Implement a new type trait __is_trivially_constructible(T, Args...)

that provides the behavior of the C++11 library trait
std::is_trivially_constructible<T, Args...>, which can't be
implemented purely as a library.

Since __is_trivially_constructible can have zero or more arguments, I
needed to add Yet Another Type Trait Expression Class, this one
handling arbitrary arguments. The next step will be to migrate
UnaryTypeTrait and BinaryTypeTrait over to this new, more general
TypeTrait class.

Fixes the Clang side of <rdar://problem/10895483> / PR12038.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@151352 91177308-0d34-0410-b5e6-96231b3b80d8

16 files changed, 426 insertions, 1 deletions

diff --git a/lib/AST/Expr.cpp b/lib/AST/Expr.cpp
index a1770c915a..37df90407d 100644
--- a/lib/AST/Expr.cpp
+++ b/lib/AST/Expr.cpp
@@ -2169,6 +2169,7 @@ Expr::CanThrowResult Expr::CanThrow(ASTContext &C) const {
   case AddrLabelExprClass:
   case ArrayTypeTraitExprClass:
   case BinaryTypeTraitExprClass:
+  case TypeTraitExprClass:
   case CXXBoolLiteralExprClass:
   case CXXNoexceptExprClass:
   case CXXNullPtrLiteralExprClass:
diff --git a/lib/AST/ExprCXX.cpp b/lib/AST/ExprCXX.cpp
index 7ef3417e6d..da89bf2798 100644
--- a/lib/AST/ExprCXX.cpp
+++ b/lib/AST/ExprCXX.cpp
@@ -199,7 +199,6 @@ SourceRange CXXPseudoDestructorExpr::getSourceRange() const {
   return SourceRange(Base->getLocStart(), End);
 }
 
-
 // UnresolvedLookupExpr
 UnresolvedLookupExpr *
 UnresolvedLookupExpr::Create(ASTContext &C, 
@@ -1262,4 +1261,51 @@ TemplateArgument SubstNonTypeTemplateParmPackExpr::getArgumentPack() const {
   return TemplateArgument(Arguments, NumArguments);
 }
 
+TypeTraitExpr::TypeTraitExpr(QualType T, SourceLocation Loc, TypeTrait Kind,
+                             ArrayRef<TypeSourceInfo *> Args,
+                             SourceLocation RParenLoc,
+                             bool Value)
+  : Expr(TypeTraitExprClass, T, VK_RValue, OK_Ordinary,
+         /*TypeDependent=*/false,
+         /*ValueDependent=*/false,
+         /*InstantiationDependent=*/false,
+         /*ContainsUnexpandedParameterPack=*/false),
+    Loc(Loc), RParenLoc(RParenLoc)
+{
+  TypeTraitExprBits.Kind = Kind;
+  TypeTraitExprBits.Value = Value;
+  TypeTraitExprBits.NumArgs = Args.size();
+
+  TypeSourceInfo **ToArgs = getTypeSourceInfos();
+  
+  for (unsigned I = 0, N = Args.size(); I != N; ++I) {
+    if (Args[I]->getType()->isDependentType())
+      setValueDependent(true);
+    if (Args[I]->getType()->isInstantiationDependentType())
+      setInstantiationDependent(true);
+    if (Args[I]->getType()->containsUnexpandedParameterPack())
+      setContainsUnexpandedParameterPack(true);
+    
+    ToArgs[I] = Args[I];
+  }
+}
+
+TypeTraitExpr *TypeTraitExpr::Create(ASTContext &C, QualType T, 
+                                     SourceLocation Loc, 
+                                     TypeTrait Kind,
+                                     ArrayRef<TypeSourceInfo *> Args,
+                                     SourceLocation RParenLoc,
+                                     bool Value) {
+  unsigned Size = sizeof(TypeTraitExpr) + sizeof(TypeSourceInfo*) * Args.size();
+  void *Mem = C.Allocate(Size);
+  return new (Mem) TypeTraitExpr(T, Loc, Kind, Args, RParenLoc, Value);
+}
+
+TypeTraitExpr *TypeTraitExpr::CreateDeserialized(ASTContext &C,
+                                                 unsigned NumArgs) {
+  unsigned Size = sizeof(TypeTraitExpr) + sizeof(TypeSourceInfo*) * NumArgs;
+  void *Mem = C.Allocate(Size);
+  return new (Mem) TypeTraitExpr(EmptyShell());
+}
+
 void ArrayTypeTraitExpr::anchor() { }
diff --git a/lib/AST/ExprClassification.cpp b/lib/AST/ExprClassification.cpp
index 79d8dc48fe..1b04428fae 100644
--- a/lib/AST/ExprClassification.cpp
+++ b/lib/AST/ExprClassification.cpp
@@ -151,6 +151,7 @@ static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E) {
   case Expr::CXXScalarValueInitExprClass:
   case Expr::UnaryTypeTraitExprClass:
   case Expr::BinaryTypeTraitExprClass:
+  case Expr::TypeTraitExprClass:
   case Expr::ArrayTypeTraitExprClass:
   case Expr::ExpressionTraitExprClass:
   case Expr::ObjCSelectorExprClass:
diff --git a/lib/AST/ExprConstant.cpp b/lib/AST/ExprConstant.cpp
index ed64153f85..85aa5ee81e 100644
--- a/lib/AST/ExprConstant.cpp
+++ b/lib/AST/ExprConstant.cpp
@@ -4119,6 +4119,10 @@ public:
     return Success(E->getValue(), E);
   }
 
