Merge branch 'master' of ssh://bitbucket.org/czan/honours

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diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp b/clang/lib/Sema/SemaTemplateDeduction.cpp
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+//===------- SemaTemplateDeduction.cpp - Template Argument Deduction ------===/
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//===----------------------------------------------------------------------===/
+//
+//  This file implements C++ template argument deduction.
+//
+//===----------------------------------------------------------------------===/
+
+#include "clang/Sema/Sema.h"
+#include "clang/Sema/DeclSpec.h"
+#include "clang/Sema/Template.h"
+#include "clang/Sema/TemplateDeduction.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/DeclObjC.h"
+#include "clang/AST/DeclTemplate.h"
+#include "clang/AST/StmtVisitor.h"
+#include "clang/AST/Expr.h"
+#include "clang/AST/ExprCXX.h"
+#include "llvm/ADT/SmallBitVector.h"
+#include "TreeTransform.h"
+#include <algorithm>
+
+namespace clang {
+  using namespace sema;
+
+  /// \brief Various flags that control template argument deduction.
+  ///
+  /// These flags can be bitwise-OR'd together.
+  enum TemplateDeductionFlags {
+    /// \brief No template argument deduction flags, which indicates the
+    /// strictest results for template argument deduction (as used for, e.g.,
+    /// matching class template partial specializations).
+    TDF_None = 0,
+    /// \brief Within template argument deduction from a function call, we are
+    /// matching with a parameter type for which the original parameter was
+    /// a reference.
+    TDF_ParamWithReferenceType = 0x1,
+    /// \brief Within template argument deduction from a function call, we
+    /// are matching in a case where we ignore cv-qualifiers.
+    TDF_IgnoreQualifiers = 0x02,
+    /// \brief Within template argument deduction from a function call,
+    /// we are matching in a case where we can perform template argument
+    /// deduction from a template-id of a derived class of the argument type.
+    TDF_DerivedClass = 0x04,
+    /// \brief Allow non-dependent types to differ, e.g., when performing
+    /// template argument deduction from a function call where conversions
+    /// may apply.
+    TDF_SkipNonDependent = 0x08,
+    /// \brief Whether we are performing template argument deduction for
+    /// parameters and arguments in a top-level template argument
+    TDF_TopLevelParameterTypeList = 0x10
+  };
+}
+
+using namespace clang;
+
+/// \brief Compare two APSInts, extending and switching the sign as
+/// necessary to compare their values regardless of underlying type.
+static bool hasSameExtendedValue(llvm::APSInt X, llvm::APSInt Y) {
+  if (Y.getBitWidth() > X.getBitWidth())
+    X = X.extend(Y.getBitWidth());
+  else if (Y.getBitWidth() < X.getBitWidth())
+    Y = Y.extend(X.getBitWidth());
+
+  // If there is a signedness mismatch, correct it.
+  if (X.isSigned() != Y.isSigned()) {
+    // If the signed value is negative, then the values cannot be the same.
+    if ((Y.isSigned() && Y.isNegative()) || (X.isSigned() && X.isNegative()))
+      return false;
+
+    Y.setIsSigned(true);
+    X.setIsSigned(true);
+  }
+
+  return X == Y;
+}
+
+static Sema::TemplateDeductionResult
+DeduceTemplateArguments(Sema &S,
+                        TemplateParameterList *TemplateParams,
+                        const TemplateArgument &Param,
+                        TemplateArgument Arg,
+                        TemplateDeductionInfo &Info,
+                      SmallVectorImpl<DeducedTemplateArgument> &Deduced);
+
+/// \brief Whether template argument deduction for two reference parameters
+/// resulted in the argument type, parameter type, or neither type being more
+/// qualified than the other.
+enum DeductionQualifierComparison {
+  NeitherMoreQualified = 0,
+  ParamMoreQualified,
+  ArgMoreQualified
+};
+
+/// \brief Stores the result of comparing two reference parameters while
+/// performing template argument deduction for partial ordering of function
+/// templates.
+struct RefParamPartialOrderingComparison {
+  /// \brief Whether the parameter type is an rvalue reference type.
+  bool ParamIsRvalueRef;
+  /// \brief Whether the argument type is an rvalue reference type.
+  bool ArgIsRvalueRef;
+
+  /// \brief Whether the parameter or argument (or neither) is more qualified.
+  DeductionQualifierComparison Qualifiers;
+};
+
+
+
+static Sema::TemplateDeductionResult
+DeduceTemplateArgumentsByTypeMatch(Sema &S,
+                                   TemplateParameterList *TemplateParams,
+                                   QualType Param,
+                                   QualType Arg,
+                                   TemplateDeductionInfo &Info,
+                                   SmallVectorImpl<DeducedTemplateArgument> &
+                                                      Deduced,
+                                   unsigned TDF,
+                                   bool PartialOrdering = false,
+                            SmallVectorImpl<RefParamPartialOrderingComparison> *
+                                                      RefParamComparisons = 0);
+
+static Sema::TemplateDeductionResult
+DeduceTemplateArguments(Sema &S,
+                        TemplateParameterList *TemplateParams,
+                        const TemplateArgument *Params, unsigned NumParams,
+                        const TemplateArgument *Args, unsigned NumArgs,
+                        TemplateDeductionInfo &Info,
+                        SmallVectorImpl<DeducedTemplateArgument> &Deduced,
+                        bool NumberOfArgumentsMustMatch = true);
+
+/// \brief If the given expression is of a form that permits the deduction
+/// of a non-type template parameter, return the declaration of that
+/// non-type template parameter.
+static NonTypeTemplateParmDecl *getDeducedParameterFromExpr(Expr *E) {
+  if (ImplicitCastExpr *IC = dyn_cast<ImplicitCastExpr>(E))
+    E = IC->getSubExpr();
+
+  if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E))
+    return dyn_cast<NonTypeTemplateParmDecl>(DRE->getDecl());
+
+  return 0;
+}
+
+/// \brief Determine whether two declaration pointers refer to the same
+/// declaration.
+static bool isSameDeclaration(Decl *X, Decl *Y) {
+  if (!X || !Y)
+    return !X && !Y;
+
+  if (NamedDecl *NX = dyn_cast<NamedDecl>(X))
+    X = NX->getUnderlyingDecl();
+  if (NamedDecl *NY = dyn_cast<NamedDecl>(Y))
+    Y = NY->getUnderlyingDecl();
+
+  return X->getCanonicalDecl() == Y->getCanonicalDecl();
+}
+
+/// \brief Verify that the given, deduced template arguments are compatible.
+///
+/// \returns The deduced template argument, or a NULL template argument if
+/// the deduced template arguments were incompatible.
+static DeducedTemplateArgument
+checkDeducedTemplateArguments(ASTContext &Context,
+                              const DeducedTemplateArgument &X,
+                              const DeducedTemplateArgument &Y) {
+  // We have no deduction for one or both of the arguments; they're compatible.
+  if (X.isNull())
+    return Y;
+  if (Y.isNull())
+    return X;
+
+  switch (X.getKind()) {
+  case TemplateArgument::Null:
+    llvm_unreachable("Non-deduced template arguments handled above");
+
+  case TemplateArgument::Type:
+    // If two template type arguments have the same type, they're compatible.
+    if (Y.getKind() == TemplateArgument::Type &&
+        Context.hasSameType(X.getAsType(), Y.getAsType()))
+      return X;
+
+    return DeducedTemplateArgument();
+
+  case TemplateArgument::Integral:
+    // If we deduced a constant in one case and either a dependent expression or
+    // declaration in another case, keep the integral constant.
+    // If both are integral constants with the same value, keep that value.
+    if (Y.getKind() == TemplateArgument::Expression ||
+        Y.getKind() == TemplateArgument::Declaration ||
+        (Y.getKind() == TemplateArgument::Integral &&
+         hasSameExtendedValue(*X.getAsIntegral(), *Y.getAsIntegral())))
+      return DeducedTemplateArgument(X,
+                                     X.wasDeducedFromArrayBound() &&
+                                     Y.wasDeducedFromArrayBound());
+
+    // All other combinations are incompatible.
+    return DeducedTemplateArgument();
+
+  case TemplateArgument::Template:
+    if (Y.getKind() == TemplateArgument::Template &&
+        Context.hasSameTemplateName(X.getAsTemplate(), Y.getAsTemplate()))
+      return X;
+
+    // All other combinations are incompatible.
+    return DeducedTemplateArgument();
+
+  case TemplateArgument::TemplateExpansion:
+    if (Y.getKind() == TemplateArgument::TemplateExpansion &&
+        Context.hasSameTemplateName(X.getAsTemplateOrTemplatePattern(),
+                                    Y.getAsTemplateOrTemplatePattern()))
+      return X;
+
+    // All other combinations are incompatible.
+    return DeducedTemplateArgument();
+
+  case TemplateArgument::Expression:
+    // If we deduced a dependent expression in one case and either an integral
+    // constant or a declaration in another case, keep the integral constant
+    // or declaration.
+    if (Y.getKind() == TemplateArgument::Integral ||
+        Y.getKind() == TemplateArgument::Declaration)
+      return DeducedTemplateArgument(Y, X.wasDeducedFromArrayBound() &&
+                                     Y.wasDeducedFromArrayBound());
+
+    if (Y.getKind() == TemplateArgument::Expression) {
+      // Compare the expressions for equality
+      llvm::FoldingSetNodeID ID1, ID2;
+      X.getAsExpr()->Profile(ID1, Context, true);
+      Y.getAsExpr()->Profile(ID2, Context, true);
+      if (ID1 == ID2)
+        return X;
+    }
+
+    // All other combinations are incompatible.
+    return DeducedTemplateArgument();
+
+  case TemplateArgument::Declaration:
+    // If we deduced a declaration and a dependent expression, keep the
+    // declaration.
+    if (Y.getKind() == TemplateArgument::Expression)
+      return X;
+
+    // If we deduced a declaration and an integral constant, keep the
+    // integral constant.
+    if (Y.getKind() == TemplateArgument::Integral)
+      return Y;
+
+    // If we deduced two declarations, make sure they they refer to the
+    // same declaration.
+    if (Y.getKind() == TemplateArgument::Declaration &&
+        isSameDeclaration(X.getAsDecl(), Y.getAsDecl()))
+      return X;
+
+    // All other combinations are incompatible.
+    return DeducedTemplateArgument();
+
+  case TemplateArgument::Pack:
+    if (Y.getKind() != TemplateArgument::Pack ||
+        X.pack_size() != Y.pack_size())
+      return DeducedTemplateArgument();
+
+    for (TemplateArgument::pack_iterator XA = X.pack_begin(),
+                                      XAEnd = X.pack_end(),
+                                         YA = Y.pack_begin();
+         XA != XAEnd; ++XA, ++YA) {
+      if (checkDeducedTemplateArguments(Context,
+                    DeducedTemplateArgument(*XA, X.wasDeducedFromArrayBound()),
+                    DeducedTemplateArgument(*YA, Y.wasDeducedFromArrayBound()))
+            .isNull())
+        return DeducedTemplateArgument();
+    }
+
+    return X;
+  }
+
+  llvm_unreachable("Invalid TemplateArgument Kind!");
+}
+
+/// \brief Deduce the value of the given non-type template parameter
+/// from the given constant.
+static Sema::TemplateDeductionResult
+DeduceNonTypeTemplateArgument(Sema &S,
+                              NonTypeTemplateParmDecl *NTTP,
+                              llvm::APSInt Value, QualType ValueType,
+                              bool DeducedFromArrayBound,
+                              TemplateDeductionInfo &Info,
+                    SmallVectorImpl<DeducedTemplateArgument> &Deduced) {
+  assert(NTTP->getDepth() == 0 &&
+         "Cannot deduce non-type template argument with depth > 0");
+
+  DeducedTemplateArgument NewDeduced(Value, ValueType, DeducedFromArrayBound);
+  DeducedTemplateArgument Result = checkDeducedTemplateArguments(S.Context,
+                                                     Deduced[NTTP->getIndex()],
+                                                                 NewDeduced);
+  if (Result.isNull()) {
+    Info.Param = NTTP;
+    Info.FirstArg = Deduced[NTTP->getIndex()];
+    Info.SecondArg = NewDeduced;
+    return Sema::TDK_Inconsistent;
+  }
+
+  Deduced[NTTP->getIndex()] = Result;
+  return Sema::TDK_Success;
+}
+
+/// \brief Deduce the value of the given non-type template parameter
+/// from the given type- or value-dependent expression.
+///
+/// \returns true if deduction succeeded, false otherwise.
+static Sema::TemplateDeductionResult
+DeduceNonTypeTemplateArgument(Sema &S,
+                              NonTypeTemplateParmDecl *NTTP,
+                              Expr *Value,
+                              TemplateDeductionInfo &Info,
+                    SmallVectorImpl<DeducedTemplateArgument> &Deduced) {
+  assert(NTTP->getDepth() == 0 &&
+         "Cannot deduce non-type template argument with depth > 0");
+  assert((Value->isTypeDependent() || Value->isValueDependent()) &&
+         "Expression template argument must be type- or value-dependent.");
+
+  DeducedTemplateArgument NewDeduced(Value);
+  DeducedTemplateArgument Result = checkDeducedTemplateArguments(S.Context,
+                                                     Deduced[NTTP->getIndex()],
+                                                                 NewDeduced);
+
+  if (Result.isNull()) {
+    Info.Param = NTTP;
+    Info.FirstArg = Deduced[NTTP->getIndex()];
+    Info.SecondArg = NewDeduced;
+    return Sema::TDK_Inconsistent;
+  }
+
+  Deduced[NTTP->getIndex()] = Result;
+  return Sema::TDK_Success;
+}
+
+/// \brief Deduce the value of the given non-type template parameter
+/// from the given declaration.
+///
+/// \returns true if deduction succeeded, false otherwise.
+static Sema::TemplateDeductionResult
+DeduceNonTypeTemplateArgument(Sema &S,
+                              NonTypeTemplateParmDecl *NTTP,
+                              Decl *D,
+                              TemplateDeductionInfo &Info,
+                    SmallVectorImpl<DeducedTemplateArgument> &Deduced) {
+  assert(NTTP->getDepth() == 0 &&
+         "Cannot deduce non-type template argument with depth > 0");
+
+  DeducedTemplateArgument NewDeduced(D? D->getCanonicalDecl() : 0);
+  DeducedTemplateArgument Result = checkDeducedTemplateArguments(S.Context,
+                                                     Deduced[NTTP->getIndex()],
+                                                                 NewDeduced);
+  if (Result.isNull()) {
+    Info.Param = NTTP;
+    Info.FirstArg = Deduced[NTTP->getIndex()];
+    Info.SecondArg = NewDeduced;
+    return Sema::TDK_Inconsistent;
+  }
+
+  Deduced[NTTP->getIndex()] = Result;
+  return Sema::TDK_Success;
+}
+
+static Sema::TemplateDeductionResult
+DeduceTemplateArguments(Sema &S,
+                        TemplateParameterList *TemplateParams,
+                        TemplateName Param,
+                        TemplateName Arg,
+                        TemplateDeductionInfo &Info,
+                    SmallVectorImpl<DeducedTemplateArgument> &Deduced) {
+  TemplateDecl *ParamDecl = Param.getAsTemplateDecl();
+  if (!ParamDecl) {
+    // The parameter type is dependent and is not a template template parameter,
+    // so there is nothing that we can deduce.
+    return Sema::TDK_Success;
+  }
+
+  if (TemplateTemplateParmDecl *TempParam
+        = dyn_cast<TemplateTemplateParmDecl>(ParamDecl)) {
+    DeducedTemplateArgument NewDeduced(S.Context.getCanonicalTemplateName(Arg));
+    DeducedTemplateArgument Result = checkDeducedTemplateArguments(S.Context,
+                                                 Deduced[TempParam->getIndex()],
+                                                                   NewDeduced);
+    if (Result.isNull()) {
+      Info.Param = TempParam;
+      Info.FirstArg = Deduced[TempParam->getIndex()];
+      Info.SecondArg = NewDeduced;
+      return Sema::TDK_Inconsistent;
+    }
+
+    Deduced[TempParam->getIndex()] = Result;
+    return Sema::TDK_Success;
+  }
+
+  // Verify that the two template names are equivalent.
+  if (S.Context.hasSameTemplateName(Param, Arg))
+    return Sema::TDK_Success;
+
+  // Mismatch of non-dependent template parameter to argument.
+  Info.FirstArg = TemplateArgument(Param);
+  Info.SecondArg = TemplateArgument(Arg);
+  return Sema::TDK_NonDeducedMismatch;
+}
+
+/// \brief Deduce the template arguments by comparing the template parameter
+/// type (which is a template-id) with the template argument type.
+///
+/// \param S the Sema
+///
+/// \param TemplateParams the template parameters that we are deducing
+///
+/// \param Param the parameter type
+///
+/// \param Arg the argument type
+///
+/// \param Info information about the template argument deduction itself
+///
+/// \param Deduced the deduced template arguments
+///
+/// \returns the result of template argument deduction so far. Note that a
+/// "success" result means that template argument deduction has not yet failed,
+/// but it may still fail, later, for other reasons.
+static Sema::TemplateDeductionResult
+DeduceTemplateArguments(Sema &S,
+                        TemplateParameterList *TemplateParams,
+                        const TemplateSpecializationType *Param,
+                        QualType Arg,
+                        TemplateDeductionInfo &Info,
+                    SmallVectorImpl<DeducedTemplateArgument> &Deduced) {
+  assert(Arg.isCanonical() && "Argument type must be canonical");
+
+  // Check whether the template argument is a dependent template-id.
+  if (const TemplateSpecializationType *SpecArg
+        = dyn_cast<TemplateSpecializationType>(Arg)) {
+    // Perform template argument deduction for the template name.
+    if (Sema::TemplateDeductionResult Result
+          = DeduceTemplateArguments(S, TemplateParams,
+                                    Param->getTemplateName(),
+                                    SpecArg->getTemplateName(),
+                                    Info, Deduced))
+      return Result;
+
+
+    // Perform template argument deduction on each template
+    // argument. Ignore any missing/extra arguments, since they could be
+    // filled in by default arguments.
+    return DeduceTemplateArguments(S, TemplateParams,
+                                   Param->getArgs(), Param->getNumArgs(),
+                                   SpecArg->getArgs(), SpecArg->getNumArgs(),
+                                   Info, Deduced,
+                                   /*NumberOfArgumentsMustMatch=*/false);
+  }
+
+  // If the argument type is a class template specialization, we
+  // perform template argument deduction using its template
+  // arguments.
+  const RecordType *RecordArg = dyn_cast<RecordType>(Arg);
+  if (!RecordArg)
+    return Sema::TDK_NonDeducedMismatch;
+
+  ClassTemplateSpecializationDecl *SpecArg
+    = dyn_cast<ClassTemplateSpecializationDecl>(RecordArg->getDecl());
+  if (!SpecArg)
+    return Sema::TDK_NonDeducedMismatch;
+
+  // Perform template argument deduction for the template name.
+  if (Sema::TemplateDeductionResult Result
+        = DeduceTemplateArguments(S,
+                                  TemplateParams,
+                                  Param->getTemplateName(),
+                               TemplateName(SpecArg->getSpecializedTemplate()),
+                                  Info, Deduced))
+    return Result;
+
+  // Perform template argument deduction for the template arguments.
+  return DeduceTemplateArguments(S, TemplateParams,
+                                 Param->getArgs(), Param->getNumArgs(),
+                                 SpecArg->getTemplateArgs().data(),
+                                 SpecArg->getTemplateArgs().size(),
+                                 Info, Deduced);
+}
+
+/// \brief Determines whether the given type is an opaque type that
+/// might be more qualified when instantiated.
+static bool IsPossiblyOpaquelyQualifiedType(QualType T) {
+  switch (T->getTypeClass()) {
+  case Type::TypeOfExpr:
+  case Type::TypeOf:
+  case Type::DependentName:
+  case Type::Decltype:
+  case Type::UnresolvedUsing:
+  case Type::TemplateTypeParm:
+    return true;
+
+  case Type::ConstantArray:
+  case Type::IncompleteArray:
+  case Type::VariableArray:
+  case Type::DependentSizedArray:
+    return IsPossiblyOpaquelyQualifiedType(
+                                      cast<ArrayType>(T)->getElementType());
+
+  default:
+    return false;
+  }
+}
+
+/// \brief Retrieve the depth and index of a template parameter.
+static std::pair<unsigned, unsigned>
+getDepthAndIndex(NamedDecl *ND) {
+  if (TemplateTypeParmDecl *TTP = dyn_cast<TemplateTypeParmDecl>(ND))
+    return std::make_pair(TTP->getDepth(), TTP->getIndex());
+
+  if (NonTypeTemplateParmDecl *NTTP = dyn_cast<NonTypeTemplateParmDecl>(ND))
+    return std::make_pair(NTTP->getDepth(), NTTP->getIndex());
+
+  TemplateTemplateParmDecl *TTP = cast<TemplateTemplateParmDecl>(ND);
+  return std::make_pair(TTP->getDepth(), TTP->getIndex());
+}
+
+/// \brief Retrieve the depth and index of an unexpanded parameter pack.
+static std::pair<unsigned, unsigned>
+getDepthAndIndex(UnexpandedParameterPack UPP) {
+  if (const TemplateTypeParmType *TTP
+                          = UPP.first.dyn_cast<const TemplateTypeParmType *>())
+    return std::make_pair(TTP->getDepth(), TTP->getIndex());
+
+  return getDepthAndIndex(UPP.first.get<NamedDecl *>());
+}
+
+/// \brief Helper function to build a TemplateParameter when we don't
+/// know its type statically.
+static TemplateParameter makeTemplateParameter(Decl *D) {
+  if (TemplateTypeParmDecl *TTP = dyn_cast<TemplateTypeParmDecl>(D))
+    return TemplateParameter(TTP);
+  else if (NonTypeTemplateParmDecl *NTTP = dyn_cast<NonTypeTemplateParmDecl>(D))
+    return TemplateParameter(NTTP);
+
+  return TemplateParameter(cast<TemplateTemplateParmDecl>(D));
+}
+
+/// \brief Prepare to perform template argument deduction for all of the
+/// arguments in a set of argument packs.
+static void PrepareArgumentPackDeduction(Sema &S,
+                       SmallVectorImpl<DeducedTemplateArgument> &Deduced,
+                                           ArrayRef<unsigned> PackIndices,
+                     SmallVectorImpl<DeducedTemplateArgument> &SavedPacks,
+         SmallVectorImpl<
+           SmallVector<DeducedTemplateArgument, 4> > &NewlyDeducedPacks) {
+  // Save the deduced template arguments for each parameter pack expanded
+  // by this pack expansion, then clear out the deduction.
+  for (unsigned I = 0, N = PackIndices.size(); I != N; ++I) {
+    // Save the previously-deduced argument pack, then clear it out so that we
+    // can deduce a new argument pack.
+    SavedPacks[I] = Deduced[PackIndices[I]];
+    Deduced[PackIndices[I]] = TemplateArgument();
+
+    // If the template arugment pack was explicitly specified, add that to
+    // the set of deduced arguments.
+    const TemplateArgument *ExplicitArgs;
+    unsigned NumExplicitArgs;
+    if (NamedDecl *PartiallySubstitutedPack
+        = S.CurrentInstantiationScope->getPartiallySubstitutedPack(
+                                                           &ExplicitArgs,
+                                                           &NumExplicitArgs)) {
+      if (getDepthAndIndex(PartiallySubstitutedPack).second == PackIndices[I])
+        NewlyDeducedPacks[I].append(ExplicitArgs,
+                                    ExplicitArgs + NumExplicitArgs);
+    }
+  }
+}
+
+/// \brief Finish template argument deduction for a set of argument packs,
+/// producing the argument packs and checking for consistency with prior
+/// deductions.
