p2p: remove vestigial READ_STATUS_CHECKBLOCK_FAILED

src/blockencodings.h

@@ -84,8 +84,6 @@ typedef enum ReadStatus_t
     READ_STATUS_OK,
     READ_STATUS_INVALID, // Invalid object, peer is sending bogus crap
     READ_STATUS_FAILED, // Failed to process object
-    READ_STATUS_CHECKBLOCK_FAILED, // Used only by FillBlock to indicate a
-                                   // failure in CheckBlock.
 } ReadStatus;
 
 class CBlockHeaderAndShortTxIDs {

src/net_processing.cpp

@@ -3381,23 +3381,7 @@ void PeerManagerImpl::ProcessCompactBlockTxns(CNode& pfrom, Peer& peer, const Bl
                 return;
             }
         } else {
-            // Block is either okay, or possibly we received
+            // Block is okay for further processing
-            // READ_STATUS_CHECKBLOCK_FAILED.
-            // Note that CheckBlock can only fail for one of a few reasons:
-            // 1. bad-proof-of-work (impossible here, because we've already
-            //    accepted the header)
-            // 2. merkleroot doesn't match the transactions given (already
-            //    caught in FillBlock with READ_STATUS_FAILED, so
-            //    impossible here)
-            // 3. the block is otherwise invalid (eg invalid coinbase,
-            //    block is too big, too many legacy sigops, etc).
-            // So if CheckBlock failed, #3 is the only possibility.
-            // Under BIP 152, we don't discourage the peer unless proof of work is
-            // invalid (we don't require all the stateless checks to have
-            // been run).  This is handled below, so just treat this as
-            // though the block was successfully read, and rely on the
-            // handling in ProcessNewBlock to ensure the block index is
-            // updated, etc.
             RemoveBlockRequest(block_transactions.blockhash, pfrom.GetId()); // it is now an empty pointer
             fBlockRead = true;
             // mapBlockSource is used for potentially punishing peers and

src/test/fuzz/partially_downloaded_block.cpp

@@ -125,7 +125,6 @@ FUZZ_TARGET(partially_downloaded_block, .init = initialize_pdb)
         assert(!fail_block_mutated);
         assert(block->GetHash() == reconstructed_block.GetHash());
         break;
-    case READ_STATUS_CHECKBLOCK_FAILED: [[fallthrough]];
     case READ_STATUS_FAILED:
         assert(fail_block_mutated);
         break;