;
+      }
+
+      if (NewMember->isInvalidDecl())
+        Instantiation->setInvalidDecl();
+    } else {
+      // FIXME: Eventually, a NULL return will mean that one of the
+      // instantiations was a semantic disaster, and we'll want to mark the
+      // declaration invalid.
+      // For now, we expect to skip some members that we can't yet handle.
+    }
+  }
+
+  // Finish checking fields.
+  ActOnFields(nullptr, Instantiation->getLocation(), Instantiation, Fields,
+              SourceLocation(), SourceLocation(), ParsedAttributesView());
+  CheckCompletedCXXClass(Instantiation);
+
+  // Default arguments are parsed, if not instantiated. We can go instantiate
+  // default arg exprs for default constructors if necessary now.
+  ActOnFinishCXXNonNestedClass(Instantiation);
+
+  // Instantiate late parsed attributes, and attach them to their decls.
+  // See Sema::InstantiateAttrs
+  for (LateInstantiatedAttrVec::iterator I = LateAttrs.begin(),
+       E = LateAttrs.end(); I != E; ++I) {
+    assert(CurrentInstantiationScope == Instantiator.getStartingScope());
+    CurrentInstantiationScope = I->Scope;
+
+    // Allow 'this' within late-parsed attributes.
+    NamedDecl *ND = dyn_cast<NamedDecl>(I->NewDecl);
+    CXXRecordDecl *ThisContext =
+        dyn_cast_or_null<CXXRecordDecl>(ND->getDeclContext());
+    CXXThisScopeRAII ThisScope(*this, ThisContext, Qualifiers(),
+                               ND && ND->isCXXInstanceMember());
+
+    Attr *NewAttr =
+      instantiateTemplateAttribute(I->TmplAttr, Context, *this, TemplateArgs);
+    I->NewDecl->addAttr(NewAttr);
+    LocalInstantiationScope::deleteScopes(I->Scope,
+                                          Instantiator.getStartingScope());
+  }
+  Instantiator.disableLateAttributeInstantiation();
+  LateAttrs.clear();
+
+  ActOnFinishDelayedMemberInitializers(Instantiation);
+
+  // FIXME: We should do something similar for explicit instantiations so they
+  // end up in the right module.
+  if (TSK == TSK_ImplicitInstantiation) {
+    Instantiation->setLocation(Pattern->getLocation());
+    Instantiation->setLocStart(Pattern->getInnerLocStart());
+    Instantiation->setBraceRange(Pattern->getBraceRange());
+  }
+
+  if (!Instantiation->isInvalidDecl()) {
+    // Perform any dependent diagnostics from the pattern.
+    PerformDependentDiagnostics(Pattern, TemplateArgs);
+
+    // Instantiate any out-of-line class template partial
+    // specializations now.
+    for (TemplateDeclInstantiator::delayed_partial_spec_iterator
+              P = Instantiator.delayed_partial_spec_begin(),
+           PEnd = Instantiator.delayed_partial_spec_end();
+         P != PEnd; ++P) {
+      if (!Instantiator.InstantiateClassTemplatePartialSpecialization(
+              P->first, P->second)) {
+        Instantiation->setInvalidDecl();
+        break;
+      }
+    }
+
+    // Instantiate any out-of-line variable template partial
+    // specializations now.
+    for (TemplateDeclInstantiator::delayed_var_partial_spec_iterator
+              P = Instantiator.delayed_var_partial_spec_begin(),
+           PEnd = Instantiator.delayed_var_partial_spec_end();
+         P != PEnd; ++P) {
+      if (!Instantiator.InstantiateVarTemplatePartialSpecialization(
+              P->first, P->second)) {
+        Instantiation->setInvalidDecl();
+        break;
+      }
+    }
+  }
+
+  // Exit the scope of this instantiation.
+  SavedContext.pop();
+
+  if (!Instantiation->isInvalidDecl()) {
+    Consumer.HandleTagDeclDefinition(Instantiation);
+
+    // Always emit the vtable for an explicit instantiation definition
+    // of a polymorphic class template specialization. Otherwise, eagerly
+    // instantiate only constexpr virtual functions in preparation for their use
+    // in constant evaluation.
+    if (TSK == TSK_ExplicitInstantiationDefinition)
+      MarkVTableUsed(PointOfInstantiation, Instantiation, true);
+    else if (MightHaveConstexprVirtualFunctions)
+      MarkVirtualMembersReferenced(PointOfInstantiation, Instantiation,
+                                   /*ConstexprOnly*/ true);
+  }
+
+  return Instantiation->isInvalidDecl();
+}
+
+/// Instantiate the definition of an enum from a given pattern.
+///
+/// \param PointOfInstantiation The point of instantiation within the
+///        source code.
+/// \param Instantiation is the declaration whose definition is being
+///        instantiated. This will be a member enumeration of a class
+///        temploid specialization, or a local enumeration within a
+///        function temploid specialization.
+/// \param Pattern The templated declaration from which the instantiation
+///        occurs.
+/// \param TemplateArgs The template arguments to be substituted into
+///        the pattern.
