diff --git a/lib/Parse/ParseDecl.cpp b/lib/Parse/ParseDecl.cpp
index 65f1124..f20c72e 100644
--- a/lib/Parse/ParseDecl.cpp
+++ b/lib/Parse/ParseDecl.cpp
@@ -1251,7 +1251,7 @@
 
   // Enter function-declaration scope, limiting any declarators to the
   // function prototype scope, including parameter declarators.
-  EnterScope(Scope::DeclScope);
+  EnterScope(Scope::FnScope|Scope::DeclScope);
   
   bool IsVariadic = false;
   while (1) {
@@ -1526,3 +1526,4 @@
   }
 }
 
+
diff --git a/lib/Sema/IdentifierResolver.cpp b/lib/Sema/IdentifierResolver.cpp
index 57e8d0a..fada62f 100644
--- a/lib/Sema/IdentifierResolver.cpp
+++ b/lib/Sema/IdentifierResolver.cpp
@@ -13,67 +13,16 @@
 //===----------------------------------------------------------------------===//
 
 #include "IdentifierResolver.h"
-#include "clang/Basic/IdentifierTable.h"
-#include "clang/AST/Decl.h"
-#include "clang/Parse/Scope.h"
 #include <list>
 #include <vector>
 
 using namespace clang;
 
-namespace {
-
-class IdDeclInfo;
-
-/// Identifier's FETokenInfo contains a Decl pointer if lower bit == 0.
-static inline bool isDeclPtr(void *Ptr) {
-  return (reinterpret_cast<uintptr_t>(Ptr) & 0x1) == 0;
-}
-
-/// Identifier's FETokenInfo contains a IdDeclInfo pointer if lower bit == 1.
-static inline IdDeclInfo *toIdDeclInfo(void *Ptr) {
-  return reinterpret_cast<IdDeclInfo*>(
-                  reinterpret_cast<uintptr_t>(Ptr) & ~0x1
-                                                          );
-}
-
-
-/// IdDeclInfo - Keeps track of information about decls associated to a
-/// particular identifier. IdDeclInfos are lazily constructed and assigned
-/// to an identifier the first time a decl with that identifier is shadowed
-/// in some scope.
-class IdDeclInfo {
-  typedef llvm::SmallVector<NamedDecl *, 2> ShadowedTy;
-  ShadowedTy ShadowedDecls;
-
-public:
-  typedef ShadowedTy::iterator ShadowedIter;
-
-  inline ShadowedIter shadowed_begin() { return ShadowedDecls.begin(); }
-  inline ShadowedIter shadowed_end() { return ShadowedDecls.end(); }
-
-  /// Add a decl in the scope chain.
-  void PushShadowed(NamedDecl *D) {
-    assert(D && "Decl null");
-    ShadowedDecls.push_back(D);
-  }
-
-  /// Add the decl at the top of scope chain.
-  void PushGlobalShadowed(NamedDecl *D) {
-    assert(D && "Decl null");
-    ShadowedDecls.insert(ShadowedDecls.begin(), D);
-  }
-
-  /// RemoveShadowed - Remove the decl from the scope chain.
-  /// The decl must already be part of the decl chain.
-  void RemoveShadowed(NamedDecl *D);
-};
-
 
 /// IdDeclInfoMap - Associates IdDeclInfos with Identifiers.
 /// Allocates 'pools' (vectors of IdDeclInfos) to avoid allocating each
 /// individual IdDeclInfo to heap.
-class IdDeclInfoMap {
+class IdentifierResolver::IdDeclInfoMap {
   static const unsigned int VECTOR_SIZE = 512;
   // Holds vectors of IdDeclInfos that serve as 'pools'.
   // New vectors are added when the current one is full.
@@ -88,17 +37,14 @@
   IdDeclInfo &operator[](IdentifierInfo *II);
 };
 
-} // end anonymous namespace
-
 
 IdentifierResolver::IdentifierResolver() : IdDeclInfos(new IdDeclInfoMap) {}
 IdentifierResolver::~IdentifierResolver() {
-  delete static_cast<IdDeclInfoMap*>(IdDeclInfos);
+  delete IdDeclInfos;
 }
 
 /// AddDecl - Link the decl to its shadowed decl chain.
-void IdentifierResolver::AddDecl(NamedDecl *D, Scope *S) {
-  assert(D && S && "null param passed");
+void IdentifierResolver::AddDecl(NamedDecl *D) {
   IdentifierInfo *II = D->getIdentifier();
   void *Ptr = II->getFETokenInfo<void>();
 
