diff --git a/language/duchain/declaration.h b/language/duchain/declaration.h
--- a/language/duchain/declaration.h
+++ b/language/duchain/declaration.h
@@ -54,14 +54,14 @@
 {
 public:
   /// Access types
-  enum AccessPolicy {
+  enum AccessPolicy : uchar {
     Public    /**< a public declaration */,
     Protected /**< a protected declaration */,
     Private   /**< a private declaration */,
     DefaultAccess /**<a declaration with default access; in java, only package-level access. */
   };
   /// Enumeration of the types of declarations
-  enum Kind {
+  enum Kind : uchar {
     Type     /**< A type is declared, like a class-declaration or function-declaration, or a typedef("class MyClass {};") */,
     Instance /**< An instance of a type is declared("MyClass m;") */,
     NamespaceAlias/**< This is a namespace-alias. You can safely cast this object to NamespaceAliasDeclaration. */,
diff --git a/language/duchain/declarationid.h b/language/duchain/declarationid.h
--- a/language/duchain/declarationid.h
+++ b/language/duchain/declarationid.h
@@ -74,20 +74,27 @@
     explicit DeclarationId(const IndexedDeclaration& decl,
                            const IndexedInstantiationInformation& specialization = IndexedInstantiationInformation());
 
+
+    DeclarationId(const DeclarationId& rhs);
+
+    ~DeclarationId();
+
+    DeclarationId& operator=(const DeclarationId& rhs);
+
     /**
      * Equality operator.
      *
      * \param rhs declaration identifier to compare.
      * \returns true if equal, otherwise false.
      */
     bool operator==(const DeclarationId& rhs) const {
-      if(m_direct != rhs.m_direct)
+      if(m_isDirect != rhs.m_isDirect)
         return false;
 
-      if(!m_direct)
-        return indirect.m_identifier == rhs.indirect.m_identifier && indirect.m_additionalIdentity == rhs.indirect.m_additionalIdentity && m_specialization == rhs.m_specialization;
+      if(!m_isDirect)
+        return m_indirectData.identifier == rhs.m_indirectData.identifier && m_indirectData.additionalIdentity == rhs.m_indirectData.additionalIdentity && m_specialization == rhs.m_specialization;
       else
-        return direct == rhs.direct && m_specialization == rhs.m_specialization;
+        return m_directData == rhs.m_directData && m_specialization == rhs.m_specialization;
     }
 
     /**
@@ -104,7 +111,7 @@
      * Determine whether this declaration identifier references a valid declaration.
      */
     bool isValid() const {
-      return (m_direct && direct.isValid()) || indirect.m_identifier.isValid();
+      return (m_isDirect && m_directData.isValid()) || m_indirectData.identifier.isValid();
     }
 
     /**
@@ -115,10 +122,10 @@
      *          and thus you cannot compare hashes for declaration equality (use operator==() instead)
      */
     uint hash() const {
-      if(m_direct)
-        return KDevHash() << direct.hash() << m_specialization.index();
+      if(m_isDirect)
+        return KDevHash() << m_directData.hash() << m_specialization.index();
       else
-        return KDevHash() << indirect.m_identifier.getIndex() << indirect.m_additionalIdentity << m_specialization.index();
+        return KDevHash() << m_indirectData.identifier.getIndex() << m_indirectData.additionalIdentity << m_specialization.index();
     }
 
