7 files changed, 278 insertions, 140 deletions

diff --git a/include/clang/AST/Expr.h b/include/clang/AST/Expr.h
index b6c6996fbc..da739002fa 100644
--- a/include/clang/AST/Expr.h
+++ b/include/clang/AST/Expr.h
@@ -1164,6 +1164,24 @@ public:
   static CStyleCastExpr* CreateImpl(llvm::Deserializer& D, ASTContext& C);
 };
 
+/// \brief A builtin binary operation expression such as "x + y" or "x <= y".
+///
+/// This expression node kind describes a builtin binary operation,
+/// such as "x + y" for integer values "x" and "y". The operands will
+/// already have been converted to appropriate types (e.g., by
+/// performing promotions or conversions).
+///
+/// In C++, where operators may be overloaded, a different kind of
+/// expression node (CXXOperatorCallExpr) is used to express the
+/// invocation of an overloaded operator with operator syntax. Within
+/// a C++ template, whether BinaryOperator or CXXOperatorCallExpr is
+/// used to store an expression "x + y" depends on the subexpressions
+/// for x and y. If neither x or y is type-dependent, and the "+"
+/// operator resolves to a built-in operation, BinaryOperator will be
+/// used to express the computation (x and y may still be
+/// value-dependent). If either x or y is type-dependent, or if the
+/// "+" resolves to an overloaded operator, CXXOperatorCallExpr will
+/// be used to express the computation.
 class BinaryOperator : public Expr {
 public:
   enum Opcode {
diff --git a/include/clang/AST/ExprCXX.h b/include/clang/AST/ExprCXX.h
index 675732aa07..d18ffb3c8e 100644
--- a/include/clang/AST/ExprCXX.h
+++ b/include/clang/AST/ExprCXX.h
@@ -26,10 +26,19 @@ namespace clang {
 // C++ Expressions.
 //===--------------------------------------------------------------------===//
 
-/// CXXOperatorCallExpr - Represents a call to an overloaded operator
-/// written using operator syntax, e.g., "x + y" or "*p". While
-/// semantically equivalent to a normal call, this AST node provides
-/// better information about the syntactic representation of the call.
+/// \brief A call to an overloaded operator written using operator
+/// syntax.
+///
+/// Represents a call to an overloaded operator written using operator
+/// syntax, e.g., "x + y" or "*p". While semantically equivalent to a
+/// normal call, this AST node provides better information about the
+/// syntactic representation of the call.
+///
+/// In a C++ template, this expression node kind will be used whenever
+/// any of the arguments are type-dependent. In this case, the
+/// function itself will be a (possibly empty) set of functions and
+/// function templates that were found by name lookup at template
+/// definition time.
 class CXXOperatorCallExpr : public CallExpr {
 public:
   CXXOperatorCallExpr(ASTContext& C, Expr *fn, Expr **args, unsigned numargs,
diff --git a/lib/Sema/Sema.h b/lib/Sema/Sema.h
index 913efaf747..fbae644568 100644
--- a/lib/Sema/Sema.h
+++ b/lib/Sema/Sema.h
@@ -928,10 +928,19 @@ public:
                                 bool RedeclarationOnly = false,
                                 bool AllowBuiltinCreation = true,
                                 SourceLocation Loc = SourceLocation());
-  
+
+  typedef llvm::SmallPtrSet<FunctionDecl *, 16> FunctionSet;
   typedef llvm::SmallPtrSet<NamespaceDecl *, 16> AssociatedNamespaceSet;
   typedef llvm::SmallPtrSet<CXXRecordDecl *, 16> AssociatedClassSet;
 
+  void LookupOverloadedOperatorName(OverloadedOperatorKind Op, Scope *S,
+                                    QualType T1, QualType T2, 
+                                    FunctionSet &Functions);
+                          
+  void ArgumentDependentLookup(DeclarationName Name,
+                               Expr **Args, unsigned NumArgs,
+                               FunctionSet &Functions);
+
   void FindAssociatedClassesAndNamespaces(Expr **Args, unsigned NumArgs,
                                    AssociatedNamespaceSet &AssociatedNamespaces,
                                    AssociatedClassSet &AssociatedClasses);
diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp
index 64a45182f2..3f8eb72a6c 100644
--- a/lib/Sema/SemaExpr.cpp
+++ b/lib/Sema/SemaExpr.cpp
@@ -3977,6 +3977,32 @@ Action::OwningExprResult Sema::CreateBuiltinBinOp(SourceLocation OpLoc,
                                                       CompTy, OpLoc));
 }
 
