- `REDUNDANT_MODIFIER_FOR_TARGET` is already reported for `open`
interfaces, but for consistency and IDE support, the compiler now
reports `REDUNDANT_MODALITY_MODIFIER` as well via the extended
checker.
- `REDUNDANT_MODIFIER_FOR_TARGET` cannot be disabled for this case
because it's reported via a basic checker while
`REDUNDANT_MODALITY_MODIFIER` is reported via an extended checker.
- Rename `implicitModality` to `redundantModalities` and return a set of
modalities. The idea of a *single* implicit/redundant modality doesn't
stand up to scrutiny. For example, for interfaces with `ABSTRACT`
implicit modality, `OPEN` is also a redundant modifier. But this is
not necessarily the case for all kinds of declarations.
Hypothetically, if it was possible to declare a class that is abstract
by default, adding an `open` modifier to that class would not be
redundant, as it would make the class instantiable.
Ivan Kochurkin