It uses the same logic as an old back-end
(see SamType#createByValueParameter and genericSamProjectedOut.kt),
split into two parts:
1. When inserting SAM casts, use SamType#createByValueParamerer to get
the target SAM type.
2. When inserting implicit casts, cast SAM conversions as arguments of
methods of out-projected types to the original type of value parameter
instead of 'Nothing'.
Consider the following example:
Java:
public class J {
public static String foo() { return null; }
}
Kotlin:
fun check(fn: () -> Any) = fn()
fun test() = check { J.foo() }
When a lambda expression returns a value of platform type ('String!'),
corresponding lambda has platform type in its return type, which is
approximated to corresponding nullable type ('String?') in IR.
However, the lambda itself could occur in position with a functional
expected type ('() -> Any'). This implies an extra implicit cast on a
return value of lambda expression ('J.foo()'), although it conforms to
the return type of lambda.
When generating bodies for members implemented by delegation, invoke
corresponding delegate member, not an interface member. Otherwise we
might lose platform-specific nullability information in case of mixed
Kotlin-Java hierarchies, as in
implicitNotNullOnDelegatedImplementation.kt
Here we introduce ONLY_IMPLICIT_RECEIVER tower level
to support extension lambda calls on local variables,
and soften extension receiver checks to make such extensions visible & applicable.
Also here we try to map arguments twice for functional types
Nullability constraints should not be chosen when proper
argument constraints for variables in contravariant position present.
^KT-32106 Fixed
^KT-33166 Fixed
NB here we have use derived class type with type arguments replaced
with star-projections. This emulates JVM erasure (to some degree),
but, unfortunately, that's best we can offer here at the moment.
Since property accessor descriptors (unlike corresponding IR elements)
do not have type parameters, we need to take them from the corresponding
property to ensure the correct IR for delegated property accessors.
Use the same instances from class declaration instead
Otherwise, primary constructor value parameter types when used
in the class body are considered as different from types
based on the class type parameters
See the test genericConstructors.kt, before this commit
"id" call was reported in inapplicable
Normally, the fact that is was Unit was not visible as enum constructors
are lowered to normal class constructors anyway. The exception is when
the arguments are reordered, causing the incorrect return type to leak
into the block that holds temporary variables.
Before this commit, we had two methods to do generally the same synthetic thing.
It's an attempt to keep only one of them.
Accessor symbols are generated in Java use-site member scopes,
at this place we know better whether we are in Java class or not.
However, we have to do this at every use-site level, which is relatively slow.
Also we could encounter problems when accessor function is overridden in Kotlin,
and accessor symbol can still contain reference to Java accessor.
Dmitry Petrov