chore: Enable clang-tidy bugprone-unhandled-self-assignment check (#6504)

.clang-tidy

@@ -64,6 +64,7 @@ Checks: "-*,
   bugprone-undefined-memory-manipulation,
   bugprone-undelegated-constructor,
   bugprone-unhandled-exception-at-new,
+  bugprone-unhandled-self-assignment,
   bugprone-unique-ptr-array-mismatch,
   bugprone-unsafe-functions,
   bugprone-unused-local-non-trivial-variable,
@@ -100,7 +101,6 @@ Checks: "-*,
 # bugprone-switch-missing-default-case,
 # bugprone-unused-return-value,
 # bugprone-use-after-move,
-# bugprone-unhandled-self-assignment,
 # bugprone-unused-raii,
 #
 # cppcoreguidelines-misleading-capture-default-by-value,

src/libxrpl/protocol/STBase.cpp

@@ -23,6 +23,9 @@ STBase::STBase(SField const& n) : fName(&n)
 STBase&
 STBase::operator=(STBase const& t)
 {
+    if (this == &t)
+        return *this;
+
     if (!fName->isUseful())
         fName = t.fName;
     return *this;

src/libxrpl/resource/Consumer.cpp

@@ -39,6 +39,9 @@ Consumer::~Consumer()
 Consumer&
 Consumer::operator=(Consumer const& other)
 {
+    if (this == &other)
+        return *this;
+
     // remove old ref
     if (m_logic && m_entry)
         m_logic->release(*m_entry);