Use castNode() in a bunch of statement-list-related code.

When I wrote commit ab1f0c82, I really missed the castNode() macro that
Peter E. had proposed shortly before.  This back-fills the uses I would
have put it to.  It's probably not all that significant, but there are
more assertions here than there were before, and conceivably they will
help catch any bugs associated with those representation changes.

I left behind a number of usages like "(Query *) copyObject(query_var)".
Those could have been converted as well, but Peter has proposed another
notational improvement that would handle copyObject cases automatically,
so I let that be for now.

src/backend/catalog/pg_proc.c

@@ -930,7 +930,7 @@ fmgr_sql_validator(PG_FUNCTION_ARGS)
 			querytree_list = NIL;
 			foreach(lc, raw_parsetree_list)
 			{
-				RawStmt    *parsetree = (RawStmt *) lfirst(lc);
+				RawStmt    *parsetree = castNode(RawStmt, lfirst(lc));
 				List	   *querytree_sublist;
 
 				querytree_sublist = pg_analyze_and_rewrite_params(parsetree,

src/backend/commands/createas.c

@@ -322,7 +322,7 @@ ExecCreateTableAs(CreateTableAsStmt *stmt, const char *queryString,
 			elog(ERROR, "unexpected rewrite result for %s",
 				 is_matview ? "CREATE MATERIALIZED VIEW" :
 				 "CREATE TABLE AS SELECT");
-		query = (Query *) linitial(rewritten);
+		query = castNode(Query, linitial(rewritten));
 		Assert(query->commandType == CMD_SELECT);
 
 		/* plan the query --- note we disallow parallelism */

src/backend/commands/explain.c

@@ -224,8 +224,7 @@ ExplainQuery(ParseState *pstate, ExplainStmt *stmt, const char *queryString,
 	 * executed repeatedly.  (See also the same hack in DECLARE CURSOR and
 	 * PREPARE.)  XXX FIXME someday.
 	 */
-	Assert(IsA(stmt->query, Query));
-	rewritten = QueryRewrite((Query *) copyObject(stmt->query));
+	rewritten = QueryRewrite(castNode(Query, copyObject(stmt->query)));
 
 	/* emit opening boilerplate */
 	ExplainBeginOutput(es);
@@ -246,7 +245,7 @@ ExplainQuery(ParseState *pstate, ExplainStmt *stmt, const char *queryString,
 		/* Explain every plan */
 		foreach(l, rewritten)
 		{
-			ExplainOneQuery((Query *) lfirst(l),
+			ExplainOneQuery(castNode(Query, lfirst(l)),
 							CURSOR_OPT_PARALLEL_OK, NULL, es,
 							queryString, params);
 
@@ -395,10 +394,9 @@ ExplainOneUtility(Node *utilityStmt, IntoClause *into, ExplainState *es,
 		CreateTableAsStmt *ctas = (CreateTableAsStmt *) utilityStmt;
 		List	   *rewritten;
 
-		Assert(IsA(ctas->query, Query));
-		rewritten = QueryRewrite((Query *) copyObject(ctas->query));
+		rewritten = QueryRewrite(castNode(Query, copyObject(ctas->query)));
 		Assert(list_length(rewritten) == 1);
-		ExplainOneQuery((Query *) linitial(rewritten),
+		ExplainOneQuery(castNode(Query, linitial(rewritten)),
 						0, ctas->into, es,
 						queryString, params);
 	}
@@ -415,10 +413,9 @@ ExplainOneUtility(Node *utilityStmt, IntoClause *into, ExplainState *es,
 		DeclareCursorStmt *dcs = (DeclareCursorStmt *) utilityStmt;
 		List	   *rewritten;
 
-		Assert(IsA(dcs->query, Query));
-		rewritten = QueryRewrite((Query *) copyObject(dcs->query));
+		rewritten = QueryRewrite(castNode(Query, copyObject(dcs->query)));
 		Assert(list_length(rewritten) == 1);
-		ExplainOneQuery((Query *) linitial(rewritten),
+		ExplainOneQuery(castNode(Query, linitial(rewritten)),
 						dcs->options, NULL, es,
 						queryString, params);
 	}

src/backend/commands/extension.c

@@ -713,7 +713,7 @@ execute_sql_string(const char *sql, const char *filename)
 	 */
 	foreach(lc1, raw_parsetree_list)
 	{
-		RawStmt    *parsetree = (RawStmt *) lfirst(lc1);
+		RawStmt    *parsetree = castNode(RawStmt, lfirst(lc1));
 		List	   *stmt_list;
 		ListCell   *lc2;
 
