This way caller don't need to first check if the symbol is allowed to
override. The current API throws for cases like Java field, or enum
entry, which is not very user-friendly.
Consider the following code:
```
fun test(a: List<String>) {
a.first()
}
```
The dispatch receiver type of `first` in this case is `List<T>` before
this change. After this change, it's `List<String>`.
In addition, this change also replace the dispatch receiver type with
the more specific type if available. For example, consider the following
```
class MyList: ArrayList<String>()
fun test(a: MyList) {
a.get(0)
}
```
The dispatch receiver type of `get` is `MyList`, instead of
`ArrayList<String>`. That is, a fake override is created in this case.
This is useful for quickfixes offering casts. We don't want to offer
user to cast incompatible types.
Also, explicitly allow compare to `Nothing` and handle `Nothing` from intersection
Tianyu Geng