qapi: Smooth another visitor error checking pattern

Convert

    visit_type_FOO(v, ..., &ptr, &err);
    ...
    if (err) {
        ...
    }

to

    visit_type_FOO(v, ..., &ptr, errp);
    ...
    if (!ptr) {
        ...
    }

for functions that set @ptr to non-null / null on success / error.

Eliminate error_propagate() that are now unnecessary.  Delete @err
that are now unused.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200707160613.848843-40-armbru@redhat.com>

1 files changed, 2 insertions, 5 deletions

diff --git a/block/qcow.c b/block/qcow.c
index dca2a1fe7d..c22d1bf6b8 100644
--- a/block/qcow.c
+++ b/block/qcow.c
@@ -943,7 +943,6 @@ static int coroutine_fn qcow_co_create_opts(BlockDriver *drv,
     QDict *qdict;
     Visitor *v;
     const char *val;
-    Error *local_err = NULL;
     int ret;
 
     static const QDictRenames opt_renames[] = {
@@ -995,11 +994,9 @@ static int coroutine_fn qcow_co_create_opts(BlockDriver *drv,
         goto fail;
     }
 
-    visit_type_BlockdevCreateOptions(v, NULL, &create_options, &local_err);
+    visit_type_BlockdevCreateOptions(v, NULL, &create_options, errp);
     visit_free(v);
-
-    if (local_err) {
-        error_propagate(errp, local_err);
+    if (!create_options) {
         ret = -EINVAL;
         goto fail;
     }