Parser allows MERGE with mismatched parentheses

The SQL parser allows invalid MERGE statements with mismatched parentheses. For example, the following invalid statement is treated as valid but is missing a trailing ')':

merge into emps as e
using temps as t on e.empno = t.empno
when not matched
then insert (a, b) (values (1, 2);

And the following invalid statement is treated as valid but has an unmatched trailing ')':

merge into emps as e
using temps as t on e.empno = t.empno
when not matched
then insert (a, b) values (1, 2));