field [fieldname] must be qualified with tablename

Rule "tablename" gives this warning when it finds a filedname that is not qualified with a tablename.

FOR EACH customer :
  DISPLAY cust-num.  /* should be customer.cust-num */
END.
/* typo in variable: should be "name" instead "nane" */
DEFINE VARIABLE nane AS CHARACTER NO-UNDO.
ASSIGN 
   name = "Bill".  /* expect to assign variable, but assigns customer.name instead! */

the risc:

Humans cannot see if "cust-num" is a variable or a database fieldname. Hard to find run-time bugs can result from small typos as illustrated in the example.