+/// \param TSK The kind of implicit or explicit instantiation to perform.
+///
+/// \return \c true if an error occurred, \c false otherwise.
+bool Sema::InstantiateEnum(SourceLocation PointOfInstantiation,
+                           EnumDecl *Instantiation, EnumDecl *Pattern,
+                           const MultiLevelTemplateArgumentList &TemplateArgs,
+                           TemplateSpecializationKind TSK) {
+  EnumDecl *PatternDef = Pattern->getDefinition();
+  if (DiagnoseUninstantiableTemplate(PointOfInstantiation, Instantiation,
+                                 Instantiation->getInstantiatedFromMemberEnum(),
+                                     Pattern, PatternDef, TSK,/*Complain*/true))
+    return true;
+  Pattern = PatternDef;
+
+  // Record the point of instantiation.
+  if (MemberSpecializationInfo *MSInfo
+        = Instantiation->getMemberSpecializationInfo()) {
+    MSInfo->setTemplateSpecializationKind(TSK);
+    MSInfo->setPointOfInstantiation(PointOfInstantiation);
+  }
+
+  InstantiatingTemplate Inst(*this, PointOfInstantiation, Instantiation);
+  if (Inst.isInvalid())
+    return true;
+  if (Inst.isAlreadyInstantiating())
+    return false;
+  PrettyDeclStackTraceEntry CrashInfo(Context, Instantiation, SourceLocation(),
+                                      "instantiating enum definition");
+
+  // The instantiation is visible here, even if it was first declared in an
+  // unimported module.
+  Instantiation->setVisibleDespiteOwningModule();
+
+  // Enter the scope of this instantiation. We don't use
+  // PushDeclContext because we don't have a scope.
+  ContextRAII SavedContext(*this, Instantiation);
+  EnterExpressionEvaluationContext EvalContext(
+      *this, Sema::ExpressionEvaluationContext::PotentiallyEvaluated);
+
+  LocalInstantiationScope Scope(*this, /*MergeWithParentScope*/true);
+
+  // Pull attributes from the pattern onto the instantiation.
+  InstantiateAttrs(TemplateArgs, Pattern, Instantiation);
+
+  TemplateDeclInstantiator Instantiator(*this, Instantiation, TemplateArgs);
+  Instantiator.InstantiateEnumDefinition(Instantiation, Pattern);
+
+  // Exit the scope of this instantiation.
+  SavedContext.pop();
+
+  return Instantiation->isInvalidDecl();
+}
+
+
+/// Instantiate the definition of a field from the given pattern.
+///
+/// \param PointOfInstantiation The point of instantiation within the
+///        source code.
+/// \param Instantiation is the declaration whose definition is being
+///        instantiated. This will be a class of a class temploid
+///        specialization, or a local enumeration within a function temploid
+///        specialization.
+/// \param Pattern The templated declaration from which the instantiation
+///        occurs.
+/// \param TemplateArgs The template arguments to be substituted into
+///        the pattern.
+///
+/// \return \c true if an error occurred, \c false otherwise.
+bool Sema::InstantiateInClassInitializer(
+    SourceLocation PointOfInstantiation, FieldDecl *Instantiation,
+    FieldDecl *Pattern, const MultiLevelTemplateArgumentList &TemplateArgs) {
+  // If there is no initializer, we don't need to do anything.
+  if (!Pattern->hasInClassInitializer())
+    return false;
+
+  assert(Instantiation->getInClassInitStyle() ==
+             Pattern->getInClassInitStyle() &&
+         "pattern and instantiation disagree about init style");
+
+  // Error out if we haven't parsed the initializer of the pattern yet because
+  // we are waiting for the closing brace of the outer class.
+  Expr *OldInit = Pattern->getInClassInitializer();
+  if (!OldInit) {
+    RecordDecl *PatternRD = Pattern->getParent();
+    RecordDecl *OutermostClass = PatternRD->getOuterLexicalRecordContext();
+    Diag(PointOfInstantiation,
+         diag::err_in_class_initializer_not_yet_parsed)
+        << OutermostClass << Pattern;
+    Diag(Pattern->getEndLoc(), diag::note_in_class_initializer_not_yet_parsed);
+    Instantiation->setInvalidDecl();
+    return true;
+  }
+
+  InstantiatingTemplate Inst(*this, PointOfInstantiation, Instantiation);
+  if (Inst.isInvalid())
+    return true;
+  if (Inst.isAlreadyInstantiating()) {
+    // Error out if we hit an instantiation cycle for this initializer.
+    Diag(PointOfInstantiation, diag::err_in_class_initializer_cycle)
+      << Instantiation;
+    return true;
+  }
+  PrettyDeclStackTraceEntry CrashInfo(Context, Instantiation, SourceLocation(),
+                                      "instantiating default member init");
+
+  // Enter the scope of this instantiation. We don't use PushDeclContext because
+  // we don't have a scope.
+  ContextRAII SavedContext(*this, Instantiation->getParent());
+  EnterExpressionEvaluationContext EvalContext(
+      *this, Sema::ExpressionEvaluationContext::PotentiallyEvaluated);
+
+  LocalInstantiationScope Scope(*this, true);
+
+  // Instantiate the initializer.
