Introduce a representation for types that we referred to via a

qualified name, e.g., 

  foo::x

so that we retain the nested-name-specifier as written in the source
code and can reproduce that qualified name when printing the types
back (e.g., in diagnostics). This is PR3493, which won't be complete
until finished the other tasks mentioned near the end of this commit.

The parser's representation of nested-name-specifiers, CXXScopeSpec,
is now a bit fatter, because it needs to contain the scopes that
precede each '::' and keep track of whether the global scoping
operator '::' was at the beginning. For example, we need to keep track
of the leading '::', 'foo', and 'bar' in
 
  ::foo::bar::x

The Action's CXXScopeTy * is no longer a DeclContext *. It's now the
opaque version of the new NestedNameSpecifier, which contains a single
component of a nested-name-specifier (either a DeclContext * or a Type
*, bitmangled). 

The new sugar type QualifiedNameType composes a sequence of
NestedNameSpecifiers with a representation of the type we're actually
referring to. At present, we only build QualifiedNameType nodes within
Sema::getTypeName. This will be extended to other type-constructing
actions (e.g., ActOnClassTemplateId).

Also on the way: QualifiedDeclRefExprs will also store a sequence of
NestedNameSpecifiers, so that we can print out the property
nested-name-specifier. I expect to also use this for handling
dependent names like Fibonacci<I - 1>::value.

llvm-svn: 67265

clang/include/clang/AST/ASTContext.h

@@ -72,6 +72,7 @@ class ASTContext {
   llvm::FoldingSet<TemplateTypeParmType> TemplateTypeParmTypes;
   llvm::FoldingSet<ClassTemplateSpecializationType> 
     ClassTemplateSpecializationTypes;
+  llvm::FoldingSet<QualifiedNameType> QualifiedNameTypes;
   llvm::FoldingSet<ObjCQualifiedInterfaceType> ObjCQualifiedInterfaceTypes;
   llvm::FoldingSet<ObjCQualifiedIdType> ObjCQualifiedIdTypes;
   /// ASTRecordLayouts - A cache mapping from RecordDecls to ASTRecordLayouts.
@@ -284,6 +285,10 @@ public:
                                               unsigned NumArgs,
                                               QualType Canon = QualType());
 
+  QualType getQualifiedNameType(const NestedNameSpecifier *Components,
+                                unsigned NumComponents,
+                                QualType NamedType);
+
   /// getObjCQualifiedInterfaceType - Return a 
   /// ObjCQualifiedInterfaceType type for the given interface decl and
   /// the conforming protocol list.

clang/include/clang/AST/NestedNameSpecifier.h

@@ -0,0 +1,111 @@
+//===--- NestedNameSpecifier.h - C++ nested name specifiers -----*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file defines the NestedNameSpecifier class, which represents
+//  a C++ nested-name-specifier.
+//
+//===----------------------------------------------------------------------===//
+#ifndef LLVM_CLANG_AST_NESTEDNAMESPECIFIER_H
+#define LLVM_CLANG_AST_NESTEDNAMESPECIFIER_H
+
+#include "llvm/Support/DataTypes.h"
+#include <cassert>
+
+namespace clang {
+
+class ASTContext;
+class DeclContext;
+class Type;
+
+/// \brief Represents a single component in a C++ nested-name-specifier.
+///
+/// C++ nested-name-specifiers are the prefixes to qualified
+/// namespaces. For example, "foo::" in "foo::x" is a
+/// nested-name-specifier. Multiple nested-name-specifiers can be
+/// strung together to build qualified names, e.g., "foo::bar::" in
+/// "foo::bar::x". Each NestedNameSpecifier class contains one of the
+/// terms, e.g., "foo::" or "bar::", which may be represented either
+/// as a type or as a DeclContext.
+class NestedNameSpecifier {
+  /// \brief A DeclContext or Type pointer, depending on whether the
+  /// low bit is set.
+  uintptr_t Data;
+
+public:
+  NestedNameSpecifier() : Data(0) { }
+
+  /// \brief Construct a nested name specifier that refers to a type.
+  NestedNameSpecifier(const Type *T) { 
+    Data = reinterpret_cast<uintptr_t>(T);
+    assert((Data & 0x01) == 0 && "cv-qualified type in nested-name-specifier");
+    Data |= 0x01;
+  }
+
+  /// \brief Construct nested name specifier that refers to a
+  /// DeclContext.
+  NestedNameSpecifier(const DeclContext *DC) {
+    Data = reinterpret_cast<uintptr_t>(DC);
+    assert((Data & 0x01) == 0 && "Badly aligned DeclContext pointer");
+  }
+
+  /// \brief Determines whether this nested-name-specifier refers to a
+  /// type. Otherwise, it refers to a DeclContext.
+  bool isType() const { return Data & 0x01; }
+
+  /// \brief Compute the declaration context to which this
+  /// nested-name-specifier refers.
+  ///
+  /// This routine computes the declaration context referenced by this
+  /// nested-name-specifier. The nested-name-specifier may store
+  /// either a DeclContext (the trivial case) or a non-dependent type
+  /// (which will have an associated DeclContext). It is an error to
+  /// invoke this routine when the nested-name-specifier refers to a
+  /// dependent type.
+  ///
+  /// \returns The stored DeclContext, if the nested-name-specifier
+  /// stores a DeclContext. If the nested-name-specifier stores a
+  /// non-dependent type, returns the DeclContext associated with that
+  /// type.
+  DeclContext *computeDeclContext(ASTContext &Context) const;
+
+  /// \brief Retrieve the nested-name-specifier as a type. 
+  ///
+  /// \returns The stored type. If the nested-name-specifier does not
+  /// store a type, returns NULL.
+  Type *getAsType() const {
+    if (Data & 0x01)
+      return reinterpret_cast<Type *>(Data & ~0x01);
+
+    return 0;
+  }
+
+  /// \brief Retrieves the nested-name-specifier as a DeclContext.
+  ///
+  /// \returns The stored DeclContext. If the nested-name-specifier
+  /// does not store a DeclContext, returns NULL.
+  DeclContext *getAsDeclContext() const {
+    if (Data & 0x01)
+      return 0;
+    return reinterpret_cast<DeclContext *>(Data);
+  }
+
+  /// \brief Retrieve nested name specifier as an opaque pointer.
+  void *getAsOpaquePtr() const { return reinterpret_cast<void *>(Data); }
+
+  /// \brief Reconstruct a nested name specifier from an opaque pointer.
+  static NestedNameSpecifier getFromOpaquePtr(void *Ptr) {
+    NestedNameSpecifier NS;
+    NS.Data = reinterpret_cast<uintptr_t>(Ptr);
+    return NS;
+  }
+};
+
+}
+
+#endif