+static Sema::TemplateDeductionResult
+FinishArgumentPackDeduction(Sema &S,
+                            TemplateParameterList *TemplateParams,
+                            bool HasAnyArguments,
+                        SmallVectorImpl<DeducedTemplateArgument> &Deduced,
+                            ArrayRef<unsigned> PackIndices,
+                    SmallVectorImpl<DeducedTemplateArgument> &SavedPacks,
+        SmallVectorImpl<
+          SmallVector<DeducedTemplateArgument, 4> > &NewlyDeducedPacks,
+                            TemplateDeductionInfo &Info) {
+  // Build argument packs for each of the parameter packs expanded by this
+  // pack expansion.
+  for (unsigned I = 0, N = PackIndices.size(); I != N; ++I) {
+    if (HasAnyArguments && NewlyDeducedPacks[I].empty()) {
+      // We were not able to deduce anything for this parameter pack,
+      // so just restore the saved argument pack.
+      Deduced[PackIndices[I]] = SavedPacks[I];
+      continue;
+    }
+
+    DeducedTemplateArgument NewPack;
+
+    if (NewlyDeducedPacks[I].empty()) {
+      // If we deduced an empty argument pack, create it now.
+      NewPack = DeducedTemplateArgument(TemplateArgument(0, 0));
+    } else {
+      TemplateArgument *ArgumentPack
+        = new (S.Context) TemplateArgument [NewlyDeducedPacks[I].size()];
+      std::copy(NewlyDeducedPacks[I].begin(), NewlyDeducedPacks[I].end(),
+                ArgumentPack);
+      NewPack
+        = DeducedTemplateArgument(TemplateArgument(ArgumentPack,
+                                                   NewlyDeducedPacks[I].size()),
+                            NewlyDeducedPacks[I][0].wasDeducedFromArrayBound());
+    }
+
+    DeducedTemplateArgument Result
+      = checkDeducedTemplateArguments(S.Context, SavedPacks[I], NewPack);
+    if (Result.isNull()) {
+      Info.Param
+        = makeTemplateParameter(TemplateParams->getParam(PackIndices[I]));
+      Info.FirstArg = SavedPacks[I];
+      Info.SecondArg = NewPack;
+      return Sema::TDK_Inconsistent;
+    }
+
+    Deduced[PackIndices[I]] = Result;
+  }
+
+  return Sema::TDK_Success;
+}
+
+/// \brief Deduce the template arguments by comparing the list of parameter
+/// types to the list of argument types, as in the parameter-type-lists of
+/// function types (C++ [temp.deduct.type]p10).
+///
+/// \param S The semantic analysis object within which we are deducing
+///
+/// \param TemplateParams The template parameters that we are deducing
+///
+/// \param Params The list of parameter types
+///
+/// \param NumParams The number of types in \c Params
+///
+/// \param Args The list of argument types
+///
+/// \param NumArgs The number of types in \c Args
+///
+/// \param Info information about the template argument deduction itself
+///
+/// \param Deduced the deduced template arguments
+///
+/// \param TDF bitwise OR of the TemplateDeductionFlags bits that describe
+/// how template argument deduction is performed.
+///
+/// \param PartialOrdering If true, we are performing template argument
+/// deduction for during partial ordering for a call
+/// (C++0x [temp.deduct.partial]).
+///
+/// \param RefParamComparisons If we're performing template argument deduction
+/// in the context of partial ordering, the set of qualifier comparisons.
+///
+/// \returns the result of template argument deduction so far. Note that a
+/// "success" result means that template argument deduction has not yet failed,
+/// but it may still fail, later, for other reasons.
+static Sema::TemplateDeductionResult
+DeduceTemplateArguments(Sema &S,
+                        TemplateParameterList *TemplateParams,
+                        const QualType *Params, unsigned NumParams,
+                        const QualType *Args, unsigned NumArgs,
+                        TemplateDeductionInfo &Info,
+                      SmallVectorImpl<DeducedTemplateArgument> &Deduced,
+                        unsigned TDF,
+                        bool PartialOrdering = false,
+                        SmallVectorImpl<RefParamPartialOrderingComparison> *
+                                                     RefParamComparisons = 0) {
+  // Fast-path check to see if we have too many/too few arguments.
+  if (NumParams != NumArgs &&
+      !(NumParams && isa<PackExpansionType>(Params[NumParams - 1])) &&
+      !(NumArgs && isa<PackExpansionType>(Args[NumArgs - 1])))
+    return Sema::TDK_NonDeducedMismatch;
+
+  // C++0x [temp.deduct.type]p10:
+  //   Similarly, if P has a form that contains (T), then each parameter type
+  //   Pi of the respective parameter-type- list of P is compared with the
+  //   corresponding parameter type Ai of the corresponding parameter-type-list
+  //   of A. [...]
+  unsigned ArgIdx = 0, ParamIdx = 0;
+  for (; ParamIdx != NumParams; ++ParamIdx) {
+    // Check argument types.
+    const PackExpansionType *Expansion
+                                = dyn_cast<PackExpansionType>(Params[ParamIdx]);
+    if (!Expansion) {
+      // Simple case: compare the parameter and argument types at this point.
+
+      // Make sure we have an argument.
+      if (ArgIdx >= NumArgs)
+        return Sema::TDK_NonDeducedMismatch;
+
+      if (isa<PackExpansionType>(Args[ArgIdx])) {
+        // C++0x [temp.deduct.type]p22:
+        //   If the original function parameter associated with A is a function
+        //   parameter pack and the function parameter associated with P is not
+        //   a function parameter pack, then template argument deduction fails.
+        return Sema::TDK_NonDeducedMismatch;
+      }
+
+      if (Sema::TemplateDeductionResult Result
+            = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
+                                                 Params[ParamIdx], Args[ArgIdx],
+                                                 Info, Deduced, TDF,
+                                                 PartialOrdering,
+                                                 RefParamComparisons))
+        return Result;
+
+      ++ArgIdx;
+      continue;
+    }
+
+    // C++0x [temp.deduct.type]p5:
+    //   The non-deduced contexts are:
+    //     - A function parameter pack that does not occur at the end of the
+    //       parameter-declaration-clause.
+    if (ParamIdx + 1 < NumParams)
+      return Sema::TDK_Success;
+
+    // C++0x [temp.deduct.type]p10:
+    //   If the parameter-declaration corresponding to Pi is a function
+    //   parameter pack, then the type of its declarator- id is compared with
+    //   each remaining parameter type in the parameter-type-list of A. Each
+    //   comparison deduces template arguments for subsequent positions in the
+    //   template parameter packs expanded by the function parameter pack.
+
+    // Compute the set of template parameter indices that correspond to
+    // parameter packs expanded by the pack expansion.
+    SmallVector<unsigned, 2> PackIndices;
+    QualType Pattern = Expansion->getPattern();
+    {
+      llvm::SmallBitVector SawIndices(TemplateParams->size());
+      SmallVector<UnexpandedParameterPack, 2> Unexpanded;
+      S.collectUnexpandedParameterPacks(Pattern, Unexpanded);
+      for (unsigned I = 0, N = Unexpanded.size(); I != N; ++I) {
+        unsigned Depth, Index;
+        llvm::tie(Depth, Index) = getDepthAndIndex(Unexpanded[I]);
+        if (Depth == 0 && !SawIndices[Index]) {
+          SawIndices[Index] = true;
+          PackIndices.push_back(Index);
+        }
+      }
+    }
+    assert(!PackIndices.empty() && "Pack expansion without unexpanded packs?");
+
+    // Keep track of the deduced template arguments for each parameter pack
+    // expanded by this pack expansion (the outer index) and for each
+    // template argument (the inner SmallVectors).
+    SmallVector<SmallVector<DeducedTemplateArgument, 4>, 2>
+      NewlyDeducedPacks(PackIndices.size());
+    SmallVector<DeducedTemplateArgument, 2>
+      SavedPacks(PackIndices.size());
+    PrepareArgumentPackDeduction(S, Deduced, PackIndices, SavedPacks,
+                                 NewlyDeducedPacks);
+
+    bool HasAnyArguments = false;
+    for (; ArgIdx < NumArgs; ++ArgIdx) {
+      HasAnyArguments = true;
+
+      // Deduce template arguments from the pattern.
+      if (Sema::TemplateDeductionResult Result
+            = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams, Pattern,
+                                                 Args[ArgIdx], Info, Deduced,
+                                                 TDF, PartialOrdering,
+                                                 RefParamComparisons))
+        return Result;
+
+      // Capture the deduced template arguments for each parameter pack expanded
+      // by this pack expansion, add them to the list of arguments we've deduced
+      // for that pack, then clear out the deduced argument.
+      for (unsigned I = 0, N = PackIndices.size(); I != N; ++I) {
+        DeducedTemplateArgument &DeducedArg = Deduced[PackIndices[I]];
+        if (!DeducedArg.isNull()) {
+          NewlyDeducedPacks[I].push_back(DeducedArg);
+          DeducedArg = DeducedTemplateArgument();
+        }
+      }
+    }
+
+    // Build argument packs for each of the parameter packs expanded by this
+    // pack expansion.
+    if (Sema::TemplateDeductionResult Result
+          = FinishArgumentPackDeduction(S, TemplateParams, HasAnyArguments,
+                                        Deduced, PackIndices, SavedPacks,
+                                        NewlyDeducedPacks, Info))
+      return Result;
+  }
+
+  // Make sure we don't have any extra arguments.
+  if (ArgIdx < NumArgs)
+    return Sema::TDK_NonDeducedMismatch;
+
+  return Sema::TDK_Success;
+}
+
+/// \brief Determine whether the parameter has qualifiers that are either
+/// inconsistent with or a superset of the argument's qualifiers.
+static bool hasInconsistentOrSupersetQualifiersOf(QualType ParamType,
+                                                  QualType ArgType) {
+  Qualifiers ParamQs = ParamType.getQualifiers();
+  Qualifiers ArgQs = ArgType.getQualifiers();
+
+  if (ParamQs == ArgQs)
+    return false;
+       
+  // Mismatched (but not missing) Objective-C GC attributes.
+  if (ParamQs.getObjCGCAttr() != ArgQs.getObjCGCAttr() && 
+      ParamQs.hasObjCGCAttr())
+    return true;
+  
+  // Mismatched (but not missing) address spaces.
+  if (ParamQs.getAddressSpace() != ArgQs.getAddressSpace() &&
+      ParamQs.hasAddressSpace())
+    return true;
+
+  // Mismatched (but not missing) Objective-C lifetime qualifiers.
+  if (ParamQs.getObjCLifetime() != ArgQs.getObjCLifetime() &&
+      ParamQs.hasObjCLifetime())
+    return true;
+  
+  // CVR qualifier superset.
+  return (ParamQs.getCVRQualifiers() != ArgQs.getCVRQualifiers()) &&
+      ((ParamQs.getCVRQualifiers() | ArgQs.getCVRQualifiers())
+                                                == ParamQs.getCVRQualifiers());
+}
+
+/// \brief Deduce the template arguments by comparing the parameter type and
+/// the argument type (C++ [temp.deduct.type]).
+///
+/// \param S the semantic analysis object within which we are deducing
+///
+/// \param TemplateParams the template parameters that we are deducing
+///
+/// \param ParamIn the parameter type
+///
+/// \param ArgIn the argument type
+///
+/// \param Info information about the template argument deduction itself
+///
+/// \param Deduced the deduced template arguments
+///
+/// \param TDF bitwise OR of the TemplateDeductionFlags bits that describe
+/// how template argument deduction is performed.
+///
+/// \param PartialOrdering Whether we're performing template argument deduction
+/// in the context of partial ordering (C++0x [temp.deduct.partial]).
+///
+/// \param RefParamComparisons If we're performing template argument deduction
+/// in the context of partial ordering, the set of qualifier comparisons.
+///
+/// \returns the result of template argument deduction so far. Note that a
+/// "success" result means that template argument deduction has not yet failed,
+/// but it may still fail, later, for other reasons.
+static Sema::TemplateDeductionResult
+DeduceTemplateArgumentsByTypeMatch(Sema &S,
+                                   TemplateParameterList *TemplateParams,
+                                   QualType ParamIn, QualType ArgIn,
+                                   TemplateDeductionInfo &Info,
+                            SmallVectorImpl<DeducedTemplateArgument> &Deduced,
+                                   unsigned TDF,
+                                   bool PartialOrdering,
+                            SmallVectorImpl<RefParamPartialOrderingComparison> *
+                                                          RefParamComparisons) {
+  // We only want to look at the canonical types, since typedefs and
+  // sugar are not part of template argument deduction.
+  QualType Param = S.Context.getCanonicalType(ParamIn);
+  QualType Arg = S.Context.getCanonicalType(ArgIn);
+
+  // If the argument type is a pack expansion, look at its pattern.
+  // This isn't explicitly called out
+  if (const PackExpansionType *ArgExpansion
+                                            = dyn_cast<PackExpansionType>(Arg))
+    Arg = ArgExpansion->getPattern();
+
+  if (PartialOrdering) {
+    // C++0x [temp.deduct.partial]p5:
+    //   Before the partial ordering is done, certain transformations are
+    //   performed on the types used for partial ordering:
+    //     - If P is a reference type, P is replaced by the type referred to.
+    const ReferenceType *ParamRef = Param->getAs<ReferenceType>();
+    if (ParamRef)
+      Param = ParamRef->getPointeeType();
+
+    //     - If A is a reference type, A is replaced by the type referred to.
+    const ReferenceType *ArgRef = Arg->getAs<ReferenceType>();
+    if (ArgRef)
+      Arg = ArgRef->getPointeeType();
+
+    if (RefParamComparisons && ParamRef && ArgRef) {
+      // C++0x [temp.deduct.partial]p6:
+      //   If both P and A were reference types (before being replaced with the
+      //   type referred to above), determine which of the two types (if any) is
+      //   more cv-qualified than the other; otherwise the types are considered
+      //   to be equally cv-qualified for partial ordering purposes. The result
+      //   of this determination will be used below.
+      //
+      // We save this information for later, using it only when deduction
+      // succeeds in both directions.
+      RefParamPartialOrderingComparison Comparison;
+      Comparison.ParamIsRvalueRef = ParamRef->getAs<RValueReferenceType>();
+      Comparison.ArgIsRvalueRef = ArgRef->getAs<RValueReferenceType>();
+      Comparison.Qualifiers = NeitherMoreQualified;
+      
+      Qualifiers ParamQuals = Param.getQualifiers();
+      Qualifiers ArgQuals = Arg.getQualifiers();
+      if (ParamQuals.isStrictSupersetOf(ArgQuals))
+        Comparison.Qualifiers = ParamMoreQualified;
+      else if (ArgQuals.isStrictSupersetOf(ParamQuals))
+        Comparison.Qualifiers = ArgMoreQualified;
+      RefParamComparisons->push_back(Comparison);
+    }
+
+    // C++0x [temp.deduct.partial]p7:
+    //   Remove any top-level cv-qualifiers:
+    //     - If P is a cv-qualified type, P is replaced by the cv-unqualified
+    //       version of P.
+    Param = Param.getUnqualifiedType();
+    //     - If A is a cv-qualified type, A is replaced by the cv-unqualified
+    //       version of A.
+    Arg = Arg.getUnqualifiedType();
+  } else {
+    // C++0x [temp.deduct.call]p4 bullet 1:
+    //   - If the original P is a reference type, the deduced A (i.e., the type
+    //     referred to by the reference) can be more cv-qualified than the
+    //     transformed A.
+    if (TDF & TDF_ParamWithReferenceType) {
+      Qualifiers Quals;
+      QualType UnqualParam = S.Context.getUnqualifiedArrayType(Param, Quals);
+      Quals.setCVRQualifiers(Quals.getCVRQualifiers() &
+                             Arg.getCVRQualifiers());
+      Param = S.Context.getQualifiedType(UnqualParam, Quals);
+    }
+
+    if ((TDF & TDF_TopLevelParameterTypeList) && !Param->isFunctionType()) {
+      // C++0x [temp.deduct.type]p10:
+      //   If P and A are function types that originated from deduction when
+      //   taking the address of a function template (14.8.2.2) or when deducing
+      //   template arguments from a function declaration (14.8.2.6) and Pi and
+      //   Ai are parameters of the top-level parameter-type-list of P and A,
+      //   respectively, Pi is adjusted if it is an rvalue reference to a
+      //   cv-unqualified template parameter and Ai is an lvalue reference, in
+      //   which case the type of Pi is changed to be the template parameter
+      //   type (i.e., T&& is changed to simply T). [ Note: As a result, when
+      //   Pi is T&& and Ai is X&, the adjusted Pi will be T, causing T to be
+      //   deduced as X&. - end note ]
+      TDF &= ~TDF_TopLevelParameterTypeList;
+
+      if (const RValueReferenceType *ParamRef
+                                        = Param->getAs<RValueReferenceType>()) {
+        if (isa<TemplateTypeParmType>(ParamRef->getPointeeType()) &&
+            !ParamRef->getPointeeType().getQualifiers())
+          if (Arg->isLValueReferenceType())
+            Param = ParamRef->getPointeeType();
+      }
+    }
+  }
+
+  // C++ [temp.deduct.type]p9:
+  //   A template type argument T, a template template argument TT or a
+  //   template non-type argument i can be deduced if P and A have one of
+  //   the following forms:
+  //
+  //     T
+  //     cv-list T
+  if (const TemplateTypeParmType *TemplateTypeParm
+        = Param->getAs<TemplateTypeParmType>()) {
+    // Just skip any attempts to deduce from a placeholder type.
+    if (Arg->isPlaceholderType())
+      return Sema::TDK_Success;
+    
+    unsigned Index = TemplateTypeParm->getIndex();
+    bool RecanonicalizeArg = false;
+
+    // If the argument type is an array type, move the qualifiers up to the
+    // top level, so they can be matched with the qualifiers on the parameter.
+    if (isa<ArrayType>(Arg)) {
+      Qualifiers Quals;
+      Arg = S.Context.getUnqualifiedArrayType(Arg, Quals);
+      if (Quals) {
+        Arg = S.Context.getQualifiedType(Arg, Quals);
+        RecanonicalizeArg = true;
+      }
+    }
+
+    // The argument type can not be less qualified than the parameter
+    // type.
+    if (!(TDF & TDF_IgnoreQualifiers) &&
+        hasInconsistentOrSupersetQualifiersOf(Param, Arg)) {
+      Info.Param = cast<TemplateTypeParmDecl>(TemplateParams->getParam(Index));
+      Info.FirstArg = TemplateArgument(Param);
+      Info.SecondArg = TemplateArgument(Arg);
+      return Sema::TDK_Underqualified;
+    }
+
+    assert(TemplateTypeParm->getDepth() == 0 && "Can't deduce with depth > 0");
+    assert(Arg != S.Context.OverloadTy && "Unresolved overloaded function");
+    QualType DeducedType = Arg;
+
+    // Remove any qualifiers on the parameter from the deduced type.
+    // We checked the qualifiers for consistency above.
+    Qualifiers DeducedQs = DeducedType.getQualifiers();
+    Qualifiers ParamQs = Param.getQualifiers();
+    DeducedQs.removeCVRQualifiers(ParamQs.getCVRQualifiers());
+    if (ParamQs.hasObjCGCAttr())
+      DeducedQs.removeObjCGCAttr();
+    if (ParamQs.hasAddressSpace())
+      DeducedQs.removeAddressSpace();
+    if (ParamQs.hasObjCLifetime())
+      DeducedQs.removeObjCLifetime();
+    
+    // Objective-C ARC:
+    //   If template deduction would produce a lifetime qualifier on a type
+    //   that is not a lifetime type, template argument deduction fails.
+    if (ParamQs.hasObjCLifetime() && !DeducedType->isObjCLifetimeType() &&
+        !DeducedType->isDependentType()) {
+      Info.Param = cast<TemplateTypeParmDecl>(TemplateParams->getParam(Index));
+      Info.FirstArg = TemplateArgument(Param);
+      Info.SecondArg = TemplateArgument(Arg);
+      return Sema::TDK_Underqualified;      
+    }
+    
+    // Objective-C ARC:
+    //   If template deduction would produce an argument type with lifetime type
+    //   but no lifetime qualifier, the __strong lifetime qualifier is inferred.
+    if (S.getLangOpts().ObjCAutoRefCount &&
+        DeducedType->isObjCLifetimeType() &&
+        !DeducedQs.hasObjCLifetime())
+      DeducedQs.setObjCLifetime(Qualifiers::OCL_Strong);
+    
+    DeducedType = S.Context.getQualifiedType(DeducedType.getUnqualifiedType(),
+                                             DeducedQs);
+    
+    if (RecanonicalizeArg)
+      DeducedType = S.Context.getCanonicalType(DeducedType);
+
+    DeducedTemplateArgument NewDeduced(DeducedType);
+    DeducedTemplateArgument Result = checkDeducedTemplateArguments(S.Context,
+                                                                 Deduced[Index],
+                                                                   NewDeduced);
+    if (Result.isNull()) {
+      Info.Param = cast<TemplateTypeParmDecl>(TemplateParams->getParam(Index));
+      Info.FirstArg = Deduced[Index];
+      Info.SecondArg = NewDeduced;
+      return Sema::TDK_Inconsistent;
+    }
+
+    Deduced[Index] = Result;
+    return Sema::TDK_Success;
+  }
+
+  // Set up the template argument deduction information for a failure.
+  Info.FirstArg = TemplateArgument(ParamIn);
+  Info.SecondArg = TemplateArgument(ArgIn);
+
+  // If the parameter is an already-substituted template parameter
+  // pack, do nothing: we don't know which of its arguments to look
+  // at, so we have to wait until all of the parameter packs in this
+  // expansion have arguments.
+  if (isa<SubstTemplateTypeParmPackType>(Param))
+    return Sema::TDK_Success;
+
+  // Check the cv-qualifiers on the parameter and argument types.
+  if (!(TDF & TDF_IgnoreQualifiers)) {
+    if (TDF & TDF_ParamWithReferenceType) {
+      if (hasInconsistentOrSupersetQualifiersOf(Param, Arg))
+        return Sema::TDK_NonDeducedMismatch;
+    } else if (!IsPossiblyOpaquelyQualifiedType(Param)) {
+      if (Param.getCVRQualifiers() != Arg.getCVRQualifiers())
+        return Sema::TDK_NonDeducedMismatch;
+    }
+    
+    // If the parameter type is not dependent, there is nothing to deduce.
+    if (!Param->isDependentType()) {
+      if (!(TDF & TDF_SkipNonDependent) && Param != Arg)
+        return Sema::TDK_NonDeducedMismatch;
+      
+      return Sema::TDK_Success;
+    }
+  } else if (!Param->isDependentType() &&
+             Param.getUnqualifiedType() == Arg.getUnqualifiedType()) {
+    return Sema::TDK_Success;
+  }
+
+  switch (Param->getTypeClass()) {
+    // Non-canonical types cannot appear here.
