Fix unnecessary casts of copyObject() result

The result is already of the correct type, so these casts don't do
anything.

Reviewed-by: Nathan Bossart <nathandbossart@gmail.com>
Reviewed-by: Tender Wang <tndrwang@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/637eeea8-5663-460b-a114-39572c0f6c6e%40eisentraut.org

src/backend/commands/trigger.c

@@ -1169,7 +1169,7 @@ CreateTriggerFiringOn(CreateTrigStmt *stmt, const char *queryString,
 			 * Initialize our fabricated parse node by copying the original
 			 * one, then resetting fields that we pass separately.
 			 */
-			childStmt = (CreateTrigStmt *) copyObject(stmt);
+			childStmt = copyObject(stmt);
 			childStmt->funcname = NIL;
 			childStmt->whenClause = NULL;
 

src/backend/nodes/nodeFuncs.c

@@ -2996,7 +2996,7 @@ expression_tree_mutator_impl(Node *node,
 		case T_SortGroupClause:
 		case T_CTESearchClause:
 		case T_MergeSupportFunc:
-			return (Node *) copyObject(node);
+			return copyObject(node);
 		case T_WithCheckOption:
 			{
 				WithCheckOption *wco = (WithCheckOption *) node;
@@ -3604,7 +3604,7 @@ expression_tree_mutator_impl(Node *node,
 			break;
 		case T_PartitionPruneStepCombine:
 			/* no expression sub-nodes */
-			return (Node *) copyObject(node);
+			return copyObject(node);
 		case T_JoinExpr:
 			{
 				JoinExpr   *join = (JoinExpr *) node;

src/backend/rewrite/rewriteManip.c

@@ -1715,7 +1715,7 @@ ReplaceVarsFromTargetList_callback(Var *var,
 				break;
 
 			case REPLACEVARS_CHANGE_VARNO:
-				var = (Var *) copyObject(var);
+				var = copyObject(var);
 				var->varno = rcon->nomatch_varno;
 				/* we leave the syntactic referent alone */
 				return (Node *) var;