+  bool VisitTypeTraitExpr(const TypeTraitExpr *E) {
+    return Success(E->getValue(), E);
+  }
+
   bool VisitArrayTypeTraitExpr(const ArrayTypeTraitExpr *E) {
     return Success(E->getValue(), E);
   }
@@ -6360,6 +6364,7 @@ static ICEDiag CheckICE(const Expr* E, ASTContext &Ctx) {
   case Expr::CXXScalarValueInitExprClass:
   case Expr::UnaryTypeTraitExprClass:
   case Expr::BinaryTypeTraitExprClass:
+  case Expr::TypeTraitExprClass:
   case Expr::ArrayTypeTraitExprClass:
   case Expr::ExpressionTraitExprClass:
   case Expr::CXXNoexceptExprClass:
diff --git a/lib/AST/ItaniumMangle.cpp b/lib/AST/ItaniumMangle.cpp
index 5e167f58dc..91e6ee5c97 100644
--- a/lib/AST/ItaniumMangle.cpp
+++ b/lib/AST/ItaniumMangle.cpp
@@ -2383,6 +2383,7 @@ recurse:
   case Expr::StmtExprClass:
   case Expr::UnaryTypeTraitExprClass:
   case Expr::BinaryTypeTraitExprClass:
+  case Expr::TypeTraitExprClass:
   case Expr::ArrayTypeTraitExprClass:
   case Expr::ExpressionTraitExprClass:
   case Expr::VAArgExprClass:
diff --git a/lib/AST/StmtPrinter.cpp b/lib/AST/StmtPrinter.cpp
index 51296ad5f4..6d3e783f22 100644
--- a/lib/AST/StmtPrinter.cpp
+++ b/lib/AST/StmtPrinter.cpp
@@ -1555,6 +1555,13 @@ static const char *getTypeTraitName(BinaryTypeTrait BTT) {
   llvm_unreachable("Binary type trait not covered by switch");
 }
 
+static const char *getTypeTraitName(TypeTrait TT) {
+  switch (TT) {
+  case clang::TT_IsTriviallyConstructible:return "__is_trivially_constructible";
+  }
+  llvm_unreachable("Type trait not covered by switch");
+}
+
 static const char *getTypeTraitName(ArrayTypeTrait ATT) {
   switch (ATT) {
   case ATT_ArrayRank:        return "__array_rank";
@@ -1582,6 +1589,16 @@ void StmtPrinter::VisitBinaryTypeTraitExpr(BinaryTypeTraitExpr *E) {
      << E->getRhsType().getAsString(Policy) << ")";
 }
 
