\fparray_new:Nn
  \g_example_fparray
  { 5 }
\tl_count:N  % error on this line
  \g_example_fparray
\str_count:N  % error on this line
  \g_example_fparray
\seq_count:N  % error on this line
  \g_example_fparray
\clist_count:N  % error on this line
  \g_example_fparray
\prop_count:N  % error on this line
  \g_example_fparray
\intarray_count:N  % error on this line
  \g_example_fparray
\fparray_count:N
  \g_example_fparray

.
