I've been trying to use mruby-require with the recent versions of mruby (see iij/mruby-require#29) and have noticed one behavior that seems like an issue with mruby 3.1.0 and above.

When I run mruby-require of the PR linked above with mruby 3.0.0, everything works fine. But when I run it using mruby 3.1.0, a const_missing error is raised complaining that File.exist? cannot be found.

Steps to reproduce:

1. Checkout mruby 3.0 support iij/mruby-require#29.
2. Build mruby with the following configuration:

MRuby::Build.new do |conf|
  conf.toolchain :gcc
  conf.gembox "default"
  conf.gem "mruby-require"
end

3. Run the following script using mruby being built:

print "#{File.file?("/")}\n"
require "/nonexistent"

When I run this script using mruby 3.0.0 being built, the first line emits "false" (because / is a directory), then complains that /nonexistent cannot be loaded. Fine.
But when I run this script using mruby 3.1.0 being built, it raises a const_missing exception here.

Why I think this is a bug of mruby:

While this error is related to mruby-require, I'm reporting it here because I suspect this is a problem of mruby, due to the following reasons:

• the version of mruby-require being used does not have external dependency outside of mrbgems bundled by mruby
• the "gem_init" function of mruby-require just calls mrb_define_method and does nothing else, the problem that we see seems to happen before any logic of mruby-require written in C is being invoked

Therefore, I'm suspecting if there's an issue with the ruby code found in mrbgems having issues with accessing constants defined in other mrbgems.