+#define NON_CANONICAL_TYPE(Class, Base) \
+  case Type::Class: llvm_unreachable("deducing non-canonical type: " #Class);
+#define TYPE(Class, Base)
+#include "clang/AST/TypeNodes.def"
+      
+    case Type::TemplateTypeParm:
+    case Type::SubstTemplateTypeParmPack:
+      llvm_unreachable("Type nodes handled above");
+
+    // These types cannot be dependent, so simply check whether the types are
+    // the same.
+    case Type::Builtin:
+    case Type::VariableArray:
+    case Type::Vector:
+    case Type::FunctionNoProto:
+    case Type::Record:
+    case Type::Enum:
+    case Type::ObjCObject:
+    case Type::ObjCInterface:
+    case Type::ObjCObjectPointer: {
+      if (TDF & TDF_SkipNonDependent)
+        return Sema::TDK_Success;
+      
+      if (TDF & TDF_IgnoreQualifiers) {
+        Param = Param.getUnqualifiedType();
+        Arg = Arg.getUnqualifiedType();
+      }
+            
+      return Param == Arg? Sema::TDK_Success : Sema::TDK_NonDeducedMismatch;
+    }
+      
+    //     _Complex T   [placeholder extension]  
+    case Type::Complex:
+      if (const ComplexType *ComplexArg = Arg->getAs<ComplexType>())
+        return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams, 
+                                    cast<ComplexType>(Param)->getElementType(), 
+                                    ComplexArg->getElementType(),
+                                    Info, Deduced, TDF);
+
+      return Sema::TDK_NonDeducedMismatch;
+
+    //     _Atomic T   [extension]
+    case Type::Atomic:
+      if (const AtomicType *AtomicArg = Arg->getAs<AtomicType>())
+        return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
+                                       cast<AtomicType>(Param)->getValueType(),
+                                       AtomicArg->getValueType(),
+                                       Info, Deduced, TDF);
+
+      return Sema::TDK_NonDeducedMismatch;
+
+    //     T *
+    case Type::Pointer: {
+      QualType PointeeType;
+      if (const PointerType *PointerArg = Arg->getAs<PointerType>()) {
+        PointeeType = PointerArg->getPointeeType();
+      } else if (const ObjCObjectPointerType *PointerArg
+                   = Arg->getAs<ObjCObjectPointerType>()) {
+        PointeeType = PointerArg->getPointeeType();
+      } else {
+        return Sema::TDK_NonDeducedMismatch;
+      }
+
+      unsigned SubTDF = TDF & (TDF_IgnoreQualifiers | TDF_DerivedClass);
+      return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
+                                     cast<PointerType>(Param)->getPointeeType(),
+                                     PointeeType,
+                                     Info, Deduced, SubTDF);
+    }
+
+    //     T &
+    case Type::LValueReference: {
+      const LValueReferenceType *ReferenceArg = Arg->getAs<LValueReferenceType>();
+      if (!ReferenceArg)
+        return Sema::TDK_NonDeducedMismatch;
+
+      return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
+                           cast<LValueReferenceType>(Param)->getPointeeType(),
+                           ReferenceArg->getPointeeType(), Info, Deduced, 0);
+    }
+
+    //     T && [C++0x]
+    case Type::RValueReference: {
+      const RValueReferenceType *ReferenceArg = Arg->getAs<RValueReferenceType>();
+      if (!ReferenceArg)
+        return Sema::TDK_NonDeducedMismatch;
+
+      return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
+                             cast<RValueReferenceType>(Param)->getPointeeType(),
+                             ReferenceArg->getPointeeType(),
+                             Info, Deduced, 0);
+    }
+
+    //     T [] (implied, but not stated explicitly)
+    case Type::IncompleteArray: {
+      const IncompleteArrayType *IncompleteArrayArg =
+        S.Context.getAsIncompleteArrayType(Arg);
+      if (!IncompleteArrayArg)
+        return Sema::TDK_NonDeducedMismatch;
+
+      unsigned SubTDF = TDF & TDF_IgnoreQualifiers;
+      return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
+                    S.Context.getAsIncompleteArrayType(Param)->getElementType(),
+                    IncompleteArrayArg->getElementType(),
+                    Info, Deduced, SubTDF);
+    }
+
+    //     T [integer-constant]
+    case Type::ConstantArray: {
+      const ConstantArrayType *ConstantArrayArg =
+        S.Context.getAsConstantArrayType(Arg);
+      if (!ConstantArrayArg)
+        return Sema::TDK_NonDeducedMismatch;
+
+      const ConstantArrayType *ConstantArrayParm =
+        S.Context.getAsConstantArrayType(Param);
+      if (ConstantArrayArg->getSize() != ConstantArrayParm->getSize())
+        return Sema::TDK_NonDeducedMismatch;
+
+      unsigned SubTDF = TDF & TDF_IgnoreQualifiers;
+      return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
+                                           ConstantArrayParm->getElementType(),
+                                           ConstantArrayArg->getElementType(),
+                                           Info, Deduced, SubTDF);
+    }
+
+    //     type [i]
+    case Type::DependentSizedArray: {
+      const ArrayType *ArrayArg = S.Context.getAsArrayType(Arg);
+      if (!ArrayArg)
+        return Sema::TDK_NonDeducedMismatch;
+
+      unsigned SubTDF = TDF & TDF_IgnoreQualifiers;
+
+      // Check the element type of the arrays
+      const DependentSizedArrayType *DependentArrayParm
+        = S.Context.getAsDependentSizedArrayType(Param);
+      if (Sema::TemplateDeductionResult Result
+            = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
+                                          DependentArrayParm->getElementType(),
+                                          ArrayArg->getElementType(),
+                                          Info, Deduced, SubTDF))
+        return Result;
+
+      // Determine the array bound is something we can deduce.
+      NonTypeTemplateParmDecl *NTTP
+        = getDeducedParameterFromExpr(DependentArrayParm->getSizeExpr());
+      if (!NTTP)
+        return Sema::TDK_Success;
+
+      // We can perform template argument deduction for the given non-type
+      // template parameter.
+      assert(NTTP->getDepth() == 0 &&
+             "Cannot deduce non-type template argument at depth > 0");
+      if (const ConstantArrayType *ConstantArrayArg
+            = dyn_cast<ConstantArrayType>(ArrayArg)) {
+        llvm::APSInt Size(ConstantArrayArg->getSize());
+        return DeduceNonTypeTemplateArgument(S, NTTP, Size,
+                                             S.Context.getSizeType(),
+                                             /*ArrayBound=*/true,
+                                             Info, Deduced);
+      }
+      if (const DependentSizedArrayType *DependentArrayArg
+            = dyn_cast<DependentSizedArrayType>(ArrayArg))
+        if (DependentArrayArg->getSizeExpr())
+          return DeduceNonTypeTemplateArgument(S, NTTP,
+                                               DependentArrayArg->getSizeExpr(),
+                                               Info, Deduced);
+
+      // Incomplete type does not match a dependently-sized array type
+      return Sema::TDK_NonDeducedMismatch;
+    }
+
+    //     type(*)(T)
+    //     T(*)()
+    //     T(*)(T)
+    case Type::FunctionProto: {
+      unsigned SubTDF = TDF & TDF_TopLevelParameterTypeList;
+      const FunctionProtoType *FunctionProtoArg =
+        dyn_cast<FunctionProtoType>(Arg);
+      if (!FunctionProtoArg)
+        return Sema::TDK_NonDeducedMismatch;
+
+      const FunctionProtoType *FunctionProtoParam =
+        cast<FunctionProtoType>(Param);
+
+      if (FunctionProtoParam->getTypeQuals()
+            != FunctionProtoArg->getTypeQuals() ||
+          FunctionProtoParam->getRefQualifier()
+            != FunctionProtoArg->getRefQualifier() ||
+          FunctionProtoParam->isVariadic() != FunctionProtoArg->isVariadic())
+        return Sema::TDK_NonDeducedMismatch;
+
+      // Check return types.
+      if (Sema::TemplateDeductionResult Result
+            = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
+                                            FunctionProtoParam->getResultType(),
+                                            FunctionProtoArg->getResultType(),
+                                            Info, Deduced, 0))
+        return Result;
+
+      return DeduceTemplateArguments(S, TemplateParams,
+                                     FunctionProtoParam->arg_type_begin(),
+                                     FunctionProtoParam->getNumArgs(),
+                                     FunctionProtoArg->arg_type_begin(),
+                                     FunctionProtoArg->getNumArgs(),
+                                     Info, Deduced, SubTDF);
+    }
+
+    case Type::InjectedClassName: {
+      // Treat a template's injected-class-name as if the template
+      // specialization type had been used.
+      Param = cast<InjectedClassNameType>(Param)
+        ->getInjectedSpecializationType();
+      assert(isa<TemplateSpecializationType>(Param) &&
+             "injected class name is not a template specialization type");
+      // fall through
+    }
+
+    //     template-name<T> (where template-name refers to a class template)
+    //     template-name<i>
+    //     TT<T>
+    //     TT<i>
+    //     TT<>
+    case Type::TemplateSpecialization: {
+      const TemplateSpecializationType *SpecParam
+        = cast<TemplateSpecializationType>(Param);
+
+      // Try to deduce template arguments from the template-id.
+      Sema::TemplateDeductionResult Result
+        = DeduceTemplateArguments(S, TemplateParams, SpecParam, Arg,
+                                  Info, Deduced);
+
+      if (Result && (TDF & TDF_DerivedClass)) {
+        // C++ [temp.deduct.call]p3b3:
+        //   If P is a class, and P has the form template-id, then A can be a
+        //   derived class of the deduced A. Likewise, if P is a pointer to a
+        //   class of the form template-id, A can be a pointer to a derived
+        //   class pointed to by the deduced A.
+        //
+        // More importantly:
+        //   These alternatives are considered only if type deduction would
+        //   otherwise fail.
+        if (const RecordType *RecordT = Arg->getAs<RecordType>()) {
+          // We cannot inspect base classes as part of deduction when the type
+          // is incomplete, so either instantiate any templates necessary to
+          // complete the type, or skip over it if it cannot be completed.
+          if (S.RequireCompleteType(Info.getLocation(), Arg, 0))
+            return Result;
+
+          // Use data recursion to crawl through the list of base classes.
+          // Visited contains the set of nodes we have already visited, while
+          // ToVisit is our stack of records that we still need to visit.
+          llvm::SmallPtrSet<const RecordType *, 8> Visited;
+          SmallVector<const RecordType *, 8> ToVisit;
+          ToVisit.push_back(RecordT);
+          bool Successful = false;
+          SmallVector<DeducedTemplateArgument, 8> DeducedOrig(Deduced.begin(),
+                                                              Deduced.end());
+          while (!ToVisit.empty()) {
+            // Retrieve the next class in the inheritance hierarchy.
+            const RecordType *NextT = ToVisit.back();
+            ToVisit.pop_back();
+
+            // If we have already seen this type, skip it.
+            if (!Visited.insert(NextT))
+              continue;
+
+            // If this is a base class, try to perform template argument
+            // deduction from it.
+            if (NextT != RecordT) {
+              Sema::TemplateDeductionResult BaseResult
+                = DeduceTemplateArguments(S, TemplateParams, SpecParam,
+                                          QualType(NextT, 0), Info, Deduced);
+
+              // If template argument deduction for this base was successful,
+              // note that we had some success. Otherwise, ignore any deductions
+              // from this base class.
+              if (BaseResult == Sema::TDK_Success) {
+                Successful = true;
+                DeducedOrig.clear();
+                DeducedOrig.append(Deduced.begin(), Deduced.end());
+              }
+              else
+                Deduced = DeducedOrig;
+            }
+
+            // Visit base classes
+            CXXRecordDecl *Next = cast<CXXRecordDecl>(NextT->getDecl());
+            for (CXXRecordDecl::base_class_iterator Base = Next->bases_begin(),
+                                                 BaseEnd = Next->bases_end();
+                 Base != BaseEnd; ++Base) {
+              assert(Base->getType()->isRecordType() &&
+                     "Base class that isn't a record?");
+              ToVisit.push_back(Base->getType()->getAs<RecordType>());
+            }
+          }
+
+          if (Successful)
+            return Sema::TDK_Success;
+        }
+
+      }
+
+      return Result;
+    }
+
+    //     T type::*
+    //     T T::*
+    //     T (type::*)()
+    //     type (T::*)()
+    //     type (type::*)(T)
+    //     type (T::*)(T)
+    //     T (type::*)(T)
+    //     T (T::*)()
+    //     T (T::*)(T)
+    case Type::MemberPointer: {
+      const MemberPointerType *MemPtrParam = cast<MemberPointerType>(Param);
+      const MemberPointerType *MemPtrArg = dyn_cast<MemberPointerType>(Arg);
+      if (!MemPtrArg)
+        return Sema::TDK_NonDeducedMismatch;
+
+      if (Sema::TemplateDeductionResult Result
+            = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
+                                                 MemPtrParam->getPointeeType(),
+                                                 MemPtrArg->getPointeeType(),
+                                                 Info, Deduced,
+                                                 TDF & TDF_IgnoreQualifiers))
+        return Result;
+
+      return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
+                                           QualType(MemPtrParam->getClass(), 0),
+                                           QualType(MemPtrArg->getClass(), 0),
+                                           Info, Deduced, 
+                                           TDF & TDF_IgnoreQualifiers);
+    }
+
+    //     (clang extension)
+    //
+    //     type(^)(T)
+    //     T(^)()
+    //     T(^)(T)
+    case Type::BlockPointer: {
+      const BlockPointerType *BlockPtrParam = cast<BlockPointerType>(Param);
+      const BlockPointerType *BlockPtrArg = dyn_cast<BlockPointerType>(Arg);
+
+      if (!BlockPtrArg)
+        return Sema::TDK_NonDeducedMismatch;
+
+      return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
+                                                BlockPtrParam->getPointeeType(),
+                                                BlockPtrArg->getPointeeType(),
+                                                Info, Deduced, 0);
+    }
+
+    //     (clang extension)
+    //
+    //     T __attribute__(((ext_vector_type(<integral constant>))))
+    case Type::ExtVector: {
+      const ExtVectorType *VectorParam = cast<ExtVectorType>(Param);
+      if (const ExtVectorType *VectorArg = dyn_cast<ExtVectorType>(Arg)) {
+        // Make sure that the vectors have the same number of elements.
+        if (VectorParam->getNumElements() != VectorArg->getNumElements())
+          return Sema::TDK_NonDeducedMismatch;
+        
+        // Perform deduction on the element types.
+        return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
+                                                  VectorParam->getElementType(),
+                                                  VectorArg->getElementType(),
+                                                  Info, Deduced, TDF);
+      }
+      
+      if (const DependentSizedExtVectorType *VectorArg 
+                                = dyn_cast<DependentSizedExtVectorType>(Arg)) {
+        // We can't check the number of elements, since the argument has a
+        // dependent number of elements. This can only occur during partial
+        // ordering.
+
+        // Perform deduction on the element types.
+        return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
+                                                  VectorParam->getElementType(),
+                                                  VectorArg->getElementType(),
+                                                  Info, Deduced, TDF);
+      }
+      
+      return Sema::TDK_NonDeducedMismatch;
+    }
+      
+    //     (clang extension)
+    //
+    //     T __attribute__(((ext_vector_type(N))))
+    case Type::DependentSizedExtVector: {
+      const DependentSizedExtVectorType *VectorParam
+        = cast<DependentSizedExtVectorType>(Param);
+
+      if (const ExtVectorType *VectorArg = dyn_cast<ExtVectorType>(Arg)) {
+        // Perform deduction on the element types.
+        if (Sema::TemplateDeductionResult Result
+              = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
+                                                  VectorParam->getElementType(),
+                                                   VectorArg->getElementType(),
+                                                   Info, Deduced, TDF))
+          return Result;
+        
+        // Perform deduction on the vector size, if we can.
+        NonTypeTemplateParmDecl *NTTP
+          = getDeducedParameterFromExpr(VectorParam->getSizeExpr());
+        if (!NTTP)
+          return Sema::TDK_Success;
+
+        llvm::APSInt ArgSize(S.Context.getTypeSize(S.Context.IntTy), false);
+        ArgSize = VectorArg->getNumElements();
+        return DeduceNonTypeTemplateArgument(S, NTTP, ArgSize, S.Context.IntTy,
+                                             false, Info, Deduced);
+      }
+      
+      if (const DependentSizedExtVectorType *VectorArg 
+                                = dyn_cast<DependentSizedExtVectorType>(Arg)) {
+        // Perform deduction on the element types.
+        if (Sema::TemplateDeductionResult Result
+            = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
+                                                 VectorParam->getElementType(),
+                                                 VectorArg->getElementType(),
+                                                 Info, Deduced, TDF))
+          return Result;
+        
+        // Perform deduction on the vector size, if we can.
+        NonTypeTemplateParmDecl *NTTP
+          = getDeducedParameterFromExpr(VectorParam->getSizeExpr());
+        if (!NTTP)
+          return Sema::TDK_Success;
+        
+        return DeduceNonTypeTemplateArgument(S, NTTP, VectorArg->getSizeExpr(),
+                                             Info, Deduced);
+      }
+      
+      return Sema::TDK_NonDeducedMismatch;
+    }
+      
+    case Type::TypeOfExpr:
+    case Type::TypeOf:
+    case Type::DependentName:
+    case Type::UnresolvedUsing:
+    case Type::Decltype:
+    case Type::UnaryTransform:
+    case Type::Auto:
+    case Type::DependentTemplateSpecialization:
+    case Type::PackExpansion:
+      // No template argument deduction for these types
+      return Sema::TDK_Success;
+  }
+
+  llvm_unreachable("Invalid Type Class!");
+}
+
+static Sema::TemplateDeductionResult
+DeduceTemplateArguments(Sema &S,
+                        TemplateParameterList *TemplateParams,
+                        const TemplateArgument &Param,
+                        TemplateArgument Arg,
+                        TemplateDeductionInfo &Info,
+                    SmallVectorImpl<DeducedTemplateArgument> &Deduced) {
+  // If the template argument is a pack expansion, perform template argument
+  // deduction against the pattern of that expansion. This only occurs during
+  // partial ordering.
+  if (Arg.isPackExpansion())
+    Arg = Arg.getPackExpansionPattern();
+
+  switch (Param.getKind()) {
+  case TemplateArgument::Null:
+    llvm_unreachable("Null template argument in parameter list");
+
+  case TemplateArgument::Type:
+    if (Arg.getKind() == TemplateArgument::Type)
+      return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
+                                                Param.getAsType(),
+                                                Arg.getAsType(),
+                                                Info, Deduced, 0);
+    Info.FirstArg = Param;
+    Info.SecondArg = Arg;
+    return Sema::TDK_NonDeducedMismatch;
+
+  case TemplateArgument::Template:
+    if (Arg.getKind() == TemplateArgument::Template)
+      return DeduceTemplateArguments(S, TemplateParams,
+                                     Param.getAsTemplate(),
+                                     Arg.getAsTemplate(), Info, Deduced);
+    Info.FirstArg = Param;
+    Info.SecondArg = Arg;
+    return Sema::TDK_NonDeducedMismatch;
+
+  case TemplateArgument::TemplateExpansion:
+    llvm_unreachable("caller should handle pack expansions");
+
+  case TemplateArgument::Declaration:
+    if (Arg.getKind() == TemplateArgument::Declaration &&
+        isSameDeclaration(Param.getAsDecl(), Arg.getAsDecl()))
+      return Sema::TDK_Success;
+
+    Info.FirstArg = Param;
+    Info.SecondArg = Arg;
+    return Sema::TDK_NonDeducedMismatch;
+
+  case TemplateArgument::Integral:
+    if (Arg.getKind() == TemplateArgument::Integral) {
+      if (hasSameExtendedValue(*Param.getAsIntegral(), *Arg.getAsIntegral()))
+        return Sema::TDK_Success;
+
+      Info.FirstArg = Param;
+      Info.SecondArg = Arg;
+      return Sema::TDK_NonDeducedMismatch;
+    }
+
+    if (Arg.getKind() == TemplateArgument::Expression) {
+      Info.FirstArg = Param;
+      Info.SecondArg = Arg;
+      return Sema::TDK_NonDeducedMismatch;
+    }
+
+    Info.FirstArg = Param;
+    Info.SecondArg = Arg;
+    return Sema::TDK_NonDeducedMismatch;
+
+  case TemplateArgument::Expression: {
+    if (NonTypeTemplateParmDecl *NTTP
+          = getDeducedParameterFromExpr(Param.getAsExpr())) {
+      if (Arg.getKind() == TemplateArgument::Integral)
+        return DeduceNonTypeTemplateArgument(S, NTTP,
+                                             *Arg.getAsIntegral(),
+                                             Arg.getIntegralType(),
+                                             /*ArrayBound=*/false,
+                                             Info, Deduced);
+      if (Arg.getKind() == TemplateArgument::Expression)
+        return DeduceNonTypeTemplateArgument(S, NTTP, Arg.getAsExpr(),
+                                             Info, Deduced);
+      if (Arg.getKind() == TemplateArgument::Declaration)
+        return DeduceNonTypeTemplateArgument(S, NTTP, Arg.getAsDecl(),
+                                             Info, Deduced);
+
+      Info.FirstArg = Param;
+      Info.SecondArg = Arg;
+      return Sema::TDK_NonDeducedMismatch;
+    }
+
+    // Can't deduce anything, but that's okay.
+    return Sema::TDK_Success;
+  }
+  case TemplateArgument::Pack:
+    llvm_unreachable("Argument packs should be expanded by the caller!");
+  }
+
+  llvm_unreachable("Invalid TemplateArgument Kind!");
+}
+
+/// \brief Determine whether there is a template argument to be used for
+/// deduction.
+///
+/// This routine "expands" argument packs in-place, overriding its input
+/// parameters so that \c Args[ArgIdx] will be the available template argument.
+///
+/// \returns true if there is another template argument (which will be at
+/// \c Args[ArgIdx]), false otherwise.
+static bool hasTemplateArgumentForDeduction(const TemplateArgument *&Args,
+                                            unsigned &ArgIdx,
+                                            unsigned &NumArgs) {
+  if (ArgIdx == NumArgs)
+    return false;
+
+  const TemplateArgument &Arg = Args[ArgIdx];
+  if (Arg.getKind() != TemplateArgument::Pack)
+    return true;
+
+  assert(ArgIdx == NumArgs - 1 && "Pack not at the end of argument list?");
+  Args = Arg.pack_begin();
+  NumArgs = Arg.pack_size();
+  ArgIdx = 0;
+  return ArgIdx < NumArgs;
+}
+
+/// \brief Determine whether the given set of template arguments has a pack
+/// expansion that is not the last template argument.
+static bool hasPackExpansionBeforeEnd(const TemplateArgument *Args,
+                                      unsigned NumArgs) {
+  unsigned ArgIdx = 0;
+  while (ArgIdx < NumArgs) {
+    const TemplateArgument &Arg = Args[ArgIdx];
+
+    // Unwrap argument packs.
+    if (Args[ArgIdx].getKind() == TemplateArgument::Pack) {
+      Args = Arg.pack_begin();
+      NumArgs = Arg.pack_size();
+      ArgIdx = 0;
+      continue;
+    }
+
+    ++ArgIdx;
+    if (ArgIdx == NumArgs)
+      return false;
+
+    if (Arg.isPackExpansion())
+      return true;
+  }
+
+  return false;
+}
+
+static Sema::TemplateDeductionResult
+DeduceTemplateArguments(Sema &S,
+                        TemplateParameterList *TemplateParams,
+                        const TemplateArgument *Params, unsigned NumParams,
+                        const TemplateArgument *Args, unsigned NumArgs,
+                        TemplateDeductionInfo &Info,
+                    SmallVectorImpl<DeducedTemplateArgument> &Deduced,
+                        bool NumberOfArgumentsMustMatch) {
+  // C++0x [temp.deduct.type]p9:
+  //   If the template argument list of P contains a pack expansion that is not
+  //   the last template argument, the entire template argument list is a
+  //   non-deduced context.