@@ -725,7 +725,7 @@ execute_sql_string(const char *sql, const char *filename)
 
 		foreach(lc2, stmt_list)
 		{
-			PlannedStmt *stmt = (PlannedStmt *) lfirst(lc2);
+			PlannedStmt *stmt = castNode(PlannedStmt, lfirst(lc2));
 
 			CommandCounterIncrement();
 

src/backend/commands/foreigncmds.c

@@ -1572,7 +1572,7 @@ ImportForeignSchema(ImportForeignSchemaStmt *stmt)
 		 */
 		foreach(lc2, raw_parsetree_list)
 		{
-			RawStmt    *rs = (RawStmt *) lfirst(lc2);
+			RawStmt    *rs = castNode(RawStmt, lfirst(lc2));
 			CreateForeignTableStmt *cstmt = (CreateForeignTableStmt *) rs->stmt;
 			PlannedStmt *pstmt;
 

src/backend/commands/portalcmds.c

@@ -42,14 +42,12 @@ void
 PerformCursorOpen(DeclareCursorStmt *cstmt, ParamListInfo params,
 				  const char *queryString, bool isTopLevel)
 {
-	Query	   *query = (Query *) cstmt->query;
+	Query	   *query = castNode(Query, cstmt->query);
 	List	   *rewritten;
 	PlannedStmt *plan;
 	Portal		portal;
 	MemoryContext oldContext;
 
-	Assert(IsA(query, Query));	/* else parse analysis wasn't done */
-
 	/*
 	 * Disallow empty-string cursor name (conflicts with protocol-level
 	 * unnamed portal).
@@ -85,7 +83,7 @@ PerformCursorOpen(DeclareCursorStmt *cstmt, ParamListInfo params,
 	if (list_length(rewritten) != 1)
 		elog(ERROR, "non-SELECT statement in DECLARE CURSOR");
 
-	query = (Query *) linitial(rewritten);
+	query = castNode(Query, linitial(rewritten));
 
 	if (query->commandType != CMD_SELECT)
 		elog(ERROR, "non-SELECT statement in DECLARE CURSOR");

src/backend/commands/prepare.c

@@ -265,8 +265,7 @@ ExecuteQuery(ExecuteStmt *stmt, IntoClause *intoClause,
 			ereport(ERROR,
 					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
 					 errmsg("prepared statement is not a SELECT")));
-		pstmt = (PlannedStmt *) linitial(plan_list);
-		Assert(IsA(pstmt, PlannedStmt));
+		pstmt = castNode(PlannedStmt, linitial(plan_list));
 		if (pstmt->commandType != CMD_SELECT)
 			ereport(ERROR,
 					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
@@ -670,9 +669,8 @@ ExplainExecuteQuery(ExecuteStmt *execstmt, IntoClause *into, ExplainState *es,
 	/* Explain each query */
 	foreach(p, plan_list)
 	{
-		PlannedStmt *pstmt = (PlannedStmt *) lfirst(p);
+		PlannedStmt *pstmt = castNode(PlannedStmt, lfirst(p));
 
-		Assert(IsA(pstmt, PlannedStmt));
 		if (pstmt->commandType != CMD_UTILITY)
 			ExplainOnePlan(pstmt, into, es, query_string, paramLI, NULL);
 		else

src/backend/commands/tablecmds.c

@@ -9281,7 +9281,7 @@ ATPostAlterTypeParse(Oid oldId, Oid oldRelId, Oid refRelId, char *cmd,
 	querytree_list = NIL;
 	foreach(list_item, raw_parsetree_list)
 	{
-		RawStmt    *rs = (RawStmt *) lfirst(list_item);
+		RawStmt    *rs = castNode(RawStmt, lfirst(list_item));
 		Node	   *stmt = rs->stmt;
 
 		if (IsA(stmt, IndexStmt))

