anchor.diff:        // to be the return type of the combined member signature of said getter
         // in the direct superinterfaces.
         if (overriddenGetters.isNotEmpty && overriddenSetters.isEmpty) {
  -        var combinedGetter = inheritance.combineSignatures(
  -          targetClass: currentClassElement,
  -          candidates: overriddenGetters,
  -          doTopMerge: true,
  -          name: getterName,
  -        );
  -        if (combinedGetter != null) {
  -          var type = combinedGetter.returnType;
  -          type = nonNullifyType(typeSystem, type);
  -          field.type = type;
  -        }
  +        field.type = combinedGetterType();
           return;
         }
   
  
positive.code:         // superinterfaces. If the types are not the same then inference
          // fails with an error.
          if (!field.isFinal) {
            var combinedGetter = inheritance.combineSignatures(
              targetClass: currentClassElement,
              candidates: overriddenGetters,
              doTopMerge: true,
              name: getterName,
            );
            var getterType = combinedGetter?.returnType;
  
            var combinedSetter = inheritance.combineSignatures(
              targetClass: currentClassElement,
              candidates: overriddenSetters,
              doTopMerge: true,
              name: setterName,
            );
            DartType setterType;
            if (combinedSetter != null) {
              setterType = combinedSetter.parameters[0].type;
            }
  
            if (getterType == setterType) {
              var type = getterType ?? _dynamicType;
              type = nonNullifyType(typeSystem, type);
              field.type = type;
            } else {
  
negative.code:       // to be the return type of the combined member signature of said getter
        // in the direct superinterfaces.
        if (overriddenGetters.isNotEmpty && overriddenSetters.isEmpty) {
          parameter.type = combinedGetterType();
          return;
        }
  
  