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diff --git a/clang/include/clang/AST/TemplateBase.h b/clang/include/clang/AST/TemplateBase.h
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+//===-- TemplateBase.h - Core classes for C++ templates ---------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file provides definitions which are common for all kinds of
+//  template representation.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_AST_TEMPLATEBASE_H
+#define LLVM_CLANG_AST_TEMPLATEBASE_H
+
+#include "llvm/ADT/APSInt.h"
+#include "clang/AST/Type.h"
+
+namespace llvm {
+  class FoldingSetNodeID;
+}
+
+namespace clang {
+
+class Decl;
+class Expr;
+
+/// \brief Represents a template argument within a class template
+/// specialization.
+class TemplateArgument {
+  union {
+    uintptr_t TypeOrValue;
+    struct {
+      char Value[sizeof(llvm::APSInt)];
+      void *Type;
+    } Integer;
+    struct {
+      TemplateArgument *Args;
+      unsigned NumArgs;
+      bool CopyArgs;
+    } Args;
+  };
+
+  /// \brief Location of the beginning of this template argument.
+  SourceLocation StartLoc;
+
+public:
+  /// \brief The type of template argument we're storing.
+  enum ArgKind {
+    Null = 0,
+    /// The template argument is a type. Its value is stored in the
+    /// TypeOrValue field.
+    Type = 1,
+    /// The template argument is a declaration
+    Declaration = 2,
+    /// The template argument is an integral value stored in an llvm::APSInt.
+    Integral = 3,
+    /// The template argument is a value- or type-dependent expression
+    /// stored in an Expr*.
+    Expression = 4,
+
+    /// The template argument is actually a parameter pack. Arguments are stored
+    /// in the Args struct.
+    Pack = 5
+  } Kind;
+
+  /// \brief Construct an empty, invalid template argument.
+  TemplateArgument() : TypeOrValue(0), StartLoc(), Kind(Null) { }
+
+  /// \brief Construct a template type argument.
+  TemplateArgument(SourceLocation Loc, QualType T) : Kind(Type) {
+    TypeOrValue = reinterpret_cast<uintptr_t>(T.getAsOpaquePtr());
+    StartLoc = Loc;
+  }
+
+  /// \brief Construct a template argument that refers to a
+  /// declaration, which is either an external declaration or a
+  /// template declaration.
+  TemplateArgument(SourceLocation Loc, Decl *D) : Kind(Declaration) {
+    // FIXME: Need to be sure we have the "canonical" declaration!
+    TypeOrValue = reinterpret_cast<uintptr_t>(D);
+    StartLoc = Loc;
+  }
+
+  /// \brief Construct an integral constant template argument.
+  TemplateArgument(SourceLocation Loc, const llvm::APSInt &Value,
+                   QualType Type)
+  : Kind(Integral) {
+    new (Integer.Value) llvm::APSInt(Value);
+    Integer.Type = Type.getAsOpaquePtr();
+    StartLoc = Loc;
+  }
+
+  /// \brief Construct a template argument that is an expression.
+  ///
+  /// This form of template argument only occurs in template argument
+  /// lists used for dependent types and for expression; it will not
+  /// occur in a non-dependent, canonical template argument list.
+  TemplateArgument(Expr *E);
+
+  /// \brief Copy constructor for a template argument.
+  TemplateArgument(const TemplateArgument &Other) : Kind(Other.Kind) {
+    if (Kind == Integral) {
+      new (Integer.Value) llvm::APSInt(*Other.getAsIntegral());
+      Integer.Type = Other.Integer.Type;
+    } else if (Kind == Pack) {
+      Args.NumArgs = Other.Args.NumArgs;
+      Args.Args = new TemplateArgument[Args.NumArgs];
+      for (unsigned I = 0; I != Args.NumArgs; ++I)
+        Args.Args[I] = Other.Args.Args[I];
+    }
+    else
+      TypeOrValue = Other.TypeOrValue;
+    StartLoc = Other.StartLoc;
+  }
+
+  TemplateArgument& operator=(const TemplateArgument& Other) {
+    // FIXME: Does not provide the strong guarantee for exception
+    // safety.