clang/include/clang/AST/Type.h

@@ -15,6 +15,7 @@
 #define LLVM_CLANG_AST_TYPE_H
 
 #include "clang/Basic/Diagnostic.h"
+#include "clang/AST/NestedNameSpecifier.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/ADT/APSInt.h"
 #include "llvm/ADT/FoldingSet.h"
@@ -47,6 +48,7 @@ namespace clang {
   class SourceLocation;
   class StmtIteratorBase;
   class TemplateArgument;
+  class QualifiedNameType;
 
   // Provide forward declarations for all of the *Type classes
 #define TYPE(Class, Base) class Class##Type;
@@ -1357,6 +1359,8 @@ public:
   void setBeingDefined(bool Def) { decl.setInt(Def? 1 : 0); }
 
   virtual void getAsStringInternal(std::string &InnerString) const;
+  void getAsStringInternal(std::string &InnerString,
+                           bool SuppressTagKind) const;
 
   static bool classof(const Type *T) { 
     return T->getTypeClass() >= TagFirst && T->getTypeClass() <= TagLast;
@@ -1548,6 +1552,64 @@ protected:
   friend class Type;
 };
 
+/// \brief Represents a type that was referred to via a qualified
+/// name, e.g., N::M::type.
+///
+/// This type is used to keep track of a type name as written in the
+/// source code, including any nested-name-specifiers.
+class QualifiedNameType : public Type, public llvm::FoldingSetNode {
+  /// \brief The number of components in the qualified name, not
+  /// counting the final type.
+  unsigned NumComponents;
+
+  /// \brief The type that this qualified name refers to.
+  QualType NamedType;
+
+  QualifiedNameType(const NestedNameSpecifier *Components,
+                    unsigned NumComponents, QualType NamedType,
+                    QualType CanonType);
+
+  friend class ASTContext;  // ASTContext creates these
+
+public:
+  typedef const NestedNameSpecifier * iterator;
+
+  iterator begin() const { return getComponents(); }
+  iterator end() const { return getComponents() + getNumComponents(); }
+
+  /// \brief Retrieve the array of nested-name-specifier components.
+  const NestedNameSpecifier *getComponents() const { 
+    return reinterpret_cast<const NestedNameSpecifier *>(this + 1);
+  }
+
+  /// \brief Retrieve the number of nested-name-specifier components.
+  unsigned getNumComponents() const { return NumComponents; }
+
+  /// \brief Retrieve the type named by the qualified-id.
+  QualType getNamedType() const { return NamedType; }
+
+  virtual void getAsStringInternal(std::string &InnerString) const;
+
+  void Profile(llvm::FoldingSetNodeID &ID) {
+    Profile(ID, getComponents(), NumComponents, NamedType);
+  }
+
+  static void Profile(llvm::FoldingSetNodeID &ID, 
+                      const NestedNameSpecifier *Components,
+                      unsigned NumComponents, 
+                      QualType NamedType);
+
+  static bool classof(const Type *T) { 
+    return T->getTypeClass() == QualifiedName; 
+  }
+  static bool classof(const QualifiedNameType *T) { return true; }
+
+protected:
+  virtual void EmitImpl(llvm::Serializer& S) const;
+  static Type* CreateImpl(ASTContext& Context, llvm::Deserializer& D);
+  friend class Type;
+};
+
 /// ObjCInterfaceType - Interfaces are the core concept in Objective-C for
 /// object oriented design.  They basically correspond to C++ classes.  There
 /// are two kinds of interface types, normal interfaces like "NSString" and

clang/include/clang/AST/TypeNodes.def

@@ -73,6 +73,7 @@ TYPE(Record, TagType)
 TYPE(Enum, TagType)
 DEPENDENT_TYPE(TemplateTypeParm, Type)
 NON_CANONICAL_TYPE(ClassTemplateSpecialization, Type)
+NON_CANONICAL_TYPE(QualifiedName, Type)
 TYPE(ObjCInterface, Type)
 TYPE(ObjCQualifiedInterface, ObjCInterfaceType)
 TYPE(ObjCQualifiedId, Type)

clang/include/clang/Parse/DeclSpec.h

@@ -397,10 +397,36 @@ private:
 /// specifier.
 class CXXScopeSpec {
   SourceRange Range;
-  Action::CXXScopeTy *ScopeRep;
+
+  /// Storage containing the scope representations for up to four
+  /// levels of nested-name-specifier. NumScopeReps specifiers how
+  /// many levels there are. If there are more than four, we use
+  /// ManyScopeReps.
+  Action::CXXScopeTy *InlineScopeReps[4];
+
+  /// The number of scope representations we've stored.
+  unsigned NumScopeReps;
+
+  /// The number of scope representations we can store without
+  /// allocating new memory.
+  unsigned Capacity;
+
+  // If there are > 4 scope representations, a pointer to those scope
+  // representations.
+  Action::CXXScopeTy **ManyScopeReps;
+
+  void reallocate();
 
 public:
-  CXXScopeSpec() : ScopeRep(0) {}
+  CXXScopeSpec() : NumScopeReps(0), Capacity(4) { }
+
+  CXXScopeSpec(const CXXScopeSpec &SS);
+
+  CXXScopeSpec &operator=(const CXXScopeSpec &SS);
+
+  ~CXXScopeSpec() {
+    clear();
+  }
 
   const SourceRange &getRange() const { return Range; }
   void setRange(const SourceRange &R) { Range = R; }
@@ -409,21 +435,82 @@ public:
   SourceLocation getBeginLoc() const { return Range.getBegin(); }
   SourceLocation getEndLoc() const { return Range.getEnd(); }
 
