The Hime grammar language reference says that regular expressions are supported and defers to an IEEE standard. In the 7th bullet point in section 9.3.5 RE Bracket Expression, which defined character classes, it says the following:
"The hyphen character shall be treated as itself if it occurs first (after an initial '^', if any) or last in the list, or as an ending range point in a range expression. As examples, the expressions "[-ac]" and "[ac-]" are equivalent and match any of the characters 'a', 'c', or '-'[..]"
In other words, including a hyphen without escaping it is permissible if done at the end. This is also congruent with every standard regex library I've used in C#, Ruby, Perl, PHP, etc.
But when I define a terminal like so:
VARIABLE_NAME -> [A-Za-z0-9-]+;
it does not match 'abc-xyz'. Whereas if I escape the hyphen:
VARIABLE_NAME -> [A-Za-z0-9\-]+;
it matches correctly.
It is not a huge bug but as a silent discrepancy from both specs and common implementations it would be a good thing to not have to look out for.