(dir-rm-parent) begin
(dir-rm-parent) mkdir "a"
(dir-rm-parent) chdir "a"
(dir-rm-parent) mkdir "b"
(dir-rm-parent) chdir "b"
(dir-rm-parent) remove "/b" (must not crash)
(dir-rm-parent) remove "/a" (must not crash)
(dir-rm-parent) end