-  Action::CXXScopeTy *getScopeRep() const { return ScopeRep; }
+  typedef Action::CXXScopeTy * const * iterator;
-  void setScopeRep(Action::CXXScopeTy *S) { ScopeRep = S; }
+
+  iterator begin() const { 
+    if (NumScopeReps > 4)
+      return ManyScopeReps;
+    else
+      return &InlineScopeReps[0];
+  }
+
+  iterator end() const { 
+    return begin() + NumScopeReps;
+  }
+
+  Action::CXXScopeTy *getScopeRep(unsigned I) const {
+    assert(I < size() && "Out-of-range scope index");
+    return begin()[I];
+  }
+  unsigned size() const { return NumScopeReps; }
+
+  void addScopeRep(Action::CXXScopeTy *S) {
+    if (!S)
+      return;
+
+    if (NumScopeReps >= Capacity)
+      reallocate();
+
+    if (Capacity == 4)
+      InlineScopeReps[NumScopeReps++] = S;
+    else
+      ManyScopeReps[NumScopeReps++] = S;
+  }
+
+  Action::CXXScopeTy *getCurrentScopeRep() const { 
+    if (size() == 0)
+      return 0;
+    return begin()[size() - 1];
+  }
+
+  void setScopeRep(Action::CXXScopeTy *S) { 
+    if (Capacity > 4)
+      delete [] ManyScopeReps;
+    Capacity = 4;
+    NumScopeReps = 0;
+    addScopeRep(S);
+  }
 
   bool isEmpty() const { return !Range.isValid(); }
   bool isNotEmpty() const { return !isEmpty(); }
 
   /// isInvalid - An error occured during parsing of the scope specifier.
-  bool isInvalid() const { return isNotEmpty() && ScopeRep == 0; }
+  bool isInvalid() const { return isNotEmpty() && NumScopeReps == 0; }
 
   /// isSet - A scope specifier was resolved to a valid C++ scope.
-  bool isSet() const { return getScopeRep() != 0; }
+  bool isSet() const { return getCurrentScopeRep() != 0; }
 
   void clear() {
     Range = SourceRange();
-    ScopeRep = 0;
+    if (NumScopeReps > 4) 
+      delete [] ManyScopeReps;
+    NumScopeReps = 0;
+    Capacity = 4;
+  }
+
+  /// \brief Allocate and build the information that will be attached
+  /// to a scope-annotation token.
+  void *buildAnnotationData() const;
+
+  /// \brief Reconstruct a scope specifier from the annotation data. 
+  ///
+  /// This routine does not free the annotation data; call
+  /// freeAnnotationData for that.
+  void setFromAnnotationData(void *Data);
+
+  /// Frees the annotation data.
+  static void freeAnnotationData(void *Data) { 
+    delete [] (uintptr_t *) Data; 
   }
 };
   

clang/lib/AST/ASTContext.cpp

@@ -1375,6 +1375,29 @@ ASTContext::getClassTemplateSpecializationType(TemplateDecl *Template,
   return QualType(Spec, 0);  
 }
 
+QualType 
+ASTContext::getQualifiedNameType(const NestedNameSpecifier *Components,
+                                 unsigned NumComponents,
+                                 QualType NamedType) {
+  llvm::FoldingSetNodeID ID;
+  QualifiedNameType::Profile(ID, Components, NumComponents, NamedType);
+
+  void *InsertPos = 0;
+  QualifiedNameType *T 
+    = QualifiedNameTypes.FindNodeOrInsertPos(ID, InsertPos);
+  if (T)
+    return QualType(T, 0);
+
+  void *Mem = Allocate((sizeof(QualifiedNameType) +
+                        sizeof(NestedNameSpecifier) * NumComponents), 
+                       8);
+  T = new (Mem) QualifiedNameType(Components, NumComponents, NamedType,
+                                  getCanonicalType(NamedType));
+  Types.push_back(T);
+  QualifiedNameTypes.InsertNode(T, InsertPos);
+  return QualType(T, 0);
+}
+
 /// CmpProtocolNames - Comparison predicate for sorting protocols
 /// alphabetically.
 static bool CmpProtocolNames(const ObjCProtocolDecl *LHS,

clang/lib/AST/CMakeLists.txt

@@ -18,6 +18,7 @@ add_clang_library(clangAST
   Expr.cpp
   ExprCXX.cpp
   InheritViz.cpp
+  NestedNameSpecifier.cpp
   ParentMap.cpp
   Stmt.cpp
   StmtDumper.cpp

clang/lib/AST/NestedNameSpecifier.cpp

@@ -0,0 +1,34 @@
+//===--- NestedNameSpecifier.cpp - C++ nested name specifiers -----*- C++ -*-=//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file defines the NestedNameSpecifier class, which represents
+//  a C++ nested-name-specifier.
+//
+//===----------------------------------------------------------------------===//
+#include "clang/AST/NestedNameSpecifier.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/Decl.h"
+#include "clang/AST/Type.h"
+using namespace clang;
+
+DeclContext *
+NestedNameSpecifier::computeDeclContext(ASTContext &Context) const {
+  // The simple case: we're storing a DeclContext
+  if ((Data & 0x01) == 0)
+    return reinterpret_cast<DeclContext *>(Data);
+
+  Type *T = getAsType();
+  if (!T)
+    return 0;
+
+  // Retrieve the DeclContext associated with this type.
+  const TagType *TagT = T->getAsTagType();
+  assert(TagT && "No DeclContext from a non-tag type");
+  return TagT->getDecl();
+}

clang/lib/AST/Type.cpp

@@ -96,6 +96,8 @@ QualType Type::getDesugaredType() const {
   if (const ClassTemplateSpecializationType *Spec 
         = dyn_cast<ClassTemplateSpecializationType>(this))
     return Spec->getCanonicalTypeInternal().getDesugaredType();
+  if (const QualifiedNameType *QualName  = dyn_cast<QualifiedNameType>(this))
+    return QualName->getNamedType().getDesugaredType();
 
