Otherwise behavior might change because enhancement may force computation
for other type parameters in cases like:
class A<X extends Y, Y extends X> {}
See the test:
org.jetbrains.kotlin.checkers.DiagnosticsTestGenerated.Tests.J_k#testRecursiveRawUpperBound3
We have an invariant that their lower bound is always
SomeType<Any?> and their upper bound is SomeType<*>.
Ehancing the latter to SomeType<out Any> making
lower bound not being a subtype of upper bound that breaks contract
for flexible types (fails with exception)
Victor Petukhov