Use the new castNode() macro in a number of places.

This is far from a pervasive conversion, but it's a good starting
point.

Author: Peter Eisentraut, with some minor changes by me
Reviewed-By: Tom Lane
Discussion: https://postgr.es/m/c5d387d9-3440-f5e0-f9d4-71d53b9fbe52@2ndquadrant.com

src/backend/executor/execAmi.c

@@ -403,11 +403,12 @@ ExecSupportsMarkRestore(Path *pathnode)
 			return true;
 
 		case T_CustomScan:
-			Assert(IsA(pathnode, CustomPath));
-			if (((CustomPath *) pathnode)->flags & CUSTOMPATH_SUPPORT_MARK_RESTORE)
+		{
+			CustomPath *customPath = castNode(CustomPath, pathnode);
+			if (customPath->flags & CUSTOMPATH_SUPPORT_MARK_RESTORE)
 				return true;
 			return false;
-
+		}
 		case T_Result:
 
 			/*

src/backend/executor/execQual.c

@@ -4640,10 +4640,9 @@ ExecInitExpr(Expr *node, PlanState *parent)
 				cstate->arg = ExecInitExpr(caseexpr->arg, parent);
 				foreach(l, caseexpr->args)
 				{
-					CaseWhen   *when = (CaseWhen *) lfirst(l);
+					CaseWhen   *when = castNode(CaseWhen, lfirst(l));
 					CaseWhenState *wstate = makeNode(CaseWhenState);
 
-					Assert(IsA(when, CaseWhen));
 					wstate->xprstate.evalfunc = NULL;	/* not used */
 					wstate->xprstate.expr = (Expr *) when;
 					wstate->expr = ExecInitExpr(when->expr, parent);
@@ -5137,9 +5136,8 @@ ExecCleanTargetListLength(List *targetlist)
 
 	foreach(tl, targetlist)
 	{
-		TargetEntry *curTle = (TargetEntry *) lfirst(tl);
+		TargetEntry *curTle = castNode(TargetEntry, lfirst(tl));
 
-		Assert(IsA(curTle, TargetEntry));
 		if (!curTle->resjunk)
 			len++;
 	}

src/backend/executor/execTuples.c

@@ -160,10 +160,7 @@ ExecResetTupleTable(List *tupleTable,	/* tuple table */
 
 	foreach(lc, tupleTable)
 	{
-		TupleTableSlot *slot = (TupleTableSlot *) lfirst(lc);
-
-		/* Sanity checks */
-		Assert(IsA(slot, TupleTableSlot));
+		TupleTableSlot *slot = castNode(TupleTableSlot, lfirst(lc));
 
 		/* Always release resources and reset the slot to empty */
 		ExecClearTuple(slot);

src/backend/executor/functions.c

@@ -479,19 +479,17 @@ init_execution_state(List *queryTree_list,
 
 	foreach(lc1, queryTree_list)
 	{
-		List	   *qtlist = (List *) lfirst(lc1);
+		List	   *qtlist = castNode(List, lfirst(lc1));
 		execution_state *firstes = NULL;
 		execution_state *preves = NULL;
 		ListCell   *lc2;
 
 		foreach(lc2, qtlist)
 		{
-			Query	   *queryTree = (Query *) lfirst(lc2);
+			Query	   *queryTree = castNode(Query, lfirst(lc2));
 			PlannedStmt *stmt;
 			execution_state *newes;
 
-			Assert(IsA(queryTree, Query));
-
 			/* Plan the query if needed */
 			if (queryTree->commandType == CMD_UTILITY)
 			{

src/backend/executor/nodeAgg.c

@@ -2572,9 +2572,8 @@ ExecInitAgg(Agg *node, EState *estate, int eflags)
 
 		if (phase > 0)
 		{
-			aggnode = list_nth(node->chain, phase - 1);
-			sortnode = (Sort *) aggnode->plan.lefttree;
-			Assert(IsA(sortnode, Sort));
+			aggnode = castNode(Agg, list_nth(node->chain, phase - 1));
+			sortnode = castNode(Sort, aggnode->plan.lefttree);
 		}
 		else
 		{
@@ -3010,10 +3009,9 @@ ExecInitAgg(Agg *node, EState *estate, int eflags)
 		 */
 		foreach(arg, pertrans->aggref->args)
 		{
-			TargetEntry *source_tle = (TargetEntry *) lfirst(arg);
+			TargetEntry *source_tle = castNode(TargetEntry, lfirst(arg));
 			TargetEntry *tle;
 
-			Assert(IsA(source_tle, TargetEntry));
 			tle = flatCopyTargetEntry(source_tle);
 			tle->resno += column_offset;
 

src/backend/executor/nodeCtescan.c

@@ -210,7 +210,7 @@ ExecInitCteScan(CteScan *node, EState *estate, int eflags)
 	prmdata = &(estate->es_param_exec_vals[node->cteParam]);
 	Assert(prmdata->execPlan == NULL);
 	Assert(!prmdata->isnull);
-	scanstate->leader = (CteScanState *) DatumGetPointer(prmdata->value);
+	scanstate->leader = castNode(CteScanState, DatumGetPointer(prmdata->value));
 	if (scanstate->leader == NULL)
 	{
 		/* I am the leader */
@@ -223,7 +223,6 @@ ExecInitCteScan(CteScan *node, EState *estate, int eflags)
 	else
 	{
 		/* Not the leader */
-		Assert(IsA(scanstate->leader, CteScanState));
 		/* Create my own read pointer, and ensure it is at start */
 		scanstate->readptr =
 			tuplestore_alloc_read_pointer(scanstate->leader->cte_table,

src/backend/executor/nodeCustom.c

@@ -35,8 +35,8 @@ ExecInitCustomScan(CustomScan *cscan, EState *estate, int eflags)
 	 * methods field correctly at this time.  Other standard fields should be
 	 * set to zero.
 	 */
-	css = (CustomScanState *) cscan->methods->CreateCustomScanState(cscan);
-	Assert(IsA(css, CustomScanState));
+	css = castNode(CustomScanState,
+				   cscan->methods->CreateCustomScanState(cscan));
 