   // FIXME: remove this cast.
   return QualType(const_cast<Type*>(this), 0);
@@ -1045,6 +1047,28 @@ ClassTemplateSpecializationType::Profile(llvm::FoldingSetNodeID &ID,
     Args[Idx].Profile(ID);
 }
 
+QualifiedNameType::QualifiedNameType(const NestedNameSpecifier *Components,
+                                     unsigned NumComponents, 
+                                     QualType NamedType,
+                                     QualType CanonType)
+  : Type(QualifiedName, CanonType, NamedType->isDependentType()),
+    NumComponents(NumComponents), NamedType(NamedType) {
+  NestedNameSpecifier *InitComponents 
+    = reinterpret_cast<NestedNameSpecifier *>(this + 1);
+  for (unsigned I = 0; I < NumComponents; ++I)
+    new (InitComponents + I) NestedNameSpecifier(Components[I]);
+}
+
+void QualifiedNameType::Profile(llvm::FoldingSetNodeID &ID, 
+                                const NestedNameSpecifier *Components,
+                                unsigned NumComponents, 
+                                QualType NamedType) {
+  ID.AddInteger(NumComponents);
+  for (unsigned I = 0; I < NumComponents; ++I)
+    ID.AddPointer(Components[I].getAsOpaquePtr());
+  NamedType.Profile(ID);
+}
+
 //===----------------------------------------------------------------------===//
 // Type Printing
 //===----------------------------------------------------------------------===//
@@ -1411,6 +1435,38 @@ getAsStringInternal(std::string &InnerString) const {
     InnerString = SpecString + ' ' + InnerString;
 }
 
+void QualifiedNameType::getAsStringInternal(std::string &InnerString) const {
+  std::string MyString;
+
+  for (iterator Comp = begin(), CompEnd = end(); Comp != CompEnd; ++Comp) {
+    if (Type *T = Comp->getAsType()) {
+      std::string TypeStr;
+      if (const TagType *TagT = dyn_cast<TagType>(T))
+        TagT->getAsStringInternal(TypeStr, true);
+      else
+        T->getAsStringInternal(TypeStr);
+
+      MyString += TypeStr;
+    } else if (NamedDecl *NamedDC 
+               = dyn_cast_or_null<NamedDecl>(Comp->getAsDeclContext()))
+      MyString += NamedDC->getNameAsString();
+    MyString += "::";
+  }
+  
+  std::string TypeStr;
+  if (const TagType *TagT = dyn_cast<TagType>(NamedType.getTypePtr())) {
+    // Suppress printing of 'enum', 'struct', 'union', or 'class'.
+    TagT->getAsStringInternal(TypeStr, true);
+  } else
+    NamedType.getAsStringInternal(TypeStr);
+
+  MyString += TypeStr;
+  if (InnerString.empty())
+    InnerString.swap(MyString);
+  else
+    InnerString = MyString + ' ' + InnerString;
+}
+
 void ObjCInterfaceType::getAsStringInternal(std::string &InnerString) const {
   if (!InnerString.empty())    // Prefix the basic type, e.g. 'typedefname X'.
     InnerString = ' ' + InnerString;
@@ -1451,10 +1507,15 @@ void ObjCQualifiedIdType::getAsStringInternal(std::string &InnerString) const {
 }
 
 void TagType::getAsStringInternal(std::string &InnerString) const {
+  getAsStringInternal(InnerString, false);
+}
+
+void TagType::getAsStringInternal(std::string &InnerString,
+                                  bool SuppressTagKind) const {
   if (!InnerString.empty())    // Prefix the basic type, e.g. 'typedefname X'.
     InnerString = ' ' + InnerString;
   
-  const char *Kind = getDecl()->getKindName();
+  const char *Kind = SuppressTagKind? 0 : getDecl()->getKindName();
   const char *ID;
   if (const IdentifierInfo *II = getDecl()->getIdentifier())
     ID = II->getName();

clang/lib/AST/TypeSerialization.cpp

@@ -417,6 +417,21 @@ CreateImpl(ASTContext& Context, Deserializer& D) {
   return 0;
 }
 
+//===----------------------------------------------------------------------===//
+// QualifiedNameType
+//===----------------------------------------------------------------------===//
+void QualifiedNameType::EmitImpl(llvm::Serializer& S) const {
+  S.EmitInt(NumComponents);
+  // FIXME: Serialize the actual components
+  S.Emit(NamedType);
+}
+
+Type* 
+QualifiedNameType::CreateImpl(ASTContext& Context, llvm::Deserializer& D) {
+  // FIXME: Implement de-serialization
+  return 0;
+}
+
 //===----------------------------------------------------------------------===//
 // VariableArrayType
 //===----------------------------------------------------------------------===//

clang/lib/CodeGen/CGDebugInfo.cpp

@@ -525,6 +525,7 @@ llvm::DIType CGDebugInfo::getOrCreateType(QualType Ty,
   case Type::BlockPointer:
   case Type::MemberPointer:
   case Type::ClassTemplateSpecialization:
+  case Type::QualifiedName:
   case Type::ObjCQualifiedClass:
     // Unsupported types
     return llvm::DIType();

clang/lib/Parse/DeclSpec.cpp

@@ -15,6 +15,7 @@
 #include "clang/Parse/ParseDiagnostic.h"
 #include "clang/Basic/LangOptions.h"
 #include "llvm/ADT/STLExtras.h"
+#include <cstring>
 using namespace clang;
 
 
@@ -23,6 +24,66 @@ static DiagnosticBuilder Diag(Diagnostic &D, SourceLocation Loc,
   return D.Report(FullSourceLoc(Loc, SrcMgr), DiagID);
 }
 
