parse is currently broken when trying do use an AbstractString whose eltype is not Char, but some other type of AbstractChar.
The issue is that the code has a type assertion ::Tuple{Char,Int} on the calls to iterate, instead of ::Tuple{eltype(s),Int}.
This breaks the Strs.jl package.
I have placed a fix in https://github.com/ScottPJones/julia/tree/spj/fixparse, if somebody can pull that in to julia as a PR.
Thanks!