diff --git a/lib/Sema/Lookup.h b/lib/Sema/Lookup.h
index 9064de6..33d1106 100644
--- a/lib/Sema/Lookup.h
+++ b/lib/Sema/Lookup.h
@@ -123,9 +123,7 @@
     Temporary
   };
 
-  typedef llvm::SmallVector<NamedDecl*, 4> DeclsTy;
-  typedef DeclsTy::const_iterator iterator;
-
+  typedef UnresolvedSetImpl::iterator iterator;
   typedef bool (*ResultFilter)(NamedDecl*, unsigned IDNS);
 
   LookupResult(Sema &SemaRef, DeclarationName Name, SourceLocation NameLoc,
@@ -224,8 +222,8 @@
     return Ambiguity;
   }
 
-  iterator begin() const { return Decls.begin(); }
-  iterator end() const { return Decls.end(); }
+  iterator begin() const { return iterator(Decls.begin()); }
+  iterator end() const { return iterator(Decls.end()); }
 
   /// \brief Return true if no decls were found
   bool empty() const { return Decls.empty(); }
@@ -247,32 +245,20 @@
     return IDNS;
   }
 
-  /// \brief Add a declaration to these results.  Does not test the
-  /// acceptance criteria.
+  /// \brief Add a declaration to these results with no access bits.
+  /// Does not test the acceptance criteria.
   void addDecl(NamedDecl *D) {
-    Decls.push_back(D);
+    Decls.addDecl(D);
     ResultKind = Found;
   }
 
   /// \brief Add all the declarations from another set of lookup
   /// results.
   void addAllDecls(const LookupResult &Other) {
-    Decls.append(Other.begin(), Other.end());
+    Decls.append(Other.Decls.begin(), Other.Decls.end());
     ResultKind = Found;
   }
 
-  /// \brief Hides a set of declarations.
-  template <class NamedDeclSet> void hideDecls(const NamedDeclSet &Set) {
-    unsigned I = 0, N = Decls.size();
-    while (I < N) {
-      if (Set.count(Decls[I]))
-        Decls[I] = Decls[--N];
-      else
-        I++;
-    }
-    Decls.set_size(N);
-  }
-
   /// \brief Determine whether no result was found because we could not
   /// search into dependent base classes of the current instantiation.
   bool wasNotFoundInCurrentInstantiation() const {
@@ -319,13 +305,13 @@
   NamedDecl *getFoundDecl() const {
     assert(getResultKind() == Found
            && "getFoundDecl called on non-unique result");
-    return Decls[0]->getUnderlyingDecl();
+    return (*begin())->getUnderlyingDecl();
   }
 
   /// Fetches a representative decl.  Useful for lazy diagnostics.
   NamedDecl *getRepresentativeDecl() const {
     assert(!Decls.empty() && "cannot get representative of empty set");
-    return Decls[0];
+    return *begin();
   }
 
   /// \brief Asks if the result is a single tag decl.
@@ -403,7 +389,7 @@
   /// sugared.
   class Filter {
     LookupResult &Results;
-    unsigned I;
+    LookupResult::iterator I;
     bool Changed;
 #ifndef NDEBUG
     bool CalledDone;
@@ -411,7 +397,7 @@
     
     friend class LookupResult;
     Filter(LookupResult &Results)
-      : Results(Results), I(0), Changed(false)
+      : Results(Results), I(Results.begin()), Changed(false)
 #ifndef NDEBUG
       , CalledDone(false)
 #endif
@@ -426,23 +412,30 @@
 #endif
 
     bool hasNext() const {
-      return I != Results.Decls.size();
+      return I != Results.end();
     }
 
     NamedDecl *next() {
-      assert(I < Results.Decls.size() && "next() called on empty filter");
-      return Results.Decls[I++];
+      assert(I != Results.end() && "next() called on empty filter");
+      return *I++;
     }
 