+/// \brief Double the capacity of this scope specifier.
+void CXXScopeSpec::reallocate() {
+  Action::CXXScopeTy **Data = new Action::CXXScopeTy *[Capacity * 2];
+
+  Action::CXXScopeTy **From 
+    = Capacity == 4? &InlineScopeReps[0] : ManyScopeReps;
+  std::memcpy(Data, From, Capacity * sizeof(Action::CXXScopeTy *));
+  
+  if (Capacity > 4)
+    delete [] ManyScopeReps;
+  ManyScopeReps = Data;
+  Capacity *= 2;
+}
+
+CXXScopeSpec::CXXScopeSpec(const CXXScopeSpec &SS) 
+  : Range(SS.Range), NumScopeReps(SS.NumScopeReps), Capacity(SS.Capacity) {
+
+  if (Capacity > 4) {
+    ManyScopeReps = new Action::CXXScopeTy *[Capacity];
+    memcpy(ManyScopeReps, SS.ManyScopeReps, 
+           Capacity * sizeof(Action::CXXScopeTy *));
+  } else {
+    memcpy(InlineScopeReps, SS.InlineScopeReps, 
+           Capacity * sizeof(Action::CXXScopeTy *));
+  }
+}
+
+CXXScopeSpec &CXXScopeSpec::operator=(const CXXScopeSpec &SS) {
+  // FIXME: Does not provide the strong exception safety guarantee.
+  this->~CXXScopeSpec();
+  new (this) CXXScopeSpec(SS);
+  return *this;
+}
+
+void *CXXScopeSpec::buildAnnotationData() const {
+  uintptr_t *Data = (uintptr_t *)malloc(sizeof(uintptr_t) * (size() + 1));
+  Data[0] = size();
+  for (unsigned I = 0; I < size(); ++I)
+    Data[I + 1] = reinterpret_cast<uintptr_t>(getScopeRep(I));
+  return Data;
+}
+
+void CXXScopeSpec::setFromAnnotationData(void *DataIn) {
+  uintptr_t *Data = static_cast<uintptr_t *>(DataIn);
+  NumScopeReps = *Data;
+
+  // Allocate enough space for the annotation data.
+  if (NumScopeReps > Capacity) {
+    if (Capacity > 4)
+      delete [] ManyScopeReps;
+    
+    Capacity = NumScopeReps;
+    ManyScopeReps = new Action::CXXScopeTy *[Capacity];
+  }
+
+  if (Capacity > 4)
+    std::memcpy(ManyScopeReps, Data + 1, sizeof(uintptr_t) * NumScopeReps);
+  else
+    std::memcpy(InlineScopeReps, Data + 1, sizeof(uintptr_t) * NumScopeReps);
+}
 
 /// DeclaratorChunk::getFunction - Return a DeclaratorChunk for a function.
 /// "TheDeclarator" is the declarator that this will be added to.

clang/lib/Parse/ParseDecl.cpp

@@ -491,7 +491,7 @@ void Parser::ParseDeclarationSpecifiers(DeclSpec &DS,
         goto DoneWithDeclSpec;
 
       CXXScopeSpec SS;
-      SS.setScopeRep(Tok.getAnnotationValue());
+      SS.setFromAnnotationData(Tok.getAnnotationValue());
       SS.setRange(Tok.getAnnotationRange());
 
       // If the next token is the name of the class type that the C++ scope
@@ -509,6 +509,7 @@ void Parser::ParseDeclarationSpecifiers(DeclSpec &DS,
       if (TypeRep == 0)
         goto DoneWithDeclSpec;
       
+      CXXScopeSpec::freeAnnotationData(Tok.getAnnotationValue());
       ConsumeToken(); // The C++ scope.
 
       isInvalid = DS.SetTypeSpecType(DeclSpec::TST_typename, Loc, PrevSpec,

clang/lib/Parse/ParseExprCXX.cpp

@@ -36,7 +36,8 @@ bool Parser::ParseOptionalCXXScopeSpecifier(CXXScopeSpec &SS) {
          "Call sites of this function should be guarded by checking for C++");
 
   if (Tok.is(tok::annot_cxxscope)) {
-    SS.setScopeRep(Tok.getAnnotationValue());
+    SS.setFromAnnotationData(Tok.getAnnotationValue());
+    CXXScopeSpec::freeAnnotationData(Tok.getAnnotationValue());
     SS.setRange(Tok.getAnnotationRange());
     ConsumeToken();
     return true;
@@ -53,7 +54,7 @@ bool Parser::ParseOptionalCXXScopeSpecifier(CXXScopeSpec &SS) {
     // '::' - Global scope qualifier.
     SourceLocation CCLoc = ConsumeToken();
     SS.setBeginLoc(CCLoc);
-    SS.setScopeRep(Actions.ActOnCXXGlobalScopeSpecifier(CurScope, CCLoc));
+    SS.addScopeRep(Actions.ActOnCXXGlobalScopeSpecifier(CurScope, CCLoc));
     SS.setEndLoc(CCLoc);
     HasScopeSpecifier = true;
   }
@@ -79,7 +80,7 @@ bool Parser::ParseOptionalCXXScopeSpecifier(CXXScopeSpec &SS) {
       if (SS.isInvalid())
         continue;
       
-      SS.setScopeRep(
+      SS.addScopeRep(
         Actions.ActOnCXXNestedNameSpecifier(CurScope, SS, IdLoc, CCLoc, *II));
       SS.setEndLoc(CCLoc);
       continue;
@@ -149,7 +150,7 @@ bool Parser::ParseOptionalCXXScopeSpecifier(CXXScopeSpec &SS) {
 
       if (TemplateId->Kind == TNK_Class_template) {
         if (AnnotateTemplateIdTokenAsType(&SS))
-          SS.setScopeRep(0);
+          SS.clear();
 
         assert(Tok.is(tok::annot_typename) && 
                "AnnotateTemplateIdTokenAsType isn't working");
@@ -164,7 +165,7 @@ bool Parser::ParseOptionalCXXScopeSpecifier(CXXScopeSpec &SS) {
           HasScopeSpecifier = true;
         }
 
