!7 set flag collectionMutex_debug. cmodule2 > DynTestModule { void test { L l = ll(); assertSame("ArrayList", collectionMutex(l), l); new HashMap hmap; assertSame("HashMap", collectionMutex(keySet(hmap)), hmap); NavigableMap map = caseInsensitiveMap(); assertSameVerbose("keySet/caseInsensitiveMap", collectionMutex(keySet(map)), map); assertSameVerbose("navigableKeys/caseInsensitiveMap", collectionMutex(navigableKeys(map)), map); map.put("bla", ""); assertSameVerbose("prefixSubSet/navigableKeys/caseInsensitiveMap", collectionMutex(printClassName(prefixSubSet(navigableKeys(map), "bla"))), map); new WeakHashSet whs; assertSameVerbose(collectionMutex(whs), whs.map); } }