+static OverloadedOperatorKind 
+getOverloadedOperator(BinaryOperator::Opcode Opc) {
+  static const OverloadedOperatorKind OverOps[] = {
+    // Overloading .* is not possible.
+    static_cast<OverloadedOperatorKind>(0), OO_ArrowStar,
+    OO_Star, OO_Slash, OO_Percent,
+    OO_Plus, OO_Minus,
+    OO_LessLess, OO_GreaterGreater,
+    OO_Less, OO_Greater, OO_LessEqual, OO_GreaterEqual,
+    OO_EqualEqual, OO_ExclaimEqual,
+    OO_Amp,
+    OO_Caret,
+    OO_Pipe,
+    OO_AmpAmp,
+    OO_PipePipe,
+    OO_Equal, OO_StarEqual,
+    OO_SlashEqual, OO_PercentEqual,
+    OO_PlusEqual, OO_MinusEqual,
+    OO_LessLessEqual, OO_GreaterGreaterEqual,
+    OO_AmpEqual, OO_CaretEqual,
+    OO_PipeEqual,
+    OO_Comma
+  };
+  return OverOps[Opc];
+}
+
 // Binary Operators.  'Tok' is the token for the operator.
 Action::OwningExprResult Sema::ActOnBinOp(Scope *S, SourceLocation TokLoc,
                                           tok::TokenKind Kind,
@@ -3988,16 +4014,39 @@ Action::OwningExprResult Sema::ActOnBinOp(Scope *S, SourceLocation TokLoc,
   assert((rhs != 0) && "ActOnBinOp(): missing right expression");
 
   // If either expression is type-dependent, just build the AST.
-  // FIXME: We'll need to perform some caching of the result of name
-  // lookup for operator+.
   if (lhs->isTypeDependent() || rhs->isTypeDependent()) {
-    if (Opc > BinaryOperator::Assign && Opc <= BinaryOperator::OrAssign)
-      return Owned(new (Context) CompoundAssignOperator(lhs, rhs, Opc,
-                                              Context.DependentTy,
-                                              Context.DependentTy, TokLoc));
-    else
+    // .* cannot be overloaded.
+    if (Opc == BinaryOperator::PtrMemD)
       return Owned(new (Context) BinaryOperator(lhs, rhs, Opc,
                                                 Context.DependentTy, TokLoc));
+    
+    // Find all of the overloaded operators visible from the template
+    // definition. We perform both an operator-name lookup from the
+    // local scope and an argument-dependent lookup based on the types
+    // of the arguments.
+    FunctionSet Functions;
+    OverloadedOperatorKind OverOp = getOverloadedOperator(Opc);
+    LookupOverloadedOperatorName(OverOp, S, lhs->getType(), rhs->getType(),
+                                 Functions);
+    Expr *Args[2] = { lhs, rhs };
+    DeclarationName OpName 
+      = Context.DeclarationNames.getCXXOperatorName(OverOp);
+    ArgumentDependentLookup(OpName, Args, 2, Functions);
+
+    OverloadedFunctionDecl *Overloads 
+      = OverloadedFunctionDecl::Create(Context, CurContext, OpName);
+    for (FunctionSet::iterator Func = Functions.begin(), 
+                            FuncEnd = Functions.end();
+         Func != FuncEnd; ++Func)
+      Overloads->addOverload(*Func);
+
+    DeclRefExpr *Fn = new (Context) DeclRefExpr(Overloads, Context.OverloadTy,
+                                                TokLoc, false, false);
+    
+    return Owned(new (Context) CXXOperatorCallExpr(Context, Fn,
+                                                   Args, 2, 
+                                                   Context.DependentTy,
+                                                   TokLoc));
   }
 
   if (getLangOptions().CPlusPlus && Opc != BinaryOperator::PtrMemD &&
@@ -4012,32 +4061,11 @@ Action::OwningExprResult Sema::ActOnBinOp(Scope *S, SourceLocation TokLoc,
     }
 
