Improve formatting of type casts in parentheses.

CHANGELOG

@@ -23,6 +23,7 @@ Bug Fixes
 * Fix parsing error when using square bracket notation (issue583).
 * Fix splitting when using DECLARE ... HANDLER (issue581).
 * Fix splitting of statements using CASE ... WHEN (issue580).
+* Improve formatting of type casts in parentheses.
 
 
 Release 0.3.1 (Feb 29, 2020)

sqlparse/filters/reindent.py

@@ -112,6 +112,8 @@ def _process_parenthesis(self, tlist):
         ttypes = T.Keyword.DML, T.Keyword.DDL
         _, is_dml_dll = tlist.token_next_by(t=ttypes)
         fidx, first = tlist.token_next_by(m=sql.Parenthesis.M_OPEN)
+        if first is None:
+            return
 
         with indent(self, 1 if is_dml_dll else 0):
             tlist.tokens.insert(0, self.nl()) if is_dml_dll else None

tests/test_regressions.py

@@ -399,3 +399,9 @@ def test_issue489_tzcasts():
     p = sqlparse.parse('select bar at time zone \'UTC\' as foo')[0]
     assert p.tokens[-1].has_alias() is True
     assert p.tokens[-1].get_alias() == 'foo'
+
+
+def test_as_in_parentheses_indents():
+    # did raise NoneType has no attribute is_group in _process_parentheses
+    formatted = sqlparse.format('(as foo)', reindent=True)
+    assert formatted == '(as foo)'