fixup! txscript: Optimize IsPayToPubKey

txscript/standard.go

@@ -108,9 +108,13 @@ func extractCompressedPubKey(script []byte) []byte {
 // passed script if it is a standard pay-to-uncompressed-secp256k1-pubkey
 // script.  It will return nil otherwise.
 func extractUncompressedPubKey(script []byte) []byte {
-	// A pay-to-compressed-pubkey script is of the form:
+	// A pay-to-uncompressed-pubkey script is of the form:
 	//   OP_DATA_65 <65-byte uncompressed pubkey> OP_CHECKSIG
+	//
 	// All non-hybrid uncompressed secp256k1 public keys must start with 0x04.
+	// Hybrid uncompressed secp256k1 public keys start with 0x06 or 0x07:
+	//   - 0x06 => hybrid format for even Y coords
+	//   - 0x07 => hybrid format for odd Y coords
 	if len(script) == 67 &&
 		script[66] == OP_CHECKSIG &&
 		script[0] == OP_DATA_65 &&