The code assigns an InferiorClasses attribute something other than a cell array of meta.class objects.

Typically, you use this attribute only when you are overloading operators. For more information on overloading operators, see “Implementing Operators for Your Class”.

Assign a cell array of meta.class objects to the InferiorClasses attribute by using class names and the ? operator. For example:

classdef (InferiorClasses = {?class1,?class2}) myClass
   ...
end

See also “Specifying Class Precedence” and metaclass.