Issue #21718 has been updated by byroot (Jean Boussier).
could the error message (and/or documentation) be improved to provide more context?
Yes, I'll work on that. the standard `Check_Type` helper was used, but since it's not clear where the failing type is common from..
I have not tried what would happen if the array returned by instance_variables_to_inspect contained some garbage ...
That has been speced in the original commit. ---------------------------------------- Bug #21718: TypeError:wrong argument type ... (expected Array) https://bugs.ruby-lang.org/issues/21718#change-115341 * Author: vo.x (Vit Ondruch) * Status: Open * ruby -v: ruby 4.0.0dev (2025-11-18 master 85abc59c32) +PRISM [x86_64-linux] * Backport: 3.2: DONTNEED, 3.3: DONTNEED, 3.4: DONTNEED ---------------------------------------- Testing Ruby 4.0 on Fedora, we observe these errors in [MiniMagick](https://github.com/minimagick/minimagick/) ~~~ 1) MiniMagick::Image#composite yields an optional block Failure/Error: yield composite if block_given? TypeError: wrong argument type MiniMagick::Tool (expected Array) # ./lib/mini_magick/image.rb:515:in 'block in MiniMagick::Image#composite' # ./lib/mini_magick/tool.rb:34:in 'MiniMagick::Tool.new' # ./lib/mini_magick.rb:28:in 'block (2 levels) in module:MiniMagick' # ./lib/mini_magick/image.rb:514:in 'MiniMagick::Image#composite' # ./spec/lib/mini_magick/image_spec.rb:609:in 'block (4 levels) in <top (required)>' # ./spec/lib/mini_magick/image_spec.rb:610:in 'block (3 levels) in <top (required)>' ~~~ and [Vagrant](https://github.com/hashicorp/vagrant) / [vagrant-libvirt](https://github.com/vagrant-libvirt/vagrant-libvirt) ~~~ 340) VagrantPlugins::ProviderLibvirt::Util::NetworkUtil #libvirt_networks should retrieve the list of networks Failure/Error: let(:machine) { iso_env.machine(:test, :libvirt) } TypeError: wrong argument type Vagrant::Config::V2::DummyConfig (expected Array) # /usr/share/vagrant/gems/gems/vagrant-2.3.4/plugins/kernel_v2/config/vm.rb:713:in 'Kernel#inspect' # /usr/share/vagrant/gems/gems/vagrant-2.3.4/plugins/kernel_v2/config/vm.rb:713:in 'VagrantPlugins::Kernel_V2::VMConfig#get_provider_config' # /usr/share/vagrant/gems/gems/vagrant-2.3.4/lib/vagrant/vagrantfile.rb:75:in 'Vagrant::Vagrantfile#machine' # /usr/share/vagrant/gems/gems/vagrant-2.3.4/lib/vagrant/environment.rb:740:in 'Vagrant::Environment#machine' # ./spec/support/unit_context.rb:26:in 'block (2 levels) in <top (required)>' # ./spec/support/unit_context.rb:37:in 'block (2 levels) in <top (required)>' # ./spec/support/unit_context.rb:51:in 'block (3 levels) in <top (required)>' # ./spec/support/unit_context.rb:43:in 'block (2 levels) in <top (required)>' # /usr/share/rubygems/rubygems.rb:303:in 'Kernel#load' # /usr/share/rubygems/rubygems.rb:303:in 'Gem.activate_and_load_bin_path' ~~~ Trying to investigate closer the vagrant-libvirt case, I really cannot wrap my head around it, because it fails with innocently looking `result.inspect` [1]. The image_magick fails at `yield composite if block_given?` line, so I suspect that the `yield composite` is the specific place. Since this does not make any sense to me, I have grepped the Ruby source code for: ~~~ $ grep -R -e TypeError | grep "wrong argument type.*Array" ... snip ... prism/extension.c: rb_raise(rb_eTypeError, "wrong argument type %"PRIsVALUE" (expected Array)", rb_obj_class(scopes)); prism/extension.c: rb_raise(rb_eTypeError, "wrong argument type %"PRIsVALUE" (expected Array)", rb_obj_class(locals)); prism/extension.c: rb_raise(rb_eTypeError, "wrong argument type %"PRIsVALUE" (expected Array)", rb_obj_class(names)); ~~~ This seems to come from https://github.com/ruby/prism/commit/21abb6b7c499b41a951eba7c8219c336a656da4... . So is it the reason? Not sure. [1]: https://github.com/hashicorp/vagrant/blob/986a01734f008d62897bb66085381090e4... [2]: https://github.com/minimagick/minimagick/blob/ddcbfe9632667876be10373e1e0125... -- https://bugs.ruby-lang.org/