"Unused expression" should be reported on unused double colon expressions, this is postponed #KT-12551 Open
In the expression "Runnable::run" we were resolving the left-hand side to the SAM constructor of Runnable. Now we detect this situation, ignore the result of such resolution, and continue resolving the LHS as a type
Tweak member extension detection a little bit to prohibit extensions imported from objects (they don't have one of the receiver parameters)