+void StmtPrinter::VisitTypeTraitExpr(TypeTraitExpr *E) {
+  OS << getTypeTraitName(E->getTrait()) << "(";
+  for (unsigned I = 0, N = E->getNumArgs(); I != N; ++I) {
+    if (I > 0)
+      OS << ", ";
+    OS << E->getArg(I)->getType().getAsString(Policy);
+  }
+  OS << ")";
+}
+
 void StmtPrinter::VisitArrayTypeTraitExpr(ArrayTypeTraitExpr *E) {
   OS << getTypeTraitName(E->getTrait()) << "("
      << E->getQueriedType().getAsString(Policy) << ")";
diff --git a/lib/AST/StmtProfile.cpp b/lib/AST/StmtProfile.cpp
index fdd0c8502d..643bca817c 100644
--- a/lib/AST/StmtProfile.cpp
+++ b/lib/AST/StmtProfile.cpp
@@ -868,6 +868,14 @@ void StmtProfiler::VisitBinaryTypeTraitExpr(const BinaryTypeTraitExpr *S) {
   VisitType(S->getRhsType());
 }
 
+void StmtProfiler::VisitTypeTraitExpr(const TypeTraitExpr *S) {
+  VisitExpr(S);
+  ID.AddInteger(S->getTrait());
+  ID.AddInteger(S->getNumArgs());
+  for (unsigned I = 0, N = S->getNumArgs(); I != N; ++I)
+    VisitType(S->getArg(I)->getType());
+}
+
 void StmtProfiler::VisitArrayTypeTraitExpr(const ArrayTypeTraitExpr *S) {
   VisitExpr(S);
   ID.AddInteger(S->getTrait());
diff --git a/lib/Lex/PPMacroExpansion.cpp b/lib/Lex/PPMacroExpansion.cpp
index 0e00996410..bc34692702 100644
--- a/lib/Lex/PPMacroExpansion.cpp
+++ b/lib/Lex/PPMacroExpansion.cpp
@@ -701,6 +701,7 @@ static bool HasFeature(const Preprocessor &PP, const IdentifierInfo *II) {
            .Case("is_polymorphic", LangOpts.CPlusPlus)
            .Case("is_trivial", LangOpts.CPlusPlus)
            .Case("is_trivially_assignable", LangOpts.CPlusPlus)
+           .Case("is_trivially_constructible", LangOpts.CPlusPlus)
            .Case("is_trivially_copyable", LangOpts.CPlusPlus)
            .Case("is_union", LangOpts.CPlusPlus)
            .Case("modules", LangOpts.Modules)
diff --git a/lib/Parse/ParseExpr.cpp b/lib/Parse/ParseExpr.cpp
index fdf40e877c..62d1f494be 100644
--- a/lib/Parse/ParseExpr.cpp
+++ b/lib/Parse/ParseExpr.cpp
@@ -1143,6 +1143,9 @@ ExprResult Parser::ParseCastExpression(bool isUnaryExpression,
   case tok::kw___is_trivially_assignable:
     return ParseBinaryTypeTrait();
 
+  case tok::kw___is_trivially_constructible:
+    return ParseTypeTrait();
+      
   case tok::kw___array_rank:
   case tok::kw___array_extent:
     return ParseArrayTypeTrait();
diff --git a/lib/Parse/ParseExprCXX.cpp b/lib/Parse/ParseExprCXX.cpp
index 19bc22020c..d8663077fd 100644
--- a/lib/Parse/ParseExprCXX.cpp
+++ b/lib/Parse/ParseExprCXX.cpp
@@ -2458,6 +2458,14 @@ static BinaryTypeTrait BinaryTypeTraitFromTokKind(tok::TokenKind kind) {
   }
 }
 
