[refactor] change Workspace::m_conflicts and adjacent funcs/structs to use Txid

It's preferable to use type-safe transaction identifiers to avoid
confusing txid and wtxid. The next commit will add a reference to this
set; we use this opportunity to change it to Txid ahead of time instead
of adding new uses of uint256.

src/policy/rbf.cpp

@@ -115,11 +115,11 @@ std::optional<std::string> HasNoNewUnconfirmed(const CTransaction& tx,
 }
 
 std::optional<std::string> EntriesAndTxidsDisjoint(const CTxMemPool::setEntries& ancestors,
-                                                   const std::set<uint256>& direct_conflicts,
+                                                   const std::set<Txid>& direct_conflicts,
                                                    const uint256& txid)
 {
     for (CTxMemPool::txiter ancestorIt : ancestors) {
-        const uint256& hashAncestor = ancestorIt->GetTx().GetHash();
+        const Txid& hashAncestor = ancestorIt->GetTx().GetHash();
         if (direct_conflicts.count(hashAncestor)) {
             return strprintf("%s spends conflicting transaction %s",
                              txid.ToString(),

src/policy/rbf.h

@@ -80,7 +80,7 @@ std::optional<std::string> HasNoNewUnconfirmed(const CTransaction& tx, const CTx
  * @returns error message if the sets intersect, std::nullopt if they are disjoint.
  */
 std::optional<std::string> EntriesAndTxidsDisjoint(const CTxMemPool::setEntries& ancestors,
-                                                   const std::set<uint256>& direct_conflicts,
+                                                   const std::set<Txid>& direct_conflicts,
                                                    const uint256& txid);
 
 /** Check that the feerate of the replacement transaction(s) is higher than the feerate of each

src/test/rbf_tests.cpp

@@ -135,8 +135,6 @@ BOOST_FIXTURE_TEST_CASE(rbf_helper_functions, TestChain100Setup)
     // Tests for EntriesAndTxidsDisjoint
     BOOST_CHECK(EntriesAndTxidsDisjoint(empty_set, {tx1->GetHash()}, unused_txid) == std::nullopt);
     BOOST_CHECK(EntriesAndTxidsDisjoint(set_12_normal, {tx3->GetHash()}, unused_txid) == std::nullopt);
-    // EntriesAndTxidsDisjoint uses txids, not wtxids.
-    BOOST_CHECK(EntriesAndTxidsDisjoint({entry2}, {tx2->GetWitnessHash()}, unused_txid) == std::nullopt);
     BOOST_CHECK(EntriesAndTxidsDisjoint({entry2}, {tx2->GetHash()}, unused_txid).has_value());
     BOOST_CHECK(EntriesAndTxidsDisjoint(set_12_normal, {tx1->GetHash()}, unused_txid).has_value());
     BOOST_CHECK(EntriesAndTxidsDisjoint(set_12_normal, {tx2->GetHash()}, unused_txid).has_value());

src/txmempool.cpp

@@ -454,7 +454,7 @@ void CTxMemPool::addUnchecked(const CTxMemPoolEntry &entry, setEntries &setAnces
     cachedInnerUsage += entry.DynamicMemoryUsage();
 
     const CTransaction& tx = newit->GetTx();
-    std::set<uint256> setParentTransactions;
+    std::set<Txid> setParentTransactions;
     for (unsigned int i = 0; i < tx.vin.size(); i++) {
         mapNextTx.insert(std::make_pair(&tx.vin[i].prevout, &tx));
         setParentTransactions.insert(tx.vin[i].prevout.hash);
@@ -969,7 +969,7 @@ std::optional<CTxMemPool::txiter> CTxMemPool::GetIter(const uint256& txid) const
     return std::nullopt;
 }
 
-CTxMemPool::setEntries CTxMemPool::GetIterSet(const std::set<uint256>& hashes) const
+CTxMemPool::setEntries CTxMemPool::GetIterSet(const std::set<Txid>& hashes) const
 {
     CTxMemPool::setEntries ret;
     for (const auto& h : hashes) {

src/txmempool.h

@@ -522,7 +522,7 @@ public:
     /** Translate a set of hashes into a set of pool iterators to avoid repeated lookups.
      * Does not require that all of the hashes correspond to actual transactions in the mempool,
      * only returns the ones that exist. */
-    setEntries GetIterSet(const std::set<uint256>& hashes) const EXCLUSIVE_LOCKS_REQUIRED(cs);
+    setEntries GetIterSet(const std::set<Txid>& hashes) const EXCLUSIVE_LOCKS_REQUIRED(cs);
 
     /** Translate a list of hashes into a list of mempool iterators to avoid repeated lookups.
      * The nth element in txids becomes the nth element in the returned vector. If any of the txids

src/validation.cpp

@@ -582,7 +582,7 @@ private:
     struct Workspace {
         explicit Workspace(const CTransactionRef& ptx) : m_ptx(ptx), m_hash(ptx->GetHash()) {}
         /** Txids of mempool transactions that this transaction directly conflicts with. */
-        std::set<uint256> m_conflicts;
+        std::set<Txid> m_conflicts;
         /** Iterators to mempool entries that this transaction directly conflicts with. */
         CTxMemPool::setEntries m_iters_conflicting;
         /** Iterators to all mempool entries that would be replaced by this transaction, including