ERROR: syntax error at or near ")" at character 20
-- no such operator
drop operator === (int4);
-ERROR: argument type missing (use NONE for unary operators)
+ERROR: missing argument
+HINT: Use NONE to denote the missing argument of a unary operator.
-- no such operator by that name
drop operator === (int4, int4);
ERROR: operator does not exist: integer === integer
-- no such type1
drop operator = (nonesuch);
-ERROR: argument type missing (use NONE for unary operators)
+ERROR: missing argument
+HINT: Use NONE to denote the missing argument of a unary operator.
-- no such type1
drop operator = ( , int4);
ERROR: syntax error at or near "," at character 19