+static TypeTrait TypeTraitFromTokKind(tok::TokenKind kind) {
+  switch (kind) {
+  default: llvm_unreachable("Not a known type trait");
+  case tok::kw___is_trivially_constructible: 
+    return TT_IsTriviallyConstructible;
+  }
+}
+
 static ArrayTypeTrait ArrayTypeTraitFromTokKind(tok::TokenKind kind) {
   switch(kind) {
   default: llvm_unreachable("Not a known binary type trait");
@@ -2540,6 +2548,58 @@ ExprResult Parser::ParseBinaryTypeTrait() {
                                       T.getCloseLocation());
 }
 
+/// \brief Parse the built-in type-trait pseudo-functions that allow 
+/// implementation of the TR1/C++11 type traits templates.
+///
+///       primary-expression:
+///          type-trait '(' type-id-seq ')'
+///
+///       type-id-seq:
+///          type-id ...[opt] type-id-seq[opt]
+///
+ExprResult Parser::ParseTypeTrait() {
+  TypeTrait Kind = TypeTraitFromTokKind(Tok.getKind());
+  SourceLocation Loc = ConsumeToken();
+  
+  BalancedDelimiterTracker Parens(*this, tok::l_paren);
+  if (Parens.expectAndConsume(diag::err_expected_lparen))
+    return ExprError();
+
+  llvm::SmallVector<ParsedType, 2> Args;
+  do {
+    // Parse the next type.
+    TypeResult Ty = ParseTypeName();
+    if (Ty.isInvalid()) {
+      Parens.skipToEnd();
+      return ExprError();
+    }
+
+    // Parse the ellipsis, if present.
+    if (Tok.is(tok::ellipsis)) {
+      Ty = Actions.ActOnPackExpansion(Ty.get(), ConsumeToken());
+      if (Ty.isInvalid()) {
+        Parens.skipToEnd();
+        return ExprError();
+      }
+    }
+    
+    // Add this type to the list of arguments.
+    Args.push_back(Ty.get());
+    
+    if (Tok.is(tok::comma)) {
+      ConsumeToken();
+      continue;
+    }
+    
+    break;
+  } while (true);
+  
+  if (Parens.consumeClose())
+    return ExprError();
+  
+  return Actions.ActOnTypeTrait(Kind, Loc, Args, Parens.getCloseLocation());
+}
+
 /// ParseArrayTypeTrait - Parse the built-in array type-trait
 /// pseudo-functions.
 ///
diff --git a/lib/Parse/ParseTentative.cpp b/lib/Parse/ParseTentative.cpp
index 011c28aaf7..92ae770fa0 100644
--- a/lib/Parse/ParseTentative.cpp
+++ b/lib/Parse/ParseTentative.cpp
@@ -690,6 +690,7 @@ Parser::isExpressionOrTypeSpecifierSimple(tok::TokenKind Kind) {
   case tok::kw___is_polymorphic:
   case tok::kw___is_trivial:
   case tok::kw___is_trivially_assignable:
+  case tok::kw___is_trivially_constructible:
   case tok::kw___is_trivially_copyable:
   case tok::kw___is_union:
   case tok::kw___uuidof:
diff --git a/lib/Sema/SemaExprCXX.cpp b/lib/Sema/SemaExprCXX.cpp
index 708db1c9a9..a4ae9be41b 100644
--- a/lib/Sema/SemaExprCXX.cpp
+++ b/lib/Sema/SemaExprCXX.cpp
@@ -3212,6 +3212,127 @@ ExprResult Sema::ActOnBinaryTypeTrait(BinaryTypeTrait BTT,
   return BuildBinaryTypeTrait(BTT, KWLoc, LhsTSInfo, RhsTSInfo, RParen);
 }
 
