Program: 61617
Project: 61617
Buggy source:
@Override protected GraphTargetItem checkLoop(LoopItem loopItem,BaseLocalData localData,List<Loop> loops){
  AVM2LocalData aLocalData=(AVM2LocalData)localData;
  if (loopItem instanceof WhileItem) {
    WhileItem w=(WhileItem)loopItem;
    if ((!w.expression.isEmpty()) && (w.expression.get(w.expression.size() - 1) instanceof HasNextAVM2Item)) {
      if (((HasNextAVM2Item)w.expression.get(w.expression.size() - 1)).collection != null) {
        if (((HasNextAVM2Item)w.expression.get(w.expression.size() - 1)).collection.getNotCoerced().getThroughRegister() instanceof FilteredCheckAVM2Item) {
          if (w.commands.size() >= 3) {
            int pos=0;
            while (w.commands.get(pos) instanceof SetLocalAVM2Item) {
              pos++;
            }
            GraphTargetItem ft=w.commands.get(pos);
            if (ft instanceof WithAVM2Item) {
              ft=w.commands.get(pos + 1);
              if (ft instanceof IfItem) {
                IfItem ift=(IfItem)ft;
                if (ift.onTrue.size() > 0) {
                  ft=ift.onTrue.get(0);
                  if (ft instanceof SetPropertyAVM2Item) {
                    SetPropertyAVM2Item spt=(SetPropertyAVM2Item)ft;
                    if (spt.object instanceof LocalRegAVM2Item) {
                      int regIndex=((LocalRegAVM2Item)spt.object).regIndex;
                      HasNextAVM2Item iti=(HasNextAVM2Item)w.expression.get(w.expression.size() - 1);
                      HashMap<Integer,GraphTargetItem> localRegs=aLocalData.localRegs;
                      localRegs.put(regIndex,new FilterAVM2Item(null,iti.collection.getThroughRegister(),ift.expression));
                      return null;
                    }
                  }
                }
              }
            }
          }
        }
 else         if (!w.commands.isEmpty()) {
          if (w.commands.get(0) instanceof SetTypeAVM2Item) {
            SetTypeAVM2Item sti=(SetTypeAVM2Item)w.commands.remove(0);
            GraphTargetItem gti=sti.getValue().getNotCoerced();
            if (gti instanceof NextValueAVM2Item) {
              return new ForEachInAVM2Item(w.src,w.loop,new InAVM2Item(null,sti.getObject(),((HasNextAVM2Item)w.expression.get(w.expression.size() - 1)).collection),w.commands);
            }
 else             if (gti instanceof NextNameAVM2Item) {
              return new ForInAVM2Item(w.src,w.loop,new InAVM2Item(null,sti.getObject(),((HasNextAVM2Item)w.expression.get(w.expression.size() - 1)).collection),w.commands);
            }
          }
        }
      }
    }
  }
  return loopItem;
}

Fixed version (ground truth):
@Override protected GraphTargetItem checkLoop(LoopItem loopItem,BaseLocalData localData,List<Loop> loops){
  AVM2LocalData aLocalData=(AVM2LocalData)localData;
  if (loopItem instanceof WhileItem) {
    WhileItem w=(WhileItem)loopItem;
    if ((!w.expression.isEmpty()) && (w.expression.get(w.expression.size() - 1) instanceof HasNextAVM2Item)) {
      HasNextAVM2Item hn=(HasNextAVM2Item)w.expression.get(w.expression.size() - 1);
      if (((HasNextAVM2Item)w.expression.get(w.expression.size() - 1)).collection != null) {
        if (((HasNextAVM2Item)w.expression.get(w.expression.size() - 1)).collection.getNotCoerced().getThroughRegister() instanceof FilteredCheckAVM2Item) {
          if (w.commands.size() >= 3) {
            int pos=0;
            while (w.commands.get(pos) instanceof SetLocalAVM2Item) {
              pos++;
            }
            GraphTargetItem ft=w.commands.get(pos);
            if (ft instanceof WithAVM2Item) {
              ft=w.commands.get(pos + 1);
              if (ft instanceof IfItem) {
                IfItem ift=(IfItem)ft;
                if (ift.onTrue.size() > 0) {
                  ft=ift.onTrue.get(0);
                  if (ft instanceof SetPropertyAVM2Item) {
                    SetPropertyAVM2Item spt=(SetPropertyAVM2Item)ft;
                    if (spt.object instanceof LocalRegAVM2Item) {
                      int regIndex=((LocalRegAVM2Item)spt.object).regIndex;
                      HasNextAVM2Item iti=(HasNextAVM2Item)w.expression.get(w.expression.size() - 1);
                      HashMap<Integer,GraphTargetItem> localRegs=aLocalData.localRegs;
                      localRegs.put(regIndex,new FilterAVM2Item(null,iti.collection.getThroughRegister(),ift.expression));
                      return null;
                    }
                  }
                }
              }
            }
          }
        }
 else         if (!w.commands.isEmpty()) {
          if (w.commands.get(0) instanceof SetTypeAVM2Item) {
            SetTypeAVM2Item sti=(SetTypeAVM2Item)w.commands.remove(0);
            GraphTargetItem gti=sti.getValue().getNotCoerced();
            if (gti instanceof NextValueAVM2Item) {
              return new ForEachInAVM2Item(w.src,w.loop,new InAVM2Item(hn.instruction,sti.getObject(),((HasNextAVM2Item)w.expression.get(w.expression.size() - 1)).collection),w.commands);
            }
 else             if (gti instanceof NextNameAVM2Item) {
              return new ForInAVM2Item(w.src,w.loop,new InAVM2Item(hn.instruction,sti.getObject(),((HasNextAVM2Item)w.expression.get(w.expression.size() - 1)).collection),w.commands);
            }
          }
        }
      }
    }
  }
  return loopItem;
}