     /**
@@ -168,20 +175,22 @@
     QualifiedIdentifier qualifiedIdentifier() const;
 
   private:
+    /// An indirect reference to the declaration, which uses the symbol-table for lookup. Should be preferred for all
+    /// declarations that are in the symbol-table
     struct Indirect {
-      IndexedQualifiedIdentifier m_identifier;
-      // Hash from signature, or similar.
-      // Used to disambiguate multiple declarations of the same name.
-      uint m_additionalIdentity;
-    } ;
-
-    //union {
-      //An indirect reference to the declaration, which uses the symbol-table for lookup. Should be preferred for all
-      //declarations that are in the symbol-table
-      Indirect indirect;
-      IndexedDeclaration direct;
-    //};
-    bool m_direct;
+      IndexedQualifiedIdentifier identifier;
+      /// Hash from signature, or similar. Used to disambiguate multiple declarations of the same name.
+      uint additionalIdentity;
+
+      Indirect& operator=(const Indirect& rhs) = default;
+    };
+
+    union {
+      Indirect m_indirectData;
+      IndexedDeclaration m_directData;
+    };
+    bool m_isDirect;
+
     // Can be used in a language-specific way to pick other versions of the declaration.
     // When the declaration is found, pickSpecialization is called on the found declaration
     // with this value, and the returned value is the actually found declaration.
diff --git a/language/duchain/declarationid.cpp b/language/duchain/declarationid.cpp
--- a/language/duchain/declarationid.cpp
+++ b/language/duchain/declarationid.cpp
@@ -33,25 +33,55 @@
 
 DeclarationId::DeclarationId(const IndexedQualifiedIdentifier& id, uint additionalId,
                              const IndexedInstantiationInformation& specialization)
-  : m_direct(false)
+  : m_indirectData{id, additionalId}
+  , m_isDirect(false)
   , m_specialization(specialization)
 {
-  indirect.m_identifier = id;
-  indirect.m_additionalIdentity = additionalId;
 }
 
 DeclarationId::DeclarationId(const IndexedDeclaration& decl,
                              const IndexedInstantiationInformation& specialization)
-  : direct(decl)
-  , m_direct(true)
+  : m_directData(decl)
+  , m_isDirect(true)
   , m_specialization(specialization)
 {
+}
 
+DeclarationId::DeclarationId(const DeclarationId& rhs)
+  : m_isDirect(rhs.m_isDirect)
+  , m_specialization(rhs.m_specialization)
+{
+  if (m_isDirect) {
+    m_directData = rhs.m_directData;
+  } else {
+    // IndexedQualifiedIdentifier doesn't like zero-initialization...
+    new (&m_indirectData.identifier) IndexedQualifiedIdentifier(rhs.m_indirectData.identifier);
+    m_indirectData.additionalIdentity = rhs.m_indirectData.additionalIdentity;
+  }
+}
+
+DeclarationId::~DeclarationId()
+{
+}
+
+DeclarationId& DeclarationId::operator=(const DeclarationId& rhs)
+{
+  if (&rhs == this)
+    return *this;
+
+  m_isDirect = rhs.m_isDirect;
+  m_specialization = rhs.m_specialization;
+  if (m_isDirect) {
+    m_directData = rhs.m_directData;
+  } else {
+    m_indirectData = rhs.m_indirectData;
+  }
+  return *this;
 }
 
 bool DeclarationId::isDirect() const
 {
-  return m_direct;
+  return m_isDirect;
 }
 
 void DeclarationId::setSpecialization(const IndexedInstantiationInformation& spec)
@@ -68,17 +98,17 @@
 {
   KDevVarLengthArray<Declaration*> ret;
 
-  if(m_direct == false) {
+  if(m_isDirect == false) {
     //Find the declaration by its qualified identifier and additionalIdentity
-    QualifiedIdentifier id(indirect.m_identifier);
+    QualifiedIdentifier id(m_indirectData.identifier);
 
     if(top) {
       //Do filtering
       PersistentSymbolTable::FilteredDeclarationIterator filter =
           PersistentSymbolTable::self().getFilteredDeclarations(id, top->recursiveImportIndices());
       for(; filter; ++filter) {
           Declaration* decl = filter->data();
-          if(decl && indirect.m_additionalIdentity == decl->additionalIdentity()) {
+          if(decl && m_indirectData.additionalIdentity == decl->additionalIdentity()) {
             //Hit
             ret.append(decl);
           }
@@ -97,15 +127,15 @@
 
         if(!top) {
           Declaration* decl = iDecl.data();
-          if(decl && indirect.m_additionalIdentity == decl->additionalIdentity()) {
+          if(decl && m_indirectData.additionalIdentity == decl->additionalIdentity()) {
             //Hit
             ret.append(decl);
           }
         }
       }
     }
   }else{
-    Declaration* decl = direct.declaration();
+    Declaration* decl = m_directData.declaration();
     if(decl)
       ret.append(decl);
   }
@@ -126,17 +156,17 @@
 {
   Declaration* ret = 0;
 