+static bool evaluateTypeTrait(Sema &S, TypeTrait Kind, SourceLocation KWLoc,
+                              ArrayRef<TypeSourceInfo *> Args,
+                              SourceLocation RParenLoc) {
+  switch (Kind) {
+  case clang::TT_IsTriviallyConstructible: {
+    // C++11 [meta.unary.prop]:
+    //   is_trivially_constructor is defined as:
+    //
+    //     is_constructible<T, Args...>::value is true and the variable 
+    //
+    ///  definition for is_constructible, as defined below, is known to call no
+    //   operation that is not trivial.
+    //
+    //   The predicate condition for a template specialization 
+    //   is_constructible<T, Args...> shall be satisfied if and only if the 
+    //   following variable definition would be well-formed for some invented 
+    //   variable t:
+    //
+    //     T t(create<Args>()...);
+    if (Args.empty()) {
+      S.Diag(KWLoc, diag::err_type_trait_arity)
+        << 1 << 1 << 1 << (int)Args.size();
+      return false;
+    }
+    
+    bool SawVoid = false;
+    for (unsigned I = 0, N = Args.size(); I != N; ++I) {
+      if (Args[I]->getType()->isVoidType()) {
+        SawVoid = true;
+        continue;
+      }
+      
+      if (!Args[I]->getType()->isIncompleteType() &&
+        S.RequireCompleteType(KWLoc, Args[I]->getType(), 
+          diag::err_incomplete_type_used_in_type_trait_expr))
+        return false;
+    }
+    
+    // If any argument was 'void', of course it won't type-check.
+    if (SawVoid)
+      return false;
+    
+    llvm::SmallVector<OpaqueValueExpr, 2> OpaqueArgExprs;
+    llvm::SmallVector<Expr *, 2> ArgExprs;
+    ArgExprs.reserve(Args.size() - 1);
+    for (unsigned I = 1, N = Args.size(); I != N; ++I) {
+      QualType T = Args[I]->getType();
+      if (T->isObjectType() || T->isFunctionType())
+        T = S.Context.getRValueReferenceType(T);
+      OpaqueArgExprs.push_back(
+        OpaqueValueExpr(Args[I]->getTypeLoc().getSourceRange().getBegin(), 
+                        T.getNonLValueExprType(S.Context),
+                        Expr::getValueKindForType(T)));
+      ArgExprs.push_back(&OpaqueArgExprs.back());
+    }
+    
+    // Perform the initialization in an unevaluated context within a SFINAE 
+    // trap at translation unit scope.
+    EnterExpressionEvaluationContext Unevaluated(S, Sema::Unevaluated);
+    Sema::SFINAETrap SFINAE(S, /*AccessCheckingSFINAE=*/true);
+    Sema::ContextRAII TUContext(S, S.Context.getTranslationUnitDecl());
+    InitializedEntity To(InitializedEntity::InitializeTemporary(Args[0]));
+    InitializationKind InitKind(InitializationKind::CreateDirect(KWLoc, KWLoc,
+                                                                 RParenLoc));
+    InitializationSequence Init(S, To, InitKind, 
+                                ArgExprs.begin(), ArgExprs.size());
+    if (Init.Failed())
+      return false;
+    
+    ExprResult Result = Init.Perform(S, To, InitKind, 
+                                     MultiExprArg(ArgExprs.data(), 
+                                                  ArgExprs.size()));
+    if (Result.isInvalid() || SFINAE.hasErrorOccurred())
+      return false;
+    
+    // The initialization succeeded; not make sure there are no non-trivial 
+    // calls.
+    return !Result.get()->hasNonTrivialCall(S.Context);
+  }
+  }
+  
+  return false;
+}
+
+ExprResult Sema::BuildTypeTrait(TypeTrait Kind, SourceLocation KWLoc, 
+                                ArrayRef<TypeSourceInfo *> Args, 
+                                SourceLocation RParenLoc) {
+  bool Dependent = false;
+  for (unsigned I = 0, N = Args.size(); I != N; ++I) {
+    if (Args[I]->getType()->isDependentType()) {
+      Dependent = true;
+      break;
+    }
+  }
+  
+  bool Value = false;
+  if (!Dependent)
+    Value = evaluateTypeTrait(*this, Kind, KWLoc, Args, RParenLoc);
+  
+  return TypeTraitExpr::Create(Context, Context.BoolTy, KWLoc, Kind,
+                               Args, RParenLoc, Value);
+}
+
+ExprResult Sema::ActOnTypeTrait(TypeTrait Kind, SourceLocation KWLoc, 
+                                ArrayRef<ParsedType> Args, 
+                                SourceLocation RParenLoc) {
+  llvm::SmallVector<TypeSourceInfo *, 4> ConvertedArgs;
+  ConvertedArgs.reserve(Args.size());
+  
+  for (unsigned I = 0, N = Args.size(); I != N; ++I) {
+    TypeSourceInfo *TInfo;
+    QualType T = GetTypeFromParser(Args[I], &TInfo);
+    if (!TInfo)
+      TInfo = Context.getTrivialTypeSourceInfo(T, KWLoc);
+    
+    ConvertedArgs.push_back(TInfo);    
+  }
+  
+  return BuildTypeTrait(Kind, KWLoc, ConvertedArgs, RParenLoc);
+}
+
 static bool EvaluateBinaryTypeTrait(Sema &Self, BinaryTypeTrait BTT,
                                     QualType LhsT, QualType RhsT,
                                     SourceLocation KeyLoc) {
diff --git a/lib/Sema/TreeTransform.h b/lib/Sema/TreeTransform.h
index 58d6a22a28..f0b5f4e241 100644
--- a/lib/Sema/TreeTransform.h
+++ b/lib/Sema/TreeTransform.h
@@ -2022,6 +2022,17 @@ public:
     return getSema().BuildBinaryTypeTrait(Trait, StartLoc, LhsT, RhsT, RParenLoc);
   }
 
