eth/downloader: use intermediate variable for better readability (#17510)

eth/downloader/downloader.go

@@ -658,8 +658,10 @@ func (d *Downloader) findAncestor(p *peerConnection, height uint64) (uint64, err
 					continue
 				}
 				// Otherwise check if we already know the header or not
-				if (d.mode == FullSync && d.blockchain.HasBlock(headers[i].Hash(), headers[i].Number.Uint64())) || (d.mode != FullSync && d.lightchain.HasHeader(headers[i].Hash(), headers[i].Number.Uint64())) {
-					number, hash = headers[i].Number.Uint64(), headers[i].Hash()
+				h := headers[i].Hash()
+				n := headers[i].Number.Uint64()
+				if (d.mode == FullSync && d.blockchain.HasBlock(h, n)) || (d.mode != FullSync && d.lightchain.HasHeader(h, n)) {
+					number, hash = n, h
 
 					// If every header is known, even future ones, the peer straight out lied about its head
 					if number > height && i == limit-1 {
@@ -723,11 +725,13 @@ func (d *Downloader) findAncestor(p *peerConnection, height uint64) (uint64, err
 				arrived = true
 
 				// Modify the search interval based on the response
-				if (d.mode == FullSync && !d.blockchain.HasBlock(headers[0].Hash(), headers[0].Number.Uint64())) || (d.mode != FullSync && !d.lightchain.HasHeader(headers[0].Hash(), headers[0].Number.Uint64())) {
+				h := headers[0].Hash()
+				n := headers[0].Number.Uint64()
+				if (d.mode == FullSync && !d.blockchain.HasBlock(h, n)) || (d.mode != FullSync && !d.lightchain.HasHeader(h, n)) {
 					end = check
 					break
 				}
-				header := d.lightchain.GetHeaderByHash(headers[0].Hash()) // Independent of sync mode, header surely exists
+				header := d.lightchain.GetHeaderByHash(h) // Independent of sync mode, header surely exists
 				if header.Number.Uint64() != check {
 					p.log.Debug("Received non requested header", "number", header.Number, "hash", header.Hash(), "request", check)
 					return 0, errBadPeer