This is needed for two reasons:
1. Before this change companion object appeared in FirRegularClass
twice: in declarations list and in companionObject field. This may
trigger twice transform of it
2. It's very hard to implement generation of companion object by plugins
because if it is part of the tree then generated declaration must be
registered in FirProvider, which is inconsistent with other generated
declarations. Replacing FIR with symbol and removing custom logic of
visiting/transforming companion FIR allows us to just replace companionSymbol
in FirClass if plugin wants to generate it without any additional work
If some java class has multiple supertypes then we need to collect
overriddens from all those types directly, even if superTypeScope
(which is FirTypeIntersectionScope in this case) returns only
one symbol from one of this types (not intersection one)
This is needed to proper enhancement in cases when some type occurs
multiple times in supertypes graph with different nullability
of arguments:
class ConcurrentHashMap<K, V> : AbstractMap<K!, V!>, MutableMap<K, V>
If we try to find method `get(key: K): V` supertype scope returns
`AbstractMap.get(key: K!): V!` (because it actually overrides
`MutableMap(key: K): V?`), but we need to get both symbols to
properly enhance types for `ConcurrentHashMap.remove`
We are going to deprecate `WITH_RUNTIME` directive. The main reason
behind this change is that `WITH_STDLIB` directive better describes
its meaning, specifically it will add kotlin stdlib to test's classpath.
`equals`/`hashCode`/`toString` don't necessarily come from `Any` - they
might be overridden in the abstract class like this:
```kt
abstract class Base {
// reinforces overriding in inheritors
abstract override equals(a: Any?): Boolean
// implementation will be replaced by the generated for data class
override hashCode(): Int = 0
// implementation is final, compiler will not replace it
final override toString(): String = ""
}
```
Custom property accessor has this property set and hence it make sense
for the default accessor to have it too. Also, FE1.0's counterpart
has this bit set and it's returned through the analysis API.
Jinseong Jeon