+  ActOnStartCXXInClassMemberInitializer();
+  CXXThisScopeRAII ThisScope(*this, Instantiation->getParent(), Qualifiers());
+
+  ExprResult NewInit = SubstInitializer(OldInit, TemplateArgs,
+                                        /*CXXDirectInit=*/false);
+  Expr *Init = NewInit.get();
+  assert((!Init || !isa<ParenListExpr>(Init)) && "call-style init in class");
+  ActOnFinishCXXInClassMemberInitializer(
+      Instantiation, Init ? Init->getBeginLoc() : SourceLocation(), Init);
+
+  if (auto *L = getASTMutationListener())
+    L->DefaultMemberInitializerInstantiated(Instantiation);
+
+  // Return true if the in-class initializer is still missing.
+  return !Instantiation->getInClassInitializer();
+}
+
+namespace {
+  /// A partial specialization whose template arguments have matched
+  /// a given template-id.
+  struct PartialSpecMatchResult {
+    ClassTemplatePartialSpecializationDecl *Partial;
+    TemplateArgumentList *Args;
+  };
+}
+
+bool Sema::usesPartialOrExplicitSpecialization(
+    SourceLocation Loc, ClassTemplateSpecializationDecl *ClassTemplateSpec) {
+  if (ClassTemplateSpec->getTemplateSpecializationKind() ==
+      TSK_ExplicitSpecialization)
+    return true;
+
+  SmallVector<ClassTemplatePartialSpecializationDecl *, 4> PartialSpecs;
+  ClassTemplateSpec->getSpecializedTemplate()
+                   ->getPartialSpecializations(PartialSpecs);
+  for (unsigned I = 0, N = PartialSpecs.size(); I != N; ++I) {
+    TemplateDeductionInfo Info(Loc);
+    if (!DeduceTemplateArguments(PartialSpecs[I],
+                                 ClassTemplateSpec->getTemplateArgs(), Info))
+      return true;
+  }
+
+  return false;
+}
+
+/// Get the instantiation pattern to use to instantiate the definition of a
+/// given ClassTemplateSpecializationDecl (either the pattern of the primary
+/// template or of a partial specialization).
+static CXXRecordDecl *
+getPatternForClassTemplateSpecialization(
+    Sema &S, SourceLocation PointOfInstantiation,
+    ClassTemplateSpecializationDecl *ClassTemplateSpec,
+    TemplateSpecializationKind TSK, bool Complain) {
+  Sema::InstantiatingTemplate Inst(S, PointOfInstantiation, ClassTemplateSpec);
+  if (Inst.isInvalid() || Inst.isAlreadyInstantiating())
+    return nullptr;
+
+  llvm::PointerUnion<ClassTemplateDecl *,
+                     ClassTemplatePartialSpecializationDecl *>
+      Specialized = ClassTemplateSpec->getSpecializedTemplateOrPartial();
+  if (!Specialized.is<ClassTemplatePartialSpecializationDecl *>()) {
+    // Find best matching specialization.
+    ClassTemplateDecl *Template = ClassTemplateSpec->getSpecializedTemplate();
+
+    // C++ [temp.class.spec.match]p1:
+    //   When a class template is used in a context that requires an
+    //   instantiation of the class, it is necessary to determine
+    //   whether the instantiation is to be generated using the primary
+    //   template or one of the partial specializations. This is done by
+    //   matching the template arguments of the class template
+    //   specialization with the template argument lists of the partial
+    //   specializations.
+    typedef PartialSpecMatchResult MatchResult;
+    SmallVector<MatchResult, 4> Matched;
+    SmallVector<ClassTemplatePartialSpecializationDecl *, 4> PartialSpecs;
+    Template->getPartialSpecializations(PartialSpecs);
+    TemplateSpecCandidateSet FailedCandidates(PointOfInstantiation);
+    for (unsigned I = 0, N = PartialSpecs.size(); I != N; ++I) {
+      ClassTemplatePartialSpecializationDecl *Partial = PartialSpecs[I];
+      TemplateDeductionInfo Info(FailedCandidates.getLocation());
+      if (Sema::TemplateDeductionResult Result = S.DeduceTemplateArguments(
+              Partial, ClassTemplateSpec->getTemplateArgs(), Info)) {
+        // Store the failed-deduction information for use in diagnostics, later.
+        // TODO: Actually use the failed-deduction info?
+        FailedCandidates.addCandidate().set(
+            DeclAccessPair::make(Template, AS_public), Partial,
+            MakeDeductionFailureInfo(S.Context, Result, Info));
+        (void)Result;
+      } else {
+        Matched.push_back(PartialSpecMatchResult());
+        Matched.back().Partial = Partial;
+        Matched.back().Args = Info.take();
+      }
+    }
+
+    // If we're dealing with a member template where the template parameters
+    // have been instantiated, this provides the original template parameters
+    // from which the member template's parameters were instantiated.
