allow types containing Union{} to be ordered

want to use the sorted part of the type cache as much as possible

src/jltypes.c

@@ -1811,7 +1811,7 @@ JL_DLLEXPORT jl_value_t *jl_tupletype_fill(size_t n, jl_value_t *v)
 
 static int contains_unions(jl_value_t *type)
 {
- if (jl_is_uniontype(type)) return 1;
+ if (jl_is_uniontype(type)) return type != jl_bottom_type;
  if (jl_is_typector(type)) return contains_unions(((jl_typector_t*)type)->body);
  if (!jl_is_datatype(type)) return 0;
  int i;
@@ -1832,7 +1832,8 @@ static int is_typekey_ordered(jl_value_t **key, size_t n)
  if (jl_is_type(k) &&
  !(jl_is_datatype(k) && (((jl_datatype_t*)k)->uid ||
  k == ((jl_datatype_t*)k)->name->primary ||
- (!jl_has_typevars_(k,1) && !contains_unions(k)))))
+ (!jl_has_typevars_(k,1) && !contains_unions(k)))) &&
+ k != jl_bottom_type)
  return 0;
  }
  return 1;