message: Comment why `deps_of` doesn't need to keep track of `profile_for` in map.
diff: @@ -52,6 +52,12 @@ fn deps_of<'a, 'b, 'cfg>(
  deps: &'b mut HashMap<Unit<'a>, Vec<Unit<'a>>>,
  profile_for: ProfileFor,
  ) -> CargoResult<&'b [Unit<'a>]> {
  + // Currently the `deps` map does not include `profile_for`. This should
  + // be safe for now. `TestDependency` only exists to clear the `panic`
  + // flag, and you'll never ask for a `unit` with `panic` set as a
  + // `TestDependency`. `CustomBuild` should also be fine since if the
  + // requested unit's settings are the same as `Any`, `CustomBuild` can't
  + // affect anything else in the hierarchy.
  if !deps.contains_key(unit) {
  let unit_deps = compute_deps(unit, cx, deps, profile_for)?;
  let to_insert: Vec<_> = unit_deps.iter().map(|&(unit, _)| unit).collect();
  