+
+    if (Matched.size() >= 1) {
+      SmallVectorImpl<MatchResult>::iterator Best = Matched.begin();
+      if (Matched.size() == 1) {
+        //   -- If exactly one matching specialization is found, the
+        //      instantiation is generated from that specialization.
+        // We don't need to do anything for this.
+      } else {
+        //   -- If more than one matching specialization is found, the
+        //      partial order rules (14.5.4.2) are used to determine
+        //      whether one of the specializations is more specialized
+        //      than the others. If none of the specializations is more
+        //      specialized than all of the other matching
+        //      specializations, then the use of the class template is
+        //      ambiguous and the program is ill-formed.
+        for (SmallVectorImpl<MatchResult>::iterator P = Best + 1,
+                                                 PEnd = Matched.end();
+             P != PEnd; ++P) {
+          if (S.getMoreSpecializedPartialSpecialization(
+                  P->Partial, Best->Partial, PointOfInstantiation) ==
+              P->Partial)
+            Best = P;
+        }
+
+        // Determine if the best partial specialization is more specialized than
+        // the others.
+        bool Ambiguous = false;
+        for (SmallVectorImpl<MatchResult>::iterator P = Matched.begin(),
+                                                 PEnd = Matched.end();
+             P != PEnd; ++P) {
+          if (P != Best && S.getMoreSpecializedPartialSpecialization(
+                               P->Partial, Best->Partial,
+                               PointOfInstantiation) != Best->Partial) {
+            Ambiguous = true;
+            break;
+          }
+        }
+
+        if (Ambiguous) {
+          // Partial ordering did not produce a clear winner. Complain.
+          Inst.Clear();
+          ClassTemplateSpec->setInvalidDecl();
+          S.Diag(PointOfInstantiation,
+                 diag::err_partial_spec_ordering_ambiguous)
+              << ClassTemplateSpec;
+
+          // Print the matching partial specializations.
+          for (SmallVectorImpl<MatchResult>::iterator P = Matched.begin(),
+                                                   PEnd = Matched.end();
+               P != PEnd; ++P)
+            S.Diag(P->Partial->getLocation(), diag::note_partial_spec_match)
+                << S.getTemplateArgumentBindingsText(
+                       P->Partial->getTemplateParameters(), *P->Args);
+
+          return nullptr;
+        }
+      }
+
+      ClassTemplateSpec->setInstantiationOf(Best->Partial, Best->Args);
+    } else {
+      //   -- If no matches are found, the instantiation is generated
+      //      from the primary template.
+    }
+  }
+
+  CXXRecordDecl *Pattern = nullptr;
+  Specialized = ClassTemplateSpec->getSpecializedTemplateOrPartial();
+  if (auto *PartialSpec =
+          Specialized.dyn_cast<ClassTemplatePartialSpecializationDecl *>()) {
+    // Instantiate using the best class template partial specialization.
+    while (PartialSpec->getInstantiatedFromMember()) {
+      // If we've found an explicit specialization of this class template,
+      // stop here and use that as the pattern.
+      if (PartialSpec->isMemberSpecialization())
+        break;
+
+      PartialSpec = PartialSpec->getInstantiatedFromMember();
+    }
+    Pattern = PartialSpec;
+  } else {
+    ClassTemplateDecl *Template = ClassTemplateSpec->getSpecializedTemplate();
+    while (Template->getInstantiatedFromMemberTemplate()) {
+      // If we've found an explicit specialization of this class template,
+      // stop here and use that as the pattern.
+      if (Template->isMemberSpecialization())
+        break;
+
+      Template = Template->getInstantiatedFromMemberTemplate();
+    }
+    Pattern = Template->getTemplatedDecl();
+  }
+
+  return Pattern;
+}
+
+bool Sema::InstantiateClassTemplateSpecialization(
+    SourceLocation PointOfInstantiation,
+    ClassTemplateSpecializationDecl *ClassTemplateSpec,
+    TemplateSpecializationKind TSK, bool Complain) {
+  // Perform the actual instantiation on the canonical declaration.
+  ClassTemplateSpec = cast<ClassTemplateSpecializationDecl>(
+      ClassTemplateSpec->getCanonicalDecl());
+  if (ClassTemplateSpec->isInvalidDecl())
+    return true;
+
+  CXXRecordDecl *Pattern = getPatternForClassTemplateSpecialization(
+      *this, PointOfInstantiation, ClassTemplateSpec, TSK, Complain);
+  if (!Pattern)
+    return true;
+
+  return InstantiateClass(PointOfInstantiation, ClassTemplateSpec, Pattern,
+                          getTemplateInstantiationArgs(ClassTemplateSpec), TSK,
+                          Complain);
+}
+
+/// Instantiates the definitions of all of the member
+/// of the given class, which is an instantiation of a class template
+/// or a member class of a template.
+void
+Sema::InstantiateClassMembers(SourceLocation PointOfInstantiation,
+                              CXXRecordDecl *Instantiation,
+                        const MultiLevelTemplateArgumentList &TemplateArgs,
+                              TemplateSpecializationKind TSK) {
+  // FIXME: We need to notify the ASTMutationListener that we did all of these
+  // things, in case we have an explicit instantiation definition in a PCM, a
+  // module, or preamble, and the declaration is in an imported AST.