+  if (hasPackExpansionBeforeEnd(Params, NumParams))
+    return Sema::TDK_Success;
+
+  // C++0x [temp.deduct.type]p9:
+  //   If P has a form that contains <T> or <i>, then each argument Pi of the
+  //   respective template argument list P is compared with the corresponding
+  //   argument Ai of the corresponding template argument list of A.
+  unsigned ArgIdx = 0, ParamIdx = 0;
+  for (; hasTemplateArgumentForDeduction(Params, ParamIdx, NumParams);
+       ++ParamIdx) {
+    if (!Params[ParamIdx].isPackExpansion()) {
+      // The simple case: deduce template arguments by matching Pi and Ai.
+
+      // Check whether we have enough arguments.
+      if (!hasTemplateArgumentForDeduction(Args, ArgIdx, NumArgs))
+        return NumberOfArgumentsMustMatch? Sema::TDK_NonDeducedMismatch
+                                         : Sema::TDK_Success;
+
+      if (Args[ArgIdx].isPackExpansion()) {
+        // FIXME: We follow the logic of C++0x [temp.deduct.type]p22 here,
+        // but applied to pack expansions that are template arguments.
+        return Sema::TDK_NonDeducedMismatch;
+      }
+
+      // Perform deduction for this Pi/Ai pair.
+      if (Sema::TemplateDeductionResult Result
+            = DeduceTemplateArguments(S, TemplateParams,
+                                      Params[ParamIdx], Args[ArgIdx],
+                                      Info, Deduced))
+        return Result;
+
+      // Move to the next argument.
+      ++ArgIdx;
+      continue;
+    }
+
+    // The parameter is a pack expansion.
+
+    // C++0x [temp.deduct.type]p9:
+    //   If Pi is a pack expansion, then the pattern of Pi is compared with
+    //   each remaining argument in the template argument list of A. Each
+    //   comparison deduces template arguments for subsequent positions in the
+    //   template parameter packs expanded by Pi.
+    TemplateArgument Pattern = Params[ParamIdx].getPackExpansionPattern();
+
+    // Compute the set of template parameter indices that correspond to
+    // parameter packs expanded by the pack expansion.
+    SmallVector<unsigned, 2> PackIndices;
+    {
+      llvm::SmallBitVector SawIndices(TemplateParams->size());
+      SmallVector<UnexpandedParameterPack, 2> Unexpanded;
+      S.collectUnexpandedParameterPacks(Pattern, Unexpanded);
+      for (unsigned I = 0, N = Unexpanded.size(); I != N; ++I) {
+        unsigned Depth, Index;
+        llvm::tie(Depth, Index) = getDepthAndIndex(Unexpanded[I]);
+        if (Depth == 0 && !SawIndices[Index]) {
+          SawIndices[Index] = true;
+          PackIndices.push_back(Index);
+        }
+      }
+    }
+    assert(!PackIndices.empty() && "Pack expansion without unexpanded packs?");
+
+    // FIXME: If there are no remaining arguments, we can bail out early
+    // and set any deduced parameter packs to an empty argument pack.
+    // The latter part of this is a (minor) correctness issue.
+
+    // Save the deduced template arguments for each parameter pack expanded
+    // by this pack expansion, then clear out the deduction.
+    SmallVector<DeducedTemplateArgument, 2>
+      SavedPacks(PackIndices.size());
+    SmallVector<SmallVector<DeducedTemplateArgument, 4>, 2>
+      NewlyDeducedPacks(PackIndices.size());
+    PrepareArgumentPackDeduction(S, Deduced, PackIndices, SavedPacks,
+                                 NewlyDeducedPacks);
+
+    // Keep track of the deduced template arguments for each parameter pack
+    // expanded by this pack expansion (the outer index) and for each
+    // template argument (the inner SmallVectors).
+    bool HasAnyArguments = false;
+    while (hasTemplateArgumentForDeduction(Args, ArgIdx, NumArgs)) {
+      HasAnyArguments = true;
+
+      // Deduce template arguments from the pattern.
+      if (Sema::TemplateDeductionResult Result
+            = DeduceTemplateArguments(S, TemplateParams, Pattern, Args[ArgIdx],
+                                      Info, Deduced))
+        return Result;
+
+      // Capture the deduced template arguments for each parameter pack expanded
+      // by this pack expansion, add them to the list of arguments we've deduced
+      // for that pack, then clear out the deduced argument.
+      for (unsigned I = 0, N = PackIndices.size(); I != N; ++I) {
+        DeducedTemplateArgument &DeducedArg = Deduced[PackIndices[I]];
+        if (!DeducedArg.isNull()) {
+          NewlyDeducedPacks[I].push_back(DeducedArg);
+          DeducedArg = DeducedTemplateArgument();
+        }
+      }
+
+      ++ArgIdx;
+    }
+
+    // Build argument packs for each of the parameter packs expanded by this
+    // pack expansion.
+    if (Sema::TemplateDeductionResult Result
+          = FinishArgumentPackDeduction(S, TemplateParams, HasAnyArguments,
+                                        Deduced, PackIndices, SavedPacks,
+                                        NewlyDeducedPacks, Info))
+      return Result;
+  }
+
+  // If there is an argument remaining, then we had too many arguments.
+  if (NumberOfArgumentsMustMatch &&
+      hasTemplateArgumentForDeduction(Args, ArgIdx, NumArgs))
+    return Sema::TDK_NonDeducedMismatch;
+
+  return Sema::TDK_Success;
+}
+
+static Sema::TemplateDeductionResult
+DeduceTemplateArguments(Sema &S,
+                        TemplateParameterList *TemplateParams,
+                        const TemplateArgumentList &ParamList,
+                        const TemplateArgumentList &ArgList,
+                        TemplateDeductionInfo &Info,
+                    SmallVectorImpl<DeducedTemplateArgument> &Deduced) {
+  return DeduceTemplateArguments(S, TemplateParams,
+                                 ParamList.data(), ParamList.size(),
+                                 ArgList.data(), ArgList.size(),
+                                 Info, Deduced);
+}
+
+/// \brief Determine whether two template arguments are the same.
+static bool isSameTemplateArg(ASTContext &Context,
+                              const TemplateArgument &X,
+                              const TemplateArgument &Y) {
+  if (X.getKind() != Y.getKind())
+    return false;
+
+  switch (X.getKind()) {
+    case TemplateArgument::Null:
+      llvm_unreachable("Comparing NULL template argument");
+
+    case TemplateArgument::Type:
+      return Context.getCanonicalType(X.getAsType()) ==
+             Context.getCanonicalType(Y.getAsType());
+
+    case TemplateArgument::Declaration:
+      return isSameDeclaration(X.getAsDecl(), Y.getAsDecl());
+
+    case TemplateArgument::Template:
+    case TemplateArgument::TemplateExpansion:
+      return Context.getCanonicalTemplateName(
+                    X.getAsTemplateOrTemplatePattern()).getAsVoidPointer() ==
+             Context.getCanonicalTemplateName(
+                    Y.getAsTemplateOrTemplatePattern()).getAsVoidPointer();
+
+    case TemplateArgument::Integral:
+      return *X.getAsIntegral() == *Y.getAsIntegral();
+
+    case TemplateArgument::Expression: {
+      llvm::FoldingSetNodeID XID, YID;
+      X.getAsExpr()->Profile(XID, Context, true);
+      Y.getAsExpr()->Profile(YID, Context, true);
+      return XID == YID;
+    }
+
+    case TemplateArgument::Pack:
+      if (X.pack_size() != Y.pack_size())
+        return false;
+
+      for (TemplateArgument::pack_iterator XP = X.pack_begin(),
+                                        XPEnd = X.pack_end(),
+                                           YP = Y.pack_begin();
+           XP != XPEnd; ++XP, ++YP)
+        if (!isSameTemplateArg(Context, *XP, *YP))
+          return false;
+
+      return true;
+  }
+
+  llvm_unreachable("Invalid TemplateArgument Kind!");
+}
+
+/// \brief Allocate a TemplateArgumentLoc where all locations have
+/// been initialized to the given location.
+///
+/// \param S The semantic analysis object.
+///
+/// \param The template argument we are producing template argument
+/// location information for.
+///
+/// \param NTTPType For a declaration template argument, the type of
+/// the non-type template parameter that corresponds to this template
+/// argument.
+///
+/// \param Loc The source location to use for the resulting template
+/// argument.
+static TemplateArgumentLoc
+getTrivialTemplateArgumentLoc(Sema &S,
+                              const TemplateArgument &Arg,
+                              QualType NTTPType,
+                              SourceLocation Loc) {
+  switch (Arg.getKind()) {
+  case TemplateArgument::Null:
+    llvm_unreachable("Can't get a NULL template argument here");
+
+  case TemplateArgument::Type:
+    return TemplateArgumentLoc(Arg,
+                     S.Context.getTrivialTypeSourceInfo(Arg.getAsType(), Loc));
+
+  case TemplateArgument::Declaration: {
+    Expr *E
+      = S.BuildExpressionFromDeclTemplateArgument(Arg, NTTPType, Loc)
+          .takeAs<Expr>();
+    return TemplateArgumentLoc(TemplateArgument(E), E);
+  }
+
+  case TemplateArgument::Integral: {
+    Expr *E
+      = S.BuildExpressionFromIntegralTemplateArgument(Arg, Loc).takeAs<Expr>();
+    return TemplateArgumentLoc(TemplateArgument(E), E);
+  }
+
+    case TemplateArgument::Template:
+    case TemplateArgument::TemplateExpansion: {
+      NestedNameSpecifierLocBuilder Builder;
+      TemplateName Template = Arg.getAsTemplate();
+      if (DependentTemplateName *DTN = Template.getAsDependentTemplateName())
+        Builder.MakeTrivial(S.Context, DTN->getQualifier(), Loc);
+      else if (QualifiedTemplateName *QTN = Template.getAsQualifiedTemplateName())
+        Builder.MakeTrivial(S.Context, QTN->getQualifier(), Loc);
+      
+      if (Arg.getKind() == TemplateArgument::Template)
+        return TemplateArgumentLoc(Arg, 
+                                   Builder.getWithLocInContext(S.Context),
+                                   Loc);
+      
+      
+      return TemplateArgumentLoc(Arg, Builder.getWithLocInContext(S.Context),
+                                 Loc, Loc);
+    }
+
+  case TemplateArgument::Expression:
+    return TemplateArgumentLoc(Arg, Arg.getAsExpr());
+
+  case TemplateArgument::Pack:
+    return TemplateArgumentLoc(Arg, TemplateArgumentLocInfo());
+  }
+
+  llvm_unreachable("Invalid TemplateArgument Kind!");
+}
+
+
+/// \brief Convert the given deduced template argument and add it to the set of
+/// fully-converted template arguments.
+static bool ConvertDeducedTemplateArgument(Sema &S, NamedDecl *Param,
+                                           DeducedTemplateArgument Arg,
+                                           NamedDecl *Template,
+                                           QualType NTTPType,
+                                           unsigned ArgumentPackIndex,
+                                           TemplateDeductionInfo &Info,
+                                           bool InFunctionTemplate,
+                             SmallVectorImpl<TemplateArgument> &Output) {
+  if (Arg.getKind() == TemplateArgument::Pack) {
+    // This is a template argument pack, so check each of its arguments against
+    // the template parameter.
+    SmallVector<TemplateArgument, 2> PackedArgsBuilder;
+    for (TemplateArgument::pack_iterator PA = Arg.pack_begin(),
+                                      PAEnd = Arg.pack_end();
+         PA != PAEnd; ++PA) {
+      // When converting the deduced template argument, append it to the
+      // general output list. We need to do this so that the template argument
+      // checking logic has all of the prior template arguments available.
+      DeducedTemplateArgument InnerArg(*PA);
+      InnerArg.setDeducedFromArrayBound(Arg.wasDeducedFromArrayBound());
+      if (ConvertDeducedTemplateArgument(S, Param, InnerArg, Template,
+                                         NTTPType, PackedArgsBuilder.size(),
+                                         Info, InFunctionTemplate, Output))
+        return true;
+
+      // Move the converted template argument into our argument pack.
+      PackedArgsBuilder.push_back(Output.back());
+      Output.pop_back();
+    }
+
+    // Create the resulting argument pack.
+    Output.push_back(TemplateArgument::CreatePackCopy(S.Context,
+                                                      PackedArgsBuilder.data(),
+                                                     PackedArgsBuilder.size()));
+    return false;
+  }
+
+  // Convert the deduced template argument into a template
+  // argument that we can check, almost as if the user had written
+  // the template argument explicitly.
+  TemplateArgumentLoc ArgLoc = getTrivialTemplateArgumentLoc(S, Arg, NTTPType,
+                                                             Info.getLocation());
+
+  // Check the template argument, converting it as necessary.
+  return S.CheckTemplateArgument(Param, ArgLoc,
+                                 Template,
+                                 Template->getLocation(),
+                                 Template->getSourceRange().getEnd(),
+                                 ArgumentPackIndex,
+                                 Output,
+                                 InFunctionTemplate
+                                  ? (Arg.wasDeducedFromArrayBound()
+                                       ? Sema::CTAK_DeducedFromArrayBound
+                                       : Sema::CTAK_Deduced)
+                                 : Sema::CTAK_Specified);
+}
+
+/// Complete template argument deduction for a class template partial
+/// specialization.
+static Sema::TemplateDeductionResult
+FinishTemplateArgumentDeduction(Sema &S,
+                                ClassTemplatePartialSpecializationDecl *Partial,
+                                const TemplateArgumentList &TemplateArgs,
+                      SmallVectorImpl<DeducedTemplateArgument> &Deduced,
+                                TemplateDeductionInfo &Info) {
+  // Unevaluated SFINAE context.
+  EnterExpressionEvaluationContext Unevaluated(S, Sema::Unevaluated);
+  Sema::SFINAETrap Trap(S);
+
+  Sema::ContextRAII SavedContext(S, Partial);
+
+  // C++ [temp.deduct.type]p2:
+  //   [...] or if any template argument remains neither deduced nor
+  //   explicitly specified, template argument deduction fails.
+  SmallVector<TemplateArgument, 4> Builder;
+  TemplateParameterList *PartialParams = Partial->getTemplateParameters();
+  for (unsigned I = 0, N = PartialParams->size(); I != N; ++I) {
+    NamedDecl *Param = PartialParams->getParam(I);
+    if (Deduced[I].isNull()) {
+      Info.Param = makeTemplateParameter(Param);
+      return Sema::TDK_Incomplete;
+    }
+
+    // We have deduced this argument, so it still needs to be
+    // checked and converted.
+
+    // First, for a non-type template parameter type that is
+    // initialized by a declaration, we need the type of the
+    // corresponding non-type template parameter.
+    QualType NTTPType;
+    if (NonTypeTemplateParmDecl *NTTP
+                                  = dyn_cast<NonTypeTemplateParmDecl>(Param)) {
+      NTTPType = NTTP->getType();
+      if (NTTPType->isDependentType()) {
+        TemplateArgumentList TemplateArgs(TemplateArgumentList::OnStack,
+                                          Builder.data(), Builder.size());
+        NTTPType = S.SubstType(NTTPType,
+                               MultiLevelTemplateArgumentList(TemplateArgs),
+                               NTTP->getLocation(),
+                               NTTP->getDeclName());
+        if (NTTPType.isNull()) {
+          Info.Param = makeTemplateParameter(Param);
+          // FIXME: These template arguments are temporary. Free them!
+          Info.reset(TemplateArgumentList::CreateCopy(S.Context,
+                                                      Builder.data(),
+                                                      Builder.size()));
+          return Sema::TDK_SubstitutionFailure;
+        }
+      }
+    }
+
+    if (ConvertDeducedTemplateArgument(S, Param, Deduced[I],
+                                       Partial, NTTPType, 0, Info, false,
+                                       Builder)) {
+      Info.Param = makeTemplateParameter(Param);
+      // FIXME: These template arguments are temporary. Free them!
+      Info.reset(TemplateArgumentList::CreateCopy(S.Context, Builder.data(),
+                                                  Builder.size()));
+      return Sema::TDK_SubstitutionFailure;
+    }
+  }
+
+  // Form the template argument list from the deduced template arguments.
+  TemplateArgumentList *DeducedArgumentList
+    = TemplateArgumentList::CreateCopy(S.Context, Builder.data(),
+                                       Builder.size());
+
+  Info.reset(DeducedArgumentList);
+
+  // Substitute the deduced template arguments into the template
+  // arguments of the class template partial specialization, and
+  // verify that the instantiated template arguments are both valid
+  // and are equivalent to the template arguments originally provided
+  // to the class template.
+  LocalInstantiationScope InstScope(S);
+  ClassTemplateDecl *ClassTemplate = Partial->getSpecializedTemplate();
+  const TemplateArgumentLoc *PartialTemplateArgs
+    = Partial->getTemplateArgsAsWritten();
+
+  // Note that we don't provide the langle and rangle locations.
+  TemplateArgumentListInfo InstArgs;
+
+  if (S.Subst(PartialTemplateArgs,
+              Partial->getNumTemplateArgsAsWritten(),
+              InstArgs, MultiLevelTemplateArgumentList(*DeducedArgumentList))) {
+    unsigned ArgIdx = InstArgs.size(), ParamIdx = ArgIdx;
+    if (ParamIdx >= Partial->getTemplateParameters()->size())
+      ParamIdx = Partial->getTemplateParameters()->size() - 1;
+
+    Decl *Param
+      = const_cast<NamedDecl *>(
+                          Partial->getTemplateParameters()->getParam(ParamIdx));
+    Info.Param = makeTemplateParameter(Param);
+    Info.FirstArg = PartialTemplateArgs[ArgIdx].getArgument();
+    return Sema::TDK_SubstitutionFailure;
+  }
+
+  SmallVector<TemplateArgument, 4> ConvertedInstArgs;
+  if (S.CheckTemplateArgumentList(ClassTemplate, Partial->getLocation(),
+                                  InstArgs, false, ConvertedInstArgs))
+    return Sema::TDK_SubstitutionFailure;
+
+  TemplateParameterList *TemplateParams
+    = ClassTemplate->getTemplateParameters();
+  for (unsigned I = 0, E = TemplateParams->size(); I != E; ++I) {
+    TemplateArgument InstArg = ConvertedInstArgs.data()[I];
+    if (!isSameTemplateArg(S.Context, TemplateArgs[I], InstArg)) {
+      Info.Param = makeTemplateParameter(TemplateParams->getParam(I));
+      Info.FirstArg = TemplateArgs[I];
+      Info.SecondArg = InstArg;
+      return Sema::TDK_NonDeducedMismatch;
+    }
+  }
+
+  if (Trap.hasErrorOccurred())
+    return Sema::TDK_SubstitutionFailure;
+
+  return Sema::TDK_Success;
+}
+
+/// \brief Perform template argument deduction to determine whether
+/// the given template arguments match the given class template
+/// partial specialization per C++ [temp.class.spec.match].
+Sema::TemplateDeductionResult
+Sema::DeduceTemplateArguments(ClassTemplatePartialSpecializationDecl *Partial,
+                              const TemplateArgumentList &TemplateArgs,
+                              TemplateDeductionInfo &Info) {
+  // C++ [temp.class.spec.match]p2:
+  //   A partial specialization matches a given actual template
+  //   argument list if the template arguments of the partial
+  //   specialization can be deduced from the actual template argument
+  //   list (14.8.2).
+
+  // Unevaluated SFINAE context.
+  EnterExpressionEvaluationContext Unevaluated(*this, Sema::Unevaluated);
+  SFINAETrap Trap(*this);
+
+  SmallVector<DeducedTemplateArgument, 4> Deduced;
+  Deduced.resize(Partial->getTemplateParameters()->size());
+  if (TemplateDeductionResult Result
+        = ::DeduceTemplateArguments(*this,
+                                    Partial->getTemplateParameters(),
+                                    Partial->getTemplateArgs(),
+                                    TemplateArgs, Info, Deduced))
+    return Result;
+
+  InstantiatingTemplate Inst(*this, Partial->getLocation(), Partial,
+                             Deduced.data(), Deduced.size(), Info);
+  if (Inst)
+    return TDK_InstantiationDepth;
+
+  if (Trap.hasErrorOccurred())
+    return Sema::TDK_SubstitutionFailure;
+
+  return ::FinishTemplateArgumentDeduction(*this, Partial, TemplateArgs,
+                                           Deduced, Info);
+}
+
+/// \brief Determine whether the given type T is a simple-template-id type.
+static bool isSimpleTemplateIdType(QualType T) {
+  if (const TemplateSpecializationType *Spec
+        = T->getAs<TemplateSpecializationType>())
+    return Spec->getTemplateName().getAsTemplateDecl() != 0;
+
+  return false;
+}
+
+/// \brief Substitute the explicitly-provided template arguments into the
+/// given function template according to C++ [temp.arg.explicit].
+///
+/// \param FunctionTemplate the function template into which the explicit
+/// template arguments will be substituted.
+///
+/// \param ExplicitTemplateArguments the explicitly-specified template
+/// arguments.
+///
+/// \param Deduced the deduced template arguments, which will be populated
+/// with the converted and checked explicit template arguments.
+///
+/// \param ParamTypes will be populated with the instantiated function
+/// parameters.
+///
+/// \param FunctionType if non-NULL, the result type of the function template
+/// will also be instantiated and the pointed-to value will be updated with
+/// the instantiated function type.
+///
+/// \param Info if substitution fails for any reason, this object will be
+/// populated with more information about the failure.
+///
+/// \returns TDK_Success if substitution was successful, or some failure
+/// condition.
+Sema::TemplateDeductionResult
+Sema::SubstituteExplicitTemplateArguments(
+                                      FunctionTemplateDecl *FunctionTemplate,
+                               TemplateArgumentListInfo &ExplicitTemplateArgs,
+                       SmallVectorImpl<DeducedTemplateArgument> &Deduced,
+                                 SmallVectorImpl<QualType> &ParamTypes,
+                                          QualType *FunctionType,
+                                          TemplateDeductionInfo &Info) {
+  FunctionDecl *Function = FunctionTemplate->getTemplatedDecl();
+  TemplateParameterList *TemplateParams
+    = FunctionTemplate->getTemplateParameters();
+
+  if (ExplicitTemplateArgs.size() == 0) {
+    // No arguments to substitute; just copy over the parameter types and
+    // fill in the function type.
+    for (FunctionDecl::param_iterator P = Function->param_begin(),
+                                   PEnd = Function->param_end();
+         P != PEnd;
+         ++P)
+      ParamTypes.push_back((*P)->getType());
+
+    if (FunctionType)
+      *FunctionType = Function->getType();
+    return TDK_Success;
+  }
+
+  // Unevaluated SFINAE context.
+  EnterExpressionEvaluationContext Unevaluated(*this, Sema::Unevaluated);
+  SFINAETrap Trap(*this);
+
+  // C++ [temp.arg.explicit]p3:
+  //   Template arguments that are present shall be specified in the
+  //   declaration order of their corresponding template-parameters. The
+  //   template argument list shall not specify more template-arguments than
+  //   there are corresponding template-parameters.
