Fix FN S2259 (`null-dereference`): when property is called `length`

[saberduck]

We don't detect the issue for S2259 (null-dereference) when property is called length

 var x;
  if (x === undefined) {
      console.log(x.length); // FN
  }

[neoligero]

Hi @saberduck , any update on this? I'd like to add that this issue not only happens with .length, Sonarlint doesn't detect not declared variables either. Example: var x; if (x === undefined) { console.log(x); // FN console.log(asdf); // Should be detected too } This is a big issue for me since we are trying to use this as a standard in the team, but seems to be not possible atm. Thanks.

[ilia-kebets-sonarsource]

For this reproducer:

let x;
  if (x === undefined) {
    x.length; // FN
}

For some reason, isUndefinedOrNull() returns false for x at line 3 when the property is .length, and true when it's anything else. So it breaks the function of the CheckNullDereference() function.