Description Boris 2010-03-11 15:44:21 EST

Build Identifier: 20090619-0625

With this piece of code and "Redundant null check" from the Java Compiler Errors and warnings enabled I get the warning
"instanceof always yields false: The variable str can only be null at this location"

  Object str = null;
  if ((str = "str") instanceof String) {
    System.out.println(str);
  }

However, as you can see, str can never be null at the instanceof-check. In this case it is even the opposite: The instanceof will always be true!


For other classes the conclusion is right, but the reason-message is wrong.

  Object str = null;
  if ((str  = "str") instanceof Number) {
    System.out.println(str);
  }

This also yields the error "instanceof always yields false: The variable str can only be null at this location". It's true that the instanceof will always be false, but its because a String is never an instance of Number and not because str is null.

Reproducible: Always

Steps to Reproduce:
1. enable "Redundant null check"
2. Use the code mentioned above
3.