src/backend/executor/functions.c

@@ -707,7 +707,7 @@ init_sql_fcache(FmgrInfo *finfo, Oid collation, bool lazyEvalOK)
 	flat_query_list = NIL;
 	foreach(lc, raw_parsetree_list)
 	{
-		RawStmt    *parsetree = (RawStmt *) lfirst(lc);
+		RawStmt    *parsetree = castNode(RawStmt, lfirst(lc));
 		List	   *queryTree_sublist;
 
 		queryTree_sublist = pg_analyze_and_rewrite_params(parsetree,
@@ -1551,7 +1551,7 @@ check_sql_fn_retval(Oid func_id, Oid rettype, List *queryTreeList,
 	parse = NULL;
 	foreach(lc, queryTreeList)
 	{
-		Query	   *q = (Query *) lfirst(lc);
+		Query	   *q = castNode(Query, lfirst(lc));
 
 		if (q->canSetTag)
 			parse = q;

src/backend/executor/spi.c

@@ -1232,9 +1232,9 @@ SPI_cursor_open_internal(const char *name, SPIPlanPtr plan,
 	if (!(portal->cursorOptions & (CURSOR_OPT_SCROLL | CURSOR_OPT_NO_SCROLL)))
 	{
 		if (list_length(stmt_list) == 1 &&
-		 ((PlannedStmt *) linitial(stmt_list))->commandType != CMD_UTILITY &&
-			((PlannedStmt *) linitial(stmt_list))->rowMarks == NIL &&
-			ExecSupportsBackwardScan(((PlannedStmt *) linitial(stmt_list))->planTree))
+			castNode(PlannedStmt, linitial(stmt_list))->commandType != CMD_UTILITY &&
+			castNode(PlannedStmt, linitial(stmt_list))->rowMarks == NIL &&
+			ExecSupportsBackwardScan(castNode(PlannedStmt, linitial(stmt_list))->planTree))
 			portal->cursorOptions |= CURSOR_OPT_SCROLL;
 		else
 			portal->cursorOptions |= CURSOR_OPT_NO_SCROLL;
@@ -1248,8 +1248,8 @@ SPI_cursor_open_internal(const char *name, SPIPlanPtr plan,
 	if (portal->cursorOptions & CURSOR_OPT_SCROLL)
 	{
 		if (list_length(stmt_list) == 1 &&
-		 ((PlannedStmt *) linitial(stmt_list))->commandType != CMD_UTILITY &&
-			((PlannedStmt *) linitial(stmt_list))->rowMarks != NIL)
+			castNode(PlannedStmt, linitial(stmt_list))->commandType != CMD_UTILITY &&
+			castNode(PlannedStmt, linitial(stmt_list))->rowMarks != NIL)
 			ereport(ERROR,
 					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 					 errmsg("DECLARE SCROLL CURSOR ... FOR UPDATE/SHARE is not supported"),
@@ -1270,7 +1270,7 @@ SPI_cursor_open_internal(const char *name, SPIPlanPtr plan,
 
 		foreach(lc, stmt_list)
 		{
-			PlannedStmt *pstmt = (PlannedStmt *) lfirst(lc);
+			PlannedStmt *pstmt = castNode(PlannedStmt, lfirst(lc));
 
 			if (!CommandIsReadOnly(pstmt))
 			{
@@ -1757,7 +1757,7 @@ _SPI_prepare_plan(const char *src, SPIPlanPtr plan)
 
 	foreach(list_item, raw_parsetree_list)
 	{
-		RawStmt    *parsetree = (RawStmt *) lfirst(list_item);
+		RawStmt    *parsetree = castNode(RawStmt, lfirst(list_item));
 		List	   *stmt_list;
 		CachedPlanSource *plansource;
 
