[analyzer] Remove custom rule for OSIterator in RetainCountChecker

[george.karpenkov]

Summary

The rule did not make sense and was not tested

[NoQ]

Ok :o

[george.karpenkov]

Actually, I'm reverting this: the rule seems fairly ubiquitous.

clang/lib/StaticAnalyzer/Core/RetainSummaryManager.cpp

static bool isSubclass(const Decl *D,
   DeclarationMatcher SubclassM = cxxRecordDecl(isSameOrDerivedFrom(ClassName));
   return !(match(SubclassM, *D, D->getASTContext()).empty());
 }
 
 static bool isOSObjectSubclass(const Decl *D) {
   return isSubclass(D, "OSObject");
 }
 
-static bool isOSIteratorSubclass(const Decl *D) {
-  return isSubclass(D, "OSIterator");
-}
-
 static bool hasRCAnnotation(const Decl *D, StringRef rcAnnotation) {
   for (const auto *Ann : D->specific_attrs<AnnotateAttr>()) {
     if (Ann->getAnnotation() == rcAnnotation)
       return true;
   }
   return false;
 }
 
RetainSummaryManager::generateSummary(const FunctionDecl *FD,
   if (RetTy->isPointerType()) {
 
     const CXXRecordDecl *PD = RetTy->getPointeeType()->getAsCXXRecordDecl();
     if (TrackOSObjects && PD && isOSObjectSubclass(PD)) {
       if (const IdentifierInfo *II = FD->getIdentifier()) {
 
         // All objects returned with functions starting with "get" are getters.
         if (II->getName().startswith("get")) {
-
-          // ...except for iterators.
-          if (isOSIteratorSubclass(PD))
-            return getOSSummaryCreateRule(FD);
           return getOSSummaryGetRule(FD);
         } else {
           return getOSSummaryCreateRule(FD);
         }
       }
     }
 
     // For CoreFoundation ('CF') types.