Avoid creating a RESULT RTE that's marked LATERAL.

Commit 7266d0997 added code to pull up simple constant function
results, converting the RTE_FUNCTION RTE to a dummy RTE_RESULT
RTE since it no longer need be scanned.  But I forgot to clear
the LATERAL flag if the RTE has it set.  If the function reduced
to a constant, it surely contains no lateral references so this
simplification is logically OK.  It's needed because various other
places will Assert that RESULT RTEs aren't LATERAL.

Per bug #17097 from Yaoguang Chen.  Back-patch to v13 where the
faulty code came in.

Discussion: https://postgr.es/m/17097-3372ef9f798fc94f@postgresql.org

src/backend/optimizer/prep/prepjointree.c

@@ -1808,10 +1808,13 @@ pull_up_constant_function(PlannerInfo *root, Node *jtnode,
 
 	/*
 	 * Convert the RTE to be RTE_RESULT type, signifying that we don't need to
-	 * scan it anymore, and zero out RTE_FUNCTION-specific fields.
+	 * scan it anymore, and zero out RTE_FUNCTION-specific fields.  Also make
+	 * sure the RTE is not marked LATERAL, since elsewhere we don't expect
+	 * RTE_RESULTs to be LATERAL.
 	 */
 	rte->rtekind = RTE_RESULT;
 	rte->functions = NIL;
+	rte->lateral = false;
 
 	/*
 	 * We can reuse the RangeTblRef node.

src/test/regress/expected/join.out

@@ -3469,6 +3469,14 @@ select unique1 from tenk1, lateral f_immutable_int4(1) x where x = unique1;
    Index Cond: (unique1 = 1)
 (2 rows)
 
+explain (costs off)
+select unique1 from tenk1, lateral f_immutable_int4(1) x where x in (select 17);
+        QUERY PLAN        
+--------------------------
+ Result
+   One-Time Filter: false
+(2 rows)
+
 explain (costs off)
 select unique1, x from tenk1 join f_immutable_int4(1) x on unique1 = x;
                   QUERY PLAN                  

src/test/regress/sql/join.sql

@@ -1113,6 +1113,9 @@ select unique1 from tenk1, f_immutable_int4(1) x where x = unique1;
 explain (costs off)
 select unique1 from tenk1, lateral f_immutable_int4(1) x where x = unique1;
 
+explain (costs off)
+select unique1 from tenk1, lateral f_immutable_int4(1) x where x in (select 17);
+
 explain (costs off)
 select unique1, x from tenk1 join f_immutable_int4(1) x on unique1 = x;