@@ -111,56 +57,40 @@
 
   if (isDeclPtr(Ptr)) {
     II->setFETokenInfo(NULL);
-    IdDeclInfoMap &Map = *static_cast<IdDeclInfoMap*>(IdDeclInfos);
-    IDI = &Map[II];
-    IDI->PushShadowed(static_cast<NamedDecl*>(Ptr));
+    IDI = &(*IdDeclInfos)[II];
+    NamedDecl *PrevD = static_cast<NamedDecl*>(Ptr);
+    IDI->AddDecl(PrevD);
   } else
     IDI = toIdDeclInfo(Ptr);
 
-  // C++ [basic.scope]p4:
-  //   -- exactly one declaration shall declare a class name or
-  //   enumeration name that is not a typedef name and the other
-  //   declarations shall all refer to the same object or
-  //   enumerator, or all refer to functions and function templates;
-  //   in this case the class name or enumeration name is hidden.
-  if (isa<TagDecl>(D) && IDI->shadowed_end() != IDI->shadowed_begin()) {
-    // We are pushing the name of a tag (enum or class).
-    IdDeclInfo::ShadowedIter TopIter = IDI->shadowed_end() - 1;
-    if (S->isDeclScope(*TopIter)) {
-      // There is already a declaration with the same name in the same
-      // scope. It must be found before we find the new declaration,
-      // so swap the order on the shadowed declaration stack.
-      NamedDecl *Temp = *TopIter;
-      *TopIter = D;
-      D = Temp;
-    }
-  }
-
-  IDI->PushShadowed(D);
+  IDI->AddDecl(D);
 }
 
-/// AddGlobalDecl - Link the decl at the top of the shadowed decl chain.
-void IdentifierResolver::AddGlobalDecl(NamedDecl *D) {
-  assert(D && "null param passed");
+/// AddShadowedDecl - Link the decl to its shadowed decl chain putting it
+/// after the decl that the iterator points to, thus the 'CIT' decl will be
+/// encountered before the 'D' decl.
+void IdentifierResolver::AddShadowedDecl(NamedDecl *D, NamedDecl *Shadow) {
+  assert(D->getIdentifier() == Shadow->getIdentifier() && "Different ids!");
+  assert(LookupContext(D) == LookupContext(Shadow) && "Different context!");
+
   IdentifierInfo *II = D->getIdentifier();
   void *Ptr = II->getFETokenInfo<void>();
-
-  if (!Ptr) {
-    II->setFETokenInfo(D);
-    return;
-  }
+  assert(Ptr && "No decl from Ptr ?");
 
   IdDeclInfo *IDI;
 
   if (isDeclPtr(Ptr)) {
     II->setFETokenInfo(NULL);
-    IdDeclInfoMap &Map = *static_cast<IdDeclInfoMap*>(IdDeclInfos);
-    IDI = &Map[II];
-    IDI->PushShadowed(static_cast<NamedDecl*>(Ptr));
-  } else
-    IDI = toIdDeclInfo(Ptr);
+    IDI = &(*IdDeclInfos)[II];
+    NamedDecl *PrevD = static_cast<NamedDecl*>(Ptr);
+    assert(PrevD == Shadow && "Invalid shadow decl ?");
+    IDI->AddDecl(D);
+    IDI->AddDecl(PrevD);
+    return;
+  }
 
-  IDI->PushGlobalShadowed(D);
+  IDI = toIdDeclInfo(Ptr);
+  IDI->AddShadowed(D, Shadow);
 }
 
 /// RemoveDecl - Unlink the decl from its shadowed decl chain.
@@ -178,71 +108,72 @@
     return;
   }
   
-  return toIdDeclInfo(Ptr)->RemoveShadowed(D);
+  return toIdDeclInfo(Ptr)->RemoveDecl(D);
 }
 
-/// Lookup - Find the non-shadowed decl that belongs to a particular
-/// Decl::IdentifierNamespace.
-NamedDecl *IdentifierResolver::Lookup(const IdentifierInfo *II, unsigned NS) {
-  assert(II && "null param passed");
-  void *Ptr = II->getFETokenInfo<void>();
+/// begin - Returns an iterator for all decls, starting at the given
+/// declaration context.
+IdentifierResolver::iterator
+IdentifierResolver::begin(const IdentifierInfo *II, DeclContext *Ctx) {
+  assert(Ctx && "null param passed");
 
-  if (!Ptr) return NULL;
+  void *Ptr = II->getFETokenInfo<void>();
+  if (!Ptr) return end(II);
+
+  LookupContext LC(Ctx);
 
   if (isDeclPtr(Ptr)) {
     NamedDecl *D = static_cast<NamedDecl*>(Ptr);
-    return (D->getIdentifierNamespace() & NS) ? D : NULL;
-  }
 
