message: globalmeshingheap: don't consider a pair for meshing if either is attached
diff: @@ -326,7 +326,10 @@ protected:
  // FIXME: is it safe to have this function not use internal::allocator?
  auto meshFound = function<void(internal::vector<MiniHeap *> &&)>(
  // std::allocator_arg, internal::allocator,
  - [&](internal::vector<MiniHeap *> &&mesh) { args.mergeSets.push_back(std::move(mesh)); });
  + [&](internal::vector<MiniHeap *> &&mesh) {
  + if (!mesh[0]->isAttached() && !mesh[1]->isAttached())
  + args.mergeSets.push_back(std::move(mesh));
  + });
  for (size_t i = 0; i < NumBins; i++) {
  method::randomSort(_prng, _littleheapCounts[i], _littleheaps[i], meshFound);
  