@@ -1859,7 +1859,7 @@ _SPI_prepare_oneshot_plan(const char *src, SPIPlanPtr plan)
 
 	foreach(list_item, raw_parsetree_list)
 	{
-		RawStmt    *parsetree = (RawStmt *) lfirst(list_item);
+		RawStmt    *parsetree = castNode(RawStmt, lfirst(list_item));
 		CachedPlanSource *plansource;
 
 		plansource = CreateOneShotCachedPlan(parsetree,
@@ -2018,7 +2018,7 @@ _SPI_execute_plan(SPIPlanPtr plan, ParamListInfo paramLI,
 
 		foreach(lc2, stmt_list)
 		{
-			PlannedStmt *stmt = (PlannedStmt *) lfirst(lc2);
+			PlannedStmt *stmt = castNode(PlannedStmt, lfirst(lc2));
 			bool		canSetTag = stmt->canSetTag;
 			DestReceiver *dest;
 

src/backend/parser/gram.y

@@ -788,7 +788,7 @@ stmtmulti:	stmtmulti ';' stmt
 					if ($1 != NIL)
 					{
 						/* update length of previous stmt */
-						updateRawStmtEnd((RawStmt *) llast($1), @2);
+						updateRawStmtEnd(castNode(RawStmt, llast($1)), @2);
 					}
 					if ($3 != NULL)
 						$$ = lappend($1, makeRawStmt($3, @2 + 1));

src/backend/parser/parse_expr.c

@@ -1502,8 +1502,7 @@ transformMultiAssignRef(ParseState *pstate, MultiAssignRef *maref)
 			sublink = (SubLink *) transformExprRecurse(pstate,
 													   (Node *) sublink);
 
-			qtree = (Query *) sublink->subselect;
-			Assert(IsA(qtree, Query));
+			qtree = castNode(Query, sublink->subselect);
 
 			/* Check subquery returns required number of columns */
 			if (count_nonjunk_tlist_entries(qtree->targetList) != maref->ncolumns)
@@ -1578,8 +1577,7 @@ transformMultiAssignRef(ParseState *pstate, MultiAssignRef *maref)
 
 		sublink = (SubLink *) tle->expr;
 		Assert(sublink->subLinkType == MULTIEXPR_SUBLINK);
-		qtree = (Query *) sublink->subselect;
-		Assert(IsA(qtree, Query));
+		qtree = castNode(Query, sublink->subselect);
 
 		/* Build a Param representing the current subquery output column */
 		tle = (TargetEntry *) list_nth(qtree->targetList, maref->colno - 1);

src/backend/parser/parse_type.c

@@ -720,7 +720,7 @@ typeStringToTypeName(const char *str)
 	 */
 	if (list_length(raw_parsetree_list) != 1)
 		goto fail;
-	stmt = (SelectStmt *) ((RawStmt *) linitial(raw_parsetree_list))->stmt;
+	stmt = (SelectStmt *) castNode(RawStmt, linitial(raw_parsetree_list))->stmt;
 	if (stmt == NULL ||
 		!IsA(stmt, SelectStmt) ||
 		stmt->distinctClause != NIL ||

src/backend/rewrite/rewriteDefine.c

@@ -173,7 +173,7 @@ InsertRule(char *rulname,
 	if (event_qual != NULL)
 	{
 		/* Find query containing OLD/NEW rtable entries */
-		Query	   *qry = (Query *) linitial(action);
+		Query	   *qry = castNode(Query, linitial(action));
 
 		qry = getInsertSelectQuery(qry, NULL);
 		recordDependencyOnExpr(&myself, event_qual, qry->rtable,
@@ -286,7 +286,7 @@ DefineQueryRewrite(char *rulename,
 	 */
 	foreach(l, action)
 	{
-		query = (Query *) lfirst(l);
+		query = castNode(Query, lfirst(l));
 		if (query->resultRelation == 0)
 			continue;
 		/* Don't be fooled by INSERT/SELECT */
@@ -328,7 +328,7 @@ DefineQueryRewrite(char *rulename,
 		/*
 		 * ... the one action must be a SELECT, ...
 		 */
-		query = (Query *) linitial(action);
+		query = castNode(Query, linitial(action));
 		if (!is_instead ||
 			query->commandType != CMD_SELECT)
 			ereport(ERROR,
@@ -482,7 +482,7 @@ DefineQueryRewrite(char *rulename,
 
 		foreach(l, action)
 		{
-			query = (Query *) lfirst(l);
+			query = castNode(Query, lfirst(l));
 
 			if (!query->returningList)
 				continue;
@@ -813,7 +813,7 @@ setRuleCheckAsUser_Query(Query *qry, Oid userid)
 	{
 		CommonTableExpr *cte = (CommonTableExpr *) lfirst(l);
 