+  SmallVector<TemplateArgument, 4> Builder;
+
+  // Enter a new template instantiation context where we check the
+  // explicitly-specified template arguments against this function template,
+  // and then substitute them into the function parameter types.
+  InstantiatingTemplate Inst(*this, FunctionTemplate->getLocation(),
+                             FunctionTemplate, Deduced.data(), Deduced.size(),
+           ActiveTemplateInstantiation::ExplicitTemplateArgumentSubstitution,
+                             Info);
+  if (Inst)
+    return TDK_InstantiationDepth;
+
+  if (CheckTemplateArgumentList(FunctionTemplate,
+                                SourceLocation(),
+                                ExplicitTemplateArgs,
+                                true,
+                                Builder) || Trap.hasErrorOccurred()) {
+    unsigned Index = Builder.size();
+    if (Index >= TemplateParams->size())
+      Index = TemplateParams->size() - 1;
+    Info.Param = makeTemplateParameter(TemplateParams->getParam(Index));
+    return TDK_InvalidExplicitArguments;
+  }
+
+  // Form the template argument list from the explicitly-specified
+  // template arguments.
+  TemplateArgumentList *ExplicitArgumentList
+    = TemplateArgumentList::CreateCopy(Context, Builder.data(), Builder.size());
+  Info.reset(ExplicitArgumentList);
+
+  // Template argument deduction and the final substitution should be
+  // done in the context of the templated declaration.  Explicit
+  // argument substitution, on the other hand, needs to happen in the
+  // calling context.
+  ContextRAII SavedContext(*this, FunctionTemplate->getTemplatedDecl());
+
+  // If we deduced template arguments for a template parameter pack,
+  // note that the template argument pack is partially substituted and record
+  // the explicit template arguments. They'll be used as part of deduction
+  // for this template parameter pack.
+  for (unsigned I = 0, N = Builder.size(); I != N; ++I) {
+    const TemplateArgument &Arg = Builder[I];
+    if (Arg.getKind() == TemplateArgument::Pack) {
+      CurrentInstantiationScope->SetPartiallySubstitutedPack(
+                                                 TemplateParams->getParam(I),
+                                                             Arg.pack_begin(),
+                                                             Arg.pack_size());
+      break;
+    }
+  }
+
+  const FunctionProtoType *Proto
+    = Function->getType()->getAs<FunctionProtoType>();
+  assert(Proto && "Function template does not have a prototype?");
+
+  // Instantiate the types of each of the function parameters given the
+  // explicitly-specified template arguments. If the function has a trailing
+  // return type, substitute it after the arguments to ensure we substitute
+  // in lexical order.
+  if (Proto->hasTrailingReturn()) {
+    if (SubstParmTypes(Function->getLocation(),
+                       Function->param_begin(), Function->getNumParams(),
+                       MultiLevelTemplateArgumentList(*ExplicitArgumentList),
+                       ParamTypes))
+      return TDK_SubstitutionFailure;
+  }
+  
+  // Instantiate the return type.
+  // FIXME: exception-specifications?
+  QualType ResultType;
+  {
+    // C++11 [expr.prim.general]p3:
+    //   If a declaration declares a member function or member function 
+    //   template of a class X, the expression this is a prvalue of type 
+    //   "pointer to cv-qualifier-seq X" between the optional cv-qualifer-seq
+    //   and the end of the function-definition, member-declarator, or 
+    //   declarator.
+    unsigned ThisTypeQuals = 0;
+    CXXRecordDecl *ThisContext = 0;
+    if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Function)) {
+      ThisContext = Method->getParent();
+      ThisTypeQuals = Method->getTypeQualifiers();
+    }
+      
+    CXXThisScopeRAII ThisScope(*this, ThisContext, ThisTypeQuals,
+                               getLangOpts().CPlusPlus0x);
+    
+    ResultType = SubstType(Proto->getResultType(),
+                   MultiLevelTemplateArgumentList(*ExplicitArgumentList),
+                   Function->getTypeSpecStartLoc(),
+                   Function->getDeclName());
+    if (ResultType.isNull() || Trap.hasErrorOccurred())
+      return TDK_SubstitutionFailure;
+  }
+  
+  // Instantiate the types of each of the function parameters given the
+  // explicitly-specified template arguments if we didn't do so earlier.
+  if (!Proto->hasTrailingReturn() &&
+      SubstParmTypes(Function->getLocation(),
+                     Function->param_begin(), Function->getNumParams(),
+                     MultiLevelTemplateArgumentList(*ExplicitArgumentList),
+                     ParamTypes))
+    return TDK_SubstitutionFailure;
+
+  if (FunctionType) {
+    *FunctionType = BuildFunctionType(ResultType,
+                                      ParamTypes.data(), ParamTypes.size(),
+                                      Proto->isVariadic(),
+                                      Proto->hasTrailingReturn(),
+                                      Proto->getTypeQuals(),
+                                      Proto->getRefQualifier(),
+                                      Function->getLocation(),
+                                      Function->getDeclName(),
+                                      Proto->getExtInfo());
+    if (FunctionType->isNull() || Trap.hasErrorOccurred())
+      return TDK_SubstitutionFailure;
+  }
+
+  // C++ [temp.arg.explicit]p2:
+  //   Trailing template arguments that can be deduced (14.8.2) may be
+  //   omitted from the list of explicit template-arguments. If all of the
+  //   template arguments can be deduced, they may all be omitted; in this
+  //   case, the empty template argument list <> itself may also be omitted.
+  //
+  // Take all of the explicitly-specified arguments and put them into
+  // the set of deduced template arguments. Explicitly-specified
+  // parameter packs, however, will be set to NULL since the deduction
+  // mechanisms handle explicitly-specified argument packs directly.
+  Deduced.reserve(TemplateParams->size());
+  for (unsigned I = 0, N = ExplicitArgumentList->size(); I != N; ++I) {
+    const TemplateArgument &Arg = ExplicitArgumentList->get(I);
+    if (Arg.getKind() == TemplateArgument::Pack)
+      Deduced.push_back(DeducedTemplateArgument());
+    else
+      Deduced.push_back(Arg);
+  }
+
+  return TDK_Success;
+}
+
+/// \brief Check whether the deduced argument type for a call to a function
+/// template matches the actual argument type per C++ [temp.deduct.call]p4.
+static bool 
+CheckOriginalCallArgDeduction(Sema &S, Sema::OriginalCallArg OriginalArg, 
+                              QualType DeducedA) {
+  ASTContext &Context = S.Context;
+  
+  QualType A = OriginalArg.OriginalArgType;
+  QualType OriginalParamType = OriginalArg.OriginalParamType;
+  
+  // Check for type equality (top-level cv-qualifiers are ignored).
+  if (Context.hasSameUnqualifiedType(A, DeducedA))
+    return false;
+  
+  // Strip off references on the argument types; they aren't needed for
+  // the following checks.
+  if (const ReferenceType *DeducedARef = DeducedA->getAs<ReferenceType>())
+    DeducedA = DeducedARef->getPointeeType();
+  if (const ReferenceType *ARef = A->getAs<ReferenceType>())
+    A = ARef->getPointeeType();
+  
+  // C++ [temp.deduct.call]p4:
+  //   [...] However, there are three cases that allow a difference:
+  //     - If the original P is a reference type, the deduced A (i.e., the 
+  //       type referred to by the reference) can be more cv-qualified than 
+  //       the transformed A.
+  if (const ReferenceType *OriginalParamRef
+      = OriginalParamType->getAs<ReferenceType>()) {
+    // We don't want to keep the reference around any more.
+    OriginalParamType = OriginalParamRef->getPointeeType();
+    
+    Qualifiers AQuals = A.getQualifiers();
+    Qualifiers DeducedAQuals = DeducedA.getQualifiers();
+    if (AQuals == DeducedAQuals) {
+      // Qualifiers match; there's nothing to do.
+    } else if (!DeducedAQuals.compatiblyIncludes(AQuals)) {
+      return true;
+    } else {        
+      // Qualifiers are compatible, so have the argument type adopt the
+      // deduced argument type's qualifiers as if we had performed the
+      // qualification conversion.
+      A = Context.getQualifiedType(A.getUnqualifiedType(), DeducedAQuals);
+    }
+  }
+  
+  //    - The transformed A can be another pointer or pointer to member 
+  //      type that can be converted to the deduced A via a qualification 
+  //      conversion.
+  //
+  // Also allow conversions which merely strip [[noreturn]] from function types
+  // (recursively) as an extension.
+  // FIXME: Currently, this doesn't place nicely with qualfication conversions.
+  bool ObjCLifetimeConversion = false;
+  QualType ResultTy;
+  if ((A->isAnyPointerType() || A->isMemberPointerType()) &&
+      (S.IsQualificationConversion(A, DeducedA, false,
+                                   ObjCLifetimeConversion) ||
+       S.IsNoReturnConversion(A, DeducedA, ResultTy)))
+    return false;
+  
+  
+  //    - If P is a class and P has the form simple-template-id, then the 
+  //      transformed A can be a derived class of the deduced A. [...]
+  //     [...] Likewise, if P is a pointer to a class of the form 
+  //      simple-template-id, the transformed A can be a pointer to a 
+  //      derived class pointed to by the deduced A.
+  if (const PointerType *OriginalParamPtr
+      = OriginalParamType->getAs<PointerType>()) {
+    if (const PointerType *DeducedAPtr = DeducedA->getAs<PointerType>()) {
+      if (const PointerType *APtr = A->getAs<PointerType>()) {
+        if (A->getPointeeType()->isRecordType()) {
+          OriginalParamType = OriginalParamPtr->getPointeeType();
+          DeducedA = DeducedAPtr->getPointeeType();
+          A = APtr->getPointeeType();
+        }
+      }
+    }
+  }
+  
+  if (Context.hasSameUnqualifiedType(A, DeducedA))
+    return false;
+  
+  if (A->isRecordType() && isSimpleTemplateIdType(OriginalParamType) &&
+      S.IsDerivedFrom(A, DeducedA))
+    return false;
+  
+  return true;
+}
+
+/// \brief Finish template argument deduction for a function template,
+/// checking the deduced template arguments for completeness and forming
+/// the function template specialization.
+///
+/// \param OriginalCallArgs If non-NULL, the original call arguments against
+/// which the deduced argument types should be compared.
+Sema::TemplateDeductionResult
+Sema::FinishTemplateArgumentDeduction(FunctionTemplateDecl *FunctionTemplate,
+                       SmallVectorImpl<DeducedTemplateArgument> &Deduced,
+                                      unsigned NumExplicitlySpecified,
+                                      FunctionDecl *&Specialization,
+                                      TemplateDeductionInfo &Info,
+        SmallVectorImpl<OriginalCallArg> const *OriginalCallArgs) {
+  TemplateParameterList *TemplateParams
+    = FunctionTemplate->getTemplateParameters();
+
+  // Unevaluated SFINAE context.
+  EnterExpressionEvaluationContext Unevaluated(*this, Sema::Unevaluated);
+  SFINAETrap Trap(*this);
+
+  // Enter a new template instantiation context while we instantiate the
+  // actual function declaration.
+  InstantiatingTemplate Inst(*this, FunctionTemplate->getLocation(),
+                             FunctionTemplate, Deduced.data(), Deduced.size(),
+              ActiveTemplateInstantiation::DeducedTemplateArgumentSubstitution,
+                             Info);
+  if (Inst)
+    return TDK_InstantiationDepth;
+
+  ContextRAII SavedContext(*this, FunctionTemplate->getTemplatedDecl());
+
+  // C++ [temp.deduct.type]p2:
+  //   [...] or if any template argument remains neither deduced nor
+  //   explicitly specified, template argument deduction fails.
+  SmallVector<TemplateArgument, 4> Builder;
+  for (unsigned I = 0, N = TemplateParams->size(); I != N; ++I) {
+    NamedDecl *Param = TemplateParams->getParam(I);
+
+    if (!Deduced[I].isNull()) {
+      if (I < NumExplicitlySpecified) {
+        // We have already fully type-checked and converted this
+        // argument, because it was explicitly-specified. Just record the
+        // presence of this argument.
+        Builder.push_back(Deduced[I]);
+        continue;
+      }
+
+      // We have deduced this argument, so it still needs to be
+      // checked and converted.
+
+      // First, for a non-type template parameter type that is
+      // initialized by a declaration, we need the type of the
+      // corresponding non-type template parameter.
+      QualType NTTPType;
+      if (NonTypeTemplateParmDecl *NTTP
+                                = dyn_cast<NonTypeTemplateParmDecl>(Param)) {
+        NTTPType = NTTP->getType();
+        if (NTTPType->isDependentType()) {
+          TemplateArgumentList TemplateArgs(TemplateArgumentList::OnStack,
+                                            Builder.data(), Builder.size());
+          NTTPType = SubstType(NTTPType,
+                               MultiLevelTemplateArgumentList(TemplateArgs),
+                               NTTP->getLocation(),
+                               NTTP->getDeclName());
+          if (NTTPType.isNull()) {
+            Info.Param = makeTemplateParameter(Param);
+            // FIXME: These template arguments are temporary. Free them!
+            Info.reset(TemplateArgumentList::CreateCopy(Context,
+                                                        Builder.data(),
+                                                        Builder.size()));
+            return TDK_SubstitutionFailure;
+          }
+        }
+      }
+
+      if (ConvertDeducedTemplateArgument(*this, Param, Deduced[I],
+                                         FunctionTemplate, NTTPType, 0, Info,
+                                         true, Builder)) {
+        Info.Param = makeTemplateParameter(Param);
+        // FIXME: These template arguments are temporary. Free them!
+        Info.reset(TemplateArgumentList::CreateCopy(Context, Builder.data(),
+                                                    Builder.size()));
+        return TDK_SubstitutionFailure;
+      }
+
+      continue;
+    }
+
+    // C++0x [temp.arg.explicit]p3:
+    //    A trailing template parameter pack (14.5.3) not otherwise deduced will
+    //    be deduced to an empty sequence of template arguments.
+    // FIXME: Where did the word "trailing" come from?
+    if (Param->isTemplateParameterPack()) {
+      // We may have had explicitly-specified template arguments for this
+      // template parameter pack. If so, our empty deduction extends the
+      // explicitly-specified set (C++0x [temp.arg.explicit]p9).
+      const TemplateArgument *ExplicitArgs;
+      unsigned NumExplicitArgs;
+      if (CurrentInstantiationScope->getPartiallySubstitutedPack(&ExplicitArgs,
+                                                             &NumExplicitArgs)
+          == Param)
+        Builder.push_back(TemplateArgument(ExplicitArgs, NumExplicitArgs));
+      else
+        Builder.push_back(TemplateArgument(0, 0));
+
+      continue;
+    }
+
+    // Substitute into the default template argument, if available.
+    TemplateArgumentLoc DefArg
+      = SubstDefaultTemplateArgumentIfAvailable(FunctionTemplate,
+                                              FunctionTemplate->getLocation(),
+                                  FunctionTemplate->getSourceRange().getEnd(),
+                                                Param,
+                                                Builder);
+
+    // If there was no default argument, deduction is incomplete.
+    if (DefArg.getArgument().isNull()) {
+      Info.Param = makeTemplateParameter(
+                         const_cast<NamedDecl *>(TemplateParams->getParam(I)));
+      return TDK_Incomplete;
+    }
+
+    // Check whether we can actually use the default argument.
+    if (CheckTemplateArgument(Param, DefArg,
+                              FunctionTemplate,
+                              FunctionTemplate->getLocation(),
+                              FunctionTemplate->getSourceRange().getEnd(),
+                              0, Builder,
+                              CTAK_Specified)) {
+      Info.Param = makeTemplateParameter(
+                         const_cast<NamedDecl *>(TemplateParams->getParam(I)));
+      // FIXME: These template arguments are temporary. Free them!
+      Info.reset(TemplateArgumentList::CreateCopy(Context, Builder.data(),
+                                                  Builder.size()));
+      return TDK_SubstitutionFailure;
+    }
+
+    // If we get here, we successfully used the default template argument.
+  }
+
+  // Form the template argument list from the deduced template arguments.
+  TemplateArgumentList *DeducedArgumentList
+    = TemplateArgumentList::CreateCopy(Context, Builder.data(), Builder.size());
+  Info.reset(DeducedArgumentList);
+
+  // Substitute the deduced template arguments into the function template
+  // declaration to produce the function template specialization.
+  DeclContext *Owner = FunctionTemplate->getDeclContext();
+  if (FunctionTemplate->getFriendObjectKind())
+    Owner = FunctionTemplate->getLexicalDeclContext();
+  Specialization = cast_or_null<FunctionDecl>(
+                      SubstDecl(FunctionTemplate->getTemplatedDecl(), Owner,
+                         MultiLevelTemplateArgumentList(*DeducedArgumentList)));
+  if (!Specialization || Specialization->isInvalidDecl())
+    return TDK_SubstitutionFailure;
+
+  assert(Specialization->getPrimaryTemplate()->getCanonicalDecl() ==
+         FunctionTemplate->getCanonicalDecl());
+
+  // If the template argument list is owned by the function template
+  // specialization, release it.
+  if (Specialization->getTemplateSpecializationArgs() == DeducedArgumentList &&
+      !Trap.hasErrorOccurred())
+    Info.take();
+
+  // There may have been an error that did not prevent us from constructing a
+  // declaration. Mark the declaration invalid and return with a substitution
+  // failure.
+  if (Trap.hasErrorOccurred()) {
+    Specialization->setInvalidDecl(true);
+    return TDK_SubstitutionFailure;
+  }
+
+  if (OriginalCallArgs) {
+    // C++ [temp.deduct.call]p4:
+    //   In general, the deduction process attempts to find template argument
+    //   values that will make the deduced A identical to A (after the type A 
+    //   is transformed as described above). [...]
+    for (unsigned I = 0, N = OriginalCallArgs->size(); I != N; ++I) {
+      OriginalCallArg OriginalArg = (*OriginalCallArgs)[I];
+      unsigned ParamIdx = OriginalArg.ArgIdx;
+      
+      if (ParamIdx >= Specialization->getNumParams())
+        continue;
+      
+      QualType DeducedA = Specialization->getParamDecl(ParamIdx)->getType();
+      if (CheckOriginalCallArgDeduction(*this, OriginalArg, DeducedA))
+        return Sema::TDK_SubstitutionFailure;
+    }
+  }
+  
+  // If we suppressed any diagnostics while performing template argument
+  // deduction, and if we haven't already instantiated this declaration,
+  // keep track of these diagnostics. They'll be emitted if this specialization
+  // is actually used.
+  if (Info.diag_begin() != Info.diag_end()) {
+    llvm::DenseMap<Decl *, SmallVector<PartialDiagnosticAt, 1> >::iterator
+      Pos = SuppressedDiagnostics.find(Specialization->getCanonicalDecl());
+    if (Pos == SuppressedDiagnostics.end())
+        SuppressedDiagnostics[Specialization->getCanonicalDecl()]
+          .append(Info.diag_begin(), Info.diag_end());
+  }
+
+  return TDK_Success;
+}
+
+/// Gets the type of a function for template-argument-deducton
+/// purposes when it's considered as part of an overload set.
+static QualType GetTypeOfFunction(ASTContext &Context,
+                                  const OverloadExpr::FindResult &R,
+                                  FunctionDecl *Fn) {
+  if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Fn))
+    if (Method->isInstance()) {
+      // An instance method that's referenced in a form that doesn't
+      // look like a member pointer is just invalid.
+      if (!R.HasFormOfMemberPointer) return QualType();
+
+      return Context.getMemberPointerType(Fn->getType(),
+               Context.getTypeDeclType(Method->getParent()).getTypePtr());
+    }
+
+  if (!R.IsAddressOfOperand) return Fn->getType();
+  return Context.getPointerType(Fn->getType());
+}
+
+/// Apply the deduction rules for overload sets.
+///
+/// \return the null type if this argument should be treated as an
+/// undeduced context
+static QualType
+ResolveOverloadForDeduction(Sema &S, TemplateParameterList *TemplateParams,
+                            Expr *Arg, QualType ParamType,
+                            bool ParamWasReference) {
+
+  OverloadExpr::FindResult R = OverloadExpr::find(Arg);
+
+  OverloadExpr *Ovl = R.Expression;
+
+  // C++0x [temp.deduct.call]p4
+  unsigned TDF = 0;
+  if (ParamWasReference)
+    TDF |= TDF_ParamWithReferenceType;
+  if (R.IsAddressOfOperand)
+    TDF |= TDF_IgnoreQualifiers;
+
+  // C++0x [temp.deduct.call]p6:
+  //   When P is a function type, pointer to function type, or pointer
+  //   to member function type:
+
+  if (!ParamType->isFunctionType() &&
+      !ParamType->isFunctionPointerType() &&
+      !ParamType->isMemberFunctionPointerType()) {
+    if (Ovl->hasExplicitTemplateArgs()) {
+      // But we can still look for an explicit specialization.
+      if (FunctionDecl *ExplicitSpec
+            = S.ResolveSingleFunctionTemplateSpecialization(Ovl))
+        return GetTypeOfFunction(S.Context, R, ExplicitSpec);
+    }
+
+    return QualType();
+  }
+  
+  // Gather the explicit template arguments, if any.
+  TemplateArgumentListInfo ExplicitTemplateArgs;
+  if (Ovl->hasExplicitTemplateArgs())
+    Ovl->getExplicitTemplateArgs().copyInto(ExplicitTemplateArgs);
+  QualType Match;
+  for (UnresolvedSetIterator I = Ovl->decls_begin(),
+         E = Ovl->decls_end(); I != E; ++I) {
+    NamedDecl *D = (*I)->getUnderlyingDecl();
+
+    if (FunctionTemplateDecl *FunTmpl = dyn_cast<FunctionTemplateDecl>(D)) {
+      //   - If the argument is an overload set containing one or more
+      //     function templates, the parameter is treated as a
+      //     non-deduced context.
+      if (!Ovl->hasExplicitTemplateArgs())
+        return QualType();
+      
+      // Otherwise, see if we can resolve a function type 
+      FunctionDecl *Specialization = 0;
+      TemplateDeductionInfo Info(S.Context, Ovl->getNameLoc());
+      if (S.DeduceTemplateArguments(FunTmpl, &ExplicitTemplateArgs,
+                                    Specialization, Info))
+        continue;
+      
+      D = Specialization;
+    }
+
+    FunctionDecl *Fn = cast<FunctionDecl>(D);
+    QualType ArgType = GetTypeOfFunction(S.Context, R, Fn);
+    if (ArgType.isNull()) continue;
+
+    // Function-to-pointer conversion.
+    if (!ParamWasReference && ParamType->isPointerType() &&
+        ArgType->isFunctionType())
+      ArgType = S.Context.getPointerType(ArgType);
+
+    //   - If the argument is an overload set (not containing function
+    //     templates), trial argument deduction is attempted using each
+    //     of the members of the set. If deduction succeeds for only one
+    //     of the overload set members, that member is used as the
+    //     argument value for the deduction. If deduction succeeds for
+    //     more than one member of the overload set the parameter is
+    //     treated as a non-deduced context.
+
+    // We do all of this in a fresh context per C++0x [temp.deduct.type]p2:
+    //   Type deduction is done independently for each P/A pair, and
+    //   the deduced template argument values are then combined.
+    // So we do not reject deductions which were made elsewhere.