-  if(m_direct == false) {
+  if(m_isDirect == false) {
     //Find the declaration by its qualified identifier and additionalIdentity
-    QualifiedIdentifier id(indirect.m_identifier);
+    QualifiedIdentifier id(m_indirectData.identifier);
 
     if(top) {
       //Do filtering
       PersistentSymbolTable::FilteredDeclarationIterator filter =
           PersistentSymbolTable::self().getFilteredDeclarations(id, top->recursiveImportIndices());
       for(; filter; ++filter) {
           Declaration* decl = filter->data();
-          if(decl && indirect.m_additionalIdentity == decl->additionalIdentity()) {
+          if(decl && m_indirectData.additionalIdentity == decl->additionalIdentity()) {
             //Hit
             ret = decl;
             if(!ret->isForwardDeclaration())
@@ -157,7 +187,7 @@
 
         if(!top) {
           Declaration* decl = iDecl.data();
-          if(decl && indirect.m_additionalIdentity == decl->additionalIdentity()) {
+          if(decl && m_indirectData.additionalIdentity == decl->additionalIdentity()) {
             //Hit
             ret = decl;
             if(!ret->isForwardDeclaration())
@@ -168,7 +198,7 @@
     }
   }else{
     //Find the declaration by m_topContext and m_declaration
-    ret = direct.declaration();
+    ret = m_directData.declaration();
   }
 
 
@@ -193,8 +223,8 @@
 QualifiedIdentifier DeclarationId::qualifiedIdentifier() const
 {
 
-  if(!m_direct) {
-    QualifiedIdentifier baseIdentifier = indirect.m_identifier.identifier();
+  if(!m_isDirect) {
+    QualifiedIdentifier baseIdentifier = m_indirectData.identifier.identifier();
     if(!m_specialization.index())
       return baseIdentifier;
     return m_specialization.information().applyToIdentifier(baseIdentifier);
@@ -206,7 +236,7 @@
     return QualifiedIdentifier(i18n("(unknown direct declaration)"));
   }
 
-  return QualifiedIdentifier(i18n("(missing)")) + indirect.m_identifier.identifier();
+  return QualifiedIdentifier(i18n("(missing)")) + m_indirectData.identifier.identifier();
 }
 
 }
diff --git a/language/duchain/duchainbase.h b/language/duchain/duchainbase.h
--- a/language/duchain/duchainbase.h
+++ b/language/duchain/duchainbase.h
@@ -76,7 +76,7 @@
     
     APPENDED_LISTS_STUB(DUChainBaseData)
     
-    uint classId;
+    quint16 classId;
 
     bool isDynamic() const {
       return m_dynamic;
@@ -90,6 +90,7 @@
     */
     template<class T>
     void setClassId(T*) {
+      static_assert(T::Identity < std::numeric_limits<decltype(classId)>::max(), "Class ID out of bounds");
       classId = T::Identity;
     }
       
diff --git a/language/duchain/ducontext.h b/language/duchain/ducontext.h
--- a/language/duchain/ducontext.h
+++ b/language/duchain/ducontext.h
@@ -95,7 +95,7 @@
    */
   virtual ~DUContext();
 
