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Build ID: I20070625-1500 Steps To Reproduce: 1. In Window->Preferences->Java->Compiler->Errors/Warnings->Unnecessary Code->Redundant null checks, set it to warning/error. 2. Try out this class in Eclipse: public class Test { public static void main(String[] args) { Object foo = randomObject(); //gives null comparison always yields false warning/error below if(!(foo instanceof String) || foo == null) { System.out.println("bar"); } } public static Object randomObject() { if(Math.random() < .5) return new String(); return null; } } 3. Observe the warning/error on the "foo == null" check, stating that foo must be null. This isn't true at all; in fact, an instanceof operation will give false if foo is null. More information:
Reproduced, will investigate.
Revisiting. If foo was null, then foo instanceof String would yield false, !(foo instanceof String) would yield true, and the second member of the || expression would not get evaluated at all. This is reflected by the message, which, for 3.4 M1, states that 'The variable foo cannot be null at that [the comparison] location' (instead of the 'foo must be null' that the bug submitter observed. Checked 3.3.1 again, which has the same behavior. I would contend that our current behavior is correct. Which already was the conclusion of bug 145202, of which this one happens to be a duplicate. *** This bug has been marked as a duplicate of bug 145202 ***
