[mempool] simplify some check() logic

No transaction in the mempool should ever be a coinbase.

Since mempoolDuplicate's backend is the chainstate coins view, it should
always contain the coins available.

Author: glozow

src/txmempool.cpp

@@ -704,14 +704,12 @@ void CTxMemPool::check(CChainState& active_chainstate) const
             if (it2 != mapTx.end()) {
                 const CTransaction& tx2 = it2->GetTx();
                 assert(tx2.vout.size() > txin.prevout.n && !tx2.vout[txin.prevout.n].IsNull());
-                // We are iterating through the mempool entries sorted in order by ancestor count.
-                // All parents must have been checked before their children and their coins added to
-                // the mempoolDuplicate coins cache.
-                assert(mempoolDuplicate.HaveCoin(txin.prevout));
                 setParentCheck.insert(*it2);
-            } else {
-                assert(active_coins_tip.HaveCoin(txin.prevout));
             }
+            // We are iterating through the mempool entries sorted in order by ancestor count.
+            // All parents must have been checked before their children and their coins added to
+            // the mempoolDuplicate coins cache.
+            assert(mempoolDuplicate.HaveCoin(txin.prevout));
             // Check whether its inputs are marked in mapNextTx.
             auto it3 = mapNextTx.find(txin.prevout);
             assert(it3 != mapNextTx.end());
@@ -766,8 +764,8 @@ void CTxMemPool::check(CChainState& active_chainstate) const
 
         TxValidationState dummy_state; // Not used. CheckTxInputs() should always pass
         CAmount txfee = 0;
-        bool fCheckResult = tx.IsCoinBase() || Consensus::CheckTxInputs(tx, dummy_state, mempoolDuplicate, spendheight, txfee);
-        assert(fCheckResult);
+        assert(!tx.IsCoinBase());
+        assert(Consensus::CheckTxInputs(tx, dummy_state, mempoolDuplicate, spendheight, txfee));
         for (const auto& input: tx.vin) mempoolDuplicate.SpendCoin(input.prevout);
         AddCoins(mempoolDuplicate, tx, std::numeric_limits<int>::max());
     }