     /// Erase the last element returned from this iterator.
     void erase() {
-      Results.Decls[--I] = Results.Decls.back();
-      Results.Decls.pop_back();
+      Results.Decls.erase(--I);
       Changed = true;
     }
 
+    /// Replaces the current entry with the given one, preserving the
+    /// access bits.
     void replace(NamedDecl *D) {
-      Results.Decls[I-1] = D;
+      Results.Decls.replace(I-1, D);
+      Changed = true;
+    }
+
+    /// Replaces the current entry with the given one.
+    void replace(NamedDecl *D, AccessSpecifier AS) {
+      Results.Decls.replace(I-1, D, AS);
       Changed = true;
     }
 
@@ -482,7 +475,7 @@
     assert(ResultKind != Found || Decls.size() == 1);
     assert(ResultKind != FoundOverloaded || Decls.size() > 1 ||
            (Decls.size() == 1 &&
-            isa<FunctionTemplateDecl>(Decls[0]->getUnderlyingDecl())));
+            isa<FunctionTemplateDecl>((*begin())->getUnderlyingDecl())));
     assert(ResultKind != FoundUnresolvedValue || sanityCheckUnresolved());
     assert(ResultKind != Ambiguous || Decls.size() > 1 ||
            (Decls.size() == 1 && Ambiguity == AmbiguousBaseSubobjects));
@@ -492,8 +485,7 @@
   }
 
   bool sanityCheckUnresolved() const {
-    for (DeclsTy::const_iterator I = Decls.begin(), E = Decls.end();
-           I != E; ++I)
+    for (iterator I = begin(), E = end(); I != E; ++I)
       if (isa<UnresolvedUsingValueDecl>(*I))
         return true;
     return false;
@@ -504,7 +496,7 @@
   // Results.
   LookupResultKind ResultKind;
   AmbiguityKind Ambiguity; // ill-defined unless ambiguous
-  DeclsTy Decls;
+  UnresolvedSet<8> Decls;
   CXXBasePaths *Paths;
 
   // Parameters.
diff --git a/lib/Sema/SemaDeclCXX.cpp b/lib/Sema/SemaDeclCXX.cpp
index 6696294..12b4565 100644
--- a/lib/Sema/SemaDeclCXX.cpp
+++ b/lib/Sema/SemaDeclCXX.cpp
@@ -4487,9 +4487,9 @@
       = dyn_cast<CXXRecordDecl>(T2->getAs<RecordType>()->getDecl());
 
     OverloadCandidateSet CandidateSet;
-    const UnresolvedSet *Conversions
+    const UnresolvedSetImpl *Conversions
       = T2RecordDecl->getVisibleConversionFunctions();
-    for (UnresolvedSet::iterator I = Conversions->begin(),
+    for (UnresolvedSetImpl::iterator I = Conversions->begin(),
            E = Conversions->end(); I != E; ++I) {
       NamedDecl *D = *I;
       CXXRecordDecl *ActingDC = cast<CXXRecordDecl>(D->getDeclContext());
diff --git a/lib/Sema/SemaExprCXX.cpp b/lib/Sema/SemaExprCXX.cpp
index e481268..b004fc3 100644
--- a/lib/Sema/SemaExprCXX.cpp
+++ b/lib/Sema/SemaExprCXX.cpp
@@ -893,9 +893,9 @@
     if (const RecordType *Record = Type->getAs<RecordType>()) {
       llvm::SmallVector<CXXConversionDecl *, 4> ObjectPtrConversions;
       CXXRecordDecl *RD = cast<CXXRecordDecl>(Record->getDecl());
-      const UnresolvedSet *Conversions = RD->getVisibleConversionFunctions();
+      const UnresolvedSetImpl *Conversions = RD->getVisibleConversionFunctions();
       
