[CALCITE-5296] In a query with ROLLUP, validator wrongly infers that a column is NOT NULL

core/src/main/java/org/apache/calcite/sql/validate/SqlValidatorImpl.java

@@ -457,9 +457,8 @@ private boolean expandSelectItem(
     selectItems.add(expanded);
     aliases.add(alias);
 
-    if (expanded != null) {
-      inferUnknownTypes(targetType, scope, expanded);
-    }
+    inferUnknownTypes(targetType, selectScope, expanded);
+
     RelDataType type = deriveType(selectScope, expanded);
     // Re-derive SELECT ITEM's data type that may be nullable in AggregatingSelectScope when it
     // appears in advanced grouping elements such as CUBE, ROLLUP , GROUPING SETS.

core/src/test/java/org/apache/calcite/test/SqlValidatorTest.java

@@ -7293,6 +7293,13 @@ public boolean isBangEqualAllowed() {
         + "group by rollup(empno), deptno")
         .ok()
         .type("RecordType(INTEGER NOT NULL DEPTNO, INTEGER EMPNO) NOT NULL");
+
+    // empno becomes NULL because it is rolled up, and so does empno + 1.
+    sql("select empno, empno + 1 as e1\n"
+        + "from emp\n"
+        + "group by rollup(empno)")
+        .ok()
+        .type("RecordType(INTEGER EMPNO, INTEGER E1) NOT NULL");
   }
 
   @Test void testGroupByCorrelatedColumn() {

core/src/test/resources/sql/agg.iq

@@ -566,6 +566,24 @@ having count(*) > 3;
 
 !ok
 
+# ROLLUP column used in expression; see [CALCITE-5296]
+# In a query with ROLLUP, validator wrongly infers that a column is NOT NULL
+select deptno, deptno + 1 as d1 from emp group by rollup(deptno);
++--------+----+
+| DEPTNO | D1 |
++--------+----+
+|     10 | 11 |
+|     20 | 21 |
+|     30 | 31 |
+|     50 | 51 |
+|     60 | 61 |
+|        |    |
+|        |    |
++--------+----+
+(7 rows)
+
+!ok
+
 # CUBE and DISTINCT
 select distinct count(*) from emp group by cube(deptno, gender);
 +--------+