+  /// \brief Build a new type trait expression.
+  ///
+  /// By default, performs semantic analysis to build the new expression.
+  /// Subclasses may override this routine to provide different behavior.
+  ExprResult RebuildTypeTrait(TypeTrait Trait,
+                              SourceLocation StartLoc,
+                              ArrayRef<TypeSourceInfo *> Args,
+                              SourceLocation RParenLoc) {
+    return getSema().BuildTypeTrait(Trait, StartLoc, Args, RParenLoc);
+  }
+  
   /// \brief Build a new array type trait expression.
   ///
   /// By default, performs semantic analysis to build the new expression.
@@ -7436,6 +7447,128 @@ TreeTransform<Derived>::TransformBinaryTypeTraitExpr(BinaryTypeTraitExpr *E) {
 
 template<typename Derived>
 ExprResult
+TreeTransform<Derived>::TransformTypeTraitExpr(TypeTraitExpr *E) {
+  bool ArgChanged = false;
+  llvm::SmallVector<TypeSourceInfo *, 4> Args;
+  for (unsigned I = 0, N = E->getNumArgs(); I != N; ++I) {
+    TypeSourceInfo *From = E->getArg(I);
+    TypeLoc FromTL = From->getTypeLoc();
+    if (!isa<PackExpansionTypeLoc>(FromTL)) {
+      TypeLocBuilder TLB;
+      TLB.reserve(FromTL.getFullDataSize());
+      QualType To = getDerived().TransformType(TLB, FromTL);
+      if (To.isNull())
+        return ExprError();
+      
+      if (To == From->getType())
+        Args.push_back(From);
+      else {
+        Args.push_back(TLB.getTypeSourceInfo(SemaRef.Context, To));
+        ArgChanged = true;
+      }
+      continue;
+    }
+    
+    ArgChanged = true;
+    
+    // We have a pack expansion. Instantiate it.
+    PackExpansionTypeLoc ExpansionTL = cast<PackExpansionTypeLoc>(FromTL);      
+    TypeLoc PatternTL = ExpansionTL.getPatternLoc();
+    SmallVector<UnexpandedParameterPack, 2> Unexpanded;
+    SemaRef.collectUnexpandedParameterPacks(PatternTL, Unexpanded);
+    
+    // Determine whether the set of unexpanded parameter packs can and should
+    // be expanded.
+    bool Expand = true;
+    bool RetainExpansion = false;
+    llvm::Optional<unsigned> OrigNumExpansions
+      = ExpansionTL.getTypePtr()->getNumExpansions();
+    llvm::Optional<unsigned> NumExpansions = OrigNumExpansions;
+    if (getDerived().TryExpandParameterPacks(ExpansionTL.getEllipsisLoc(),
+                                             PatternTL.getSourceRange(),
+                                             Unexpanded,
+                                             Expand, RetainExpansion,
+                                             NumExpansions))
+      return ExprError();
+    
+    if (!Expand) {
+      // The transform has determined that we should perform a simple
+      // transformation on the pack expansion, producing another pack 
+      // expansion.
+      Sema::ArgumentPackSubstitutionIndexRAII SubstIndex(getSema(), -1);
+      
+      TypeLocBuilder TLB;
+      TLB.reserve(From->getTypeLoc().getFullDataSize());
+
+      QualType To = getDerived().TransformType(TLB, PatternTL);