     // Determine which overloaded operator we're dealing with.
-    static const OverloadedOperatorKind OverOps[] = {
-      // Overloading .* is not possible.
-      static_cast<OverloadedOperatorKind>(0), OO_ArrowStar,
-      OO_Star, OO_Slash, OO_Percent,
-      OO_Plus, OO_Minus,
-      OO_LessLess, OO_GreaterGreater,
-      OO_Less, OO_Greater, OO_LessEqual, OO_GreaterEqual,
-      OO_EqualEqual, OO_ExclaimEqual,
-      OO_Amp,
-      OO_Caret,
-      OO_Pipe,
-      OO_AmpAmp,
-      OO_PipePipe,
-      OO_Equal, OO_StarEqual,
-      OO_SlashEqual, OO_PercentEqual,
-      OO_PlusEqual, OO_MinusEqual,
-      OO_LessLessEqual, OO_GreaterGreaterEqual,
-      OO_AmpEqual, OO_CaretEqual,
-      OO_PipeEqual,
-      OO_Comma
-    };
-    OverloadedOperatorKind OverOp = OverOps[Opc];
 
     // Add the appropriate overloaded operators (C++ [over.match.oper])
     // to the candidate set.
     OverloadCandidateSet CandidateSet;
+    OverloadedOperatorKind OverOp = getOverloadedOperator(Opc);
     Expr *Args[2] = { lhs, rhs };
     if (AddOperatorCandidates(OverOp, S, TokLoc, Args, 2, CandidateSet))
       return ExprError();
diff --git a/lib/Sema/SemaLookup.cpp b/lib/Sema/SemaLookup.cpp
index a93689c9a0..d391c07b3f 100644
--- a/lib/Sema/SemaLookup.cpp
+++ b/lib/Sema/SemaLookup.cpp
@@ -1382,3 +1382,118 @@ Sema::FindAssociatedClassesAndNamespaces(Expr **Args, unsigned NumArgs,
     }
   }
 }
+
+/// IsAcceptableNonMemberOperatorCandidate - Determine whether Fn is
+/// an acceptable non-member overloaded operator for a call whose
+/// arguments have types T1 (and, if non-empty, T2). This routine
+/// implements the check in C++ [over.match.oper]p3b2 concerning
+/// enumeration types.
+static bool 
+IsAcceptableNonMemberOperatorCandidate(FunctionDecl *Fn,
+                                       QualType T1, QualType T2,
+                                       ASTContext &Context) {
+  if (T1->isRecordType() || (!T2.isNull() && T2->isRecordType()))
+    return true;
+
+  const FunctionProtoType *Proto = Fn->getType()->getAsFunctionProtoType();
+  if (Proto->getNumArgs() < 1)
+    return false;
+
+  if (T1->isEnumeralType()) {
+    QualType ArgType = Proto->getArgType(0).getNonReferenceType();
+    if (Context.getCanonicalType(T1).getUnqualifiedType()
+          == Context.getCanonicalType(ArgType).getUnqualifiedType())
+      return true;
+  }
+
+  if (Proto->getNumArgs() < 2)
+    return false;
+
+  if (!T2.isNull() && T2->isEnumeralType()) {
+    QualType ArgType = Proto->getArgType(1).getNonReferenceType();
+    if (Context.getCanonicalType(T2).getUnqualifiedType()
+          == Context.getCanonicalType(ArgType).getUnqualifiedType())
+      return true;
+  }
+
+  return false;
+}
+
+void Sema::LookupOverloadedOperatorName(OverloadedOperatorKind Op, Scope *S,
+                                        QualType T1, QualType T2, 
+                                        FunctionSet &Functions) {
+  // C++ [over.match.oper]p3:
+  //     -- The set of non-member candidates is the result of the
+  //        unqualified lookup of operator@ in the context of the
+  //        expression according to the usual rules for name lookup in
+  //        unqualified function calls (3.4.2) except that all member
+  //        functions are ignored. However, if no operand has a class
+  //        type, only those non-member functions in the lookup set
+  //        that have a first parameter of type T1 or “reference to
+  //        (possibly cv-qualified) T1”, when T1 is an enumeration
+  //        type, or (if there is a right operand) a second parameter
+  //        of type T2 or “reference to (possibly cv-qualified) T2”,
+  //        when T2 is an enumeration type, are candidate functions.
+  DeclarationName OpName = Context.DeclarationNames.getCXXOperatorName(Op);
+  LookupResult Operators = LookupName(S, OpName, LookupOperatorName);
+  
+  assert(!Operators.isAmbiguous() && "Operator lookup cannot be ambiguous");
+
+  if (!Operators)
+    return;
+
+  for (LookupResult::iterator Op = Operators.begin(), OpEnd = Operators.end();
+       Op != OpEnd; ++Op) {
+    if (FunctionDecl *FD = dyn_cast<FunctionDecl>(*Op))
+      if (IsAcceptableNonMemberOperatorCandidate(FD, T1, T2, Context))
+        Functions.insert(FD); // FIXME: canonical FD
+  }
+}
+
+void Sema::ArgumentDependentLookup(DeclarationName Name,
+                                   Expr **Args, unsigned NumArgs,
+                                   FunctionSet &Functions) {
+  // Find all of the associated namespaces and classes based on the
+  // arguments we have.
+  AssociatedNamespaceSet AssociatedNamespaces;
+  AssociatedClassSet AssociatedClasses;
+  FindAssociatedClassesAndNamespaces(Args, NumArgs, 
+                                     AssociatedNamespaces, AssociatedClasses);
+
+  // C++ [basic.lookup.argdep]p3:
+  //
+  //   Let X be the lookup set produced by unqualified lookup (3.4.1)
+  //   and let Y be the lookup set produced by argument dependent
+  //   lookup (defined as follows). If X contains [...] then Y is
+  //   empty. Otherwise Y is the set of declarations found in the
+  //   namespaces associated with the argument types as described
+  //   below. The set of declarations found by the lookup of the name
+  //   is the union of X and Y.
+  //
+  // Here, we compute Y and add its members to the overloaded
+  // candidate set.
+  for (AssociatedNamespaceSet::iterator NS = AssociatedNamespaces.begin(),
+                                     NSEnd = AssociatedNamespaces.end(); 
+       NS != NSEnd; ++NS) { 
+    //   When considering an associated namespace, the lookup is the
+    //   same as the lookup performed when the associated namespace is
+    //   used as a qualifier (3.4.3.2) except that:
+    //
+    //     -- Any using-directives in the associated namespace are
+    //        ignored.
+    //
+    //     -- FIXME: Any namespace-scope friend functions declared in
+    //        associated classes are visible within their respective
+    //        namespaces even if they are not visible during an ordinary
+    //        lookup (11.4).
+    DeclContext::lookup_iterator I, E;
+    for (llvm::tie(I, E) = (*NS)->lookup(Name); I != E; ++I) {
+      FunctionDecl *Func = dyn_cast<FunctionDecl>(*I);
+      if (!Func)
+        break;
+
+      Functions.insert(Func);
+    }
+  }
+}
+
diff --git a/lib/Sema/SemaOverload.cpp b/lib/Sema/SemaOverload.cpp
index fe12eb74b9..53174b68a1 100644
--- a/lib/Sema/SemaOverload.cpp
+++ b/lib/Sema/SemaOverload.cpp
@@ -2308,42 +2308,6 @@ void Sema::AddSurrogateCandidate(CXXConversionDecl *Conversion,
   }
 }
 
