Please correct me if I'm wrong, but I think `askReload` type-checks all "loaded" units, starting with the ones that are changed (passed to [askReload](https://github.com/scala/scala/blob/master/src/interactive/scala/tools/nsc/interactive/CompilerControl.scala#L114)). So, the only units that need to be passed to `askReload` are the ones that have actual changes since the last call to reload.