What does it mean dead code in programming languages(especially in dart)?

Question

I was following the flutter guide(fileio) of voiderealms(youtube) and i had this problem on the function readfile, the editor says that is dead code but i dont know what does it mean

i have tried to search on the web

String readFile(String file) {
  try {
    File f = new File(file);
    return f.readAsStringSync();
  }
  catch(e) {
    print(e.toString());
  }
}


main(List<String> arguments) {
  String path = 'C:/Users/danis/Desktop';
  String txtFile = 'C:/Users/danis/Desktop/test.txt';
  list(path);

  if(readFile(txtFile, 'Hello World\n', FileMode.APPEND));{
    print(readFile(txtFile));
  }
}

Answer 1

Due to the ; after the if the if statement gets seperated from the block ({}), which means that it always gets executed, no matter what the condition says. However that code is not "dead" as it actually gets executed.

What does [...] dead code [/unreachable code] in [a] programming language [mean]?

Dead code is code that is useless, because it will never execute. A function is dead if it is not called anywhere, statements can be dead if they are after a return or throw:

 // 1
 print("alive");
 return;
 print("dead");

 // 2
 if(false) print("dead");

Answer 2

This is a bit of code that will never be executed because it doesn't make sense.

For instance:

if (false) {
  print("Hello World");
}

---

In your case you have such warning because you wrote:

if (something);

Notice the ;, it means that there's nothing to execute within the if.