-/// IsAcceptableNonMemberOperatorCandidate - Determine whether Fn is
-/// an acceptable non-member overloaded operator for a call whose
-/// arguments have types T1 (and, if non-empty, T2). This routine
-/// implements the check in C++ [over.match.oper]p3b2 concerning
-/// enumeration types.
-static bool 
-IsAcceptableNonMemberOperatorCandidate(FunctionDecl *Fn,
-                                       QualType T1, QualType T2,
-                                       ASTContext &Context) {
-  if (T1->isRecordType() || (!T2.isNull() && T2->isRecordType()))
-    return true;
-
-  const FunctionProtoType *Proto = Fn->getType()->getAsFunctionProtoType();
-  if (Proto->getNumArgs() < 1)
-    return false;
-
-  if (T1->isEnumeralType()) {
-    QualType ArgType = Proto->getArgType(0).getNonReferenceType();
-    if (Context.getCanonicalType(T1).getUnqualifiedType()
-          == Context.getCanonicalType(ArgType).getUnqualifiedType())
-      return true;
-  }
-
-  if (Proto->getNumArgs() < 2)
-    return false;
-
-  if (!T2.isNull() && T2->isEnumeralType()) {
-    QualType ArgType = Proto->getArgType(1).getNonReferenceType();
-    if (Context.getCanonicalType(T2).getUnqualifiedType()
-          == Context.getCanonicalType(ArgType).getUnqualifiedType())
-      return true;
-  }
-
-  return false;
-}
-
 /// AddOperatorCandidates - Add the overloaded operator candidates for
 /// the operator Op that was used in an operator expression such as "x
 /// Op y". S is the scope in which the expression occurred (used for
@@ -2383,6 +2347,8 @@ bool Sema::AddOperatorCandidates(OverloadedOperatorKind Op, Scope *S,
                          /*SuppressUserConversions=*/false);
   }
 
