Try to report most of the errors on the actual members of the impl
class. In many cases, there's a 1:1 mapping of header to impl class
members, so the error "some members are not implemented" on the class
declaration itself is redundant. Exceptions include functions/properties
from supertypes (there may be no other place to report a signature
mismatch error in this case), functions/properties not marked with
'impl' (the checker is only run for declarations explicitly marked with
'impl') and default constructors (the checker is not run for them)
#KT-18447 Fixed
Try to report most mismatch errors on the 'impl' declaration. Only
report a mismatch error on the 'header' declaration if no error would be
otherwise reported on any 'impl' declaration in the compilation unit.
Also render declaration kind in the message
#KT-18447 In Progress
