FIR simply ignores anything after the first comma if the when expression
doesn't have a subject. Hence, the checker has to rely on PSI structure
instead.
This change touches the following diagnostics to make them behave closer
to FE1.0
* SUPER_NOT_AVAILABLE
* SUPER_IS_NOT_AN_EXPRESSION
* INSTANCE_ACCESS_BEFORE_SUPER_CALL
* NOT_A_SUPERTYPE
Other than tweaking the diagnostics, this change also alters resolution
by consider marking `super` with mismatched type parameter as
errorenous. As a result, the following code no longer resolves.
```
class A: B() {
fun test() {
super<String>.length
// ^^^^^^ FIR currently resolves this to `String.length`.
// With this change, `length` becomes unresolved
// instead
}
}
```
Also, now we report `UNRESOLVED_LABEL` on unresolved label on `super`
reference, though FE1.0 reports `UNRESOLVED_REFERENCE`.
All the errors above are reported as ConeDiagnostics and hence some
checkers are deleted.
In addition, it also suppresses more downstream (mostly unresolved)
errors if the receiver has errors. FE1.0 doesn't do it for all the cases
we have here. But it seems nicer to reduce these "redundant" unresolved
errors.
FE1.0 only reports SENSELESS_COMPARISON if one of the operand is `null`.
This change makes FIR reports also in case one of the operand has type
`Nothing?`.
In addition, fix handling of type alias in ConeTypeContext#isNullableType
In order to make resolution still work for members not available from
`Nothing`, we track the type without `Nothing?` and use that for
resolution instead.
As part of this change, we also extend the usage of RealVariable in more
places during DFA. Now mutable properties, property with custom getters,
delegated properties, etc are also treatd as a `RealVariable`. In
general this is needed in order to carry out smartcast computation in
order to report `SMARTCAST_IMPOSSIBLE`. It seems to also have side
effects that improves behavior of some test files.
As part of this change, we also extend the usage of RealVariable in more
places during DFA. Now mutable properties, property with custom getters,
delegated properties, etc are also treatd as a `RealVariable`. In
general this is needed in order to carry out smartcast computation in
order to report `SMARTCAST_IMPOSSIBLE`. It seems to also have side
effects that improves behavior of some test files.
Mikhail Glukhikh