[Octave-bug-tracker] [bug #58953] Error with 'end' in index expression with nested function calls

[Fernando]

Follow-up Comment #41, bug #58953 (project octave):

We are very close. You have solved two problems:

- Incorrect dispatch for 'end' in cases like obj.data(end). 
- Builtin 'end' ignores arguments when called from user code

There is still a third problem, which I had not provided a test for

- Incorrect dispatch for 'subsref' when used to obtain the object on which
'end' is to be applied.

To show the third problem, I defined the following class, where subsref
transforms obj.data to obj.data_ 


classdef myclass3 < handle
  properties
    data_
  end
  methods
    function obj = myclass3(data)
      obj.data_ = data;
    end
    function r = subsref(obj,S)
      fprintf('-----------------\n')
      S.type
      S.subs
      fprintf('-----------------\n')
      if strcmp(S(1).type,'.') && strcmp(S(1).subs,'data') 
        S(1).subs='data_';
      end
      r = builtin('subsref',obj,S);
    end
    function r = end(obj,k,n)
      fprintf('''end'' called with index=%d of %d\n',k,n);
      r = builtin('end',obj.data,k,n)-1;
    end
  end
end


then in Matlab:


>> obj=myclass3(1:5)
obj = 
  myclass3 with properties:

    data_: [1 2 3 4 5]
>> obj.data(end)
-----------------
ans =
    '.'
ans =
    'data'
-----------------
-----------------
ans =
    '.'
ans =
    '()'
ans =
    'data'
ans =
  1×1 cell array
    {[5]}
-----------------
ans =
     5


and in Octave:


octave:33> obj.data(end)
error: subsref: unknown method or property: data


What is happening is that in order to evaluate 'end', we must first evaluate
'obj.data', which should be done using the custom subsref, not the builtin
subsref.

Sure, I can provide help writing some tests for problems like those three.

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