+  assert(
+      (TSK == TSK_ExplicitInstantiationDefinition ||
+       TSK == TSK_ExplicitInstantiationDeclaration ||
+       (TSK == TSK_ImplicitInstantiation && Instantiation->isLocalClass())) &&
+      "Unexpected template specialization kind!");
+  for (auto *D : Instantiation->decls()) {
+    bool SuppressNew = false;
+    if (auto *Function = dyn_cast<FunctionDecl>(D)) {
+      if (FunctionDecl *Pattern =
+              Function->getInstantiatedFromMemberFunction()) {
+
+        if (Function->hasAttr<ExcludeFromExplicitInstantiationAttr>())
+          continue;
+
+        MemberSpecializationInfo *MSInfo =
+            Function->getMemberSpecializationInfo();
+        assert(MSInfo && "No member specialization information?");
+        if (MSInfo->getTemplateSpecializationKind()
+                                                 == TSK_ExplicitSpecialization)
+          continue;
+
+        if (CheckSpecializationInstantiationRedecl(PointOfInstantiation, TSK,
+                                                   Function,
+                                        MSInfo->getTemplateSpecializationKind(),
+                                              MSInfo->getPointOfInstantiation(),
+                                                   SuppressNew) ||
+            SuppressNew)
+          continue;
+
+        // C++11 [temp.explicit]p8:
+        //   An explicit instantiation definition that names a class template
+        //   specialization explicitly instantiates the class template
+        //   specialization and is only an explicit instantiation definition
+        //   of members whose definition is visible at the point of
+        //   instantiation.
+        if (TSK == TSK_ExplicitInstantiationDefinition && !Pattern->isDefined())
+          continue;
+
+        Function->setTemplateSpecializationKind(TSK, PointOfInstantiation);
+
+        if (Function->isDefined()) {
+          // Let the ASTConsumer know that this function has been explicitly
+          // instantiated now, and its linkage might have changed.
+          Consumer.HandleTopLevelDecl(DeclGroupRef(Function));
+        } else if (TSK == TSK_ExplicitInstantiationDefinition) {
+          InstantiateFunctionDefinition(PointOfInstantiation, Function);
+        } else if (TSK == TSK_ImplicitInstantiation) {
+          PendingLocalImplicitInstantiations.push_back(
+              std::make_pair(Function, PointOfInstantiation));
+        }
+      }
+    } else if (auto *Var = dyn_cast<VarDecl>(D)) {
+      if (isa<VarTemplateSpecializationDecl>(Var))
+        continue;
+
+      if (Var->isStaticDataMember()) {
+        if (Var->hasAttr<ExcludeFromExplicitInstantiationAttr>())
+          continue;
+
+        MemberSpecializationInfo *MSInfo = Var->getMemberSpecializationInfo();
+        assert(MSInfo && "No member specialization information?");
+        if (MSInfo->getTemplateSpecializationKind()
+                                                 == TSK_ExplicitSpecialization)
+          continue;
+
+        if (CheckSpecializationInstantiationRedecl(PointOfInstantiation, TSK,
+                                                   Var,
+                                        MSInfo->getTemplateSpecializationKind(),
+                                              MSInfo->getPointOfInstantiation(),
+                                                   SuppressNew) ||
+            SuppressNew)
+          continue;
+
+        if (TSK == TSK_ExplicitInstantiationDefinition) {
+          // C++0x [temp.explicit]p8:
+          //   An explicit instantiation definition that names a class template
+          //   specialization explicitly instantiates the class template
+          //   specialization and is only an explicit instantiation definition
+          //   of members whose definition is visible at the point of
+          //   instantiation.
+          if (!Var->getInstantiatedFromStaticDataMember()->getDefinition())
+            continue;
+
+          Var->setTemplateSpecializationKind(TSK, PointOfInstantiation);
+          InstantiateVariableDefinition(PointOfInstantiation, Var);
+        } else {
+          Var->setTemplateSpecializationKind(TSK, PointOfInstantiation);
+        }
+      }
+    } else if (auto *Record = dyn_cast<CXXRecordDecl>(D)) {
+      if (Record->hasAttr<ExcludeFromExplicitInstantiationAttr>())
+        continue;
+
+      // Always skip the injected-class-name, along with any
+      // redeclarations of nested classes, since both would cause us
+      // to try to instantiate the members of a class twice.
+      // Skip closure types; they'll get instantiated when we instantiate
+      // the corresponding lambda-expression.
+      if (Record->isInjectedClassName() || Record->getPreviousDecl() ||
+          Record->isLambda())
+        continue;
+
+      MemberSpecializationInfo *MSInfo = Record->getMemberSpecializationInfo();
+      assert(MSInfo && "No member specialization information?");
+
+      if (MSInfo->getTemplateSpecializationKind()
+                                                == TSK_ExplicitSpecialization)
+        continue;
+
+      if (Context.getTargetInfo().getTriple().isOSWindows() &&
+          TSK == TSK_ExplicitInstantiationDeclaration) {
+        // On Windows, explicit instantiation decl of the outer class doesn't
+        // affect the inner class. Typically extern template declarations are
+        // used in combination with dll import/export annotations, but those
+        // are not propagated from the outer class templates to inner classes.