-        SS.setScopeRep(
+        SS.addScopeRep(
           Actions.ActOnCXXNestedNameSpecifier(CurScope, SS, 
                                               TypeToken.getAnnotationValue(),
                                               TypeToken.getAnnotationRange(),

clang/lib/Parse/Parser.cpp

@@ -856,7 +856,7 @@ bool Parser::TryAnnotateTypeOrScopeToken() {
   else
     PP.EnterToken(Tok);
   Tok.setKind(tok::annot_cxxscope);
-  Tok.setAnnotationValue(SS.getScopeRep());
+  Tok.setAnnotationValue(SS.buildAnnotationData());
   Tok.setAnnotationRange(SS.getRange());
 
   // In case the tokens were cached, have Preprocessor replace them with the
@@ -888,7 +888,7 @@ bool Parser::TryAnnotateCXXScopeToken() {
   else
     PP.EnterToken(Tok);
   Tok.setKind(tok::annot_cxxscope);
-  Tok.setAnnotationValue(SS.getScopeRep());
+  Tok.setAnnotationValue(SS.buildAnnotationData());
   Tok.setAnnotationRange(SS.getRange());
 
   // In case the tokens were cached, have Preprocessor replace them with the

clang/lib/Sema/Sema.h

@@ -1452,20 +1452,7 @@ public:
 
   bool RequireCompleteDeclContext(const CXXScopeSpec &SS);
   
-  /// \brief Build a scope representation from a declaration context.
+  DeclContext *computeDeclContext(const CXXScopeSpec &SS);
-  CXXScopeTy *createScopeRep(DeclContext *DC) {
-    return static_cast<CXXScopeTy *>(DC);
-  }
-
-  /// \brief Build a scope representation from a type.
-  CXXScopeTy *createScopeRep(QualType T);
-
-  DeclContext *getScopeRepAsDeclContext(const CXXScopeSpec &SS);
-  QualType getScopeRepAsType(const CXXScopeSpec &SS);
-
-  /// \brief Determines whether this scope specifier is represented as
-  /// a type.
-  bool isScopeRepType(const CXXScopeSpec &SS);
 
   /// ActOnCXXGlobalScopeSpecifier - Return the object that represents the
   /// global scope ('::').

clang/lib/Sema/SemaCXXScopeSpec.cpp

@@ -13,51 +13,20 @@
 
 #include "Sema.h"
 #include "clang/AST/ASTContext.h"
+#include "clang/AST/NestedNameSpecifier.h"
 #include "clang/Parse/DeclSpec.h"
 #include "llvm/ADT/STLExtras.h"
 using namespace clang;
 
-/// \brief Retrieve the scope represented by this scope specifier as a
+/// \brief Compute the DeclContext that is associated with the given
-/// DeclContext.
+/// scope specifier.
-DeclContext *Sema::getScopeRepAsDeclContext(const CXXScopeSpec &SS) {
+DeclContext *Sema::computeDeclContext(const CXXScopeSpec &SS) {
-  if (SS.isInvalid() || !SS.getScopeRep())
+  if (!SS.isSet() || SS.isInvalid())
-    return 0;
-  uintptr_t Rep = reinterpret_cast<uintptr_t>(SS.getScopeRep());
-  if ((Rep & 0x01) == 0)
-    return reinterpret_cast<DeclContext *>(Rep);
-
-  // Retrieve the DeclContext associated with this type.
-  QualType T = QualType(reinterpret_cast<Type *>(Rep & ~0x01), 0);
-  const TagType *TagT = T->getAsTagType();
-  assert(TagT && "No DeclContext from a non-tag type");
-  return TagT->getDecl();
-}
-
-/// \brief Retrieve the scope represented by this scope specifier as a
-/// type.
-QualType Sema::getScopeRepAsType(const CXXScopeSpec &SS) {
-  if (SS.isInvalid() || !SS.getScopeRep())
-    return QualType();
-  
-  uintptr_t Rep = reinterpret_cast<uintptr_t>(SS.getScopeRep());
-  if ((Rep & 0x01) == 0)
-    return QualType();
-  return QualType(reinterpret_cast<Type *>(Rep & ~0x01), 0);
-}
-
-Action::CXXScopeTy *Sema::createScopeRep(QualType T) {
-  assert(((reinterpret_cast<uintptr_t>(T.getAsOpaquePtr()) & 0x01) == 0) && 
-         "Scope type with cv-qualifiers");
-  if (T.isNull())
     return 0;
 
-  return reinterpret_cast<CXXScopeTy *>(
+  NestedNameSpecifier NNS
-           reinterpret_cast<uintptr_t>(T.getAsOpaquePtr()) | 0x01);
+    = NestedNameSpecifier::getFromOpaquePtr(SS.getCurrentScopeRep());
-}
+  return NNS.computeDeclContext(Context);
-
-bool Sema::isScopeRepType(const CXXScopeSpec &SS) {
-  uintptr_t Rep = reinterpret_cast<uintptr_t>(SS.getScopeRep());
-  return Rep & 0x01;
 }
 
 /// \brief Require that the context specified by SS be complete.
@@ -73,7 +42,7 @@ bool Sema::RequireCompleteDeclContext(const CXXScopeSpec &SS) {
   if (!SS.isSet() || SS.isInvalid())
     return false;
   
-  DeclContext *DC = getScopeRepAsDeclContext(SS);
+  DeclContext *DC = computeDeclContext(SS);
   if (TagDecl *Tag = dyn_cast<TagDecl>(DC)) {
     // If we're currently defining this type, then lookup into the
     // type is okay: don't complain that it isn't complete yet.
@@ -95,7 +64,7 @@ bool Sema::RequireCompleteDeclContext(const CXXScopeSpec &SS) {
 /// global scope ('::').
 Sema::CXXScopeTy *Sema::ActOnCXXGlobalScopeSpecifier(Scope *S,
                                                      SourceLocation CCLoc) {
-  return createScopeRep(Context.getTranslationUnitDecl());
+  return NestedNameSpecifier(Context.getTranslationUnitDecl()).getAsOpaquePtr();
 }
 
