Fix improper expression aliasing during pushdown

core/trino-main/src/main/java/io/trino/sql/planner/NullabilityAnalyzer.java

@@ -21,6 +21,7 @@
 import io.trino.sql.tree.IfExpression;
 import io.trino.sql.tree.InPredicate;
 import io.trino.sql.tree.NullIfExpression;
+import io.trino.sql.tree.NullLiteral;
 import io.trino.sql.tree.SearchedCaseExpression;
 import io.trino.sql.tree.SimpleCaseExpression;
 import io.trino.sql.tree.SubscriptExpression;
@@ -65,6 +66,7 @@ protected Void visitCast(Cast node, AtomicBoolean result)
             // except for the CAST(NULL AS x) case -- we should fix this at some point)
             //
             // Also, try_cast (i.e., safe cast) can return null
+            process(node.getExpression(), result);
             result.compareAndSet(false, node.isSafe() || !node.isTypeOnly());
             return null;
         }
@@ -132,5 +134,12 @@ protected Void visitFunctionCall(FunctionCall node, AtomicBoolean result)
             result.set(true);
             return null;
         }
+
+        @Override
+        protected Void visitNullLiteral(NullLiteral node, AtomicBoolean result)
+        {
+            result.set(true);
+            return null;
+        }
     }
 }

core/trino-main/src/test/java/io/trino/sql/query/TestJoin.java

@@ -21,6 +21,9 @@
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.TestInstance;
 
+import java.util.List;
+
+import static io.trino.spi.type.VarcharType.VARCHAR;
 import static io.trino.sql.planner.assertions.PlanMatchPattern.aggregation;
 import static io.trino.sql.planner.assertions.PlanMatchPattern.anyTree;
 import static io.trino.sql.planner.assertions.PlanMatchPattern.functionCall;
@@ -111,6 +114,21 @@ FROM t1 JOIN t2 ON (t1.id = t2.id))
                 .matches("VALUES (10, CAST('b' AS varchar(2)))");
     }
 
+    @Test
+    public void testAliasingOfNullCasts()
+    {
+        // Test for https://github.com/trinodb/trino/issues/13565
+        assertThat(assertions.query("""
+                WITH t AS (
+                    SELECT CAST(null AS varchar) AS x, CAST(null AS varchar) AS y
+                    FROM (VALUES 1) t(a) JOIN (VALUES 1) u(a) USING (a))
+                SELECT * FROM t
+                WHERE CAST(x AS bigint) IS NOT NULL AND y = 'hello'
+                """))
+                .hasOutputTypes(List.of(VARCHAR, VARCHAR))
+                .returnsEmptyResult();
+    }
+
     @Test
     public void testInPredicateInJoinCriteria()
     {