Previously, when a candidate was found with an applicability that is
better than the current best applicability, all previous candidates were
thrown away. Now we keep them, unless the new applicability is
successful. If no successful candidates are found, we fully resolve all
the unsuccessful ones and select the ones with the least bad
applicability. This improves diagnostics for unresolved calls.
#KT-57844 Fixed
Previously if an unsafe call is to an overloaded function, FIR checkers
report NONE_APPLICABLE. This change instead report them as UNSAFE_CALL
or its variants.
To do so, inside the root cause of inapplicable candidate errors,
we will record expected/actual type of receiver, if any.
That will help identifying inapplicable calls on nullable receiver.
Nikolay Lunyak