Confusing error message matching a non-ASCII string with ASCII-regex
irb(main):001:0> "\u2603".match(/./n) (irb):1: warning: regexp match /.../n against to UTF-8 string => #<MatchData "☃">
I actually had to read the source to discover the intention of this error (partly because I copied the
/n from somewhere without knowing what it meant). Replacing "against to" with just "against" would improve the grammar (full disclosure: English isn't my native language either, I'm open to other suggestions here).