Fixed bug with wrong line numbers in error messages. Some examples refactoring and bug fixes. (0.39.15)

examples/blocking/net/tcp_echo_server.fun

@@ -0,0 +1,33 @@
+#!/usr/bin/env fun
+
+/*
+ * This file is part of the Fun programming language.
+ * https://fun-lang.xyz/
+ *
+ * Copyright 2026 Johannes Findeisen
+ * Licensed under the terms of the Apache-2.0 license.
+ * https://opensource.org/license/apache-2-0
+ *
+ * Added: 2026-03-25
+ */
+
+#include <io/socket.fun>
+
+port = 9090
+srv = TcpServer(port, 10)
+if (srv.listen() <= 0)
+  print("listen failed on :" + to_string(port))
+  return 0
+print("Echo server on :" + to_string(port))
+while true
+  fd = srv.accept()
+  if (fd > 0)
+    msg = sock_recv(fd, 4096)
+    if (len(msg) > 0) sock_send(fd, msg)
+    sock_close(fd)
+
+/* Expected output (on start):
+Echo server on :9090
+
+Then, from another shell: `nc 127.0.0.1 9090` and type "ping" — the server echoes it back.
+*/