-		setRuleCheckAsUser_Query((Query *) cte->ctequery, userid);
+		setRuleCheckAsUser_Query(castNode(Query, cte->ctequery), userid);
 	}
 
 	/* If there are sublinks, search for them and process their RTEs */

src/backend/tcop/postgres.c

@@ -962,7 +962,7 @@ exec_simple_query(const char *query_string)
 	 */
 	foreach(parsetree_item, parsetree_list)
 	{
-		RawStmt    *parsetree = (RawStmt *) lfirst(parsetree_item);
+		RawStmt    *parsetree = castNode(RawStmt, lfirst(parsetree_item));
 		bool		snapshot_set = false;
 		const char *commandTag;
 		char		completionTag[COMPLETION_TAG_BUFSIZE];
@@ -1286,7 +1286,7 @@ exec_parse_message(const char *query_string,	/* string to execute */
 		bool		snapshot_set = false;
 		int			i;
 
-		raw_parse_tree = (RawStmt *) linitial(parsetree_list);
+		raw_parse_tree = castNode(RawStmt, linitial(parsetree_list));
 
 		/*
 		 * Get the command name for possible use in status display.
@@ -2148,7 +2148,7 @@ errdetail_execute(List *raw_parsetree_list)
 
 	foreach(parsetree_item, raw_parsetree_list)
 	{
-		RawStmt    *parsetree = (RawStmt *) lfirst(parsetree_item);
+		RawStmt    *parsetree = castNode(RawStmt, lfirst(parsetree_item));
 
 		if (IsA(parsetree->stmt, ExecuteStmt))
 		{
@@ -2502,9 +2502,8 @@ IsTransactionExitStmtList(List *pstmts)
 {
 	if (list_length(pstmts) == 1)
 	{
-		PlannedStmt *pstmt = (PlannedStmt *) linitial(pstmts);
+		PlannedStmt *pstmt = castNode(PlannedStmt, linitial(pstmts));
 
-		Assert(IsA(pstmt, PlannedStmt));
 		if (pstmt->commandType == CMD_UTILITY &&
 			IsTransactionExitStmt(pstmt->utilityStmt))
 			return true;
@@ -2518,9 +2517,8 @@ IsTransactionStmtList(List *pstmts)
 {
 	if (list_length(pstmts) == 1)
 	{
-		PlannedStmt *pstmt = (PlannedStmt *) linitial(pstmts);
+		PlannedStmt *pstmt = castNode(PlannedStmt, linitial(pstmts));
 
-		Assert(IsA(pstmt, PlannedStmt));
 		if (pstmt->commandType == CMD_UTILITY &&
 			IsA(pstmt->utilityStmt, TransactionStmt))
 			return true;

src/backend/tcop/pquery.c

@@ -487,7 +487,7 @@ PortalStart(Portal portal, ParamListInfo params,
 				 * Create QueryDesc in portal's context; for the moment, set
 				 * the destination to DestNone.
 				 */
-				queryDesc = CreateQueryDesc((PlannedStmt *) linitial(portal->stmts),
+				queryDesc = CreateQueryDesc(castNode(PlannedStmt, linitial(portal->stmts)),
 											portal->sourceText,
 											GetActiveSnapshot(),
 											InvalidSnapshot,
@@ -1020,7 +1020,7 @@ FillPortalStore(Portal portal, bool isTopLevel)
 			break;
 
 		case PORTAL_UTIL_SELECT:
-			PortalRunUtility(portal, (PlannedStmt *) linitial(portal->stmts),
+			PortalRunUtility(portal, castNode(PlannedStmt, linitial(portal->stmts)),
 							 isTopLevel, true, treceiver, completionTag);
 			break;
 
@@ -1215,7 +1215,7 @@ PortalRunMulti(Portal portal,
 	 */
 	foreach(stmtlist_item, portal->stmts)
 	{
-		PlannedStmt *pstmt = (PlannedStmt *) lfirst(stmtlist_item);
+		PlannedStmt *pstmt = castNode(PlannedStmt, lfirst(stmtlist_item));
 