+    if (LC.isEqOrContainedBy(LookupContext(D)))
+      return iterator(D);
+    else
+      return end(II);
+
+  }
+  
   IdDeclInfo *IDI = toIdDeclInfo(Ptr);
-
-  // ShadowedDecls are ordered from most shadowed to less shadowed.
-  // So we do a reverse iteration from end to begin.
-  for (IdDeclInfo::ShadowedIter SI = IDI->shadowed_end();
-       SI != IDI->shadowed_begin(); --SI) {
-    NamedDecl *D = *(SI-1);
-    if (D->getIdentifierNamespace() & NS)
-      return D;
-  }
-
-  // we didn't find the decl.
-  return NULL;
+  return iterator(IDI->FindContext(LC));
 }
 
-/// RemoveShadowed - Remove the decl from the scope chain.
-/// The decl must already be part of the decl chain.
-void IdDeclInfo::RemoveShadowed(NamedDecl *D) {
-  assert(D && "null decl passed");
-  assert(!ShadowedDecls.empty() &&
-         "Didn't find this decl on its identifier's chain!");
+/// ctx_begin - Returns an iterator for only decls that belong to the given
+/// declaration context.
+IdentifierResolver::ctx_iterator
+IdentifierResolver::ctx_begin(const IdentifierInfo *II, DeclContext *Ctx) {
+  assert(Ctx && "null param passed");
 
-  // common case
-  if (D == ShadowedDecls.back()) {
-    ShadowedDecls.pop_back();
-    return;
+  void *Ptr = II->getFETokenInfo<void>();
+  if (!Ptr) return ctx_end(II);
+
+  LookupContext LC(Ctx);
+
+  if (isDeclPtr(Ptr)) {
+    NamedDecl *D = static_cast<NamedDecl*>(Ptr);
+
+    if (LC == LookupContext(D))
+      return ctx_iterator(D);
+    else
+      return ctx_end(II);
+
   }
+  
+  IdDeclInfo *IDI = toIdDeclInfo(Ptr);
+  IdDeclInfo::DeclsTy::iterator I = IDI->FindContext(LookupContext(Ctx));
+  if (I != IDI->decls_begin() && LC != LookupContext(*(I-1)))
+    I = IDI->decls_begin();
 
-  for (ShadowedIter SI = ShadowedDecls.end()-1;
-       SI != ShadowedDecls.begin(); --SI) {
-    if (*(SI-1) == D) {
-      ShadowedDecls.erase(SI-1);
-      return;
-    }
-  }
-
-  assert(false && "Didn't find this decl on its identifier's chain!");
+  return ctx_iterator(I);
 }
 
+
 /// Returns the IdDeclInfo associated to the IdentifierInfo.
 /// It creates a new IdDeclInfo if one was not created before for this id.
-IdDeclInfo &IdDeclInfoMap::operator[](IdentifierInfo *II) {
+IdentifierResolver::IdDeclInfo &
+IdentifierResolver::IdDeclInfoMap::operator[](IdentifierInfo *II) {
   assert (II && "null IdentifierInfo passed");
   void *Ptr = II->getFETokenInfo<void>();
 
-  if (Ptr) {
-    assert(!isDeclPtr(Ptr) && "didn't clear decl for FEToken");
-    return *toIdDeclInfo(Ptr);
-  }
+  if (Ptr) return *toIdDeclInfo(Ptr);
 
   if (CurIndex == VECTOR_SIZE) {
     // Add a IdDeclInfo vector 'pool'
diff --git a/lib/Sema/IdentifierResolver.h b/lib/Sema/IdentifierResolver.h
index 34b4764..da1327b 100644
--- a/lib/Sema/IdentifierResolver.h
+++ b/lib/Sema/IdentifierResolver.h
@@ -15,37 +15,354 @@
 #ifndef LLVM_CLANG_AST_SEMA_IDENTIFIERRESOLVER_H
 #define LLVM_CLANG_AST_SEMA_IDENTIFIERRESOLVER_H
 
+#include "clang/Basic/IdentifierTable.h"
+#include "clang/Parse/Scope.h"
+#include "clang/AST/Decl.h"
+
 namespace clang {
-  class IdentifierInfo;
-  class NamedDecl;
-  class Scope;
 