+        // Therefore, do not instantiate inner classes on this platform, so
+        // that users don't end up with undefined symbols during linking.
+        continue;
+      }
+
+      if (CheckSpecializationInstantiationRedecl(PointOfInstantiation, TSK,
+                                                 Record,
+                                        MSInfo->getTemplateSpecializationKind(),
+                                              MSInfo->getPointOfInstantiation(),
+                                                 SuppressNew) ||
+          SuppressNew)
+        continue;
+
+      CXXRecordDecl *Pattern = Record->getInstantiatedFromMemberClass();
+      assert(Pattern && "Missing instantiated-from-template information");
+
+      if (!Record->getDefinition()) {
+        if (!Pattern->getDefinition()) {
+          // C++0x [temp.explicit]p8:
+          //   An explicit instantiation definition that names a class template
+          //   specialization explicitly instantiates the class template
+          //   specialization and is only an explicit instantiation definition
+          //   of members whose definition is visible at the point of
+          //   instantiation.
+          if (TSK == TSK_ExplicitInstantiationDeclaration) {
+            MSInfo->setTemplateSpecializationKind(TSK);
+            MSInfo->setPointOfInstantiation(PointOfInstantiation);
+          }
+
+          continue;
+        }
+
+        InstantiateClass(PointOfInstantiation, Record, Pattern,
+                         TemplateArgs,
+                         TSK);
+      } else {
+        if (TSK == TSK_ExplicitInstantiationDefinition &&
+            Record->getTemplateSpecializationKind() ==
+                TSK_ExplicitInstantiationDeclaration) {
+          Record->setTemplateSpecializationKind(TSK);
+          MarkVTableUsed(PointOfInstantiation, Record, true);
+        }
+      }
+
+      Pattern = cast_or_null<CXXRecordDecl>(Record->getDefinition());
+      if (Pattern)
+        InstantiateClassMembers(PointOfInstantiation, Pattern, TemplateArgs,
+                                TSK);
+    } else if (auto *Enum = dyn_cast<EnumDecl>(D)) {
+      MemberSpecializationInfo *MSInfo = Enum->getMemberSpecializationInfo();
+      assert(MSInfo && "No member specialization information?");
+
+      if (MSInfo->getTemplateSpecializationKind()
+            == TSK_ExplicitSpecialization)
+        continue;
+
+      if (CheckSpecializationInstantiationRedecl(
+            PointOfInstantiation, TSK, Enum,
+            MSInfo->getTemplateSpecializationKind(),
+            MSInfo->getPointOfInstantiation(), SuppressNew) ||
+          SuppressNew)
+        continue;
+
+      if (Enum->getDefinition())
+        continue;
+
+      EnumDecl *Pattern = Enum->getTemplateInstantiationPattern();
+      assert(Pattern && "Missing instantiated-from-template information");
+
+      if (TSK == TSK_ExplicitInstantiationDefinition) {
+        if (!Pattern->getDefinition())
+          continue;
+
+        InstantiateEnum(PointOfInstantiation, Enum, Pattern, TemplateArgs, TSK);
+      } else {
+        MSInfo->setTemplateSpecializationKind(TSK);
+        MSInfo->setPointOfInstantiation(PointOfInstantiation);
+      }
+    } else if (auto *Field = dyn_cast<FieldDecl>(D)) {
+      // No need to instantiate in-class initializers during explicit
+      // instantiation.
+      if (Field->hasInClassInitializer() && TSK == TSK_ImplicitInstantiation) {
+        CXXRecordDecl *ClassPattern =
+            Instantiation->getTemplateInstantiationPattern();
+        DeclContext::lookup_result Lookup =
+            ClassPattern->lookup(Field->getDeclName());
+        FieldDecl *Pattern = cast<FieldDecl>(Lookup.front());
+        InstantiateInClassInitializer(PointOfInstantiation, Field, Pattern,
+                                      TemplateArgs);
+      }
+    }
+  }
+}
+
+/// Instantiate the definitions of all of the members of the
+/// given class template specialization, which was named as part of an
+/// explicit instantiation.
+void
+Sema::InstantiateClassTemplateSpecializationMembers(
+                                           SourceLocation PointOfInstantiation,
+                            ClassTemplateSpecializationDecl *ClassTemplateSpec,
+                                               TemplateSpecializationKind TSK) {
+  // C++0x [temp.explicit]p7:
+  //   An explicit instantiation that names a class template
+  //   specialization is an explicit instantion of the same kind
+  //   (declaration or definition) of each of its members (not
+  //   including members inherited from base classes) that has not
+  //   been previously explicitly specialized in the translation unit
+  //   containing the explicit instantiation, except as described
+  //   below.
