This cop checks for invalid character literals with a non-escaped whitespace character (e.g. `? `). However, currently it's unclear whether there's a way to emit this warning without syntax errors.
$ ruby -w p(? ) -:1: warning: invalid character syntax; use ?\s -:1: syntax error, unexpected '?', expecting ')' p(? ) ^
@example
p(? )
Generated with the Darkfish Rdoc Generator 2.