 /// IdentifierResolver - Keeps track of shadowed decls on enclosing scopes.
 /// It manages the shadowing chains of identifiers and implements efficent decl
 /// lookup based on an identifier.
 class IdentifierResolver {
+
+  /// LookupContext - A wrapper for DeclContext. DeclContext is only part of
+  /// ScopedDecls, LookupContext can be used with all decls (assumes
+  /// translation unit context for non ScopedDecls).
+  class LookupContext {
+    DeclContext *Ctx;
+
+    /// TUCtx - Provides a common value for translation unit context for all
+    /// decls.
+    /// FIXME: When (if ?) all decls can point to their translation unit context
+    /// remove this hack.
+    static inline DeclContext *TUCtx() {
+      return reinterpret_cast<DeclContext*>(-1);
+    }
+
+    /// getContext - Returns translation unit context for non ScopedDecls and
+    /// for EnumConstantDecls returns the parent context of their EnumDecl.
+    static DeclContext *getContext(Decl *D) {
+      DeclContext *Ctx;
+
+      if (EnumConstantDecl *EnumD = dyn_cast<EnumConstantDecl>(D)) {
+        Ctx = EnumD->getDeclContext()->getParent();
+      } else if (ScopedDecl *SD = dyn_cast<ScopedDecl>(D))
+        Ctx = SD->getDeclContext();
+      else
+        return TUCtx();
+
+      if (isa<TranslationUnitDecl>(Ctx))
+        return TUCtx();
+
+      return Ctx;
+    }
+
+  public:
+    LookupContext(Decl *D) {
+      Ctx = getContext(D);
+    }
+    LookupContext(DeclContext *DC) {
+      if (!DC || isa<TranslationUnitDecl>(DC))
+        Ctx = TUCtx();
+      else
+        Ctx = DC;
+    }
+
+    bool isTU() const {
+      return (Ctx == TUCtx());
+    }
+
+    /// getParent - Returns the parent context. This should not be called for
+    /// a translation unit context.
+    LookupContext getParent() const {
+      assert(!isTU() && "TU has no parent!");
+      return LookupContext(Ctx->getParent());
+    }
+
+    /// isEqOrContainedBy - Returns true of the given context is the same or a
+    /// parent of this one.
+    bool isEqOrContainedBy(const LookupContext &PC) const {
+      if (PC.isTU()) return true;
+
+      for (LookupContext Next = *this; !Next.isTU();  Next = Next.getParent())
+        if (Next.Ctx == PC.Ctx) return true;
+
+      return false;
+    }
+
+    bool operator==(const LookupContext &RHS) const {
+      return Ctx == RHS.Ctx;
+    }
+    bool operator!=(const LookupContext &RHS) const {
+      return Ctx != RHS.Ctx;
+    }
+  };
+
+  /// IdDeclInfo - Keeps track of information about decls associated to a
+  /// particular identifier. IdDeclInfos are lazily constructed and assigned
+  /// to an identifier the first time a decl with that identifier is shadowed
+  /// in some scope.
+  class IdDeclInfo {
+  public:
+    typedef llvm::SmallVector<NamedDecl*, 2> DeclsTy;
+
+    inline DeclsTy::iterator decls_begin() { return Decls.begin(); }
+    inline DeclsTy::iterator decls_end() { return Decls.end(); }
+
+    /// FindContext - Returns an iterator pointing just after the decl that is
+    /// in the given context or in a parent of it. The search is in reverse
+    /// order, from end to begin.
+    DeclsTy::iterator FindContext(const LookupContext &Ctx) {
+      return FindContext(Ctx, Decls.end());
+    }
+
+    /// FindContext - Returns an iterator pointing just after the decl that is
+    /// in the given context or in a parent of it. The search is in reverse
+    /// order, from end to begin.
+    DeclsTy::iterator FindContext(const LookupContext &Ctx,
+                                  const DeclsTy::iterator &Start) {
+      for (DeclsTy::iterator I = Start; I != Decls.begin(); --I) {
+        if (Ctx.isEqOrContainedBy(LookupContext(*(I-1))))
+          return I;
+      }
+
+      return Decls.begin();
+    }
+
+    /// iterator - Iterate over the decls by walking their parent contexts too.
+    class iterator {
+    public:
+      typedef DeclsTy::iterator BaseIter;
+
+      iterator(const BaseIter &DeclIt) : DI(DeclIt) {}
+      const BaseIter &getBase() { return DI; }
+
+      NamedDecl *&operator*() const {
+        return *(DI-1);
+      }
+      
+      bool operator==(const iterator &RHS) const {
+        return DI == RHS.DI;
+      }
+      bool operator!=(const iterator &RHS) const {
+        return DI != RHS.DI;
+      }
+      
+      // Preincrement.
+      iterator& operator++() {
+        NamedDecl *D = **this;
+        void *Ptr = D->getIdentifier()->getFETokenInfo<void>();
+        assert(!isDeclPtr(Ptr) && "Decl with wrong id ?");
+        DI = toIdDeclInfo(Ptr)->FindContext(LookupContext(D), DI-1);
+        return *this;
+      }
+
+    private:
+      BaseIter DI;
+    };
+
+    /// ctx_iterator - Iterator over the decls of a specific context only.
+    class ctx_iterator {
+    public:
+      typedef DeclsTy::iterator BaseIter;
+
+      ctx_iterator(const BaseIter &DeclIt) : DI(DeclIt) {}
+      const BaseIter &getBase() { return DI; }
+
+      NamedDecl *&operator*() const {
