Don't always call numArgumentsFromSubscript in classdef susbsref (bug #67403).

* ov-classdef.cc (octave_classdef::subsref): Only call numArgumentsFromSubscript
if nargout<=0 (not an assignment) and the last index type is not '()'. Change
maybe_cs_list_query variable by the condition that last index type is not '()'.
* test/bug-67403/class_bug67403.m: Add class for test.
* test/bug-67403/bug-67403.tst: Add test.
* test/bug-67403/module.mk: Add new files to build system.

Author: Fernando Alvarruiz

libinterp/octave-value/ov-classdef.cc

@@ -489,46 +489,50 @@ octave_classdef::subsref (const std::string& type,
           m_count++;
           args(0) = octave_value (this);
 
-          octave::cdef_method meth_nargout
-            = cls.find_method ("numArgumentsFromSubscript");
-          if (meth_nargout.ok ())
+          if (nargout <= 0) 
             {
-              octave_value_list args_nargout (3);
-
-              args_nargout(0) = args(0);
-              args_nargout(1) = args(1);
-              // FIXME: Third argument should be one of the possible values of
-              //        the matlab.mixin.util.IndexingContext enumeration class.
-              args_nargout(2) = octave_value (Matrix ());
-              retval = meth_nargout.execute (args_nargout, 1, true,
-                                             "numArgumentsFromSubscript");
-
-              nargout = retval(0).strict_int_value
-                ("subsref: return value of 'numArgumentsFromSubscript' must be integer");
-            }
-          else if (nargout <= 0)
-            {
-              // If the number of output arguments is unknown, attempt to set up
-              // a proper value for nargout at least in the simple case where the
-              // cs-list-type expression - i.e., {} or ().x, is the leading one.
-              bool maybe_cs_list_query = (type[0] == '.' || type[0] == '{'
-                                          || (type.length () > 1 && type[0] == '('
-                                              && type[1] == '.'));
-
-              if (maybe_cs_list_query)
+              // If the last index type is not '()', the final value of nargout is
+              // unknown. Try to get its value
+              if (type.back () != '(')
                 {
-                  // Set up a proper nargout for the subsref call by calling numel.
-                  octave_value_list tmp;
-                  int nout;
-                  if (type[0] != '.')
-                    tmp = idx.front ();
-
-                  nout = xnumel (tmp);
-                  // Take nout as nargout for subsref, unless the index expression
-                  // is a whole sentence starting with the form id.member and id is
-                  // one element (in that case, nargout remains 0).
-                  if (type[0] != '.' || nout != 1 || nargout < 0)
-                    nargout = nout;
+                  // See if method numArgumentsFromSubscript is defined
+                  octave::cdef_method meth_nargout
+                    = cls.find_method ("numArgumentsFromSubscript");
+
+                  if (meth_nargout.ok ())
+                    {
+                      octave_value_list args_nargout (3);
+
+                      args_nargout(0) = args(0);
+                      args_nargout(1) = args(1);
+                      // FIXME: Third argument should be one of the possible values of
+                      //        the matlab.mixin.util.IndexingContext enumeration class.
+                      args_nargout(2) = octave_value (Matrix ());
+                      retval = meth_nargout.execute (args_nargout, 1, true,
+                                                    "numArgumentsFromSubscript");
+
+                      nargout = retval(0).strict_int_value
+                        ("subsref: return value of 'numArgumentsFromSubscript' must be integer");
+                    }
+                  else
+                    {
+                      // Method numArgumentsFromSubscript undefined. Attempt to set up
+                      // a proper value for nargout at least in the simple case where the
+                      // cs-list-type expression - i.e., {} or ().x, is the leading one.
+
+                      // Set up a proper nargout for the subsref call by calling numel.
+                      octave_value_list tmp;
+                      int nout;
+                      if (type[0] != '.')
+                        tmp = idx.front ();
+
+                      nout = xnumel (tmp);
+                      // Take nout as nargout for subsref, unless the index expression
+                      // is a whole sentence starting with the form id.member and id is
+                      // one element (in that case, nargout remains 0).
+                      if (type[0] != '.' || nout != 1 || nargout < 0)
+                        nargout = nout;
+                    }
                 }
               else if (nargout < 0)
                 nargout = 1;

test/bug-67403/bug-67403.tst

@@ -0,0 +1,10 @@
+%!test <*67403>
+%! cb = class_bug67403 ();
+%! # Check numArgumentsFromSubscript is not called
+%! [a, b, c] = cb (1);
+%! assert ([a, b, c], [3, 3, 3]);
+%! assert (cb(1:3), 1);
+%! assert (cb{1}.a(1:3), 1);
+%! # Check numArgumentsFromSubscript is called
+%! assert ([cb{1:10}], [2, 2]);
+%! assert ([cb.a], [2, 2]);

test/bug-67403/class_bug67403.m

@@ -0,0 +1,11 @@
+classdef class_bug67403
+  methods
+    function [varargout] = subsref (obj, s)
+      varargout = cell(1, max (nargout, 1));
+      varargout(:) = {nargout};
+    endfunction
+    function n = numArgumentsFromSubscript(obj, s, indexingContext)
+      n = 2;
+    endfunction
+  endmethods
+endclassdef

test/bug-67403/module.mk

@@ -0,0 +1,5 @@
+bug_67403_TEST_FILES = \
+  %reldir%/bug-67403.tst \
+  %reldir%/class_bug67403.m
+
+TEST_FILES += $(bug_67403_TEST_FILES)