`cargo miri test --features collections` fails

[konsumlamm]

Currently, the CI only runs Miri without any features enabled. When I tried to enable all features, I got an "Undefined Behavior" error, see https://github.com/fitzgen/bumpalo/runs/7022998455?check_suite_focus=true.

[Nick Fitzgerald]

Not sure it is worth fixing this old forked std code. Would probably be better to either

• Update to new forked std code, which presumably has been fixed and runs green under MIRI, or
• wait for custom allocators to stabilize in std and delete the collections submodule.