+        return *(DI-1);
+      }
+      
+      bool operator==(const ctx_iterator &RHS) const {
+        return DI == RHS.DI;
+      }
+      bool operator!=(const ctx_iterator &RHS) const {
+        return DI != RHS.DI;
+      }
+      
+      // Preincrement.
+      ctx_iterator& operator++() {
+        NamedDecl *D = **this;
+        void *Ptr = D->getIdentifier()->getFETokenInfo<void>();
+        assert(!isDeclPtr(Ptr) && "Decl with wrong id ?");
+        IdDeclInfo *Info = toIdDeclInfo(Ptr);
+        
+        --DI;
+        if (DI != Info->Decls.begin() &&
+            LookupContext(D) != LookupContext(**this))
+          DI = Info->Decls.begin();
+        return *this;
+      }
+
+    private:
+      BaseIter DI;
+    };
+
+    void AddDecl(NamedDecl *D) {
+      Decls.insert(FindContext(LookupContext(D)), D);
+    }
+
+    /// AddShadowed - Add a decl by putting it directly above the 'Shadow' decl.
+    /// Later lookups will find the 'Shadow' decl first. The 'Shadow' decl must
+    /// be already added to the scope chain and must be in the same context as
+    /// the decl that we want to add.
+    void AddShadowed(NamedDecl *D, NamedDecl *Shadow) {
+      assert(LookupContext(D) == LookupContext(Shadow) &&
+             "Decl and Shadow not in same context!");
+
+      for (DeclsTy::iterator I = Decls.end(); I != Decls.begin(); --I) {
+        if (Shadow == *(I-1)) {
+          Decls.insert(I-1, D);
+          return;
+        }
+      }
+
+      assert(0 && "Shadow wasn't in scope chain!");
+    }
+
+    /// RemoveDecl - Remove the decl from the scope chain.
+    /// The decl must already be part of the decl chain.
+    void RemoveDecl(NamedDecl *D) {
+      for (DeclsTy::iterator I = Decls.end(); I != Decls.begin(); --I) {
+        if (D == *(I-1)) {
+          Decls.erase(I-1);
+          return;
+        }
+      }
+
+      assert(0 && "Didn't find this decl on its identifier's chain!");
+    }
+
+  private:
+    DeclsTy Decls;
+  };
+
+  /// SwizzledIterator - Can be instantiated either with a single NamedDecl*
+  /// (the common case where only one decl is associated with an identifier) or
+  /// with an 'Iter' iterator, when there are more than one decls to lookup.
+  template<typename Iter>
+  class SwizzledIterator {
+    uintptr_t Ptr;
+
+    SwizzledIterator() : Ptr(0) {}
+    SwizzledIterator(NamedDecl *D) {
+      Ptr = reinterpret_cast<uintptr_t>(D);
+    }
+    SwizzledIterator(Iter I) {
+      Ptr = reinterpret_cast<uintptr_t>(I.getBase()) | 0x1;
+    }
+
+    bool isIterator() const { return (Ptr & 0x1); }
+
+    Iter getIterator() const {
+      assert(isIterator() && "Ptr not an iterator.");
+      return reinterpret_cast<typename Iter::BaseIter>(Ptr & ~0x1);
+    }
+
+    friend class IdentifierResolver;
+  public:
+    NamedDecl *operator*() const {
+      if (isIterator())
+        return *getIterator();
+      else
+        return reinterpret_cast<NamedDecl*>(Ptr);
+    }
+    
+    bool operator==(const SwizzledIterator &RHS) const {
+      return Ptr == RHS.Ptr;
+    }
+    bool operator!=(const SwizzledIterator &RHS) const {
+      return Ptr != RHS.Ptr;
+    }
+
+    // Preincrement.
+    SwizzledIterator& operator++() {
+      if (isIterator()) {
+        Iter I = getIterator();
+        ++I;
+        Ptr = reinterpret_cast<uintptr_t>(I.getBase()) | 0x1;
+      }
+      else  // This is a single NamedDecl*.
+        Ptr = 0;
+
+      return *this;
+    }
+  };
+
 public:
-  IdentifierResolver();
-  ~IdentifierResolver();
+
+  typedef SwizzledIterator<IdDeclInfo::iterator> iterator;
+  typedef SwizzledIterator<IdDeclInfo::ctx_iterator> ctx_iterator;
+
+  /// begin - Returns an iterator for all decls, starting at the given
+  /// declaration context.
+  static iterator begin(const IdentifierInfo *II, DeclContext *Ctx);
+
+  static iterator end(const IdentifierInfo *II) {
+    void *Ptr = II->getFETokenInfo<void>();
+    if (!Ptr || isDeclPtr(Ptr))
+      return iterator();
+
+    IdDeclInfo *IDI = toIdDeclInfo(Ptr);
+    return iterator(IDI->decls_begin());
+  }
+
+  /// ctx_begin - Returns an iterator for only decls that belong to the given
+  /// declaration context.
+  static ctx_iterator ctx_begin(const IdentifierInfo *II, DeclContext *Ctx);
+
+  static ctx_iterator ctx_end(const IdentifierInfo *II) {
+    void *Ptr = II->getFETokenInfo<void>();
+    if (!Ptr || isDeclPtr(Ptr))
+      return ctx_iterator();
+
+    IdDeclInfo *IDI = toIdDeclInfo(Ptr);
+    return ctx_iterator(IDI->decls_begin());
+  }
+
+  /// isDeclInScope - If 'Ctx' is a function/method, isDeclInScope returns true
+  /// if 'D' is in Scope 'S', otherwise 'S' is ignored and isDeclInScope returns
+  /// true if 'D' belongs to the given declaration context.
+  static bool isDeclInScope(Decl *D, DeclContext *Ctx, Scope *S = 0) {
+    if (Ctx->isFunctionOrMethod())
+      return S->isDeclScope(D);
+
+    return LookupContext(D) == LookupContext(Ctx);
+  }
 
