message: clarify comment on drop glue
diff: @@ -120,8 +120,10 @@ pub enum Function<'tcx> {
  Concrete(FunctionDefinition<'tcx>),
  /// Glue required to call a regular function through a Fn(Mut|Once) trait object
  FnDefAsTraitObject(FunctionDefinition<'tcx>),
  - /// A drop glue function only needs to know the real type, and then miri can extract the
  - /// actual type at runtime.
  + /// A drop glue function only needs to know the real type, and then miri can extract
  + /// that type from a vtable's drop pointer.
  + /// Instead of storing some drop function, we act as if there are no trait objects, by
  + /// mapping trait objects to their real types before acting on them.
  DropGlue(ty::Ty<'tcx>),
  /// Glue required to treat the ptr part of a fat pointer
  /// as a function pointer
  