-      for (UnresolvedSet::iterator I = Conversions->begin(),
+      for (UnresolvedSetImpl::iterator I = Conversions->begin(),
              E = Conversions->end(); I != E; ++I) {
         // Skip over templated conversion functions; they aren't considered.
         if (isa<FunctionTemplateDecl>(*I))
diff --git a/lib/Sema/SemaInit.cpp b/lib/Sema/SemaInit.cpp
index 1970f56..29209d9 100644
--- a/lib/Sema/SemaInit.cpp
+++ b/lib/Sema/SemaInit.cpp
@@ -2141,11 +2141,10 @@
     // refers to.
     QualType ToType = AllowRValues? cv1T1 : DestType;
 
-    const UnresolvedSet *Conversions
+    const UnresolvedSetImpl *Conversions
       = T2RecordDecl->getVisibleConversionFunctions();
-    for (UnresolvedSet::iterator I = Conversions->begin(),
-         E = Conversions->end(); 
-         I != E; ++I) {
+    for (UnresolvedSetImpl::const_iterator I = Conversions->begin(),
+           E = Conversions->end(); I != E; ++I) {
       NamedDecl *D = *I;
       CXXRecordDecl *ActingDC = cast<CXXRecordDecl>(D->getDeclContext());
       if (isa<UsingShadowDecl>(D))
@@ -2662,9 +2661,9 @@
       CXXRecordDecl *SourceRecordDecl
         = cast<CXXRecordDecl>(SourceRecordType->getDecl());
       
-      const UnresolvedSet *Conversions
+      const UnresolvedSetImpl *Conversions
         = SourceRecordDecl->getVisibleConversionFunctions();
-      for (UnresolvedSet::iterator I = Conversions->begin(),
+      for (UnresolvedSetImpl::const_iterator I = Conversions->begin(),
            E = Conversions->end(); 
            I != E; ++I) {
         NamedDecl *D = *I;
diff --git a/lib/Sema/SemaLookup.cpp b/lib/Sema/SemaLookup.cpp
index 70baefd..da76267 100644
--- a/lib/Sema/SemaLookup.cpp
+++ b/lib/Sema/SemaLookup.cpp
@@ -324,9 +324,9 @@
   // If there's a single decl, we need to examine it to decide what
   // kind of lookup this is.
   if (N == 1) {
-    if (isa<FunctionTemplateDecl>(Decls[0]))
+    if (isa<FunctionTemplateDecl>(*Decls.begin()))
       ResultKind = FoundOverloaded;
-    else if (isa<UnresolvedUsingValueDecl>(Decls[0]))
+    else if (isa<UnresolvedUsingValueDecl>(*Decls.begin()))
       ResultKind = FoundUnresolvedValue;
     return;
   }
@@ -463,10 +463,9 @@
     if (!Record->isDefinition())
       return Found;
 
-    const UnresolvedSet *Unresolved = Record->getConversionFunctions();
-    for (UnresolvedSet::iterator U = Unresolved->begin(), 
-                              UEnd = Unresolved->end();
-         U != UEnd; ++U) {
+    const UnresolvedSetImpl *Unresolved = Record->getConversionFunctions();
+    for (UnresolvedSetImpl::iterator U = Unresolved->begin(), 
+           UEnd = Unresolved->end(); U != UEnd; ++U) {
       FunctionTemplateDecl *ConvTemplate = dyn_cast<FunctionTemplateDecl>(*U);
       if (!ConvTemplate)
         continue;
@@ -1243,7 +1242,12 @@
         Diag((*DI)->getLocation(), diag::note_hiding_object);
 