 /// ActOnCXXNestedNameSpecifier - Called during parsing of a
@@ -114,9 +83,10 @@ Sema::CXXScopeTy *Sema::ActOnCXXNestedNameSpecifier(Scope *S,
   if (SD) {
     if (TypedefDecl *TD = dyn_cast<TypedefDecl>(SD)) {
       if (TD->getUnderlyingType()->isRecordType())
-        return createScopeRep(Context.getTypeDeclType(TD));
+        return NestedNameSpecifier(Context.getTypeDeclType(TD).getTypePtr())
+                .getAsOpaquePtr();
     } else if (isa<NamespaceDecl>(SD) || isa<RecordDecl>(SD)) {
-      return createScopeRep(cast<DeclContext>(SD));
+      return NestedNameSpecifier(cast<DeclContext>(SD)).getAsOpaquePtr();
     }
 
     // FIXME: Template parameters and dependent types.
@@ -152,7 +122,8 @@ Sema::CXXScopeTy *Sema::ActOnCXXNestedNameSpecifier(Scope *S,
                                                     TypeTy *Ty,
                                                     SourceRange TypeRange,
                                                     SourceLocation CCLoc) {
-  return createScopeRep(QualType::getFromOpaquePtr(Ty));
+  return NestedNameSpecifier(QualType::getFromOpaquePtr(Ty).getTypePtr())
+           .getAsOpaquePtr();
 }
 
 /// ActOnCXXEnterDeclaratorScope - Called when a C++ scope specifier (global
@@ -165,7 +136,7 @@ void Sema::ActOnCXXEnterDeclaratorScope(Scope *S, const CXXScopeSpec &SS) {
   assert(SS.isSet() && "Parser passed invalid CXXScopeSpec.");
   assert(PreDeclaratorDC == 0 && "Previous declarator context not popped?");
   PreDeclaratorDC = static_cast<DeclContext*>(S->getEntity());
-  CurContext = getScopeRepAsDeclContext(SS);
+  CurContext = computeDeclContext(SS);
   S->setEntity(CurContext);
 }
 
@@ -176,8 +147,7 @@ void Sema::ActOnCXXEnterDeclaratorScope(Scope *S, const CXXScopeSpec &SS) {
 /// defining scope.
 void Sema::ActOnCXXExitDeclaratorScope(Scope *S, const CXXScopeSpec &SS) {
   assert(SS.isSet() && "Parser passed invalid CXXScopeSpec.");
-  assert(S->getEntity() == getScopeRepAsDeclContext(SS) && 
+  assert(S->getEntity() == computeDeclContext(SS) && "Context imbalance!");
-         "Context imbalance!");
   S->setEntity(PreDeclaratorDC);
   PreDeclaratorDC = 0;
 

clang/lib/Sema/SemaDecl.cpp

@@ -72,22 +72,32 @@ Sema::TypeTy *Sema::getTypeName(IdentifierInfo &II, SourceLocation NameLoc,
   }
 
   if (IIDecl) {
+    QualType T;
+  
     if (TypeDecl *TD = dyn_cast<TypeDecl>(IIDecl)) {
       // Check whether we can use this type
       (void)DiagnoseUseOfDecl(IIDecl, NameLoc);
       
-      return Context.getTypeDeclType(TD).getAsOpaquePtr();
+      T = Context.getTypeDeclType(TD);
-    }
+    } else if (ObjCInterfaceDecl *IDecl = dyn_cast<ObjCInterfaceDecl>(IIDecl)) {
-    
-    if (ObjCInterfaceDecl *IDecl = dyn_cast<ObjCInterfaceDecl>(IIDecl)) {
       // Check whether we can use this interface.
       (void)DiagnoseUseOfDecl(IIDecl, NameLoc);
       
-      return Context.getObjCInterfaceType(IDecl).getAsOpaquePtr();
+      T = Context.getObjCInterfaceType(IDecl);
+    } else
+      return 0;
+
+    if (SS && SS->isNotEmpty() && SS->isSet()) {
+      llvm::SmallVector<NestedNameSpecifier, 4> TNNs;
+      for (CXXScopeSpec::iterator TNN = SS->begin(), TNNEnd = SS->end();
+           TNN != TNNEnd; ++TNN)
+        TNNs.push_back(NestedNameSpecifier::getFromOpaquePtr(*TNN));
+      T = Context.getQualifiedNameType(&TNNs[0], TNNs.size(), T);
     }
 
-    // Otherwise, could be a variable, function etc.
+    return T.getAsOpaquePtr();
   }
+
   return 0;
 }
 
@@ -1257,7 +1267,7 @@ Sema::ActOnDeclarator(Scope *S, Declarator &D, DeclTy *lastDecl,
                             DeclSpec::SCS_static,
                           D.getIdentifierLoc());
   } else { // Something like "int foo::x;"
-    DC = getScopeRepAsDeclContext(D.getCXXScopeSpec());
+    DC = computeDeclContext(D.getCXXScopeSpec());
     // FIXME: RequireCompleteDeclContext(D.getCXXScopeSpec()); ?
     PrevDecl = LookupQualifiedName(DC, Name, LookupOrdinaryName, true);
 
@@ -3020,7 +3030,7 @@ Sema::DeclTy *Sema::ActOnTag(Scope *S, unsigned TagSpec, TagKind TK,
     }
 
     // FIXME: RequireCompleteDeclContext(SS)?
-    DC = getScopeRepAsDeclContext(SS);
+    DC = computeDeclContext(SS);
     SearchDC = DC;
     // Look-up name inside 'foo::'.
     PrevDecl = dyn_cast_or_null<TagDecl>(

clang/lib/Sema/SemaDeclCXX.cpp

@@ -299,8 +299,8 @@ void Sema::CheckCXXDefaultArguments(FunctionDecl *FD) {
 bool Sema::isCurrentClassName(const IdentifierInfo &II, Scope *,
                               const CXXScopeSpec *SS) {
   CXXRecordDecl *CurDecl;
-  if (SS) {
+  if (SS && SS->isSet() && !SS->isInvalid()) {
-    DeclContext *DC = getScopeRepAsDeclContext(*SS);
+    DeclContext *DC = computeDeclContext(*SS);
     CurDecl = dyn_cast_or_null<CXXRecordDecl>(DC);
   } else
     CurDecl = dyn_cast_or_null<CXXRecordDecl>(CurContext);