+  FunctionSet Functions;
+
   //     -- The set of non-member candidates is the result of the
   //        unqualified lookup of operator@ in the context of the
   //        expression according to the usual rules for name lookup in
@@ -2394,24 +2360,19 @@ bool Sema::AddOperatorCandidates(OverloadedOperatorKind Op, Scope *S,
   //        type, or (if there is a right operand) a second parameter
   //        of type T2 or “reference to (possibly cv-qualified) T2”,
   //        when T2 is an enumeration type, are candidate functions.
-  LookupResult Operators = LookupName(S, OpName, LookupOperatorName);
-  
-  if (Operators.isAmbiguous())
-    return DiagnoseAmbiguousLookup(Operators, OpName, OpLoc, OpRange);
-  else if (Operators) {
-    for (LookupResult::iterator Op = Operators.begin(), OpEnd = Operators.end();
-         Op != OpEnd; ++Op) {
-      if (FunctionDecl *FD = dyn_cast<FunctionDecl>(*Op))
-        if (IsAcceptableNonMemberOperatorCandidate(FD, T1, T2, Context))
-          AddOverloadCandidate(FD, Args, NumArgs, CandidateSet,
-                               /*SuppressUserConversions=*/false);
-    }
-  }
+  LookupOverloadedOperatorName(Op, S, T1, T2, Functions);
 
   // Since the set of non-member candidates corresponds to
   // *unqualified* lookup of the operator name, we also perform
   // argument-dependent lookup (C++ [basic.lookup.argdep]).
-  AddArgumentDependentLookupCandidates(OpName, Args, NumArgs, CandidateSet);
+  ArgumentDependentLookup(OpName, Args, NumArgs, Functions);
+
+  // Add all of the functions found via operator name lookup and
+  // argument-dependent lookup to the candidate set.
+  for (FunctionSet::iterator Func = Functions.begin(),
+                          FuncEnd = Functions.end();
+       Func != FuncEnd; ++Func)
+    AddOverloadCandidate(*Func, Args, NumArgs, CandidateSet);
 
   // Add builtin overload candidates (C++ [over.built]).
   AddBuiltinOperatorCandidates(Op, Args, NumArgs, CandidateSet);
@@ -3250,62 +3211,33 @@ void
 Sema::AddArgumentDependentLookupCandidates(DeclarationName Name,
                                            Expr **Args, unsigned NumArgs,
                                            OverloadCandidateSet& CandidateSet) {
-  // Find all of the associated namespaces and classes based on the
-  // arguments we have.
-  AssociatedNamespaceSet AssociatedNamespaces;
-  AssociatedClassSet AssociatedClasses;
-  FindAssociatedClassesAndNamespaces(Args, NumArgs, 
-                                     AssociatedNamespaces, AssociatedClasses);
-
-  // C++ [basic.lookup.argdep]p3:
-  //
-  //   Let X be the lookup set produced by unqualified lookup (3.4.1)
-  //   and let Y be the lookup set produced by argument dependent
-  //   lookup (defined as follows). If X contains [...] then Y is
-  //   empty. Otherwise Y is the set of declarations found in the
-  //   namespaces associated with the argument types as described
-  //   below. The set of declarations found by the lookup of the name
-  //   is the union of X and Y.
-  //
-  // Here, we compute Y and add its members to the overloaded
-  // candidate set.
-  llvm::SmallPtrSet<FunctionDecl *, 16> KnownCandidates;
-  for (AssociatedNamespaceSet::iterator NS = AssociatedNamespaces.begin(),
-                                     NSEnd = AssociatedNamespaces.end(); 
-       NS != NSEnd; ++NS) { 
-    //   When considering an associated namespace, the lookup is the
-    //   same as the lookup performed when the associated namespace is
-    //   used as a qualifier (3.4.3.2) except that:
-    //
-    //     -- Any using-directives in the associated namespace are
-    //        ignored.
-    //
-    //     -- FIXME: Any namespace-scope friend functions declared in
-    //        associated classes are visible within their respective
-    //        namespaces even if they are not visible during an ordinary
-    //        lookup (11.4).
-    DeclContext::lookup_iterator I, E;
-    for (llvm::tie(I, E) = (*NS)->lookup(Name); I != E; ++I) {
-      FunctionDecl *Func = dyn_cast<FunctionDecl>(*I);
-      if (!Func)
-        break;
-
-      if (KnownCandidates.empty()) {
-        // Record all of the function candidates that we've already
-        // added to the overload set, so that we don't add those same
-        // candidates a second time.
-        for (OverloadCandidateSet::iterator Cand = CandidateSet.begin(),
-                                         CandEnd = CandidateSet.end();
-             Cand != CandEnd; ++Cand)
-          KnownCandidates.insert(Cand->Function);
-      }
-
-      // If we haven't seen this function before, add it as a
-      // candidate.
-      if (KnownCandidates.insert(Func))
-        AddOverloadCandidate(Func, Args, NumArgs, CandidateSet);
-    }
-  }
+  FunctionSet Functions;
+
+  // Record all of the function candidates that we've already
+  // added to the overload set, so that we don't add those same
+  // candidates a second time.
+  for (OverloadCandidateSet::iterator Cand = CandidateSet.begin(),
+                                   CandEnd = CandidateSet.end();
+       Cand != CandEnd; ++Cand)
+    if (Cand->Function)
+      Functions.insert(Cand->Function);
+
+  ArgumentDependentLookup(Name, Args, NumArgs, Functions);
+
+  // Erase all of the candidates we already knew about.
+  // FIXME: This is suboptimal. Is there a better way?
+  for (OverloadCandidateSet::iterator Cand = CandidateSet.begin(),
+                                   CandEnd = CandidateSet.end();
+       Cand != CandEnd; ++Cand)
+    if (Cand->Function)
+      Functions.erase(Cand->Function);
+
+  // For each of the ADL candidates we found, add it to the overload
+  // set.
+  for (FunctionSet::iterator Func = Functions.begin(),
+                          FuncEnd = Functions.end();
+       Func != FuncEnd; ++Func)
+    AddOverloadCandidate(*Func, Args, NumArgs, CandidateSet);
 }
 