+  InstantiateClassMembers(PointOfInstantiation, ClassTemplateSpec,
+                          getTemplateInstantiationArgs(ClassTemplateSpec),
+                          TSK);
+}
+
+StmtResult
+Sema::SubstStmt(Stmt *S, const MultiLevelTemplateArgumentList &TemplateArgs) {
+  if (!S)
+    return S;
+
+  TemplateInstantiator Instantiator(*this, TemplateArgs,
+                                    SourceLocation(),
+                                    DeclarationName());
+  return Instantiator.TransformStmt(S);
+}
+
+ExprResult
+Sema::SubstExpr(Expr *E, const MultiLevelTemplateArgumentList &TemplateArgs) {
+  if (!E)
+    return E;
+
+  TemplateInstantiator Instantiator(*this, TemplateArgs,
+                                    SourceLocation(),
+                                    DeclarationName());
+  return Instantiator.TransformExpr(E);
+}
+
+ExprResult Sema::SubstInitializer(Expr *Init,
+                          const MultiLevelTemplateArgumentList &TemplateArgs,
+                          bool CXXDirectInit) {
+  TemplateInstantiator Instantiator(*this, TemplateArgs,
+                                    SourceLocation(),
+                                    DeclarationName());
+  return Instantiator.TransformInitializer(Init, CXXDirectInit);
+}
+
+bool Sema::SubstExprs(ArrayRef<Expr *> Exprs, bool IsCall,
+                      const MultiLevelTemplateArgumentList &TemplateArgs,
+                      SmallVectorImpl<Expr *> &Outputs) {
+  if (Exprs.empty())
+    return false;
+
+  TemplateInstantiator Instantiator(*this, TemplateArgs,
+                                    SourceLocation(),
+                                    DeclarationName());
+  return Instantiator.TransformExprs(Exprs.data(), Exprs.size(),
+                                     IsCall, Outputs);
+}
+
+NestedNameSpecifierLoc
+Sema::SubstNestedNameSpecifierLoc(NestedNameSpecifierLoc NNS,
+                        const MultiLevelTemplateArgumentList &TemplateArgs) {
+  if (!NNS)
+    return NestedNameSpecifierLoc();
+
+  TemplateInstantiator Instantiator(*this, TemplateArgs, NNS.getBeginLoc(),
+                                    DeclarationName());
+  return Instantiator.TransformNestedNameSpecifierLoc(NNS);
+}
+
+/// Do template substitution on declaration name info.
+DeclarationNameInfo
+Sema::SubstDeclarationNameInfo(const DeclarationNameInfo &NameInfo,
+                         const MultiLevelTemplateArgumentList &TemplateArgs) {
+  TemplateInstantiator Instantiator(*this, TemplateArgs, NameInfo.getLoc(),
+                                    NameInfo.getName());
+  return Instantiator.TransformDeclarationNameInfo(NameInfo);
+}
+
+TemplateName
+Sema::SubstTemplateName(NestedNameSpecifierLoc QualifierLoc,
+                        TemplateName Name, SourceLocation Loc,
+                        const MultiLevelTemplateArgumentList &TemplateArgs) {
+  TemplateInstantiator Instantiator(*this, TemplateArgs, Loc,
+                                    DeclarationName());
+  CXXScopeSpec SS;
+  SS.Adopt(QualifierLoc);
+  return Instantiator.TransformTemplateName(SS, Name, Loc);
+}
+
+bool Sema::Subst(const TemplateArgumentLoc *Args, unsigned NumArgs,
+                 TemplateArgumentListInfo &Result,
+                 const MultiLevelTemplateArgumentList &TemplateArgs) {
+  TemplateInstantiator Instantiator(*this, TemplateArgs, SourceLocation(),
+                                    DeclarationName());
+
+  return Instantiator.TransformTemplateArguments(Args, NumArgs, Result);
+}
+
+static const Decl *getCanonicalParmVarDecl(const Decl *D) {
+  // When storing ParmVarDecls in the local instantiation scope, we always
+  // want to use the ParmVarDecl from the canonical function declaration,
+  // since the map is then valid for any redeclaration or definition of that
+  // function.
+  if (const ParmVarDecl *PV = dyn_cast<ParmVarDecl>(D)) {
+    if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(PV->getDeclContext())) {
+      unsigned i = PV->getFunctionScopeIndex();
+      // This parameter might be from a freestanding function type within the
+      // function and isn't necessarily referring to one of FD's parameters.
+      if (i < FD->getNumParams() && FD->getParamDecl(i) == PV)
+        return FD->getCanonicalDecl()->getParamDecl(i);
+    }
+  }
+  return D;
+}
+
+
+llvm::PointerUnion<Decl *, LocalInstantiationScope::DeclArgumentPack *> *
+LocalInstantiationScope::findInstantiationOf(const Decl *D) {
+  D = getCanonicalParmVarDecl(D);
+  for (LocalInstantiationScope *Current = this; Current;
+       Current = Current->Outer) {
+
+    // Check if we found something within this scope.
+    const Decl *CheckD = D;
+    do {
+      LocalDeclsMap::iterator Found = Current->LocalDecls.find(CheckD);
+      if (Found != Current->LocalDecls.end())
+        return &Found->second;
+
+      // If this is a tag declaration, it's possible that we need to look for
+      // a previous declaration.