clang/lib/Sema/SemaExpr.cpp

@@ -727,7 +727,7 @@ Sema::ActOnDeclarationNameExpr(Scope *S, SourceLocation Loc,
   // implicit member ref, because we want a pointer to the member in general,
   // not any specific instance's member.
   if (isAddressOfOperand && SS && !SS->isEmpty() && !HasTrailingLParen) {
-    DeclContext *DC = getScopeRepAsDeclContext(*SS);
+    DeclContext *DC = computeDeclContext(*SS);
     if (D && isa<CXXRecordDecl>(DC)) {
       QualType DType;
       if (FieldDecl *FD = dyn_cast<FieldDecl>(D)) {
@@ -942,7 +942,7 @@ Sema::ActOnDeclarationNameExpr(Scope *S, SourceLocation Loc,
     //     - a nested-name-specifier that contains a class-name that
     //       names a dependent type.
     else if (SS && !SS->isEmpty()) {
-      for (DeclContext *DC = getScopeRepAsDeclContext(*SS);
+      for (DeclContext *DC = computeDeclContext(*SS);
            DC; DC = DC->getParent()) {
         // FIXME: could stop early at namespace scope.
         if (DC->isRecord()) {

clang/lib/Sema/SemaLookup.cpp

@@ -1038,9 +1038,10 @@ Sema::LookupParsedName(Scope *S, const CXXScopeSpec *SS,
     if (SS->isInvalid() || RequireCompleteDeclContext(*SS))
       return LookupResult::CreateLookupResult(Context, 0);
 
-    if (SS->isSet())
+    if (SS->isSet()) {
-      return LookupQualifiedName(getScopeRepAsDeclContext(*SS),
+      return LookupQualifiedName(computeDeclContext(*SS),
                                  Name, NameKind, RedeclarationOnly);
+    }
   }
 
   return LookupName(S, Name, NameKind, RedeclarationOnly, 

clang/lib/Sema/SemaTemplate.cpp

@@ -399,7 +399,7 @@ Sema::ActOnClassTemplate(Scope *S, unsigned TagSpec, TagKind TK,
 
   DeclContext *SemanticContext = CurContext;
   if (SS.isNotEmpty() && !SS.isInvalid()) {
-    SemanticContext = getScopeRepAsDeclContext(SS);
+    SemanticContext = computeDeclContext(SS);
 
     // FIXME: need to match up several levels of template parameter
     // lists here.

clang/lib/Sema/SemaTemplateInstantiate.cpp

@@ -490,6 +490,14 @@ InstantiateClassTemplateSpecializationType(
                                       SourceLocation());
 }
 
+QualType 
+TemplateTypeInstantiator::
+InstantiateQualifiedNameType(const QualifiedNameType *T, 
+                             unsigned Quals) const {
+  assert(false && "Cannot have dependent qualified name types (yet)");
+  return QualType();
+}
+
 QualType 
 TemplateTypeInstantiator::
 InstantiateObjCInterfaceType(const ObjCInterfaceType *T,

clang/lib/Sema/SemaType.cpp

@@ -742,7 +742,7 @@ QualType Sema::GetTypeForDeclarator(Declarator &D, Scope *S, unsigned Skip) {
     }
     case DeclaratorChunk::MemberPointer:
       // The scope spec must refer to a class, or be dependent.
-      DeclContext *DC = getScopeRepAsDeclContext(DeclType.Mem.Scope());
+      DeclContext *DC = computeDeclContext(DeclType.Mem.Scope());
       QualType ClsType;
       // FIXME: Extend for dependent types when it's actually supported.
       // See ActOnCXXNestedNameSpecifier.
@@ -810,8 +810,7 @@ QualType Sema::GetTypeForDeclarator(Declarator &D, Scope *S, unsigned Skip) {
         D.getDeclSpec().getStorageClassSpec() != DeclSpec::SCS_typedef &&
         ((D.getContext() != Declarator::MemberContext &&
           (!D.getCXXScopeSpec().isSet() ||
-           !static_cast<DeclContext*>(D.getCXXScopeSpec().getScopeRep())
+           !computeDeclContext(D.getCXXScopeSpec())->isRecord())) ||
-              ->isRecord())) ||
          D.getDeclSpec().getStorageClassSpec() == DeclSpec::SCS_static)) {
       if (D.isFunctionDeclarator())
         Diag(D.getIdentifierLoc(), diag::err_invalid_qualified_function_type);

clang/test/SemaCXX/qualified-names-diag.cpp

@@ -0,0 +1,28 @@
+// RUN: clang -fsyntax-only -verify %s
+namespace foo {
+  namespace wibble {
+    struct x { int y; };
+
+    namespace bar {
+      namespace wonka {
+        struct x {
+          struct y { };
+        };
+      }
+    }
+  }
+}
+
+namespace bar {
+  typedef int y;
+}
+void test() {
+  foo::wibble::x a;
+  ::bar::y b;
+  a + b; // expected-error{{invalid operands to binary expression ('foo::wibble::x' (aka 'struct x') and '::bar::y' (aka 'int'))}}
+
+  ::foo::wibble::bar::wonka::x::y c;
+  c + b; // expected-error{{invalid operands to binary expression ('::foo::wibble::bar::wonka::x::y' (aka 'struct y') and '::bar::y' (aka 'int'))}}
+}
+
+int ::foo::wibble::bar::wonka::x::y::* ptrmem;

clang/test/SemaTemplate/instantiate-typedef.cpp

@@ -8,7 +8,7 @@ struct add_pointer {
 add_pointer<int>::type test1(int * ptr) { return ptr; }
 
 add_pointer<float>::type test2(int * ptr) { 
-  return ptr; // expected-error{{incompatible type returning 'int *', expected 'type' (aka 'float *')}}
+  return ptr; // expected-error{{incompatible type returning 'int *', expected 'add_pointer<float>::type' (aka 'float *')}}
 }
 
 add_pointer<int&>::type // expected-note{{in instantiation of template class 'struct add_pointer<int &>' requested here}}