 	/* ensure flags is filled correctly */
 	css->flags = cscan->flags;

src/backend/executor/nodeHashjoin.c

@@ -519,12 +519,9 @@ ExecInitHashJoin(HashJoin *node, EState *estate, int eflags)
 	hoperators = NIL;
 	foreach(l, hjstate->hashclauses)
 	{
-		FuncExprState *fstate = (FuncExprState *) lfirst(l);
-		OpExpr	   *hclause;
+		FuncExprState *fstate = castNode(FuncExprState, lfirst(l));
+		OpExpr	   *hclause = castNode(OpExpr, fstate->xprstate.expr);
 
-		Assert(IsA(fstate, FuncExprState));
-		hclause = (OpExpr *) fstate->xprstate.expr;
-		Assert(IsA(hclause, OpExpr));
 		lclauses = lappend(lclauses, linitial(fstate->args));
 		rclauses = lappend(rclauses, lsecond(fstate->args));
 		hoperators = lappend_oid(hoperators, hclause->opno);

src/backend/executor/nodeLockRows.c

@@ -401,12 +401,10 @@ ExecInitLockRows(LockRows *node, EState *estate, int eflags)
 	epq_arowmarks = NIL;
 	foreach(lc, node->rowMarks)
 	{
-		PlanRowMark *rc = (PlanRowMark *) lfirst(lc);
+		PlanRowMark *rc = castNode(PlanRowMark, lfirst(lc));
 		ExecRowMark *erm;
 		ExecAuxRowMark *aerm;
 
-		Assert(IsA(rc, PlanRowMark));
-
 		/* ignore "parent" rowmarks; they are irrelevant at runtime */
 		if (rc->isParent)
 			continue;

src/backend/executor/nodeModifyTable.c

@@ -1958,11 +1958,9 @@ ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags)
 	 */
 	foreach(l, node->rowMarks)
 	{
-		PlanRowMark *rc = (PlanRowMark *) lfirst(l);
+		PlanRowMark *rc = castNode(PlanRowMark, lfirst(l));
 		ExecRowMark *erm;
 
-		Assert(IsA(rc, PlanRowMark));
-
 		/* ignore "parent" rowmarks; they are irrelevant at runtime */
 		if (rc->isParent)
 			continue;

src/backend/executor/nodeSubplan.c

@@ -808,8 +808,7 @@ ExecInitSubPlan(SubPlan *subplan, PlanState *parent)
 		else if (and_clause((Node *) sstate->testexpr->expr))
 		{
 			/* multiple combining operators */
-			Assert(IsA(sstate->testexpr, BoolExprState));
-			oplist = ((BoolExprState *) sstate->testexpr)->args;
+			oplist = castNode(BoolExprState, sstate->testexpr)->args;
 		}
 		else
 		{
@@ -829,8 +828,8 @@ ExecInitSubPlan(SubPlan *subplan, PlanState *parent)
 		i = 1;
 		foreach(l, oplist)
 		{
-			FuncExprState *fstate = (FuncExprState *) lfirst(l);
-			OpExpr	   *opexpr = (OpExpr *) fstate->xprstate.expr;
+			FuncExprState *fstate = castNode(FuncExprState, lfirst(l));
+			OpExpr	   *opexpr = castNode(OpExpr, fstate->xprstate.expr);
 			ExprState  *exstate;
 			Expr	   *expr;
 			TargetEntry *tle;
@@ -839,8 +838,6 @@ ExecInitSubPlan(SubPlan *subplan, PlanState *parent)
 			Oid			left_hashfn;
 			Oid			right_hashfn;
 
-			Assert(IsA(fstate, FuncExprState));
-			Assert(IsA(opexpr, OpExpr));
 			Assert(list_length(fstate->args) == 2);
 
 			/* Process lefthand argument */
@@ -1218,10 +1215,8 @@ ExecAlternativeSubPlan(AlternativeSubPlanState *node,
 					   bool *isNull)
 {
 	/* Just pass control to the active subplan */
-	SubPlanState *activesp = (SubPlanState *) list_nth(node->subplans,
-													   node->active);
-
-	Assert(IsA(activesp, SubPlanState));
+	SubPlanState *activesp = castNode(SubPlanState,
+									  list_nth(node->subplans, node->active));
 
 	return ExecSubPlan(activesp, econtext, isNull);
 }

src/backend/executor/nodeWorktablescan.c

@@ -95,8 +95,8 @@ ExecWorkTableScan(WorkTableScanState *node)
 		param = &(estate->es_param_exec_vals[plan->wtParam]);
 		Assert(param->execPlan == NULL);
 		Assert(!param->isnull);
-		node->rustate = (RecursiveUnionState *) DatumGetPointer(param->value);
-		Assert(node->rustate && IsA(node->rustate, RecursiveUnionState));
+		node->rustate = castNode(RecursiveUnionState, DatumGetPointer(param->value));
+		Assert(node->rustate);
 
 		/*
 		 * The scan tuple type (ie, the rowtype we expect to find in the work