     // For recovery purposes, go ahead and implement the hiding.
-    Result.hideDecls(TagDecls);
+    LookupResult::Filter F = Result.makeFilter();
+    while (F.hasNext()) {
+      if (TagDecls.count(F.next()))
+        F.erase();
+    }
+    F.done();
 
     return true;
   }
diff --git a/lib/Sema/SemaOverload.cpp b/lib/Sema/SemaOverload.cpp
index d710d96..3b6cf89 100644
--- a/lib/Sema/SemaOverload.cpp
+++ b/lib/Sema/SemaOverload.cpp
@@ -1533,9 +1533,9 @@
     if (CXXRecordDecl *FromRecordDecl
          = dyn_cast<CXXRecordDecl>(FromRecordType->getDecl())) {
       // Add all of the conversion functions as candidates.
-      const UnresolvedSet *Conversions
+      const UnresolvedSetImpl *Conversions
         = FromRecordDecl->getVisibleConversionFunctions();
-      for (UnresolvedSet::iterator I = Conversions->begin(),
+      for (UnresolvedSetImpl::iterator I = Conversions->begin(),
              E = Conversions->end(); I != E; ++I) {
         NamedDecl *D = *I;
         CXXRecordDecl *ActingContext = cast<CXXRecordDecl>(D->getDeclContext());
@@ -3280,9 +3280,9 @@
       }
 
       CXXRecordDecl *ClassDecl = cast<CXXRecordDecl>(TyRec->getDecl());
-      const UnresolvedSet *Conversions
+      const UnresolvedSetImpl *Conversions
         = ClassDecl->getVisibleConversionFunctions();
-      for (UnresolvedSet::iterator I = Conversions->begin(),
+      for (UnresolvedSetImpl::iterator I = Conversions->begin(),
              E = Conversions->end(); I != E; ++I) {
 
         // Skip conversion function templates; they don't tell us anything
@@ -3344,10 +3344,10 @@
     }
     
     CXXRecordDecl *ClassDecl = cast<CXXRecordDecl>(TyRec->getDecl());
-    const UnresolvedSet *Conversions =
+    const UnresolvedSetImpl *Conversions =
       ClassDecl->getVisibleConversionFunctions();
     
-    for (UnresolvedSet::iterator I = Conversions->begin(),
+    for (UnresolvedSetImpl::iterator I = Conversions->begin(),
            E = Conversions->end(); I != E; ++I) {
       if (CXXConversionDecl *Conv = dyn_cast<CXXConversionDecl>(*I)) {
         QualType CanTy = Context.getCanonicalType(Conv->getConversionType());
@@ -5938,9 +5938,9 @@
   //   functions for each conversion function declared in an
   //   accessible base class provided the function is not hidden
   //   within T by another intervening declaration.
-  const UnresolvedSet *Conversions
+  const UnresolvedSetImpl *Conversions
     = cast<CXXRecordDecl>(Record->getDecl())->getVisibleConversionFunctions();
-  for (UnresolvedSet::iterator I = Conversions->begin(),
+  for (UnresolvedSetImpl::iterator I = Conversions->begin(),
          E = Conversions->end(); I != E; ++I) {
     NamedDecl *D = *I;
     CXXRecordDecl *ActingContext = cast<CXXRecordDecl>(D->getDeclContext());
diff --git a/lib/Sema/SemaStmt.cpp b/lib/Sema/SemaStmt.cpp
index f0bbdfe..0c207fa 100644
--- a/lib/Sema/SemaStmt.cpp
+++ b/lib/Sema/SemaStmt.cpp
@@ -412,10 +412,10 @@
   llvm::SmallVector<CXXConversionDecl *, 4> ViableConversions;
   llvm::SmallVector<CXXConversionDecl *, 4> ExplicitConversions;
   if (const RecordType *RecordTy = CondType->getAs<RecordType>()) {
-    const UnresolvedSet *Conversions
+    const UnresolvedSetImpl *Conversions
       = cast<CXXRecordDecl>(RecordTy->getDecl())
                                              ->getVisibleConversionFunctions();
-    for (UnresolvedSet::iterator I = Conversions->begin(),
+    for (UnresolvedSetImpl::iterator I = Conversions->begin(),
            E = Conversions->end(); I != E; ++I) {
       if (CXXConversionDecl *Conversion = dyn_cast<CXXConversionDecl>(*I))
         if (Conversion->getConversionType().getNonReferenceType()