eliminate one form of PythonObject::Reset()

Summary:
I'd like to eliminate all forms of Reset() and all public constructors
on these objects, so the only way to make them is with Take<> and Retain<>
and the only way to copy or move them is with actual c++ copy, move, or
assignment.

This is a simple place to start.

Reviewers: JDevlieghere, clayborg, labath, jingham

Reviewed By: labath

Subscribers: lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D69080

llvm-svn: 375182

lldb/source/Plugins/ScriptInterpreter/Python/PythonDataObjects.h

@@ -182,7 +182,8 @@ public:
     Reset(type, py_obj);
   }
 
-  PythonObject(const PythonObject &rhs) : m_py_obj(nullptr) { Reset(rhs); }
+  PythonObject(const PythonObject &rhs)
+      : PythonObject(PyRefType::Borrowed, rhs.m_py_obj) {}
 
   PythonObject(PythonObject &&rhs) {
     m_py_obj = rhs.m_py_obj;
@@ -197,19 +198,6 @@ public:
     m_py_obj = nullptr;
   }
 
-  void Reset(const PythonObject &rhs) {
-    if (!rhs.IsValid())
-      Reset();
-    else
-      Reset(PyRefType::Borrowed, rhs.m_py_obj);
-  }
-
-  // PythonObject is implicitly convertible to PyObject *, which will call the
-  // wrong overload.  We want to explicitly disallow this, since a PyObject
-  // *always* owns its reference.  Therefore the overload which takes a
-  // PyRefType doesn't make sense, and the copy constructor should be used.
-  void Reset(PyRefType type, const PythonObject &ref) = delete;
-
   void Reset(PyRefType type, PyObject *py_obj) {
     if (py_obj == m_py_obj)
       return;
@@ -244,19 +232,9 @@ public:
     return result;
   }
 
-  PythonObject &operator=(const PythonObject &other) {
-    Reset(PyRefType::Borrowed, other.get());
-    return *this;
-  }
-
-  void Reset(PythonObject &&other) {
+  PythonObject &operator=(PythonObject other) {
     Reset();
-    m_py_obj = other.m_py_obj;
-    other.m_py_obj = nullptr;
-  }
-
-  PythonObject &operator=(PythonObject &&other) {
-    Reset(std::move(other));
+    m_py_obj = std::exchange(other.m_py_obj, nullptr);
     return *this;
   }