Improve castNode notation by introducing list-extraction-specific variants.

This extends the castNode() notation introduced by commit 5bcab1114 to
provide, in one step, extraction of a list cell's pointer and coercion to
a concrete node type.  For example, "lfirst_node(Foo, lc)" is the same
as "castNode(Foo, lfirst(lc))".  Almost half of the uses of castNode
that have appeared so far include a list extraction call, so this is
pretty widely useful, and it saves a few more keystrokes compared to the
old way.

As with the previous patch, back-patch the addition of these macros to
pg_list.h, so that the notation will be available when back-patching.

Patch by me, after an idea of Andrew Gierth's.

Discussion: https://postgr.es/m/14197.1491841216@sss.pgh.pa.us

1 files changed, 2 insertions, 2 deletions

diff --git a/src/backend/commands/extension.c b/src/backend/commands/extension.c
index 6be9bc457c2..d371a2a3c15 100644
--- a/src/backend/commands/extension.c
+++ b/src/backend/commands/extension.c
@@ -714,7 +714,7 @@ execute_sql_string(const char *sql, const char *filename)
 	 */
 	foreach(lc1, raw_parsetree_list)
 	{
-		RawStmt    *parsetree = castNode(RawStmt, lfirst(lc1));
+		RawStmt    *parsetree = lfirst_node(RawStmt, lc1);
 		List	   *stmt_list;
 		ListCell   *lc2;
 
@@ -727,7 +727,7 @@ execute_sql_string(const char *sql, const char *filename)
 
 		foreach(lc2, stmt_list)
 		{
-			PlannedStmt *stmt = castNode(PlannedStmt, lfirst(lc2));
+			PlannedStmt *stmt = lfirst_node(PlannedStmt, lc2);
 
 			CommandCounterIncrement();