 		/*
 		 * If we got a cancel signal in prior command, quit

src/backend/tcop/utility.c

@@ -1829,22 +1829,19 @@ UtilityContainsQuery(Node *parsetree)
 	switch (nodeTag(parsetree))
 	{
 		case T_DeclareCursorStmt:
-			qry = (Query *) ((DeclareCursorStmt *) parsetree)->query;
-			Assert(IsA(qry, Query));
+			qry = castNode(Query, ((DeclareCursorStmt *) parsetree)->query);
 			if (qry->commandType == CMD_UTILITY)
 				return UtilityContainsQuery(qry->utilityStmt);
 			return qry;
 
 		case T_ExplainStmt:
-			qry = (Query *) ((ExplainStmt *) parsetree)->query;
-			Assert(IsA(qry, Query));
+			qry = castNode(Query, ((ExplainStmt *) parsetree)->query);
 			if (qry->commandType == CMD_UTILITY)
 				return UtilityContainsQuery(qry->utilityStmt);
 			return qry;
 
 		case T_CreateTableAsStmt:
-			qry = (Query *) ((CreateTableAsStmt *) parsetree)->query;
-			Assert(IsA(qry, Query));
+			qry = castNode(Query, ((CreateTableAsStmt *) parsetree)->query);
 			if (qry->commandType == CMD_UTILITY)
 				return UtilityContainsQuery(qry->utilityStmt);
 			return qry;

src/backend/utils/cache/plancache.c

@@ -975,7 +975,7 @@ BuildCachedPlan(CachedPlanSource *plansource, List *qlist,
 	is_transient = false;
 	foreach(lc, plist)
 	{
-		PlannedStmt *plannedstmt = (PlannedStmt *) lfirst(lc);
+		PlannedStmt *plannedstmt = castNode(PlannedStmt, lfirst(lc));
 
 		if (plannedstmt->commandType == CMD_UTILITY)
 			continue;			/* Ignore utility statements */
@@ -1070,7 +1070,7 @@ cached_plan_cost(CachedPlan *plan, bool include_planner)
 
 	foreach(lc, plan->stmt_list)
 	{
-		PlannedStmt *plannedstmt = (PlannedStmt *) lfirst(lc);
+		PlannedStmt *plannedstmt = castNode(PlannedStmt, lfirst(lc));
 
 		if (plannedstmt->commandType == CMD_UTILITY)
 			continue;			/* Ignore utility statements */
@@ -1457,9 +1457,7 @@ QueryListGetPrimaryStmt(List *stmts)
 
 	foreach(lc, stmts)
 	{
-		Query	   *stmt = (Query *) lfirst(lc);
-
-		Assert(IsA(stmt, Query));
+		Query	   *stmt = castNode(Query, lfirst(lc));
 
 		if (stmt->canSetTag)
 			return stmt;
@@ -1478,12 +1476,10 @@ AcquireExecutorLocks(List *stmt_list, bool acquire)
 
 	foreach(lc1, stmt_list)
 	{
-		PlannedStmt *plannedstmt = (PlannedStmt *) lfirst(lc1);
+		PlannedStmt *plannedstmt = castNode(PlannedStmt, lfirst(lc1));
 		int			rt_index;
 		ListCell   *lc2;
 
-		Assert(IsA(plannedstmt, PlannedStmt));
-
 		if (plannedstmt->commandType == CMD_UTILITY)
 		{
 			/*
@@ -1549,9 +1545,7 @@ AcquirePlannerLocks(List *stmt_list, bool acquire)
 
 	foreach(lc, stmt_list)
 	{
-		Query	   *query = (Query *) lfirst(lc);
-
-		Assert(IsA(query, Query));
+		Query	   *query = castNode(Query, lfirst(lc));
 
 		if (query->commandType == CMD_UTILITY)
 		{
@@ -1618,9 +1612,9 @@ ScanQueryForLocks(Query *parsetree, bool acquire)
 	/* Recurse into subquery-in-WITH */
 	foreach(lc, parsetree->cteList)
 	{
-		CommonTableExpr *cte = (CommonTableExpr *) lfirst(lc);
+		CommonTableExpr *cte = castNode(CommonTableExpr, lfirst(lc));
 
-		ScanQueryForLocks((Query *) cte->ctequery, acquire);
+		ScanQueryForLocks(castNode(Query, cte->ctequery), acquire);
 	}
 
 	/*
@@ -1648,7 +1642,7 @@ ScanQueryWalker(Node *node, bool *acquire)
 		SubLink    *sub = (SubLink *) node;
 