+    SmallVector<DeducedTemplateArgument, 8>
+      Deduced(TemplateParams->size());
+    TemplateDeductionInfo Info(S.Context, Ovl->getNameLoc());
+    Sema::TemplateDeductionResult Result
+      = DeduceTemplateArgumentsByTypeMatch(S, TemplateParams, ParamType,
+                                           ArgType, Info, Deduced, TDF);
+    if (Result) continue;
+    if (!Match.isNull()) return QualType();
+    Match = ArgType;
+  }
+
+  return Match;
+}
+
+/// \brief Perform the adjustments to the parameter and argument types
+/// described in C++ [temp.deduct.call].
+///
+/// \returns true if the caller should not attempt to perform any template
+/// argument deduction based on this P/A pair.
+static bool AdjustFunctionParmAndArgTypesForDeduction(Sema &S,
+                                          TemplateParameterList *TemplateParams,
+                                                      QualType &ParamType,
+                                                      QualType &ArgType,
+                                                      Expr *Arg,
+                                                      unsigned &TDF) {
+  // C++0x [temp.deduct.call]p3:
+  //   If P is a cv-qualified type, the top level cv-qualifiers of P's type
+  //   are ignored for type deduction.
+  if (ParamType.hasQualifiers())
+    ParamType = ParamType.getUnqualifiedType();
+  const ReferenceType *ParamRefType = ParamType->getAs<ReferenceType>();
+  if (ParamRefType) {
+    QualType PointeeType = ParamRefType->getPointeeType();
+
+    // If the argument has incomplete array type, try to complete it's type.
+    if (ArgType->isIncompleteArrayType() &&
+        !S.RequireCompleteExprType(Arg, S.PDiag(), 
+                                   std::make_pair(SourceLocation(), S.PDiag())))
+      ArgType = Arg->getType();
+
+    //   [C++0x] If P is an rvalue reference to a cv-unqualified
+    //   template parameter and the argument is an lvalue, the type
+    //   "lvalue reference to A" is used in place of A for type
+    //   deduction.
+    if (isa<RValueReferenceType>(ParamType)) {
+      if (!PointeeType.getQualifiers() &&
+          isa<TemplateTypeParmType>(PointeeType) &&
+          Arg->Classify(S.Context).isLValue() &&
+          Arg->getType() != S.Context.OverloadTy &&
+          Arg->getType() != S.Context.BoundMemberTy)
+        ArgType = S.Context.getLValueReferenceType(ArgType);
+    }
+
+    //   [...] If P is a reference type, the type referred to by P is used
+    //   for type deduction.
+    ParamType = PointeeType;
+  }
+
+  // Overload sets usually make this parameter an undeduced
+  // context, but there are sometimes special circumstances.
+  if (ArgType == S.Context.OverloadTy) {
+    ArgType = ResolveOverloadForDeduction(S, TemplateParams,
+                                          Arg, ParamType,
+                                          ParamRefType != 0);
+    if (ArgType.isNull())
+      return true;
+  }
+
+  if (ParamRefType) {
+    // C++0x [temp.deduct.call]p3:
+    //   [...] If P is of the form T&&, where T is a template parameter, and
+    //   the argument is an lvalue, the type A& is used in place of A for
+    //   type deduction.
+    if (ParamRefType->isRValueReferenceType() &&
+        ParamRefType->getAs<TemplateTypeParmType>() &&
+        Arg->isLValue())
+      ArgType = S.Context.getLValueReferenceType(ArgType);
+  } else {
+    // C++ [temp.deduct.call]p2:
+    //   If P is not a reference type:
+    //   - If A is an array type, the pointer type produced by the
+    //     array-to-pointer standard conversion (4.2) is used in place of
+    //     A for type deduction; otherwise,
+    if (ArgType->isArrayType())
+      ArgType = S.Context.getArrayDecayedType(ArgType);
+    //   - If A is a function type, the pointer type produced by the
+    //     function-to-pointer standard conversion (4.3) is used in place
+    //     of A for type deduction; otherwise,
+    else if (ArgType->isFunctionType())
+      ArgType = S.Context.getPointerType(ArgType);
+    else {
+      // - If A is a cv-qualified type, the top level cv-qualifiers of A's
+      //   type are ignored for type deduction.
+      ArgType = ArgType.getUnqualifiedType();
+    }
+  }
+
+  // C++0x [temp.deduct.call]p4:
+  //   In general, the deduction process attempts to find template argument
+  //   values that will make the deduced A identical to A (after the type A
+  //   is transformed as described above). [...]
+  TDF = TDF_SkipNonDependent;
+
+  //     - If the original P is a reference type, the deduced A (i.e., the
+  //       type referred to by the reference) can be more cv-qualified than
+  //       the transformed A.
+  if (ParamRefType)
+    TDF |= TDF_ParamWithReferenceType;
+  //     - The transformed A can be another pointer or pointer to member
+  //       type that can be converted to the deduced A via a qualification
+  //       conversion (4.4).
+  if (ArgType->isPointerType() || ArgType->isMemberPointerType() ||
+      ArgType->isObjCObjectPointerType())
+    TDF |= TDF_IgnoreQualifiers;
+  //     - If P is a class and P has the form simple-template-id, then the
+  //       transformed A can be a derived class of the deduced A. Likewise,
+  //       if P is a pointer to a class of the form simple-template-id, the
+  //       transformed A can be a pointer to a derived class pointed to by
+  //       the deduced A.
+  if (isSimpleTemplateIdType(ParamType) ||
+      (isa<PointerType>(ParamType) &&
+       isSimpleTemplateIdType(
+                              ParamType->getAs<PointerType>()->getPointeeType())))
+    TDF |= TDF_DerivedClass;
+
+  return false;
+}
+
+static bool hasDeducibleTemplateParameters(Sema &S,
+                                           FunctionTemplateDecl *FunctionTemplate,
+                                           QualType T);
+
+/// \brief Perform template argument deduction by matching a parameter type
+///        against a single expression, where the expression is an element of
+///        an initializer list that was originally matched against the argument
+///        type.
+static Sema::TemplateDeductionResult
+DeduceTemplateArgumentByListElement(Sema &S,
+                                    TemplateParameterList *TemplateParams,
+                                    QualType ParamType, Expr *Arg,
+                                    TemplateDeductionInfo &Info,
+                              SmallVectorImpl<DeducedTemplateArgument> &Deduced,
+                                    unsigned TDF) {
+  // Handle the case where an init list contains another init list as the
+  // element.
+  if (InitListExpr *ILE = dyn_cast<InitListExpr>(Arg)) {
+    QualType X;
+    if (!S.isStdInitializerList(ParamType.getNonReferenceType(), &X))
+      return Sema::TDK_Success; // Just ignore this expression.
+
+    // Recurse down into the init list.
+    for (unsigned i = 0, e = ILE->getNumInits(); i < e; ++i) {
+      if (Sema::TemplateDeductionResult Result =
+            DeduceTemplateArgumentByListElement(S, TemplateParams, X,
+                                                 ILE->getInit(i),
+                                                 Info, Deduced, TDF))
+        return Result;
+    }
+    return Sema::TDK_Success;
+  }
+
+  // For all other cases, just match by type.
+  QualType ArgType = Arg->getType();
+  if (AdjustFunctionParmAndArgTypesForDeduction(S, TemplateParams, ParamType, 
+                                                ArgType, Arg, TDF))
+    return Sema::TDK_FailedOverloadResolution;
+  return DeduceTemplateArgumentsByTypeMatch(S, TemplateParams, ParamType,
+                                            ArgType, Info, Deduced, TDF);
+}
+
+/// \brief Perform template argument deduction from a function call
+/// (C++ [temp.deduct.call]).
+///
+/// \param FunctionTemplate the function template for which we are performing
+/// template argument deduction.
+///
+/// \param ExplicitTemplateArguments the explicit template arguments provided
+/// for this call.
+///
+/// \param Args the function call arguments
+///
+/// \param NumArgs the number of arguments in Args
+///
+/// \param Name the name of the function being called. This is only significant
+/// when the function template is a conversion function template, in which
+/// case this routine will also perform template argument deduction based on
+/// the function to which
+///
+/// \param Specialization if template argument deduction was successful,
+/// this will be set to the function template specialization produced by
+/// template argument deduction.
+///
+/// \param Info the argument will be updated to provide additional information
+/// about template argument deduction.
+///
+/// \returns the result of template argument deduction.
+Sema::TemplateDeductionResult
+Sema::DeduceTemplateArguments(FunctionTemplateDecl *FunctionTemplate,
+                              TemplateArgumentListInfo *ExplicitTemplateArgs,
+                              llvm::ArrayRef<Expr *> Args,
+                              FunctionDecl *&Specialization,
+                              TemplateDeductionInfo &Info) {
+  FunctionDecl *Function = FunctionTemplate->getTemplatedDecl();
+
+  // C++ [temp.deduct.call]p1:
+  //   Template argument deduction is done by comparing each function template
+  //   parameter type (call it P) with the type of the corresponding argument
+  //   of the call (call it A) as described below.
+  unsigned CheckArgs = Args.size();
+  if (Args.size() < Function->getMinRequiredArguments())
+    return TDK_TooFewArguments;
+  else if (Args.size() > Function->getNumParams()) {
+    const FunctionProtoType *Proto
+      = Function->getType()->getAs<FunctionProtoType>();
+    if (Proto->isTemplateVariadic())
+      /* Do nothing */;
+    else if (Proto->isVariadic())
+      CheckArgs = Function->getNumParams();
+    else
+      return TDK_TooManyArguments;
+  }
+
+  // The types of the parameters from which we will perform template argument
+  // deduction.
+  LocalInstantiationScope InstScope(*this);
+  TemplateParameterList *TemplateParams
+    = FunctionTemplate->getTemplateParameters();
+  SmallVector<DeducedTemplateArgument, 4> Deduced;
+  SmallVector<QualType, 4> ParamTypes;
+  unsigned NumExplicitlySpecified = 0;
+  if (ExplicitTemplateArgs) {
+    TemplateDeductionResult Result =
+      SubstituteExplicitTemplateArguments(FunctionTemplate,
+                                          *ExplicitTemplateArgs,
+                                          Deduced,
+                                          ParamTypes,
+                                          0,
+                                          Info);
+    if (Result)
+      return Result;
+
+    NumExplicitlySpecified = Deduced.size();
+  } else {
+    // Just fill in the parameter types from the function declaration.
+    for (unsigned I = 0, N = Function->getNumParams(); I != N; ++I)
+      ParamTypes.push_back(Function->getParamDecl(I)->getType());
+  }
+
+  // Deduce template arguments from the function parameters.
+  Deduced.resize(TemplateParams->size());
+  unsigned ArgIdx = 0;
+  SmallVector<OriginalCallArg, 4> OriginalCallArgs;
+  for (unsigned ParamIdx = 0, NumParams = ParamTypes.size();
+       ParamIdx != NumParams; ++ParamIdx) {
+    QualType OrigParamType = ParamTypes[ParamIdx];
+    QualType ParamType = OrigParamType;
+    
+    const PackExpansionType *ParamExpansion
+      = dyn_cast<PackExpansionType>(ParamType);
+    if (!ParamExpansion) {
+      // Simple case: matching a function parameter to a function argument.
+      if (ArgIdx >= CheckArgs)
+        break;
+
+      Expr *Arg = Args[ArgIdx++];
+      QualType ArgType = Arg->getType();
+      
+      unsigned TDF = 0;
+      if (AdjustFunctionParmAndArgTypesForDeduction(*this, TemplateParams,
+                                                    ParamType, ArgType, Arg,
+                                                    TDF))
+        continue;
+
+      // If we have nothing to deduce, we're done.
+      if (!hasDeducibleTemplateParameters(*this, FunctionTemplate, ParamType))
+        continue;
+
+      // If the argument is an initializer list ...
+      if (InitListExpr *ILE = dyn_cast<InitListExpr>(Arg)) {
+        // ... then the parameter is an undeduced context, unless the parameter
+        // type is (reference to cv) std::initializer_list<P'>, in which case
+        // deduction is done for each element of the initializer list, and the
+        // result is the deduced type if it's the same for all elements.
+        QualType X;
+        // Removing references was already done.
+        if (!isStdInitializerList(ParamType, &X))
+          continue;
+
+        for (unsigned i = 0, e = ILE->getNumInits(); i < e; ++i) {
+          if (TemplateDeductionResult Result =
+                DeduceTemplateArgumentByListElement(*this, TemplateParams, X,
+                                                     ILE->getInit(i),
+                                                     Info, Deduced, TDF))
+            return Result;
+        }
+        // Don't track the argument type, since an initializer list has none.
+        continue;
+      }
+
+      // Keep track of the argument type and corresponding parameter index,
+      // so we can check for compatibility between the deduced A and A.
+      OriginalCallArgs.push_back(OriginalCallArg(OrigParamType, ArgIdx-1, 
+                                                 ArgType));
+
+      if (TemplateDeductionResult Result
+            = DeduceTemplateArgumentsByTypeMatch(*this, TemplateParams,
+                                                 ParamType, ArgType,
+                                                 Info, Deduced, TDF))
+        return Result;
+
+      continue;
+    }
+
+    // C++0x [temp.deduct.call]p1:
+    //   For a function parameter pack that occurs at the end of the
+    //   parameter-declaration-list, the type A of each remaining argument of
+    //   the call is compared with the type P of the declarator-id of the
+    //   function parameter pack. Each comparison deduces template arguments
+    //   for subsequent positions in the template parameter packs expanded by
+    //   the function parameter pack. For a function parameter pack that does
+    //   not occur at the end of the parameter-declaration-list, the type of
+    //   the parameter pack is a non-deduced context.
+    if (ParamIdx + 1 < NumParams)
+      break;
+
+    QualType ParamPattern = ParamExpansion->getPattern();
+    SmallVector<unsigned, 2> PackIndices;
+    {
+      llvm::SmallBitVector SawIndices(TemplateParams->size());
+      SmallVector<UnexpandedParameterPack, 2> Unexpanded;
+      collectUnexpandedParameterPacks(ParamPattern, Unexpanded);
+      for (unsigned I = 0, N = Unexpanded.size(); I != N; ++I) {
+        unsigned Depth, Index;
+        llvm::tie(Depth, Index) = getDepthAndIndex(Unexpanded[I]);
+        if (Depth == 0 && !SawIndices[Index]) {
+          SawIndices[Index] = true;
+          PackIndices.push_back(Index);
+        }
+      }
+    }
+    assert(!PackIndices.empty() && "Pack expansion without unexpanded packs?");
+
+    // Keep track of the deduced template arguments for each parameter pack
+    // expanded by this pack expansion (the outer index) and for each
+    // template argument (the inner SmallVectors).
+    SmallVector<SmallVector<DeducedTemplateArgument, 4>, 2>
+      NewlyDeducedPacks(PackIndices.size());
+    SmallVector<DeducedTemplateArgument, 2>
+      SavedPacks(PackIndices.size());
+    PrepareArgumentPackDeduction(*this, Deduced, PackIndices, SavedPacks,
+                                 NewlyDeducedPacks);
+    bool HasAnyArguments = false;
+    for (; ArgIdx < Args.size(); ++ArgIdx) {
+      HasAnyArguments = true;
+
+      QualType OrigParamType = ParamPattern;
+      ParamType = OrigParamType;
+      Expr *Arg = Args[ArgIdx];
+      QualType ArgType = Arg->getType();
+      
+      unsigned TDF = 0;
+      if (AdjustFunctionParmAndArgTypesForDeduction(*this, TemplateParams,
+                                                    ParamType, ArgType, Arg,
+                                                    TDF)) {
+        // We can't actually perform any deduction for this argument, so stop
+        // deduction at this point.
+        ++ArgIdx;
+        break;
+      }
+
+      // As above, initializer lists need special handling.
+      if (InitListExpr *ILE = dyn_cast<InitListExpr>(Arg)) {
+        QualType X;
+        if (!isStdInitializerList(ParamType, &X)) {
+          ++ArgIdx;
+          break;
+        }
+
+        for (unsigned i = 0, e = ILE->getNumInits(); i < e; ++i) {
+          if (TemplateDeductionResult Result =
+                DeduceTemplateArgumentsByTypeMatch(*this, TemplateParams, X,
+                                                   ILE->getInit(i)->getType(),
+                                                   Info, Deduced, TDF))
+            return Result;
+        }
+      } else {
+
+        // Keep track of the argument type and corresponding argument index,
+        // so we can check for compatibility between the deduced A and A.
+        if (hasDeducibleTemplateParameters(*this, FunctionTemplate, ParamType))
+          OriginalCallArgs.push_back(OriginalCallArg(OrigParamType, ArgIdx, 
+                                                     ArgType));
+
+        if (TemplateDeductionResult Result
+            = DeduceTemplateArgumentsByTypeMatch(*this, TemplateParams,
+                                                 ParamType, ArgType, Info,
+                                                 Deduced, TDF))
+          return Result;
+      }
+
+      // Capture the deduced template arguments for each parameter pack expanded
+      // by this pack expansion, add them to the list of arguments we've deduced
+      // for that pack, then clear out the deduced argument.
+      for (unsigned I = 0, N = PackIndices.size(); I != N; ++I) {
+        DeducedTemplateArgument &DeducedArg = Deduced[PackIndices[I]];
+        if (!DeducedArg.isNull()) {
+          NewlyDeducedPacks[I].push_back(DeducedArg);
+          DeducedArg = DeducedTemplateArgument();
+        }
+      }
+    }
+
+    // Build argument packs for each of the parameter packs expanded by this
+    // pack expansion.
+    if (Sema::TemplateDeductionResult Result
+          = FinishArgumentPackDeduction(*this, TemplateParams, HasAnyArguments,
+                                        Deduced, PackIndices, SavedPacks,
+                                        NewlyDeducedPacks, Info))
+      return Result;
+
+    // After we've matching against a parameter pack, we're done.
+    break;
+  }
+
+  return FinishTemplateArgumentDeduction(FunctionTemplate, Deduced,
+                                         NumExplicitlySpecified,
+                                         Specialization, Info, &OriginalCallArgs);
+}
+
+/// \brief Deduce template arguments when taking the address of a function
+/// template (C++ [temp.deduct.funcaddr]) or matching a specialization to
+/// a template.
+///
+/// \param FunctionTemplate the function template for which we are performing
+/// template argument deduction.
+///
+/// \param ExplicitTemplateArguments the explicitly-specified template
+/// arguments.
+///
+/// \param ArgFunctionType the function type that will be used as the
+/// "argument" type (A) when performing template argument deduction from the
+/// function template's function type. This type may be NULL, if there is no
+/// argument type to compare against, in C++0x [temp.arg.explicit]p3.
+///
+/// \param Specialization if template argument deduction was successful,
+/// this will be set to the function template specialization produced by
+/// template argument deduction.
+///
+/// \param Info the argument will be updated to provide additional information
+/// about template argument deduction.
+///
+/// \returns the result of template argument deduction.
+Sema::TemplateDeductionResult
+Sema::DeduceTemplateArguments(FunctionTemplateDecl *FunctionTemplate,
+                              TemplateArgumentListInfo *ExplicitTemplateArgs,
+                              QualType ArgFunctionType,
+                              FunctionDecl *&Specialization,
+                              TemplateDeductionInfo &Info) {
+  FunctionDecl *Function = FunctionTemplate->getTemplatedDecl();
+  TemplateParameterList *TemplateParams
+    = FunctionTemplate->getTemplateParameters();
+  QualType FunctionType = Function->getType();
+
+  // Substitute any explicit template arguments.
+  LocalInstantiationScope InstScope(*this);
+  SmallVector<DeducedTemplateArgument, 4> Deduced;
+  unsigned NumExplicitlySpecified = 0;
+  SmallVector<QualType, 4> ParamTypes;
+  if (ExplicitTemplateArgs) {
+    if (TemplateDeductionResult Result
+          = SubstituteExplicitTemplateArguments(FunctionTemplate,
+                                                *ExplicitTemplateArgs,
+                                                Deduced, ParamTypes,
+                                                &FunctionType, Info))
+      return Result;
+
+    NumExplicitlySpecified = Deduced.size();
+  }
+
+  // Unevaluated SFINAE context.
+  EnterExpressionEvaluationContext Unevaluated(*this, Sema::Unevaluated);
+  SFINAETrap Trap(*this);
+
+  Deduced.resize(TemplateParams->size());
+
+  if (!ArgFunctionType.isNull()) {
+    // Deduce template arguments from the function type.
+    if (TemplateDeductionResult Result
+          = DeduceTemplateArgumentsByTypeMatch(*this, TemplateParams,
+                                      FunctionType, ArgFunctionType, Info,
+                                      Deduced, TDF_TopLevelParameterTypeList))
+      return Result;
+  }
+
+  if (TemplateDeductionResult Result
+        = FinishTemplateArgumentDeduction(FunctionTemplate, Deduced,
+                                          NumExplicitlySpecified,
+                                          Specialization, Info))
+    return Result;
+
+  // If the requested function type does not match the actual type of the
+  // specialization, template argument deduction fails.
+  if (!ArgFunctionType.isNull() &&
+      !Context.hasSameType(ArgFunctionType, Specialization->getType()))
+    return TDK_NonDeducedMismatch;
+
+  return TDK_Success;
+}
+
+/// \brief Deduce template arguments for a templated conversion
+/// function (C++ [temp.deduct.conv]) and, if successful, produce a
+/// conversion function template specialization.
+Sema::TemplateDeductionResult
+Sema::DeduceTemplateArguments(FunctionTemplateDecl *FunctionTemplate,
+                              QualType ToType,
+                              CXXConversionDecl *&Specialization,
+                              TemplateDeductionInfo &Info) {
+  CXXConversionDecl *Conv
+    = cast<CXXConversionDecl>(FunctionTemplate->getTemplatedDecl());
+  QualType FromType = Conv->getConversionType();
+
+  // Canonicalize the types for deduction.
+  QualType P = Context.getCanonicalType(FromType);
+  QualType A = Context.getCanonicalType(ToType);
+
+  // C++0x [temp.deduct.conv]p2:
+  //   If P is a reference type, the type referred to by P is used for
+  //   type deduction.
+  if (const ReferenceType *PRef = P->getAs<ReferenceType>())
+    P = PRef->getPointeeType();
+
+  // C++0x [temp.deduct.conv]p4:
+  //   [...] If A is a reference type, the type referred to by A is used
+  //   for type deduction.
+  if (const ReferenceType *ARef = A->getAs<ReferenceType>())
+    A = ARef->getPointeeType().getUnqualifiedType();
+  // C++ [temp.deduct.conv]p3:
+  //
+  //   If A is not a reference type:
+  else {
+    assert(!A->isReferenceType() && "Reference types were handled above");
+
+    //   - If P is an array type, the pointer type produced by the
+    //     array-to-pointer standard conversion (4.2) is used in place
+    //     of P for type deduction; otherwise,
+    if (P->isArrayType())
+      P = Context.getArrayDecayedType(P);
+    //   - If P is a function type, the pointer type produced by the
+    //     function-to-pointer standard conversion (4.3) is used in
+    //     place of P for type deduction; otherwise,
+    else if (P->isFunctionType())
+      P = Context.getPointerType(P);
+    //   - If P is a cv-qualified type, the top level cv-qualifiers of
+    //     P's type are ignored for type deduction.
+    else
+      P = P.getUnqualifiedType();
+
+    // C++0x [temp.deduct.conv]p4:
+    //   If A is a cv-qualified type, the top level cv-qualifiers of A's
+    //   type are ignored for type deduction. If A is a reference type, the type 
+    //   referred to by A is used for type deduction.