-  enum ContextType {
+  enum ContextType : uchar {
     Global    /**< A context that declares functions, namespaces or classes */,
     Namespace /**< A context that declares namespace members */,
     Class     /**< A context that declares class members */,
diff --git a/language/duchain/ducontextdata.h b/language/duchain/ducontextdata.h
--- a/language/duchain/ducontextdata.h
+++ b/language/duchain/ducontextdata.h
@@ -48,7 +48,7 @@
   DUContextData();
   ~DUContextData();
   DUContextData(const DUContextData& rhs);
-  DUContext::ContextType m_contextType;
+
   IndexedQualifiedIdentifier m_scopeIdentifier;
   IndexedDeclaration m_owner;
   typedef DUContext::Import Import;
@@ -69,6 +69,7 @@
   APPENDED_LIST(DUContextData, Use, m_uses, m_localDeclarations);
   END_APPENDED_LISTS(DUContextData, m_uses);
 
+  DUContext::ContextType m_contextType;
   bool m_inSymbolTable : 1;
   bool m_anonymousInParent : 1; //Whether this context was added anonymously into the parent. This means that it cannot be found as child-context in the parent.
   bool m_propagateDeclarations : 1;
diff --git a/language/duchain/topducontext.h b/language/duchain/topducontext.h
--- a/language/duchain/topducontext.h
+++ b/language/duchain/topducontext.h
@@ -177,7 +177,7 @@
     Identity = 4
   };
 
-  enum Features {
+  enum Features : ushort {
     ///Top-context features standard that can be requested from the duchain, and that are stored in the features() member.
     Empty = 0, //Only the top-context structure (imports etc.) is built, but no declarations and no contexts
     SimplifiedVisibleDeclarationsAndContexts = 2, //The top-context should only contain publically simplified accessible declarations and contexts, without doing type look-up,
diff --git a/language/duchain/topducontext.cpp b/language/duchain/topducontext.cpp
--- a/language/duchain/topducontext.cpp
+++ b/language/duchain/topducontext.cpp
@@ -916,7 +916,6 @@
 
 bool TopDUContext::deleting() const
 {
-  ///@todo remove d_func()->m_deleting, not used any more
   return m_dynamicData->m_deleting;
 }
 
diff --git a/language/duchain/topducontextdata.h b/language/duchain/topducontextdata.h
--- a/language/duchain/topducontextdata.h
+++ b/language/duchain/topducontextdata.h
@@ -38,7 +38,6 @@
 public:
   explicit TopDUContextData(IndexedString url)
     : DUContextData()
-    , m_deleting(false)
     , m_url(url)
     , m_ownIndex(0)
     , m_currentUsedDeclarationIndex(0)
@@ -48,7 +47,6 @@
 
   TopDUContextData(const TopDUContextData& rhs)
     : DUContextData(rhs)
-    , m_deleting(false)
   {
     initializeAppendedLists();
     copyListsFrom(rhs);
@@ -65,8 +63,6 @@
 
   TopDUContext::Features m_features;
 
-  bool m_deleting : 1; ///@todo remove
-
   IndexedString m_url;
   uint m_ownIndex;
 
diff --git a/language/duchain/types/abstracttype.h b/language/duchain/types/abstracttype.h
--- a/language/duchain/types/abstracttype.h
+++ b/language/duchain/types/abstracttype.h
@@ -101,6 +101,7 @@
    */
   enum CommonModifiers {
     NoModifiers                 = 0,
+
     ConstModifier               = 1 << 0,
     VolatileModifier            = 1 << 1,
     TransientModifier           = 1 << 2,
@@ -113,7 +114,8 @@
     LongLongModifier            = 1 << 9,
     SignedModifier              = 1 << 10,
     UnsignedModifier            = 1 << 11,
-    LanguageSpecificModifier    = 1 << 12 //TODO make this support 64 bit values
+
+    LanguageSpecificModifier    = 1 << 16
   };
 
   /// Constructor.
@@ -128,14 +130,14 @@
    *
    * \returns the type's modifiers.
    */
-  quint64 modifiers() const;
+  quint32 modifiers() const;
 
