Symbol#slice is equivalent to sym.to_s.slice, per ruby-doc. Also,
String#slice is an alias of String#[].
Switch to [] as method with slice as alias.
Some tag/untag madness in symbol/slice_tags.txt
untags for Symbol#[]
Merge pull request #702 from tobarja/Symbol#slice

Symbol#slice is equivalent to sym.to_s.slice, per ruby-doc.