The problem here is that we have separate bootstrap compiler and
artifacts (stdlib, for example) that are used in tests and implicitly
participate in them.
For example, this test started to fail when bootstrap compiler was
advanced to a version where pre_release flag is enabled. As a result,
dependent stdlib become pre_release as well and now we have additional
error about `Unit` type
Mikhail Zarechenskiy
8fdc39ecbc