 		/* Do what we came for */
-		ScanQueryForLocks((Query *) sub->subselect, *acquire);
+		ScanQueryForLocks(castNode(Query, sub->subselect), *acquire);
 		/* Fall through to process lefthand args of SubLink */
 	}
 
@@ -1676,8 +1670,7 @@ PlanCacheComputeResultDesc(List *stmt_list)
 	{
 		case PORTAL_ONE_SELECT:
 		case PORTAL_ONE_MOD_WITH:
-			query = (Query *) linitial(stmt_list);
-			Assert(IsA(query, Query));
+			query = castNode(Query, linitial(stmt_list));
 			return ExecCleanTypeFromTL(query->targetList, false);
 
 		case PORTAL_ONE_RETURNING:
@@ -1686,8 +1679,7 @@ PlanCacheComputeResultDesc(List *stmt_list)
 			return ExecCleanTypeFromTL(query->returningList, false);
 
 		case PORTAL_UTIL_SELECT:
-			query = (Query *) linitial(stmt_list);
-			Assert(IsA(query, Query));
+			query = castNode(Query, linitial(stmt_list));
 			Assert(query->utilityStmt);
 			return UtilityTupleDescriptor(query->utilityStmt);
 
@@ -1744,7 +1736,7 @@ PlanCacheRelCallback(Datum arg, Oid relid)
 
 			foreach(lc, plansource->gplan->stmt_list)
 			{
-				PlannedStmt *plannedstmt = (PlannedStmt *) lfirst(lc);
+				PlannedStmt *plannedstmt = castNode(PlannedStmt, lfirst(lc));
 
 				if (plannedstmt->commandType == CMD_UTILITY)
 					continue;	/* Ignore utility statements */
@@ -1817,7 +1809,7 @@ PlanCacheFuncCallback(Datum arg, int cacheid, uint32 hashvalue)
 		{
 			foreach(lc, plansource->gplan->stmt_list)
 			{
-				PlannedStmt *plannedstmt = (PlannedStmt *) lfirst(lc);
+				PlannedStmt *plannedstmt = castNode(PlannedStmt, lfirst(lc));
 				ListCell   *lc3;
 
 				if (plannedstmt->commandType == CMD_UTILITY)
@@ -1890,9 +1882,8 @@ ResetPlanCache(void)
 		 */
 		foreach(lc, plansource->query_list)
 		{
-			Query	   *query = (Query *) lfirst(lc);
+			Query	   *query = castNode(Query, lfirst(lc));
 
-			Assert(IsA(query, Query));
 			if (query->commandType != CMD_UTILITY ||
 				UtilityContainsQuery(query->utilityStmt))
 			{

src/backend/utils/mmgr/portalmem.c

@@ -153,9 +153,7 @@ PortalGetPrimaryStmt(Portal portal)
 
 	foreach(lc, portal->stmts)
 	{
-		PlannedStmt *stmt = (PlannedStmt *) lfirst(lc);
-
-		Assert(IsA(stmt, PlannedStmt));
+		PlannedStmt *stmt = castNode(PlannedStmt, lfirst(lc));
 
 		if (stmt->canSetTag)
 			return stmt;

src/pl/plpgsql/src/pl_exec.c

@@ -3634,9 +3634,8 @@ exec_stmt_execsql(PLpgSQL_execstate *estate,
 
 			foreach(l2, plansource->query_list)
 			{
-				Query	   *q = (Query *) lfirst(l2);
+				Query	   *q = castNode(Query, lfirst(l2));
 
-				Assert(IsA(q, Query));
 				if (q->canSetTag)
 				{
 					if (q->commandType == CMD_INSERT ||
@@ -6825,8 +6824,7 @@ exec_simple_recheck_plan(PLpgSQL_expr *expr, CachedPlan *cplan)
 	 */
 	if (list_length(cplan->stmt_list) != 1)
 		return;
-	stmt = (PlannedStmt *) linitial(cplan->stmt_list);
-	Assert(IsA(stmt, PlannedStmt));
+	stmt = castNode(PlannedStmt, linitial(cplan->stmt_list));
 
 	/*
 	 * 2. It must be a RESULT plan --> no scan's required