+      if (To.isNull())
+        return ExprError();
+
+      To = getDerived().RebuildPackExpansionType(To, 
+                                                 PatternTL.getSourceRange(),
+                                                 ExpansionTL.getEllipsisLoc(),
+                                                 NumExpansions);
+      if (To.isNull())
+        return ExprError();
+      
+      PackExpansionTypeLoc ToExpansionTL
+        = TLB.push<PackExpansionTypeLoc>(To);
+      ToExpansionTL.setEllipsisLoc(ExpansionTL.getEllipsisLoc());
+      Args.push_back(TLB.getTypeSourceInfo(SemaRef.Context, To));
+      continue;
+    }
+
+    // Expand the pack expansion by substituting for each argument in the
+    // pack(s).
+    for (unsigned I = 0; I != *NumExpansions; ++I) {
+      Sema::ArgumentPackSubstitutionIndexRAII SubstIndex(SemaRef, I);
+      TypeLocBuilder TLB;
+      TLB.reserve(PatternTL.getFullDataSize());
+      QualType To = getDerived().TransformType(TLB, PatternTL);
+      if (To.isNull())
+        return ExprError();
+
+      Args.push_back(TLB.getTypeSourceInfo(SemaRef.Context, To));
+    }
+    
+    if (!RetainExpansion)
+      continue;
+    
+    // If we're supposed to retain a pack expansion, do so by temporarily
+    // forgetting the partially-substituted parameter pack.
+    ForgetPartiallySubstitutedPackRAII Forget(getDerived());
+
+    TypeLocBuilder TLB;
+    TLB.reserve(From->getTypeLoc().getFullDataSize());
+    
+    QualType To = getDerived().TransformType(TLB, PatternTL);
+    if (To.isNull())
+      return ExprError();
+    
+    To = getDerived().RebuildPackExpansionType(To, 
+                                               PatternTL.getSourceRange(),
+                                               ExpansionTL.getEllipsisLoc(),
+                                               NumExpansions);
+    if (To.isNull())
+      return ExprError();
+    
+    PackExpansionTypeLoc ToExpansionTL
+      = TLB.push<PackExpansionTypeLoc>(To);
+    ToExpansionTL.setEllipsisLoc(ExpansionTL.getEllipsisLoc());
+    Args.push_back(TLB.getTypeSourceInfo(SemaRef.Context, To));
+  }
+  
+  if (!getDerived().AlwaysRebuild() && !ArgChanged)
+    return SemaRef.Owned(E);
+
+  return getDerived().RebuildTypeTrait(E->getTrait(),
+                                       E->getLocStart(),
+                                       Args,
+                                       E->getLocEnd());
+}
+
+template<typename Derived>
+ExprResult
 TreeTransform<Derived>::TransformArrayTypeTraitExpr(ArrayTypeTraitExpr *E) {
   TypeSourceInfo *T = getDerived().TransformType(E->getQueriedTypeSourceInfo());
   if (!T)
diff --git a/lib/Serialization/ASTReaderStmt.cpp b/lib/Serialization/ASTReaderStmt.cpp
index 77e4541669..2d308fb030 100644
--- a/lib/Serialization/ASTReaderStmt.cpp
+++ b/lib/Serialization/ASTReaderStmt.cpp
@@ -1327,6 +1327,17 @@ void ASTStmtReader::VisitBinaryTypeTraitExpr(BinaryTypeTraitExpr *E) {
   E->RhsType = GetTypeSourceInfo(Record, Idx);
 }
 