+      if (const TagDecl *Tag = dyn_cast<TagDecl>(CheckD))
+        CheckD = Tag->getPreviousDecl();
+      else
+        CheckD = nullptr;
+    } while (CheckD);
+
+    // If we aren't combined with our outer scope, we're done.
+    if (!Current->CombineWithOuterScope)
+      break;
+  }
+
+  // If we're performing a partial substitution during template argument
+  // deduction, we may not have values for template parameters yet.
+  if (isa<NonTypeTemplateParmDecl>(D) || isa<TemplateTypeParmDecl>(D) ||
+      isa<TemplateTemplateParmDecl>(D))
+    return nullptr;
+
+  // Local types referenced prior to definition may require instantiation.
+  if (const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(D))
+    if (RD->isLocalClass())
+      return nullptr;
+
+  // Enumeration types referenced prior to definition may appear as a result of
+  // error recovery.
+  if (isa<EnumDecl>(D))
+    return nullptr;
+
+  // If we didn't find the decl, then we either have a sema bug, or we have a
+  // forward reference to a label declaration.  Return null to indicate that
+  // we have an uninstantiated label.
+  assert(isa<LabelDecl>(D) && "declaration not instantiated in this scope");
+  return nullptr;
+}
+
+void LocalInstantiationScope::InstantiatedLocal(const Decl *D, Decl *Inst) {
+  D = getCanonicalParmVarDecl(D);
+  llvm::PointerUnion<Decl *, DeclArgumentPack *> &Stored = LocalDecls[D];
+  if (Stored.isNull()) {
+#ifndef NDEBUG
+    // It should not be present in any surrounding scope either.
+    LocalInstantiationScope *Current = this;
+    while (Current->CombineWithOuterScope && Current->Outer) {
+      Current = Current->Outer;
+      assert(Current->LocalDecls.find(D) == Current->LocalDecls.end() &&
+             "Instantiated local in inner and outer scopes");
+    }
+#endif
+    Stored = Inst;
+  } else if (DeclArgumentPack *Pack = Stored.dyn_cast<DeclArgumentPack *>()) {
+    Pack->push_back(cast<VarDecl>(Inst));
+  } else {
+    assert(Stored.get<Decl *>() == Inst && "Already instantiated this local");
+  }
+}
+
+void LocalInstantiationScope::InstantiatedLocalPackArg(const Decl *D,
+                                                       VarDecl *Inst) {
+  D = getCanonicalParmVarDecl(D);
+  DeclArgumentPack *Pack = LocalDecls[D].get<DeclArgumentPack *>();
+  Pack->push_back(Inst);
+}
+
+void LocalInstantiationScope::MakeInstantiatedLocalArgPack(const Decl *D) {
+#ifndef NDEBUG
+  // This should be the first time we've been told about this decl.
+  for (LocalInstantiationScope *Current = this;
+       Current && Current->CombineWithOuterScope; Current = Current->Outer)
+    assert(Current->LocalDecls.find(D) == Current->LocalDecls.end() &&
+           "Creating local pack after instantiation of local");
+#endif
+
+  D = getCanonicalParmVarDecl(D);
+  llvm::PointerUnion<Decl *, DeclArgumentPack *> &Stored = LocalDecls[D];
+  DeclArgumentPack *Pack = new DeclArgumentPack;
+  Stored = Pack;
+  ArgumentPacks.push_back(Pack);
+}
+
+void LocalInstantiationScope::SetPartiallySubstitutedPack(NamedDecl *Pack,
+                                          const TemplateArgument *ExplicitArgs,
+                                                    unsigned NumExplicitArgs) {
+  assert((!PartiallySubstitutedPack || PartiallySubstitutedPack == Pack) &&
+         "Already have a partially-substituted pack");
+  assert((!PartiallySubstitutedPack
+          || NumArgsInPartiallySubstitutedPack == NumExplicitArgs) &&
+         "Wrong number of arguments in partially-substituted pack");
+  PartiallySubstitutedPack = Pack;
+  ArgsInPartiallySubstitutedPack = ExplicitArgs;
+  NumArgsInPartiallySubstitutedPack = NumExplicitArgs;
+}
+
+NamedDecl *LocalInstantiationScope::getPartiallySubstitutedPack(
+                                         const TemplateArgument **ExplicitArgs,
+                                              unsigned *NumExplicitArgs) const {
+  if (ExplicitArgs)
+    *ExplicitArgs = nullptr;
+  if (NumExplicitArgs)
+    *NumExplicitArgs = 0;
+
+  for (const LocalInstantiationScope *Current = this; Current;
+       Current = Current->Outer) {
+    if (Current->PartiallySubstitutedPack) {
+      if (ExplicitArgs)
+        *ExplicitArgs = Current->ArgsInPartiallySubstitutedPack;
+      if (NumExplicitArgs)
+        *NumExplicitArgs = Current->NumArgsInPartiallySubstitutedPack;
+
+      return Current->PartiallySubstitutedPack;
+    }
+
+    if (!Current->CombineWithOuterScope)
+      break;
+  }
+
+  return nullptr;
+}