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/qcow2.c b/block/qcow2.c
index f419860..ea33673 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -3685,7 +3685,6 @@ static int coroutine_fn qcow2_co_create_opts(BlockDriver *drv,
     Visitor *v;
     BlockDriverState *bs = NULL;
     BlockDriverState *data_bs = NULL;
-    Error *local_err = NULL;
     const char *val;
     int ret;
 
@@ -3781,11 +3780,9 @@ static int coroutine_fn qcow2_co_create_opts(BlockDriver *drv,
         goto finish;
     }
 
-    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 finish;
     }