 /// isBetterOverloadCandidate - Determines whether the first overload
diff --git a/lib/Sema/SemaTemplateInstantiate.cpp b/lib/Sema/SemaTemplateInstantiate.cpp
index 4b98d30b47..3f7756ef3e 100644
--- a/lib/Sema/SemaTemplateInstantiate.cpp
+++ b/lib/Sema/SemaTemplateInstantiate.cpp
@@ -577,6 +577,7 @@ namespace {
     Sema::OwningExprResult VisitDeclRefExpr(DeclRefExpr *E);
     Sema::OwningExprResult VisitParenExpr(ParenExpr *E);
     Sema::OwningExprResult VisitBinaryOperator(BinaryOperator *E);
+    Sema::OwningExprResult VisitCXXOperatorCallExpr(CXXOperatorCallExpr *E);
 
     // Base case. I'm supposed to ignore this.
     Sema::OwningExprResult VisitStmt(Stmt *) { 
@@ -646,6 +647,32 @@ TemplateExprInstantiator::VisitBinaryOperator(BinaryOperator *E) {
 }
 
 Sema::OwningExprResult 
+TemplateExprInstantiator::VisitCXXOperatorCallExpr(CXXOperatorCallExpr *E) {
+  // FIXME: HACK HACK HACK. This is so utterly and completely wrong
+  // that I don't want to explain it here. I'll just fix it tomorrow
+  // instead.
+  Sema::OwningExprResult LHS = Visit(E->getArg(0));
+  if (LHS.isInvalid())
+    return SemaRef.ExprError();
+
+  Sema::OwningExprResult RHS = Visit(E->getArg(1));
+  if (RHS.isInvalid())
+    return SemaRef.ExprError();
+
+  Sema::OwningExprResult Result
+    = SemaRef.CreateBuiltinBinOp(E->getOperatorLoc(), 
+                                 BinaryOperator::Add,
+                                 (Expr *)LHS.get(),
+                                 (Expr *)RHS.get());
+  if (Result.isInvalid())
+    return SemaRef.ExprError();
+
+  LHS.release();
+  RHS.release();
+  return move(Result);  
+}
+
+Sema::OwningExprResult 
 Sema::InstantiateExpr(Expr *E, const TemplateArgument *TemplateArgs,
                       unsigned NumTemplateArgs) {
   TemplateExprInstantiator Instantiator(*this, TemplateArgs, NumTemplateArgs);