missing_return

This function has a return type of '{0}', but doesn't end with a return statement.

Any function or method that doesn't end with either an explicit return or a throw implicitly returns null. This is rarely the desired behavior. The analyzer produces this diagnostic when it finds an implicit return.

The following code produces this diagnostic because f doesn't end with a return:

int f(int x) {
  if (x < 0) {
    return 0;
  }
}

Add a return statement that makes the return value explicit, even if null is the appropriate value.