+    A = A.getUnqualifiedType();
+  }
+
+  // Unevaluated SFINAE context.
+  EnterExpressionEvaluationContext Unevaluated(*this, Sema::Unevaluated);
+  SFINAETrap Trap(*this);
+
+  // C++ [temp.deduct.conv]p1:
+  //   Template argument deduction is done by comparing the return
+  //   type of the template conversion function (call it P) with the
+  //   type that is required as the result of the conversion (call it
+  //   A) as described in 14.8.2.4.
+  TemplateParameterList *TemplateParams
+    = FunctionTemplate->getTemplateParameters();
+  SmallVector<DeducedTemplateArgument, 4> Deduced;
+  Deduced.resize(TemplateParams->size());
+
+  // C++0x [temp.deduct.conv]p4:
+  //   In general, the deduction process attempts to find template
+  //   argument values that will make the deduced A identical to
+  //   A. However, there are two cases that allow a difference:
+  unsigned TDF = 0;
+  //     - If the original A is a reference type, A can be more
+  //       cv-qualified than the deduced A (i.e., the type referred to
+  //       by the reference)
+  if (ToType->isReferenceType())
+    TDF |= TDF_ParamWithReferenceType;
+  //     - The deduced A can be another pointer or pointer to member
+  //       type that can be converted to A via a qualification
+  //       conversion.
+  //
+  // (C++0x [temp.deduct.conv]p6 clarifies that this only happens when
+  // both P and A are pointers or member pointers. In this case, we
+  // just ignore cv-qualifiers completely).
+  if ((P->isPointerType() && A->isPointerType()) ||
+      (P->isMemberPointerType() && A->isMemberPointerType()))
+    TDF |= TDF_IgnoreQualifiers;
+  if (TemplateDeductionResult Result
+        = DeduceTemplateArgumentsByTypeMatch(*this, TemplateParams,
+                                             P, A, Info, Deduced, TDF))
+    return Result;
+
+  // Finish template argument deduction.
+  LocalInstantiationScope InstScope(*this);
+  FunctionDecl *Spec = 0;
+  TemplateDeductionResult Result
+    = FinishTemplateArgumentDeduction(FunctionTemplate, Deduced, 0, Spec,
+                                      Info);
+  Specialization = cast_or_null<CXXConversionDecl>(Spec);
+  return Result;
+}
+
+/// \brief Deduce template arguments for a function template when there is
+/// nothing to deduce against (C++0x [temp.arg.explicit]p3).
+///
+/// \param FunctionTemplate the function template for which we are performing
+/// template argument deduction.
+///
+/// \param ExplicitTemplateArguments the explicitly-specified template
+/// arguments.
+///
+/// \param Specialization if template argument deduction was successful,
+/// this will be set to the function template specialization produced by
+/// template argument deduction.
+///
+/// \param Info the argument will be updated to provide additional information
+/// about template argument deduction.
+///
+/// \returns the result of template argument deduction.
+Sema::TemplateDeductionResult
+Sema::DeduceTemplateArguments(FunctionTemplateDecl *FunctionTemplate,
+                              TemplateArgumentListInfo *ExplicitTemplateArgs,
+                              FunctionDecl *&Specialization,
+                              TemplateDeductionInfo &Info) {
+  return DeduceTemplateArguments(FunctionTemplate, ExplicitTemplateArgs,
+                                 QualType(), Specialization, Info);
+}
+
+namespace {
+  /// Substitute the 'auto' type specifier within a type for a given replacement
+  /// type.
+  class SubstituteAutoTransform :
+    public TreeTransform<SubstituteAutoTransform> {
+    QualType Replacement;
+  public:
+    SubstituteAutoTransform(Sema &SemaRef, QualType Replacement) :
+      TreeTransform<SubstituteAutoTransform>(SemaRef), Replacement(Replacement) {
+    }
+    QualType TransformAutoType(TypeLocBuilder &TLB, AutoTypeLoc TL) {
+      // If we're building the type pattern to deduce against, don't wrap the
+      // substituted type in an AutoType. Certain template deduction rules
+      // apply only when a template type parameter appears directly (and not if
+      // the parameter is found through desugaring). For instance:
+      //   auto &&lref = lvalue;
+      // must transform into "rvalue reference to T" not "rvalue reference to
+      // auto type deduced as T" in order for [temp.deduct.call]p3 to apply.
+      if (isa<TemplateTypeParmType>(Replacement)) {
+        QualType Result = Replacement;
+        TemplateTypeParmTypeLoc NewTL = TLB.push<TemplateTypeParmTypeLoc>(Result);
+        NewTL.setNameLoc(TL.getNameLoc());
+        return Result;
+      } else {
+        QualType Result = RebuildAutoType(Replacement);
+        AutoTypeLoc NewTL = TLB.push<AutoTypeLoc>(Result);
+        NewTL.setNameLoc(TL.getNameLoc());
+        return Result;
+      }
+    }
+
+    ExprResult TransformLambdaExpr(LambdaExpr *E) {
+      // Lambdas never need to be transformed.
+      return E;
+    }
+  };
+}
+
+/// \brief Deduce the type for an auto type-specifier (C++0x [dcl.spec.auto]p6)
+///
+/// \param Type the type pattern using the auto type-specifier.
+///
+/// \param Init the initializer for the variable whose type is to be deduced.
+///
+/// \param Result if type deduction was successful, this will be set to the
+/// deduced type. This may still contain undeduced autos if the type is
+/// dependent. This will be set to null if deduction succeeded, but auto
+/// substitution failed; the appropriate diagnostic will already have been
+/// produced in that case.
+Sema::DeduceAutoResult
+Sema::DeduceAutoType(TypeSourceInfo *Type, Expr *&Init,
+                     TypeSourceInfo *&Result) {
+  if (Init->getType()->isNonOverloadPlaceholderType()) {
+    ExprResult result = CheckPlaceholderExpr(Init);
+    if (result.isInvalid()) return DAR_FailedAlreadyDiagnosed;
+    Init = result.take();
+  }
+
+  if (Init->isTypeDependent()) {
+    Result = Type;
+    return DAR_Succeeded;
+  }
+
+  SourceLocation Loc = Init->getExprLoc();
+
+  LocalInstantiationScope InstScope(*this);
+
+  // Build template<class TemplParam> void Func(FuncParam);
+  TemplateTypeParmDecl *TemplParam =
+    TemplateTypeParmDecl::Create(Context, 0, SourceLocation(), Loc, 0, 0, 0,
+                                 false, false);
+  QualType TemplArg = QualType(TemplParam->getTypeForDecl(), 0);
+  NamedDecl *TemplParamPtr = TemplParam;
+  FixedSizeTemplateParameterList<1> TemplateParams(Loc, Loc, &TemplParamPtr,
+                                                   Loc);
+
+  TypeSourceInfo *FuncParamInfo =
+    SubstituteAutoTransform(*this, TemplArg).TransformType(Type);
+  assert(FuncParamInfo && "substituting template parameter for 'auto' failed");
+  QualType FuncParam = FuncParamInfo->getType();
+
+  // Deduce type of TemplParam in Func(Init)
+  SmallVector<DeducedTemplateArgument, 1> Deduced;
+  Deduced.resize(1);
+  QualType InitType = Init->getType();
+  unsigned TDF = 0;
+
+  TemplateDeductionInfo Info(Context, Loc);
+
+  InitListExpr * InitList = dyn_cast<InitListExpr>(Init);
+  if (InitList) {
+    for (unsigned i = 0, e = InitList->getNumInits(); i < e; ++i) {
+      if (DeduceTemplateArgumentByListElement(*this, &TemplateParams, 
+                                              TemplArg,
+                                              InitList->getInit(i),
+                                              Info, Deduced, TDF))
+        return DAR_Failed;
+    }
+  } else {
+    if (AdjustFunctionParmAndArgTypesForDeduction(*this, &TemplateParams,
+                                                  FuncParam, InitType, Init,
+                                                  TDF))
+      return DAR_Failed;
+    
+    if (DeduceTemplateArgumentsByTypeMatch(*this, &TemplateParams, FuncParam,
+                                           InitType, Info, Deduced, TDF))
+      return DAR_Failed;
+  }
+
+  QualType DeducedType = Deduced[0].getAsType();
+  if (DeducedType.isNull())
+    return DAR_Failed;
+
+  if (InitList) {
+    DeducedType = BuildStdInitializerList(DeducedType, Loc);
+    if (DeducedType.isNull())
+      return DAR_FailedAlreadyDiagnosed;
+  }
+
+  Result = SubstituteAutoTransform(*this, DeducedType).TransformType(Type);
+
+  // Check that the deduced argument type is compatible with the original
+  // argument type per C++ [temp.deduct.call]p4.
+  if (!InitList && Result &&
+      CheckOriginalCallArgDeduction(*this, 
+                                    Sema::OriginalCallArg(FuncParam,0,InitType),
+                                    Result->getType())) {
+    Result = 0;
+    return DAR_Failed;
+  }
+
+  return DAR_Succeeded;
+}
+
+void Sema::DiagnoseAutoDeductionFailure(VarDecl *VDecl, Expr *Init) {
+  if (isa<InitListExpr>(Init))
+    Diag(VDecl->getLocation(),
+         diag::err_auto_var_deduction_failure_from_init_list)
+      << VDecl->getDeclName() << VDecl->getType() << Init->getSourceRange();
+  else
+    Diag(VDecl->getLocation(), diag::err_auto_var_deduction_failure)
+      << VDecl->getDeclName() << VDecl->getType() << Init->getType()
+      << Init->getSourceRange();
+}
+
+static void
+MarkUsedTemplateParameters(ASTContext &Ctx, QualType T,
+                           bool OnlyDeduced,
+                           unsigned Level,
+                           llvm::SmallBitVector &Deduced);
+
+/// \brief If this is a non-static member function,
+static void MaybeAddImplicitObjectParameterType(ASTContext &Context,
+                                                CXXMethodDecl *Method,
+                                 SmallVectorImpl<QualType> &ArgTypes) {
+  if (Method->isStatic())
+    return;
+
+  // C++ [over.match.funcs]p4:
+  //
+  //   For non-static member functions, the type of the implicit
+  //   object parameter is
+  //     - "lvalue reference to cv X" for functions declared without a
+  //       ref-qualifier or with the & ref-qualifier
+  //     - "rvalue reference to cv X" for functions declared with the
+  //       && ref-qualifier
+  //
+  // FIXME: We don't have ref-qualifiers yet, so we don't do that part.
+  QualType ArgTy = Context.getTypeDeclType(Method->getParent());
+  ArgTy = Context.getQualifiedType(ArgTy,
+                        Qualifiers::fromCVRMask(Method->getTypeQualifiers()));
+  ArgTy = Context.getLValueReferenceType(ArgTy);
+  ArgTypes.push_back(ArgTy);
+}
+
+/// \brief Determine whether the function template \p FT1 is at least as
+/// specialized as \p FT2.
+static bool isAtLeastAsSpecializedAs(Sema &S,
+                                     SourceLocation Loc,
+                                     FunctionTemplateDecl *FT1,
+                                     FunctionTemplateDecl *FT2,
+                                     TemplatePartialOrderingContext TPOC,
+                                     unsigned NumCallArguments,
+    SmallVectorImpl<RefParamPartialOrderingComparison> *RefParamComparisons) {
+  FunctionDecl *FD1 = FT1->getTemplatedDecl();
+  FunctionDecl *FD2 = FT2->getTemplatedDecl();
+  const FunctionProtoType *Proto1 = FD1->getType()->getAs<FunctionProtoType>();
+  const FunctionProtoType *Proto2 = FD2->getType()->getAs<FunctionProtoType>();
+
+  assert(Proto1 && Proto2 && "Function templates must have prototypes");
+  TemplateParameterList *TemplateParams = FT2->getTemplateParameters();
+  SmallVector<DeducedTemplateArgument, 4> Deduced;
+  Deduced.resize(TemplateParams->size());
+
+  // C++0x [temp.deduct.partial]p3:
+  //   The types used to determine the ordering depend on the context in which
+  //   the partial ordering is done:
+  TemplateDeductionInfo Info(S.Context, Loc);
+  CXXMethodDecl *Method1 = 0;
+  CXXMethodDecl *Method2 = 0;
+  bool IsNonStatic2 = false;
+  bool IsNonStatic1 = false;
+  unsigned Skip2 = 0;
+  switch (TPOC) {
+  case TPOC_Call: {
+    //   - In the context of a function call, the function parameter types are
+    //     used.
+    Method1 = dyn_cast<CXXMethodDecl>(FD1);
+    Method2 = dyn_cast<CXXMethodDecl>(FD2);
+    IsNonStatic1 = Method1 && !Method1->isStatic();
+    IsNonStatic2 = Method2 && !Method2->isStatic();
+
+    // C++0x [temp.func.order]p3:
+    //   [...] If only one of the function templates is a non-static
+    //   member, that function template is considered to have a new
+    //   first parameter inserted in its function parameter list. The
+    //   new parameter is of type "reference to cv A," where cv are
+    //   the cv-qualifiers of the function template (if any) and A is
+    //   the class of which the function template is a member.
+    //
+    // C++98/03 doesn't have this provision, so instead we drop the
+    // first argument of the free function or static member, which
+    // seems to match existing practice.
+    SmallVector<QualType, 4> Args1;
+    unsigned Skip1 = !S.getLangOpts().CPlusPlus0x &&
+      IsNonStatic2 && !IsNonStatic1;
+    if (S.getLangOpts().CPlusPlus0x && IsNonStatic1 && !IsNonStatic2)
+      MaybeAddImplicitObjectParameterType(S.Context, Method1, Args1);
+    Args1.insert(Args1.end(),
+                 Proto1->arg_type_begin() + Skip1, Proto1->arg_type_end());
+
+    SmallVector<QualType, 4> Args2;
+    Skip2 = !S.getLangOpts().CPlusPlus0x &&
+      IsNonStatic1 && !IsNonStatic2;
+    if (S.getLangOpts().CPlusPlus0x && IsNonStatic2 && !IsNonStatic1)
+      MaybeAddImplicitObjectParameterType(S.Context, Method2, Args2);
+    Args2.insert(Args2.end(),
+                 Proto2->arg_type_begin() + Skip2, Proto2->arg_type_end());
+
+    // C++ [temp.func.order]p5:
+    //   The presence of unused ellipsis and default arguments has no effect on
+    //   the partial ordering of function templates.
+    if (Args1.size() > NumCallArguments)
+      Args1.resize(NumCallArguments);
+    if (Args2.size() > NumCallArguments)
+      Args2.resize(NumCallArguments);
+    if (DeduceTemplateArguments(S, TemplateParams, Args2.data(), Args2.size(),
+                                Args1.data(), Args1.size(), Info, Deduced,
+                                TDF_None, /*PartialOrdering=*/true,
+                                RefParamComparisons))
+        return false;
+
+    break;
+  }
+
+  case TPOC_Conversion:
+    //   - In the context of a call to a conversion operator, the return types
+    //     of the conversion function templates are used.
+    if (DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
+                                           Proto2->getResultType(),
+                                           Proto1->getResultType(),
+                                           Info, Deduced, TDF_None,
+                                           /*PartialOrdering=*/true,
+                                           RefParamComparisons))
+      return false;
+    break;
+
+  case TPOC_Other:
+    //   - In other contexts (14.6.6.2) the function template's function type
+    //     is used.
+    if (DeduceTemplateArgumentsByTypeMatch(S, TemplateParams,
+                                           FD2->getType(), FD1->getType(),
+                                           Info, Deduced, TDF_None,
+                                           /*PartialOrdering=*/true,
+                                           RefParamComparisons))
+      return false;
+    break;
+  }
+
+  // C++0x [temp.deduct.partial]p11:
+  //   In most cases, all template parameters must have values in order for
+  //   deduction to succeed, but for partial ordering purposes a template
+  //   parameter may remain without a value provided it is not used in the
+  //   types being used for partial ordering. [ Note: a template parameter used
+  //   in a non-deduced context is considered used. -end note]
+  unsigned ArgIdx = 0, NumArgs = Deduced.size();
+  for (; ArgIdx != NumArgs; ++ArgIdx)
+    if (Deduced[ArgIdx].isNull())
+      break;
+
+  if (ArgIdx == NumArgs) {
+    // All template arguments were deduced. FT1 is at least as specialized
+    // as FT2.
+    return true;
+  }
+
+  // Figure out which template parameters were used.
+  llvm::SmallBitVector UsedParameters(TemplateParams->size());
+  switch (TPOC) {
+  case TPOC_Call: {
+    unsigned NumParams = std::min(NumCallArguments,
+                                  std::min(Proto1->getNumArgs(),
+                                           Proto2->getNumArgs()));
+    if (S.getLangOpts().CPlusPlus0x && IsNonStatic2 && !IsNonStatic1)
+      ::MarkUsedTemplateParameters(S.Context, Method2->getThisType(S.Context),
+                                   false,
+                                   TemplateParams->getDepth(), UsedParameters);
+    for (unsigned I = Skip2; I < NumParams; ++I)
+      ::MarkUsedTemplateParameters(S.Context, Proto2->getArgType(I), false,
+                                   TemplateParams->getDepth(),
+                                   UsedParameters);
+    break;
+  }
+
+  case TPOC_Conversion:
+    ::MarkUsedTemplateParameters(S.Context, Proto2->getResultType(), false,
+                                 TemplateParams->getDepth(),
+                                 UsedParameters);
+    break;
+
+  case TPOC_Other:
+    ::MarkUsedTemplateParameters(S.Context, FD2->getType(), false,
+                                 TemplateParams->getDepth(),
+                                 UsedParameters);
+    break;
+  }
+
+  for (; ArgIdx != NumArgs; ++ArgIdx)
+    // If this argument had no value deduced but was used in one of the types
+    // used for partial ordering, then deduction fails.
+    if (Deduced[ArgIdx].isNull() && UsedParameters[ArgIdx])
+      return false;
+
+  return true;
+}
+
+/// \brief Determine whether this a function template whose parameter-type-list
+/// ends with a function parameter pack.
+static bool isVariadicFunctionTemplate(FunctionTemplateDecl *FunTmpl) {
+  FunctionDecl *Function = FunTmpl->getTemplatedDecl();
+  unsigned NumParams = Function->getNumParams();
+  if (NumParams == 0)
+    return false;
+
+  ParmVarDecl *Last = Function->getParamDecl(NumParams - 1);
+  if (!Last->isParameterPack())
+    return false;
+
+  // Make sure that no previous parameter is a parameter pack.
+  while (--NumParams > 0) {
+    if (Function->getParamDecl(NumParams - 1)->isParameterPack())
+      return false;
+  }
+
+  return true;
+}
+
+/// \brief Returns the more specialized function template according
+/// to the rules of function template partial ordering (C++ [temp.func.order]).
+///
+/// \param FT1 the first function template
+///
+/// \param FT2 the second function template
+///
+/// \param TPOC the context in which we are performing partial ordering of
+/// function templates.
+///
+/// \param NumCallArguments The number of arguments in a call, used only
+/// when \c TPOC is \c TPOC_Call.
+///
+/// \returns the more specialized function template. If neither
+/// template is more specialized, returns NULL.
+FunctionTemplateDecl *
+Sema::getMoreSpecializedTemplate(FunctionTemplateDecl *FT1,
+                                 FunctionTemplateDecl *FT2,
+                                 SourceLocation Loc,
+                                 TemplatePartialOrderingContext TPOC,
+                                 unsigned NumCallArguments) {
+  SmallVector<RefParamPartialOrderingComparison, 4> RefParamComparisons;
+  bool Better1 = isAtLeastAsSpecializedAs(*this, Loc, FT1, FT2, TPOC,
+                                          NumCallArguments, 0);
+  bool Better2 = isAtLeastAsSpecializedAs(*this, Loc, FT2, FT1, TPOC,
+                                          NumCallArguments,
+                                          &RefParamComparisons);
+
+  if (Better1 != Better2) // We have a clear winner
+    return Better1? FT1 : FT2;
+
+  if (!Better1 && !Better2) // Neither is better than the other
+    return 0;
+
+  // C++0x [temp.deduct.partial]p10:
+  //   If for each type being considered a given template is at least as
+  //   specialized for all types and more specialized for some set of types and
+  //   the other template is not more specialized for any types or is not at
+  //   least as specialized for any types, then the given template is more
+  //   specialized than the other template. Otherwise, neither template is more
+  //   specialized than the other.
+  Better1 = false;
+  Better2 = false;
+  for (unsigned I = 0, N = RefParamComparisons.size(); I != N; ++I) {
+    // C++0x [temp.deduct.partial]p9:
+    //   If, for a given type, deduction succeeds in both directions (i.e., the
+    //   types are identical after the transformations above) and both P and A
+    //   were reference types (before being replaced with the type referred to
+    //   above):
+
+    //     -- if the type from the argument template was an lvalue reference
+    //        and the type from the parameter template was not, the argument
+    //        type is considered to be more specialized than the other;
+    //        otherwise,
+    if (!RefParamComparisons[I].ArgIsRvalueRef &&
+        RefParamComparisons[I].ParamIsRvalueRef) {
+      Better2 = true;
+      if (Better1)
+        return 0;
+      continue;
+    } else if (!RefParamComparisons[I].ParamIsRvalueRef &&
+               RefParamComparisons[I].ArgIsRvalueRef) {
+      Better1 = true;
+      if (Better2)
+        return 0;
+      continue;
+    }
+
+    //     -- if the type from the argument template is more cv-qualified than
+    //        the type from the parameter template (as described above), the
+    //        argument type is considered to be more specialized than the
+    //        other; otherwise,
+    switch (RefParamComparisons[I].Qualifiers) {
+    case NeitherMoreQualified:
+      break;
+
+    case ParamMoreQualified:
+      Better1 = true;
+      if (Better2)
+        return 0;
+      continue;
+
+    case ArgMoreQualified:
+      Better2 = true;
+      if (Better1)
+        return 0;
+      continue;
+    }
+
+    //     -- neither type is more specialized than the other.
+  }
+
+  assert(!(Better1 && Better2) && "Should have broken out in the loop above");
+  if (Better1)
+    return FT1;
+  else if (Better2)
+    return FT2;
+
+  // FIXME: This mimics what GCC implements, but doesn't match up with the
+  // proposed resolution for core issue 692. This area needs to be sorted out,
+  // but for now we attempt to maintain compatibility.
+  bool Variadic1 = isVariadicFunctionTemplate(FT1);
+  bool Variadic2 = isVariadicFunctionTemplate(FT2);
+  if (Variadic1 != Variadic2)
+    return Variadic1? FT2 : FT1;
+
+  return 0;
+}
+
+/// \brief Determine if the two templates are equivalent.
+static bool isSameTemplate(TemplateDecl *T1, TemplateDecl *T2) {
+  if (T1 == T2)
+    return true;
+
+  if (!T1 || !T2)
+    return false;
+
+  return T1->getCanonicalDecl() == T2->getCanonicalDecl();
+}
+
+/// \brief Retrieve the most specialized of the given function template
+/// specializations.
+///
+/// \param SpecBegin the start iterator of the function template
+/// specializations that we will be comparing.
+///
+/// \param SpecEnd the end iterator of the function template
+/// specializations, paired with \p SpecBegin.
+///
+/// \param TPOC the partial ordering context to use to compare the function
+/// template specializations.
+///
+/// \param NumCallArguments The number of arguments in a call, used only
+/// when \c TPOC is \c TPOC_Call.
+///
+/// \param Loc the location where the ambiguity or no-specializations
+/// diagnostic should occur.
