It's effectively a breaking change (^KT-62558)
K2 assigns flexible type to all static fields (from Java) and, for example,
`String? becomes String unlike K1. It affects IR signature generating.
That's why signature dump is disabled for some tests.
^KT-57811 Fixed
^KT-61786 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.
Ivan Kochurkin