Unit casting ends up with weird spacing

[maranomynet]

  $foo = 100;
  width: ($foo)px;

becomes:

  $foo = 100;
  width: $foo px;

While this is technically still valid Stylus code, it just looks and feels weird/ambiguous.

I'd much prefer the formatter to either leave such (...)em unit casting constructs alone, or enforce the formatting style of including parentheses and the unit tacked tight at the end.