   /// AddDecl - Link the decl to its shadowed decl chain.
-  void AddDecl(NamedDecl *D, Scope *S);
+  void AddDecl(NamedDecl *D);
 
-  /// AddGlobalDecl - Link the decl at the top of the shadowed decl chain.
-  void AddGlobalDecl(NamedDecl *D);
+  /// AddShadowedDecl - Link the decl to its shadowed decl chain putting it
+  /// after the decl that the iterator points to, thus the 'CIT' decl will be
+  /// encountered before the 'D' decl.
+  void AddShadowedDecl(NamedDecl *D, NamedDecl *Shadow);
 
   /// RemoveDecl - Unlink the decl from its shadowed decl chain.
   /// The decl must already be part of the decl chain.
   void RemoveDecl(NamedDecl *D);
 
-  /// Lookup - Find the non-shadowed decl that belongs to one or more
-  /// of the specified Decl::IdentifierNamespaces.
-  NamedDecl *Lookup(const IdentifierInfo *II, unsigned NSI);
+  IdentifierResolver();
+  ~IdentifierResolver();
 
 private:
-  // An instance of IdDeclInfoMap class, that's hidden away in the
-  // implementation file.
-  void *IdDeclInfos;
+  class IdDeclInfoMap;
+  IdDeclInfoMap *IdDeclInfos;
+
+  /// Identifier's FETokenInfo contains a Decl pointer if lower bit == 0.
+  static inline bool isDeclPtr(void *Ptr) {
+    return (reinterpret_cast<uintptr_t>(Ptr) & 0x1) == 0;
+  }
+
+  /// Identifier's FETokenInfo contains a IdDeclInfo pointer if lower bit == 1.
+  static inline IdDeclInfo *toIdDeclInfo(void *Ptr) {
+    assert((reinterpret_cast<uintptr_t>(Ptr) & 0x1) == 1
+          && "Ptr not a IdDeclInfo* !");
+    return reinterpret_cast<IdDeclInfo*>(
+                    reinterpret_cast<uintptr_t>(Ptr) & ~0x1
+                                                            );
+  }
 };
 
 } // end namespace clang
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index afe877f..933a361 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -59,13 +59,40 @@
 
