Return the element representing the setter that results from looking up
setterName in the superclass of this class with respect to the
library, ignoring abstract setters, or
null if the look up
fails. The behavior of this method is defined by the Dart Language
Specification in section 16.15.2:
The result of looking up getter (respectively setter) m in class C with respect to library L is: If C declares an instance getter (respectively setter) named m that is accessible to L, then that getter (respectively setter) is the result of the lookup. Otherwise, if C has a superclass S, then the result of the lookup is the result of looking up getter (respectively setter) m in S with respect to L. Otherwise, we say that the lookup has failed.
PropertyAccessorElement lookUpInheritedConcreteSetter( String setterName, LibraryElement library);