We don't have true flexible types in the IR, but we approximate it with
internal type annotations, such as FlexibleNullability,
FlexibleMutability, RawType. These annotations are then handled
specially in JvmIrTypeSystemContext, which can construct a fake flexible
type so that type checker on IR types would behave exactly as on
frontend types.
As shown in KT-63441, one instance of flexible types where flexibility
was lost during conversion to IR is Java array/vararg types. It's
necessary to support it so that IR fake overrides could be constructed
correctly, because IR fake override checker requires parameter types to
be equal. So this change introduces another internal type annotation,
FlexibleArrayElementVariance, which is only applicable to types with
classifier kotlin/Array, and which signifies that the annotated type
`Array<X>` should rather be seen as `Array<X>..Array<out X>`.
#KT-63441 Fixed
#KT-63446 Fixed
This doesn't reduce the quality of tests, because the flags are still
printed for declarations themselves. We only omit them in references.
However, this makes the tests more compatible with non-JVM backends
(see KT-58605), because flags of referenced stdlib declarations may
differ among target platforms.
Pavel Kunyavskiy