+///
+/// \param NoneDiag partial diagnostic used to diagnose cases where there are
+/// no matching candidates.
+///
+/// \param AmbigDiag partial diagnostic used to diagnose an ambiguity, if one
+/// occurs.
+///
+/// \param CandidateDiag partial diagnostic used for each function template
+/// specialization that is a candidate in the ambiguous ordering. One parameter
+/// in this diagnostic should be unbound, which will correspond to the string
+/// describing the template arguments for the function template specialization.
+///
+/// \param Index if non-NULL and the result of this function is non-nULL,
+/// receives the index corresponding to the resulting function template
+/// specialization.
+///
+/// \returns the most specialized function template specialization, if
+/// found. Otherwise, returns SpecEnd.
+///
+/// \todo FIXME: Consider passing in the "also-ran" candidates that failed
+/// template argument deduction.
+UnresolvedSetIterator
+Sema::getMostSpecialized(UnresolvedSetIterator SpecBegin,
+                        UnresolvedSetIterator SpecEnd,
+                         TemplatePartialOrderingContext TPOC,
+                         unsigned NumCallArguments,
+                         SourceLocation Loc,
+                         const PartialDiagnostic &NoneDiag,
+                         const PartialDiagnostic &AmbigDiag,
+                         const PartialDiagnostic &CandidateDiag,
+                         bool Complain,
+                         QualType TargetType) {
+  if (SpecBegin == SpecEnd) {
+    if (Complain)
+      Diag(Loc, NoneDiag);
+    return SpecEnd;
+  }
+
+  if (SpecBegin + 1 == SpecEnd)
+    return SpecBegin;
+
+  // Find the function template that is better than all of the templates it
+  // has been compared to.
+  UnresolvedSetIterator Best = SpecBegin;
+  FunctionTemplateDecl *BestTemplate
+    = cast<FunctionDecl>(*Best)->getPrimaryTemplate();
+  assert(BestTemplate && "Not a function template specialization?");
+  for (UnresolvedSetIterator I = SpecBegin + 1; I != SpecEnd; ++I) {
+    FunctionTemplateDecl *Challenger
+      = cast<FunctionDecl>(*I)->getPrimaryTemplate();
+    assert(Challenger && "Not a function template specialization?");
+    if (isSameTemplate(getMoreSpecializedTemplate(BestTemplate, Challenger,
+                                                  Loc, TPOC, NumCallArguments),
+                       Challenger)) {
+      Best = I;
+      BestTemplate = Challenger;
+    }
+  }
+
+  // Make sure that the "best" function template is more specialized than all
+  // of the others.
+  bool Ambiguous = false;
+  for (UnresolvedSetIterator I = SpecBegin; I != SpecEnd; ++I) {
+    FunctionTemplateDecl *Challenger
+      = cast<FunctionDecl>(*I)->getPrimaryTemplate();
+    if (I != Best &&
+        !isSameTemplate(getMoreSpecializedTemplate(BestTemplate, Challenger,
+                                                   Loc, TPOC, NumCallArguments),
+                        BestTemplate)) {
+      Ambiguous = true;
+      break;
+    }
+  }
+
+  if (!Ambiguous) {
+    // We found an answer. Return it.
+    return Best;
+  }
+
+  // Diagnose the ambiguity.
+  if (Complain)
+    Diag(Loc, AmbigDiag);
+
+  if (Complain)
+  // FIXME: Can we order the candidates in some sane way?
+    for (UnresolvedSetIterator I = SpecBegin; I != SpecEnd; ++I) {
+      PartialDiagnostic PD = CandidateDiag;
+      PD << getTemplateArgumentBindingsText(
+          cast<FunctionDecl>(*I)->getPrimaryTemplate()->getTemplateParameters(),
+                    *cast<FunctionDecl>(*I)->getTemplateSpecializationArgs());
+      if (!TargetType.isNull())
+        HandleFunctionTypeMismatch(PD, cast<FunctionDecl>(*I)->getType(),
+                                   TargetType);
+      Diag((*I)->getLocation(), PD);
+    }
+
+  return SpecEnd;
+}
+
+/// \brief Returns the more specialized class template partial specialization
+/// according to the rules of partial ordering of class template partial
+/// specializations (C++ [temp.class.order]).
+///
+/// \param PS1 the first class template partial specialization
+///
+/// \param PS2 the second class template partial specialization
+///
+/// \returns the more specialized class template partial specialization. If
+/// neither partial specialization is more specialized, returns NULL.
+ClassTemplatePartialSpecializationDecl *
+Sema::getMoreSpecializedPartialSpecialization(
+                                  ClassTemplatePartialSpecializationDecl *PS1,
+                                  ClassTemplatePartialSpecializationDecl *PS2,
+                                              SourceLocation Loc) {
+  // C++ [temp.class.order]p1:
+  //   For two class template partial specializations, the first is at least as
+  //   specialized as the second if, given the following rewrite to two
+  //   function templates, the first function template is at least as
+  //   specialized as the second according to the ordering rules for function
+  //   templates (14.6.6.2):
+  //     - the first function template has the same template parameters as the
+  //       first partial specialization and has a single function parameter
+  //       whose type is a class template specialization with the template
+  //       arguments of the first partial specialization, and
+  //     - the second function template has the same template parameters as the
+  //       second partial specialization and has a single function parameter
+  //       whose type is a class template specialization with the template
+  //       arguments of the second partial specialization.
+  //
+  // Rather than synthesize function templates, we merely perform the
+  // equivalent partial ordering by performing deduction directly on
+  // the template arguments of the class template partial
+  // specializations. This computation is slightly simpler than the
+  // general problem of function template partial ordering, because
+  // class template partial specializations are more constrained. We
+  // know that every template parameter is deducible from the class
+  // template partial specialization's template arguments, for
+  // example.
+  SmallVector<DeducedTemplateArgument, 4> Deduced;
+  TemplateDeductionInfo Info(Context, Loc);
+
+  QualType PT1 = PS1->getInjectedSpecializationType();
+  QualType PT2 = PS2->getInjectedSpecializationType();
+
+  // Determine whether PS1 is at least as specialized as PS2
+  Deduced.resize(PS2->getTemplateParameters()->size());
+  bool Better1 = !DeduceTemplateArgumentsByTypeMatch(*this,
+                                            PS2->getTemplateParameters(),
+                                            PT2, PT1, Info, Deduced, TDF_None,
+                                            /*PartialOrdering=*/true,
+                                            /*RefParamComparisons=*/0);
+  if (Better1) {
+    InstantiatingTemplate Inst(*this, PS2->getLocation(), PS2,
+                               Deduced.data(), Deduced.size(), Info);
+    Better1 = !::FinishTemplateArgumentDeduction(*this, PS2,
+                                                 PS1->getTemplateArgs(),
+                                                 Deduced, Info);
+  }
+
+  // Determine whether PS2 is at least as specialized as PS1
+  Deduced.clear();
+  Deduced.resize(PS1->getTemplateParameters()->size());
+  bool Better2 = !DeduceTemplateArgumentsByTypeMatch(*this,
+                                            PS1->getTemplateParameters(),
+                                            PT1, PT2, Info, Deduced, TDF_None,
+                                            /*PartialOrdering=*/true,
+                                            /*RefParamComparisons=*/0);
+  if (Better2) {
+    InstantiatingTemplate Inst(*this, PS1->getLocation(), PS1,
+                               Deduced.data(), Deduced.size(), Info);
+    Better2 = !::FinishTemplateArgumentDeduction(*this, PS1,
+                                                 PS2->getTemplateArgs(),
+                                                 Deduced, Info);
+  }
+
+  if (Better1 == Better2)
+    return 0;
+
+  return Better1? PS1 : PS2;
+}
+
+static void
+MarkUsedTemplateParameters(ASTContext &Ctx,
+                           const TemplateArgument &TemplateArg,
+                           bool OnlyDeduced,
+                           unsigned Depth,
+                           llvm::SmallBitVector &Used);
+
+/// \brief Mark the template parameters that are used by the given
+/// expression.
+static void
+MarkUsedTemplateParameters(ASTContext &Ctx,
+                           const Expr *E,
+                           bool OnlyDeduced,
+                           unsigned Depth,
+                           llvm::SmallBitVector &Used) {
+  // We can deduce from a pack expansion.
+  if (const PackExpansionExpr *Expansion = dyn_cast<PackExpansionExpr>(E))
+    E = Expansion->getPattern();
+
+  // Skip through any implicit casts we added while type-checking.
+  while (const ImplicitCastExpr *ICE = dyn_cast<ImplicitCastExpr>(E))
+    E = ICE->getSubExpr();
+
+  // FIXME: if !OnlyDeduced, we have to walk the whole subexpression to
+  // find other occurrences of template parameters.
+  const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E);
+  if (!DRE)
+    return;
+
+  const NonTypeTemplateParmDecl *NTTP
+    = dyn_cast<NonTypeTemplateParmDecl>(DRE->getDecl());
+  if (!NTTP)
+    return;
+
+  if (NTTP->getDepth() == Depth)
+    Used[NTTP->getIndex()] = true;
+}
+
+/// \brief Mark the template parameters that are used by the given
+/// nested name specifier.
+static void
+MarkUsedTemplateParameters(ASTContext &Ctx,
+                           NestedNameSpecifier *NNS,
+                           bool OnlyDeduced,
+                           unsigned Depth,
+                           llvm::SmallBitVector &Used) {
+  if (!NNS)
+    return;
+
+  MarkUsedTemplateParameters(Ctx, NNS->getPrefix(), OnlyDeduced, Depth,
+                             Used);
+  MarkUsedTemplateParameters(Ctx, QualType(NNS->getAsType(), 0),
+                             OnlyDeduced, Depth, Used);
+}
+
+/// \brief Mark the template parameters that are used by the given
+/// template name.
+static void
+MarkUsedTemplateParameters(ASTContext &Ctx,
+                           TemplateName Name,
+                           bool OnlyDeduced,
+                           unsigned Depth,
+                           llvm::SmallBitVector &Used) {
+  if (TemplateDecl *Template = Name.getAsTemplateDecl()) {
+    if (TemplateTemplateParmDecl *TTP
+          = dyn_cast<TemplateTemplateParmDecl>(Template)) {
+      if (TTP->getDepth() == Depth)
+        Used[TTP->getIndex()] = true;
+    }
+    return;
+  }
+
+  if (QualifiedTemplateName *QTN = Name.getAsQualifiedTemplateName())
+    MarkUsedTemplateParameters(Ctx, QTN->getQualifier(), OnlyDeduced,
+                               Depth, Used);
+  if (DependentTemplateName *DTN = Name.getAsDependentTemplateName())
+    MarkUsedTemplateParameters(Ctx, DTN->getQualifier(), OnlyDeduced,
+                               Depth, Used);
+}
+
+/// \brief Mark the template parameters that are used by the given
+/// type.
+static void
+MarkUsedTemplateParameters(ASTContext &Ctx, QualType T,
+                           bool OnlyDeduced,
+                           unsigned Depth,
+                           llvm::SmallBitVector &Used) {
+  if (T.isNull())
+    return;
+
+  // Non-dependent types have nothing deducible
+  if (!T->isDependentType())
+    return;
+
+  T = Ctx.getCanonicalType(T);
+  switch (T->getTypeClass()) {
+  case Type::Pointer:
+    MarkUsedTemplateParameters(Ctx,
+                               cast<PointerType>(T)->getPointeeType(),
+                               OnlyDeduced,
+                               Depth,
+                               Used);
+    break;
+
+  case Type::BlockPointer:
+    MarkUsedTemplateParameters(Ctx,
+                               cast<BlockPointerType>(T)->getPointeeType(),
+                               OnlyDeduced,
+                               Depth,
+                               Used);
+    break;
+
+  case Type::LValueReference:
+  case Type::RValueReference:
+    MarkUsedTemplateParameters(Ctx,
+                               cast<ReferenceType>(T)->getPointeeType(),
+                               OnlyDeduced,
+                               Depth,
+                               Used);
+    break;
+
+  case Type::MemberPointer: {
+    const MemberPointerType *MemPtr = cast<MemberPointerType>(T.getTypePtr());
+    MarkUsedTemplateParameters(Ctx, MemPtr->getPointeeType(), OnlyDeduced,
+                               Depth, Used);
+    MarkUsedTemplateParameters(Ctx, QualType(MemPtr->getClass(), 0),
+                               OnlyDeduced, Depth, Used);
+    break;
+  }
+
+  case Type::DependentSizedArray:
+    MarkUsedTemplateParameters(Ctx,
+                               cast<DependentSizedArrayType>(T)->getSizeExpr(),
+                               OnlyDeduced, Depth, Used);
+    // Fall through to check the element type
+
+  case Type::ConstantArray:
+  case Type::IncompleteArray:
+    MarkUsedTemplateParameters(Ctx,
+                               cast<ArrayType>(T)->getElementType(),
+                               OnlyDeduced, Depth, Used);
+    break;
+
+  case Type::Vector:
+  case Type::ExtVector:
+    MarkUsedTemplateParameters(Ctx,
+                               cast<VectorType>(T)->getElementType(),
+                               OnlyDeduced, Depth, Used);
+    break;
+
+  case Type::DependentSizedExtVector: {
+    const DependentSizedExtVectorType *VecType
+      = cast<DependentSizedExtVectorType>(T);
+    MarkUsedTemplateParameters(Ctx, VecType->getElementType(), OnlyDeduced,
+                               Depth, Used);
+    MarkUsedTemplateParameters(Ctx, VecType->getSizeExpr(), OnlyDeduced,
+                               Depth, Used);
+    break;
+  }
+
+  case Type::FunctionProto: {
+    const FunctionProtoType *Proto = cast<FunctionProtoType>(T);
+    MarkUsedTemplateParameters(Ctx, Proto->getResultType(), OnlyDeduced,
+                               Depth, Used);
+    for (unsigned I = 0, N = Proto->getNumArgs(); I != N; ++I)
+      MarkUsedTemplateParameters(Ctx, Proto->getArgType(I), OnlyDeduced,
+                                 Depth, Used);
+    break;
+  }
+
+  case Type::TemplateTypeParm: {
+    const TemplateTypeParmType *TTP = cast<TemplateTypeParmType>(T);
+    if (TTP->getDepth() == Depth)
+      Used[TTP->getIndex()] = true;
+    break;
+  }
+
+  case Type::SubstTemplateTypeParmPack: {
+    const SubstTemplateTypeParmPackType *Subst
+      = cast<SubstTemplateTypeParmPackType>(T);
+    MarkUsedTemplateParameters(Ctx,
+                               QualType(Subst->getReplacedParameter(), 0),
+                               OnlyDeduced, Depth, Used);
+    MarkUsedTemplateParameters(Ctx, Subst->getArgumentPack(),
+                               OnlyDeduced, Depth, Used);
+    break;
+  }
+
+  case Type::InjectedClassName:
+    T = cast<InjectedClassNameType>(T)->getInjectedSpecializationType();
+    // fall through
+
+  case Type::TemplateSpecialization: {
+    const TemplateSpecializationType *Spec
+      = cast<TemplateSpecializationType>(T);
+    MarkUsedTemplateParameters(Ctx, Spec->getTemplateName(), OnlyDeduced,
+                               Depth, Used);
+
+    // C++0x [temp.deduct.type]p9:
+    //   If the template argument list of P contains a pack expansion that is not
+    //   the last template argument, the entire template argument list is a
+    //   non-deduced context.
+    if (OnlyDeduced &&
+        hasPackExpansionBeforeEnd(Spec->getArgs(), Spec->getNumArgs()))
+      break;
+
+    for (unsigned I = 0, N = Spec->getNumArgs(); I != N; ++I)
+      MarkUsedTemplateParameters(Ctx, Spec->getArg(I), OnlyDeduced, Depth,
+                                 Used);
+    break;
+  }
+
+  case Type::Complex:
+    if (!OnlyDeduced)
+      MarkUsedTemplateParameters(Ctx,
+                                 cast<ComplexType>(T)->getElementType(),
+                                 OnlyDeduced, Depth, Used);
+    break;
+
+  case Type::Atomic:
+    if (!OnlyDeduced)
+      MarkUsedTemplateParameters(Ctx,
+                                 cast<AtomicType>(T)->getValueType(),
+                                 OnlyDeduced, Depth, Used);
+    break;
+
+  case Type::DependentName:
+    if (!OnlyDeduced)
+      MarkUsedTemplateParameters(Ctx,
+                                 cast<DependentNameType>(T)->getQualifier(),
+                                 OnlyDeduced, Depth, Used);
+    break;
+
+  case Type::DependentTemplateSpecialization: {
+    const DependentTemplateSpecializationType *Spec
+      = cast<DependentTemplateSpecializationType>(T);
+    if (!OnlyDeduced)
+      MarkUsedTemplateParameters(Ctx, Spec->getQualifier(),
+                                 OnlyDeduced, Depth, Used);
+
+    // C++0x [temp.deduct.type]p9:
+    //   If the template argument list of P contains a pack expansion that is not
+    //   the last template argument, the entire template argument list is a
+    //   non-deduced context.
+    if (OnlyDeduced &&
+        hasPackExpansionBeforeEnd(Spec->getArgs(), Spec->getNumArgs()))
+      break;
+
+    for (unsigned I = 0, N = Spec->getNumArgs(); I != N; ++I)
+      MarkUsedTemplateParameters(Ctx, Spec->getArg(I), OnlyDeduced, Depth,
+                                 Used);
+    break;
+  }
+
+  case Type::TypeOf:
+    if (!OnlyDeduced)
+      MarkUsedTemplateParameters(Ctx,
+                                 cast<TypeOfType>(T)->getUnderlyingType(),
+                                 OnlyDeduced, Depth, Used);
+    break;
+
+  case Type::TypeOfExpr:
+    if (!OnlyDeduced)
+      MarkUsedTemplateParameters(Ctx,
+                                 cast<TypeOfExprType>(T)->getUnderlyingExpr(),
+                                 OnlyDeduced, Depth, Used);
+    break;
+
+  case Type::Decltype:
+    if (!OnlyDeduced)
+      MarkUsedTemplateParameters(Ctx,
+                                 cast<DecltypeType>(T)->getUnderlyingExpr(),
+                                 OnlyDeduced, Depth, Used);
+    break;
+
+  case Type::UnaryTransform:
+    if (!OnlyDeduced)
+      MarkUsedTemplateParameters(Ctx,
+                               cast<UnaryTransformType>(T)->getUnderlyingType(),
+                                 OnlyDeduced, Depth, Used);
+    break;
+
+  case Type::PackExpansion:
+    MarkUsedTemplateParameters(Ctx,
+                               cast<PackExpansionType>(T)->getPattern(),
+                               OnlyDeduced, Depth, Used);
+    break;
+
+  case Type::Auto:
+    MarkUsedTemplateParameters(Ctx,
+                               cast<AutoType>(T)->getDeducedType(),
+                               OnlyDeduced, Depth, Used);
+
+  // None of these types have any template parameters in them.
+  case Type::Builtin:
+  case Type::VariableArray:
+  case Type::FunctionNoProto:
+  case Type::Record:
+  case Type::Enum:
+  case Type::ObjCInterface:
+  case Type::ObjCObject:
+  case Type::ObjCObjectPointer:
+  case Type::UnresolvedUsing:
+#define TYPE(Class, Base)
+#define ABSTRACT_TYPE(Class, Base)
+#define DEPENDENT_TYPE(Class, Base)
+#define NON_CANONICAL_TYPE(Class, Base) case Type::Class:
+#include "clang/AST/TypeNodes.def"
+    break;
+  }
+}
+
+/// \brief Mark the template parameters that are used by this
+/// template argument.
+static void
+MarkUsedTemplateParameters(ASTContext &Ctx,
+                           const TemplateArgument &TemplateArg,
+                           bool OnlyDeduced,
+                           unsigned Depth,
+                           llvm::SmallBitVector &Used) {
+  switch (TemplateArg.getKind()) {
+  case TemplateArgument::Null:
+  case TemplateArgument::Integral:
+  case TemplateArgument::Declaration:
+    break;
+
+  case TemplateArgument::Type:
+    MarkUsedTemplateParameters(Ctx, TemplateArg.getAsType(), OnlyDeduced,
+                               Depth, Used);
+    break;
+
+  case TemplateArgument::Template:
+  case TemplateArgument::TemplateExpansion:
+    MarkUsedTemplateParameters(Ctx,
+                               TemplateArg.getAsTemplateOrTemplatePattern(),
+                               OnlyDeduced, Depth, Used);
+    break;
+
+  case TemplateArgument::Expression:
+    MarkUsedTemplateParameters(Ctx, TemplateArg.getAsExpr(), OnlyDeduced,
+                               Depth, Used);
+    break;
+
+  case TemplateArgument::Pack:
+    for (TemplateArgument::pack_iterator P = TemplateArg.pack_begin(),
+                                      PEnd = TemplateArg.pack_end();
+         P != PEnd; ++P)
+      MarkUsedTemplateParameters(Ctx, *P, OnlyDeduced, Depth, Used);
+    break;
+  }
+}
+
+/// \brief Mark the template parameters can be deduced by the given
+/// template argument list.
+///
+/// \param TemplateArgs the template argument list from which template
+/// parameters will be deduced.
+///
+/// \param Deduced a bit vector whose elements will be set to \c true
+/// to indicate when the corresponding template parameter will be
+/// deduced.
+void
+Sema::MarkUsedTemplateParameters(const TemplateArgumentList &TemplateArgs,
+                                 bool OnlyDeduced, unsigned Depth,
+                                 llvm::SmallBitVector &Used) {
+  // C++0x [temp.deduct.type]p9:
+  //   If the template argument list of P contains a pack expansion that is not
+  //   the last template argument, the entire template argument list is a
+  //   non-deduced context.
+  if (OnlyDeduced &&
+      hasPackExpansionBeforeEnd(TemplateArgs.data(), TemplateArgs.size()))
+    return;
+
+  for (unsigned I = 0, N = TemplateArgs.size(); I != N; ++I)
+    ::MarkUsedTemplateParameters(Context, TemplateArgs[I], OnlyDeduced,
+                                 Depth, Used);
+}
+
+/// \brief Marks all of the template parameters that will be deduced by a
+/// call to the given function template.
+void
+Sema::MarkDeducedTemplateParameters(ASTContext &Ctx,
+                                    FunctionTemplateDecl *FunctionTemplate,
+                                    llvm::SmallBitVector &Deduced) {
+  TemplateParameterList *TemplateParams
+    = FunctionTemplate->getTemplateParameters();
+  Deduced.clear();
+  Deduced.resize(TemplateParams->size());
+
+  FunctionDecl *Function = FunctionTemplate->getTemplatedDecl();
+  for (unsigned I = 0, N = Function->getNumParams(); I != N; ++I)
+    ::MarkUsedTemplateParameters(Ctx, Function->getParamDecl(I)->getType(),
+                                 true, TemplateParams->getDepth(), Deduced);
+}
+
+bool hasDeducibleTemplateParameters(Sema &S,
+                                    FunctionTemplateDecl *FunctionTemplate,
+                                    QualType T) {
+  if (!T->isDependentType())
+    return false;
+
+  TemplateParameterList *TemplateParams
+    = FunctionTemplate->getTemplateParameters();
+  llvm::SmallBitVector Deduced(TemplateParams->size());
+  ::MarkUsedTemplateParameters(S.Context, T, true, TemplateParams->getDepth(), 
+                               Deduced);
+
+  return Deduced.any();
+}