+void ASTStmtReader::VisitTypeTraitExpr(TypeTraitExpr *E) {
+  VisitExpr(E);
+  E->TypeTraitExprBits.NumArgs = Record[Idx++];
+  E->TypeTraitExprBits.Kind = Record[Idx++];
+  E->TypeTraitExprBits.Value = Record[Idx++];
+  
+  TypeSourceInfo **Args = E->getTypeSourceInfos();
+  for (unsigned I = 0, N = E->getNumArgs(); I != N; ++I)
+    Args[I] = GetTypeSourceInfo(Record, Idx);
+}
+
 void ASTStmtReader::VisitArrayTypeTraitExpr(ArrayTypeTraitExpr *E) {
   VisitExpr(E);
   E->ATT = (ArrayTypeTrait)Record[Idx++];
@@ -2046,6 +2057,11 @@ Stmt *ASTReader::ReadStmtFromStream(ModuleFile &F) {
       S = new (Context) BinaryTypeTraitExpr(Empty);
       break;
 
+    case EXPR_TYPE_TRAIT:
+      S = TypeTraitExpr::CreateDeserialized(Context, 
+            Record[ASTStmtReader::NumExprFields]);
+      break;
+        
     case EXPR_ARRAY_TYPE_TRAIT:
       S = new (Context) ArrayTypeTraitExpr(Empty);
       break;
diff --git a/lib/Serialization/ASTWriterStmt.cpp b/lib/Serialization/ASTWriterStmt.cpp
index 0ba413df72..f9c3c5de43 100644
--- a/lib/Serialization/ASTWriterStmt.cpp
+++ b/lib/Serialization/ASTWriterStmt.cpp
@@ -1341,6 +1341,16 @@ void ASTStmtWriter::VisitBinaryTypeTraitExpr(BinaryTypeTraitExpr *E) {
   Code = serialization::EXPR_BINARY_TYPE_TRAIT;
 }
 
+void ASTStmtWriter::VisitTypeTraitExpr(TypeTraitExpr *E) {
+  VisitExpr(E);
+  Record.push_back(E->TypeTraitExprBits.NumArgs);
+  Record.push_back(E->TypeTraitExprBits.Kind); // FIXME: Stable encoding
+  Record.push_back(E->TypeTraitExprBits.Value);
+  for (unsigned I = 0, N = E->getNumArgs(); I != N; ++I)
+    Writer.AddTypeSourceInfo(E->getArg(I), Record);
+  Code = serialization::EXPR_TYPE_TRAIT;
+}
+
 void ASTStmtWriter::VisitArrayTypeTraitExpr(ArrayTypeTraitExpr *E) {
   VisitExpr(E);
   Record.push_back(E->getTrait());
diff --git a/lib/StaticAnalyzer/Core/ExprEngine.cpp b/lib/StaticAnalyzer/Core/ExprEngine.cpp
index 34ad23a429..a61c0272b5 100644
--- a/lib/StaticAnalyzer/Core/ExprEngine.cpp
+++ b/lib/StaticAnalyzer/Core/ExprEngine.cpp
@@ -478,6 +478,7 @@ void ExprEngine::Visit(const Stmt *S, ExplodedNode *Pred,
     case Stmt::DependentScopeDeclRefExprClass:
     case Stmt::UnaryTypeTraitExprClass:
     case Stmt::BinaryTypeTraitExprClass:
+    case Stmt::TypeTraitExprClass:
     case Stmt::ArrayTypeTraitExprClass:
     case Stmt::ExpressionTraitExprClass:
     case Stmt::UnresolvedLookupExprClass: