$ datafusion-cli
DataFusion CLI v43.0.0
> create table t1(s string);
0 row(s) fetched.
Elapsed 0.003 seconds.

> insert t1 (s) values ('aaa'), ('bbb');
+-------+
| count |
+-------+
| 2     |
+-------+
1 row(s) fetched.
Elapsed 0.002 seconds.

> select * from t1;
+-----+
| s   |
+-----+
| aaa |
| bbb |
+-----+
2 row(s) fetched.
Elapsed 0.001 seconds.

> select case when (NULL and (s = 'aaa')) then 'unreachable!' else null end from t1;
+-------------------------------------------------------------------------------+
| CASE WHEN NULL AND t1.s = Utf8("aaa") THEN Utf8("unreachable!") ELSE NULL END |
+-------------------------------------------------------------------------------+
|                                                                               |
|                                                                               |
+-------------------------------------------------------------------------------+
2 row(s) fetched.
Elapsed 0.002 seconds.

> select case when (NULL and (s = 'aaa')) then s else 'always here!' end from t1;
+-------------------------------------------------------------------------------+
| CASE WHEN NULL AND t1.s = Utf8("aaa") THEN t1.s ELSE Utf8("always here!") END |
+-------------------------------------------------------------------------------+
| always here!                                                                  |
| always here!                                                                  |
+-------------------------------------------------------------------------------+
2 row(s) fetched.
Elapsed 0.001 seconds.

> select case when (NULL and (s = 'aaa')) then s else null end from t1;
+---------------------------------------------------------------+
| CASE WHEN NULL AND t1.s = Utf8("aaa") THEN t1.s ELSE NULL END |
+---------------------------------------------------------------+
| aaa                                                           | <- BUGGY, should be NULL
|                                                               |
+---------------------------------------------------------------+
2 row(s) fetched.
Elapsed 0.001 seconds.

select case when (NULL and (s = 'aaa')) then s else null end from t1;