That issue might be fixed via changing
TypeVariableMarker.shouldBeFlexible at ConeConstraintSystemUtilContext
but this and some other tricks have been added because of incorrect
handling of constraints where type variable has a flexible bound
^KT-51168 Fixed
1. this should've been only done if the language feature for validating
that is disabled;
2. that feature probably won't matter by the time FIR is stable;
3. it only worked because type enhancement of type arguments is broken
anyway - a more correct hack would be to provide a custom
ConeTypePreparator.
Ilya Kirillov