   /**
    * Set the type's modifiers.
    *
    * \param modifiers modifiers of this type.
    */
-  void setModifiers(quint64 modifiers);
+  void setModifiers(quint32 modifiers);
 
   /**
    * Visitor method.  Called by TypeVisitor to visit the type heirachy.
@@ -184,7 +186,7 @@
   IndexedType indexed() const;
 
   /// Enumeration of major data types.
-  enum WhichType {
+  enum WhichType : uchar {
     TypeAbstract  /**< an abstract type */,
     TypeIntegral  /**< an integral */,
     TypePointer   /**< a pointer*/,
diff --git a/language/duchain/types/abstracttype.cpp b/language/duchain/types/abstracttype.cpp
--- a/language/duchain/types/abstracttype.cpp
+++ b/language/duchain/types/abstracttype.cpp
@@ -47,12 +47,12 @@
 {
 }
 
-quint64 AbstractType::modifiers() const
+quint32 AbstractType::modifiers() const
 {
   return d_func()->m_modifiers;
 }
 
-void AbstractType::setModifiers(quint64 modifiers)
+void AbstractType::setModifiers(quint32 modifiers)
 {
   d_func_dynamic()->m_modifiers = modifiers;
 }
diff --git a/language/duchain/types/delayedtype.h b/language/duchain/types/delayedtype.h
--- a/language/duchain/types/delayedtype.h
+++ b/language/duchain/types/delayedtype.h
@@ -42,7 +42,7 @@
   typedef TypePtr<DelayedType> Ptr;
 
   /// An enumeration of
-  enum Kind {
+  enum Kind : uchar {
     Delayed /**< The type should be resolved later. This is the default. */,
     Unresolved /**< The type could not be resolved */
   };
diff --git a/language/duchain/types/typesystem.cpp b/language/duchain/types/typesystem.cpp
--- a/language/duchain/types/typesystem.cpp
+++ b/language/duchain/types/typesystem.cpp
@@ -31,8 +31,9 @@
 {
 
 AbstractTypeData::AbstractTypeData()
-  : m_modifiers(AbstractType::NoModifiers)
-  , inRepository(false), refCount(0)
+  : refCount(0)
+  , m_modifiers(AbstractType::NoModifiers)
+  , inRepository(false)
 {
   initializeAppendedLists(true);
 }
@@ -51,8 +52,9 @@
 }
 
 AbstractTypeData::AbstractTypeData( const AbstractTypeData& rhs )
-  : m_modifiers(rhs.m_modifiers)
-  , inRepository(false), refCount(0)
+  : refCount(0)
+  , m_modifiers(rhs.m_modifiers)
+  , inRepository(false)
 {
   initializeAppendedLists(!rhs.m_dynamic); //This type will be dynamic exactly if the copied one is not.
   typeClassId = rhs.typeClassId;
diff --git a/language/duchain/types/typesystemdata.h b/language/duchain/types/typesystemdata.h
--- a/language/duchain/types/typesystemdata.h
+++ b/language/duchain/types/typesystemdata.h
@@ -68,20 +68,21 @@
    */
   template<class T>
   void setTypeClassId() {
+    static_assert(T::Identity < std::numeric_limits<decltype(typeClassId)>::max(), "TypeClass ID out of bounds");
     typeClassId = T::Identity;
   }
 
-  /// Remember which type this data was created for. \sa setTypeClassId()
-  uint typeClassId;
+  /// Reference-count for this type within the repository. Not used for comparison or hashes.
+  uint refCount;
 
   /// Type modifier flags
-  quint64 m_modifiers;
+  quint32 m_modifiers;
+
+  /// Remember which type this data was created for. \sa setTypeClassId()
+  quint16 typeClassId;
 
   /// Remember whether this type is in a TypeRepository. Not used for comparison or hashes.
   bool inRepository : 1;
-  
-  /// Reference-count for this type within the repository. Not used for comparison or hashes.
-  uint refCount;
 
   APPENDED_LISTS_STUB(AbstractTypeData)