[lldb][NFC] Don't inherit from UserID in ValueObject

[teemperor]

Summary

ValueObject inherits from UserID which is just a bad idea:

• The inheritance gives ValueObject some member functions that are at best misleading (such as Clear() which doesn't clear any value beside id).
• It allows passing ValueObject to the overloaded operators for UserID (such as == or << which won't actually compare or print anything in the ValueObject).
• It exposes the SetID and Clear which both allow users to change the internal id value.

Similar to D91699 which did the same for Process

[shafik]

lldb/include/lldb/Core/ValueObject.h

892

This makes more sense, ValueObject is not a UserID but contains one.

[teemperor]

• Rebased.
• Add a GetID() call where we relied on the == overload before.

lldb/include/lldb/Core/ValueObject.h

 /// However, if you are making an derived ValueObject that will be contained in
 /// a parent value object, you should just
 /// hold onto a pointer to it internally, and by virtue of passing the parent
 /// ValueObject into its constructor, it will
 /// be added to the ClusterManager for the parent.  Then if you ever hand out a
 /// Shared Pointer to the contained ValueObject,
 /// just do so by calling GetSP() on the contained object.
 
-class ValueObject : public UserID {
+class ValueObject {
 public:
   enum GetExpressionPathFormat {
     eGetExpressionPathFormatDereferencePointers = 1,
     eGetExpressionPathFormatHonorPointers
   };
 
   enum ValueObjectRepresentationStyle {
     eValueObjectRepresentationStyleValue = 1,
public:
 
   virtual bool GetDeclaration(Declaration &decl);
 
   // The functions below should NOT be modified by subclasses
   const Status &GetError();
 
   ConstString GetName() const;
 
+  /// Returns a unique id for this ValueObject.
+  lldb::user_id_t GetID() const { return m_id.GetID(); }
+
   virtual lldb::ValueObjectSP GetChildAtIndex(size_t idx, bool can_create);
 
   // this will always create the children if necessary
   lldb::ValueObjectSP GetChildAtIndexPath(llvm::ArrayRef<size_t> idxs,
                                           size_t *index_of_error = nullptr);
 
   lldb::ValueObjectSP
   GetChildAtIndexPath(llvm::ArrayRef<std::pair<size_t, bool>> idxs,
protected:
   AddressType m_address_type_of_ptr_or_ref_children = eAddressTypeInvalid;
 
   llvm::SmallVector<uint8_t, 16> m_value_checksum;
 
   lldb::LanguageType m_preferred_display_language = lldb::eLanguageTypeUnknown;
 
   uint64_t m_language_flags = 0;
 
+  /// Unique identifier for every value object.
+  UserID m_id;
+
   // Utility class for initializing all bitfields in ValueObject's constructors.
   // FIXME: This could be done via default initializers once we have C++20.
   struct Bitflags {
     bool m_value_is_valid : 1, m_value_did_change : 1,
         m_children_count_valid : 1, m_old_value_valid : 1,
         m_is_deref_of_parent : 1, m_is_array_item_for_pointer : 1,
         m_is_bitfield_for_scalar : 1, m_is_child_at_offset : 1,
         m_is_getting_summary : 1, m_did_calculate_complete_objc_class_type : 1,

lldb/source/Core/ValueObject.cpp

 
 using namespace lldb;
 using namespace lldb_private;
 
 static user_id_t g_value_obj_uid = 0;
 
 // ValueObject constructor
 ValueObject::ValueObject(ValueObject &parent)
-    : UserID(++g_value_obj_uid), // Unique identifier for every value object
-      m_parent(&parent), m_update_point(parent.GetUpdatePoint()),
-      m_manager(parent.GetManager()) {
+    : m_parent(&parent), m_update_point(parent.GetUpdatePoint()),
+      m_manager(parent.GetManager()), m_id(++g_value_obj_uid) {
   m_flags.m_is_synthetic_children_generated =
       parent.m_flags.m_is_synthetic_children_generated;
   m_data.SetByteOrder(parent.GetDataExtractor().GetByteOrder());
   m_data.SetAddressByteSize(parent.GetDataExtractor().GetAddressByteSize());
   m_manager->ManageObject(this);
 }
 
 // ValueObject constructor
 ValueObject::ValueObject(ExecutionContextScope *exe_scope,
                          ValueObjectManager &manager,
                          AddressType child_ptr_or_ref_addr_type)
-    : UserID(++g_value_obj_uid), // Unique identifier for every value object
-      m_update_point(exe_scope), m_manager(&manager),
-      m_address_type_of_ptr_or_ref_children(child_ptr_or_ref_addr_type) {
+    : m_update_point(exe_scope), m_manager(&manager),
+      m_address_type_of_ptr_or_ref_children(child_ptr_or_ref_addr_type),
+      m_id(++g_value_obj_uid) {
   if (exe_scope) {
     TargetSP target_sp(exe_scope->CalculateTarget());
     if (target_sp) {
       const ArchSpec &arch = target_sp->GetArchitecture();
       m_data.SetByteOrder(arch.GetByteOrder());
       m_data.SetAddressByteSize(arch.GetAddressByteSize());
     }
   }

lldb/source/DataFormatters/TypeSynthetic.cpp

if (valobj_sp)
     valobj_sp->SetSyntheticChildrenGenerated(true);
   return valobj_sp;
 }
 
 ScriptedSyntheticChildren::FrontEnd::FrontEnd(std::string pclass,
                                               ValueObject &backend)
     : SyntheticChildrenFrontEnd(backend), m_python_class(pclass),
       m_wrapper_sp(), m_interpreter(nullptr) {
-  if (backend == LLDB_INVALID_UID)
+  if (backend.GetID() == LLDB_INVALID_UID)
     return;
 
   TargetSP target_sp = backend.GetTargetSP();
 
   if (!target_sp)
     return;
 
   m_interpreter = target_sp->GetDebugger().GetScriptInterpreter();