+    using llvm::APSInt;
+
+    // FIXME: Handle Packs
+    assert(Kind != Pack && "FIXME: Handle packs");
+    assert(Other.Kind != Pack && "FIXME: Handle packs");
+
+    if (Kind == Other.Kind && Kind == Integral) {
+      // Copy integral values.
+      *this->getAsIntegral() = *Other.getAsIntegral();
+      Integer.Type = Other.Integer.Type;
+    } else {
+      // Destroy the current integral value, if that's what we're holding.
+      if (Kind == Integral)
+        getAsIntegral()->~APSInt();
+
+      Kind = Other.Kind;
+
+      if (Other.Kind == Integral) {
+        new (Integer.Value) llvm::APSInt(*Other.getAsIntegral());
+        Integer.Type = Other.Integer.Type;
+      } else
+        TypeOrValue = Other.TypeOrValue;
+    }
+    StartLoc = Other.StartLoc;
+
+    return *this;
+  }
+
+  ~TemplateArgument() {
+    using llvm::APSInt;
+
+    if (Kind == Integral)
+      getAsIntegral()->~APSInt();
+    else if (Kind == Pack && Args.CopyArgs)
+      delete[] Args.Args;
+  }
+
+  /// \brief Return the kind of stored template argument.
+  ArgKind getKind() const { return Kind; }
+
+  /// \brief Determine whether this template argument has no value.
+  bool isNull() const { return Kind == Null; }
+
+  /// \brief Retrieve the template argument as a type.
+  QualType getAsType() const {
+    if (Kind != Type)
+      return QualType();
+
+    return QualType::getFromOpaquePtr(reinterpret_cast<void*>(TypeOrValue));
+  }
+
+  /// \brief Retrieve the template argument as a declaration.
+  Decl *getAsDecl() const {
+    if (Kind != Declaration)
+      return 0;
+    return reinterpret_cast<Decl *>(TypeOrValue);
+  }
+
+  /// \brief Retrieve the template argument as an integral value.
+  llvm::APSInt *getAsIntegral() {
+    if (Kind != Integral)
+      return 0;
+    return reinterpret_cast<llvm::APSInt*>(&Integer.Value[0]);
+  }
+
+  const llvm::APSInt *getAsIntegral() const {
+    return const_cast<TemplateArgument*>(this)->getAsIntegral();
+  }
+
+  /// \brief Retrieve the type of the integral value.
+  QualType getIntegralType() const {
+    if (Kind != Integral)
+      return QualType();
+
+    return QualType::getFromOpaquePtr(Integer.Type);
+  }
+
+  void setIntegralType(QualType T) {
+    assert(Kind == Integral &&
+           "Cannot set the integral type of a non-integral template argument");
+    Integer.Type = T.getAsOpaquePtr();
+  };
+
+  /// \brief Retrieve the template argument as an expression.
+  Expr *getAsExpr() const {
+    if (Kind != Expression)
+      return 0;
+
+    return reinterpret_cast<Expr *>(TypeOrValue);
+  }
+
+  /// \brief Iterator that traverses the elements of a template argument pack.
+  typedef const TemplateArgument * pack_iterator;
+
+  /// \brief Iterator referencing the first argument of a template argument
+  /// pack.
+  pack_iterator pack_begin() const {
+    assert(Kind == Pack);
+    return Args.Args;
+  }
+
+  /// \brief Iterator referencing one past the last argument of a template
+  /// argument pack.
+  pack_iterator pack_end() const {
+    assert(Kind == Pack);
+    return Args.Args + Args.NumArgs;
+  }
+
+  /// \brief The number of template arguments in the given template argument
+  /// pack.
+  unsigned pack_size() const {
+    assert(Kind == Pack);
+    return Args.NumArgs;
+  }
+
+  /// \brief Retrieve the location where the template argument starts.
+  SourceLocation getLocation() const { return StartLoc; }
+
+  /// \brief Construct a template argument pack.
+  void setArgumentPack(TemplateArgument *Args, unsigned NumArgs, bool CopyArgs);
+
+  /// \brief Used to insert TemplateArguments into FoldingSets.
+  void Profile(llvm::FoldingSetNodeID &ID, ASTContext &Context) const;
+};
+
+}
+
+#endif