[java] AvoidReassigningLoopVariables - false negatives within for-loops and skip allowed

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Affects PMD Version: 7.0.0-rc1

Rule: AvoidReassigningLoopVariables

Description:

This rule might not report anymore all reassignments of the control variable in for-loops when the property forReassign is set to skip.

Code Sample demonstrating the issue:

public class Foo {
    void foo(int bar) {
        for (int i=0; i < 10; i++) {
            doSomethingWith(i);
            if (foo()) {
                i++;
                i--;
                ++i;
                --i;
                i += 1;
                i -= 1;
                doSomethingWith(i++);
                i += 2;    // not OK (line 13)
                i -= 2;    // not OK (line 14)
                i &= 1;    // not OK (line 15)
                i |= 1;    // not OK (line 16)
                i *= 1;    // not OK - is not reported anymore (line 17)
                i /= 1;    // not OK - is not reported anymore (line 18)
                i = i + 1; // not OK - is reported with 7.0.0-rc1 (line 19)
                i = i - 1; // not OK - is reported with 7.0.0-rc1 (line 20)
                i = 5;     // not OK - is reported with 7.0.0-rc1 (line 21)
                doSomethingWith(i = 5); // not OK - is reported with 7.0.0-rc1 (line 22)
            }
        }
    }
}

Expected outcome:

PMD should report violations at lines 13 to 22, but only lines 19 to 22 are reported.

More context:

• [doc] Differences in rules in pmd 7 vs pmd 6 #3123
• According to the rule description, only increments/decrements should be allowed in this case. That means ++, -- and += and -=. Multiplication/Division shouldn't be allowed. Also not the bitwise operators (not tested: % modulo, <</>> shift, ^ xor).
• We probably should only allow +/- operators - as that's how increments/decrements work.
• We probably should deny any multiplication/division -> lines 17,18
• We probably should deny any other operators (logical, bitwise) -> lines 15,16
• We probably should allow the longer form of increments/decrements -> lines 19,20. Note: This is then a false positive right now.