Confusing wildcard-related error with Resource Leak Checker

          So most of the problems went away. However, now I can see a weird one:

    [javac] Compiling 1 source file to /home/jlewandowski/dev/cassandra/c18239-static-analysis/build/checkerframework-output
    [javac] /home/jlewandowski/dev/cassandra/c18239-static-analysis/src/java/org/apache/cassandra/utils/IntervalTree.java
    [javac] /home/jlewandowski/dev/cassandra/c18239-static-analysis/src/java/org/apache/cassandra/utils/IntervalTree.java:345: error: [mustcall:bound] incompatible bounds in wildcard
    [javac]                     C min = pointSerializer.deserialize(in);
    [javac]                       ^
    [javac]   type: ?[ extends @MustCall Object super C[ extends @MustCallUnknown Comparable<?> super @MustCallUnknown Void]]
    [javac]   upper bound: @MustCall Object
    [javac]   lower bound: C[ extends @MustCallUnknown Comparable<?[ extends @MustCall Object super C]> super @MustCallUnknown Void]
    [javac] /home/jlewandowski/dev/cassandra/c18239-static-analysis/src/java/org/apache/cassandra/utils/IntervalTree.java:346: error: [mustcall:bound] incompatible bounds in wildcard
    [javac]                     C max = pointSerializer.deserialize(in);
    [javac]                       ^
    [javac]   type: ?[ extends @MustCall Object super C[ extends @MustCallUnknown Comparable<?> super @MustCallUnknown Void]]
    [javac]   upper bound: @MustCall Object
    [javac]   lower bound: C[ extends @MustCallUnknown Comparable<?[ extends @MustCall Object super C]> super @MustCallUnknown Void]
    [javac] 2 errors

That can be reproduced with the following command:

ant cf-only '-Dcf.check.only=**/IntervalTree.java'

on this branch: https://github.com/jacek-lewandowski/cassandra/tree/checker-framework-testing

Originally posted by @jacek-lewandowski in https://github.com/typetools/checker-framework/issues/6077#issuecomment-1640221392

Reproduce the report with ant cf-only '-Dcf.check.only=**/IntervalTree.java' on the checker-framework-testing branch. Start at src/java/org/apache/cassandra/utils/IntervalTree.java, especially lines 345–346, and investigate the Resource Leak Checker’s wildcard-bound errors. Done means the cause is explained and the checker behavior is corrected or clearly resolved.