 /// Add this decl to the scope shadowed decl chains.
 void Sema::PushOnScopeChains(NamedDecl *D, Scope *S) {
-  IdResolver.AddDecl(D, S);
   S->AddDecl(D);
+
+  // C++ [basic.scope]p4:
+  //   -- exactly one declaration shall declare a class name or
+  //   enumeration name that is not a typedef name and the other
+  //   declarations shall all refer to the same object or
+  //   enumerator, or all refer to functions and function templates;
+  //   in this case the class name or enumeration name is hidden.
+  if (TagDecl *TD = dyn_cast<TagDecl>(D)) {
+    // We are pushing the name of a tag (enum or class).
+    IdentifierResolver::ctx_iterator
+      CIT = IdResolver.ctx_begin(TD->getIdentifier(), TD->getDeclContext());
+    if (CIT != IdResolver.ctx_end(TD->getIdentifier()) &&
+        IdResolver.isDeclInScope(*CIT, TD->getDeclContext(), S)) {
+      // There is already a declaration with the same name in the same
+      // scope. It must be found before we find the new declaration,
+      // so swap the order on the shadowed declaration chain.
+
+      IdResolver.AddShadowedDecl(TD, *CIT);
+      return;
+    }
+  }
+
+  IdResolver.AddDecl(D);
 }
 
 void Sema::ActOnPopScope(SourceLocation Loc, Scope *S) {
   if (S->decl_empty()) return;
   assert((S->getFlags() & Scope::DeclScope) &&"Scope shouldn't contain decls!");
+
+  // We only want to remove the decls from the identifier decl chains for local
+  // scopes, when inside a function/method.
+  if (S->getFnParent() == 0)
+    return;
          
   for (Scope::decl_iterator I = S->decl_begin(), E = S->decl_end();
        I != E; ++I) {
@@ -115,8 +142,10 @@
   // Scan up the scope chain looking for a decl that matches this identifier
   // that is in the appropriate namespace.  This search should not take long, as
   // shadowing of names is uncommon, and deep shadowing is extremely uncommon.
-  NamedDecl *ND = IdResolver.Lookup(II, NS);
-  if (ND) return ND;
+  for (IdentifierResolver::iterator
+       I = IdResolver.begin(II, CurContext), E = IdResolver.end(II); I != E; ++I)
+    if ((*I)->getIdentifierNamespace() & NS)
+      return *I;
 
   // If we didn't find a use of this identifier, and if the identifier
   // corresponds to a compiler builtin, create the decl object for the builtin
@@ -184,11 +213,7 @@
   
   
   // TUScope is the translation-unit scope to insert this function into.
-  TUScope->AddDecl(New);
-  
-  // Add this decl to the end of the identifier info.
-  IdResolver.AddGlobalDecl(New);
-
+  PushOnScopeChains(New, TUScope);
   return New;
 }
 
@@ -797,12 +822,12 @@
                          D.getAttributes());
     // Merge the decl with the existing one if appropriate. If the decl is
     // in an outer scope, it isn't the same thing.
-    if (PrevDecl && S->isDeclScope(PrevDecl)) {
+    if (PrevDecl && IdResolver.isDeclInScope(PrevDecl, CurContext, S)) {
       NewTD = MergeTypeDefDecl(NewTD, PrevDecl);
       if (NewTD == 0) return 0;
     }
     New = NewTD;
-    if (S->getParent() == 0) {
+    if (S->getFnParent() == 0) {
       // C99 6.7.7p2: If a typedef name specifies a variably modified type
       // then it shall have block scope.
       if (NewTD->getUnderlyingType()->isVariablyModifiedType()) {
@@ -873,7 +898,9 @@
 
