Refactor boxable value to conditional introduces unexpected side effect

[hjohn]

Given the following program:

public static void main(String[] args) {
  Object s = "Hi";

  Number number;
  if(s instanceof String) {
    number = Long.parseLong("1");
  }
  else {
    number = Double.parseDouble("1");
  }

  System.out.println(number);
}

This prints:

class java.lang.Long = 1

When applying the refactoring to conditional the program becomes:

public static void main(String[] args) {
  Object s = "Hi";

  Number number;
  number = s instanceof String ? Long.parseLong("1") : Double.parseDouble("1");

  System.out.println(number.getClass() + " = " + number);
}

This prints:

class java.lang.Double = 1.0

Expected

I would expect this refactoring to not be available when it changes the results.

Cause

The refactoring doesn't take into account that unboxed values can be implicitly cast (long to double in this case). The conditional s instanceof String ? 1 : 1.0 is always a double, and after boxing would always be Double instead of Long or Double.