txgraph: drop move assignment operator

src/test/fuzz/txgraph.cpp

@@ -138,19 +138,18 @@ struct SimTxGraph
     }
 
     /** Add a new transaction to the simulation. */
-    TxGraph::Ref* AddTransaction(const FeePerWeight& feerate)
+    void AddTransaction(TxGraph::Ref&& ref, const FeePerWeight& feerate)
     {
         assert(graph.TxCount() < MAX_TRANSACTIONS);
         auto simpos = graph.AddTransaction(feerate);
         real_is_optimal = false;
         MakeModified(simpos);
         assert(graph.Positions()[simpos]);
-        simmap[simpos] = std::make_shared<TxGraph::Ref>();
+        simmap[simpos] = std::make_shared<TxGraph::Ref>(std::move(ref));
         auto ptr = simmap[simpos].get();
         simrevmap[ptr] = simpos;
         // This may invalidate our cached oversized value.
         if (oversized.has_value() && !*oversized) oversized = std::nullopt;
-        return ptr;
     }
 
     /** Add a dependency between two positions in this graph. */
@@ -459,9 +458,7 @@ FUZZ_TARGET(txgraph)
                 // Create a real TxGraph::Ref.
                 auto ref = real->AddTransaction(feerate);
                 // Create a shared_ptr place in the simulation to put the Ref in.
-                auto ref_loc = top_sim.AddTransaction(feerate);
+                top_sim.AddTransaction(std::move(ref), feerate);
-                // Move it in place.
-                *ref_loc = std::move(ref);
                 break;
             } else if ((block_builders.empty() || sims.size() > 1) && top_sim.GetTransactionCount() + top_sim.removed.size() > 1 && command-- == 0) {
                 // AddDependency.

src/txgraph.cpp

@@ -3451,20 +3451,6 @@ TxGraph::Ref::~Ref()
     }
 }
 
-TxGraph::Ref& TxGraph::Ref::operator=(Ref&& other) noexcept
-{
-    // Unlink the current graph, if any.
-    if (m_graph) m_graph->UnlinkRef(m_index);
-    // Inform the other's graph about the move, if any.
-    if (other.m_graph) other.m_graph->UpdateRef(other.m_index, *this);
-    // Actually update the contents.
-    m_graph = other.m_graph;
-    m_index = other.m_index;
-    other.m_graph = nullptr;
-    other.m_index = GraphIndex(-1);
-    return *this;
-}
-
 TxGraph::Ref::Ref(Ref&& other) noexcept
 {
     // Inform the TxGraph of other that its Ref is being moved.

src/txgraph.h

@@ -241,8 +241,8 @@ public:
         /** Destroy this Ref. If it is not empty, the corresponding transaction is removed (in both
          *  main and staging, if it exists). */
         virtual ~Ref();
-        // Support moving a Ref.
+        // Support move-constructing a Ref.
-        Ref& operator=(Ref&& other) noexcept;
+        Ref& operator=(Ref&& other) noexcept = delete;
         Ref(Ref&& other) noexcept;
         // Do not permit copy constructing or copy assignment. A TxGraph entry can have at most one
         // Ref pointing to it.