     // Merge the decl with the existing one if appropriate. Since C functions
     // are in a flat namespace, make sure we consider decls in outer scopes.
-    if (PrevDecl) {
+    if (PrevDecl &&
+        (!getLangOptions().CPlusPlus ||
+         IdResolver.isDeclInScope(PrevDecl, CurContext, S)) ) {
       bool Redeclaration = false;
       NewFD = MergeFunctionDecl(NewFD, PrevDecl, Redeclaration);
       if (NewFD == 0) return 0;
@@ -914,7 +941,7 @@
     case DeclSpec::SCS_register:       SC = VarDecl::Register; break;
     case DeclSpec::SCS_private_extern: SC = VarDecl::PrivateExtern; break;
     }    
-    if (S->getParent() == 0) {
+    if (S->getFnParent() == 0) {
       // C99 6.9p2: The storage-class specifiers auto and register shall not
       // appear in the declaration specifiers in an external declaration.
       if (SC == VarDecl::Auto || SC == VarDecl::Register) {
@@ -942,7 +969,7 @@
     }
     // Merge the decl with the existing one if appropriate. If the decl is
     // in an outer scope, it isn't the same thing.
-    if (PrevDecl && S->isDeclScope(PrevDecl)) {
+    if (PrevDecl && IdResolver.isDeclInScope(PrevDecl, CurContext, S)) {
       NewVD = MergeVarDecl(NewVD, PrevDecl);
       if (NewVD == 0) return 0;
     }
@@ -1221,12 +1248,14 @@
   // See if this is a redefinition.
   Decl *PrevDcl = LookupDecl(D.getIdentifier(), Decl::IDNS_Ordinary,
                              GlobalScope);
-  if (FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(PrevDcl)) {
-    const FunctionDecl *Definition;
-    if (FD->getBody(Definition)) {
-      Diag(D.getIdentifierLoc(), diag::err_redefinition, 
-           D.getIdentifier()->getName());
-      Diag(Definition->getLocation(), diag::err_previous_definition);
+  if (PrevDcl && IdResolver.isDeclInScope(PrevDcl, CurContext)) {
+    if (FunctionDecl *FD = dyn_cast<FunctionDecl>(PrevDcl)) {
+      const FunctionDecl *Definition;
+      if (FD->getBody(Definition)) {
+        Diag(D.getIdentifierLoc(), diag::err_redefinition, 
+             D.getIdentifier()->getName());
+        Diag(Definition->getLocation(), diag::err_previous_definition);
+      }
     }
   }
   Decl *decl = static_cast<Decl*>(ActOnDeclarator(GlobalScope, D, 0));
@@ -1375,7 +1404,8 @@
       // If this is a use of a previous tag, or if the tag is already declared in
       // the same scope (so that the definition/declaration completes or
       // rementions the tag), reuse the decl.
-      if (TK == TK_Reference || S->isDeclScope(PrevDecl)) {
+      if (TK == TK_Reference ||
+          IdResolver.isDeclInScope(PrevDecl, CurContext, S)) {
         // Make sure that this wasn't declared as an enum and now used as a struct
         // or something similar.
         if (PrevDecl->getKind() != Kind) {
@@ -1733,7 +1763,7 @@
   // Verify that there isn't already something declared with this name in this
   // scope.
   if (Decl *PrevDecl = LookupDecl(Id, Decl::IDNS_Ordinary, S)) {
-    if (S->isDeclScope(PrevDecl)) {
+    if (IdResolver.isDeclInScope(PrevDecl, CurContext, S)) {
       if (isa<EnumConstantDecl>(PrevDecl))
         Diag(IdLoc, diag::err_redefinition_of_enumerator, Id->getName());
       else
diff --git a/lib/Sema/SemaDeclCXX.cpp b/lib/Sema/SemaDeclCXX.cpp
index c3b6bce..f403858 100644
--- a/lib/Sema/SemaDeclCXX.cpp
+++ b/lib/Sema/SemaDeclCXX.cpp
@@ -335,7 +335,8 @@
         LookupDecl(II, Decl::IDNS_Tag | Decl::IDNS_Ordinary, DeclRegionScope,
                    /*enableLazyBuiltinCreation=*/false);
 
-    if (PrevDecl && DeclRegionScope->isDeclScope(PrevDecl)) {
+    if (PrevDecl &&
+        IdResolver.isDeclInScope(PrevDecl, CurContext, DeclRegionScope)) {
       if (NamespaceDecl *OrigNS = dyn_cast<NamespaceDecl>(PrevDecl)) {
         // This is an extended namespace definition.
         // Attach this namespace decl to the chain of extended namespace
diff --git a/test/Sema/cxx-namespace.cpp b/test/Sema/cxx-namespace.cpp
index 05b791c..df0fa25 100644
--- a/test/Sema/cxx-namespace.cpp
+++ b/test/Sema/cxx-namespace.cpp
@@ -8,8 +8,46 @@
 int A; // expected-error {{error: redefinition of 'A' as different kind of symbol}}
 class A; // expected-error {{error: redefinition of 'A' as different kind of symbol}}
 
-class B; // expected-error {{error: previous definition is here}}
+class B {}; // expected-error {{error: previous definition is here}}
 namespace B {} // expected-error {{error: redefinition of 'B' as different kind of symbol}}
 
 void C(); // expected-error {{error: previous definition is here}}
 namespace C {} // expected-error {{error: redefinition of 'C' as different kind of symbol}}
+
+namespace S1 {
+  int x;
+
+  namespace S2 {
+
+    namespace S3 {
+      B x;
+    }
+  }
+}
+
+namespace S1 {
+  void f() {
+    x = 0;
+  }
+
+  namespace S2 {
+    
+    namespace S3 {
+      void f() {
+        x = 0; // expected-error {{error: incompatible type assigning 'int', expected 'class B'}}
+      }
+    }
+
+    int y;
+  }
+}
+
+namespace S1 {
+  namespace S2 {
+    namespace S3 {
+      void f3() {
+        y = 0;
+      }
+    }
+  }
+}