mruby-regexp: fix wrong comments on the String#split override - #7065

Three comments around the String#split override describe mechanisms that are not
there. Comments only; no behavior change.

__split is a Ruby alias, not a C one

mrbgems/mruby-regexp/mrblib/string_regexp.rb says:

  # Regexp-aware split.  Falls back to the C-defined split (aliased as
  # `__split` in mrb_mruby_regexp_gem_init before this override loads) for
  # nil or string patterns, and handles regexp patterns in Ruby.

__split is not installed anywhere in C. mrb_mruby_regexp_gem_init() defines
Regexp and MatchData and their methods only, and never touches String;
nothing under mrbgems/mruby-regexp/src/ mentions __split. The alias is made
in Ruby, at the top of the class body in the same file:

  alias __split split

The fix points the parenthetical there:

  # Regexp-aware split.  Falls back to the C-defined split (aliased as
  # `__split` above) for nil or string patterns, and handles regexp patterns
  # in Ruby.

That is the wording the file already uses for its three other captured methods.
String#[] reads "Falls back to the C-defined [] (aliased as __aref
above)", and String#[]= and String#slice! say the same for __aset and
__slice_bang. Deleting the clause instead would leave split the only one of
the four saying nothing about where its fallback comes from.

The bintest repeats it

mrbgems/mruby-bin-mruby/bintest/mruby.rb makes the same claim about the same
helper, so it is corrected in the same change.

__to_int no longer exists

Inside the override, the limit conversion is explained as:

    # `__to_int` is `mrb_ensure_integer_type()`, which asks the object nothing.

Two things are wrong with the one line. __to_int was bound to
mrb_ensure_int_type(), not mrb_ensure_integer_type(); the two differ on a
BigInt, which the first narrows and the second returns unchanged. And __to_int
is gone: it was removed by the change closing #7014, which replaced the call with
Integer.__ensure(limit). The same comment block already names __ensure five
lines on, so the paragraph contradicted itself. It now reads:

    # `Integer.__ensure` is `mrb_ensure_int_type()`, which asks the object nothing.

Testing

The change touches comments only, so there is nothing to reproduce and no
behavior to compare against CRuby. ruby -c passes on both edited files.

Summary by CodeRabbit

• Documentation

  • Clarified internal comments describing how String#split delegates to its aliased implementation.
  • Documented the integer conversion helper used by String#split.
  • Updated regression test commentary for improved accuracy.

• Bug Fixes

  • No runtime behavior changes.