Simple unions predate flat unions.  Having both complicates the QAPI
schema language and the QAPI generator.  We haven't been using simple
unions in new code for a long time, because they are less flexible and
somewhat awkward on the wire.

To prepare for their removal, convert simple union KeyValue to an
equivalent flat one.  Adds some boilerplate to the schema, which is a
bit ugly, but a lot easier to maintain than the simple union feature.

Cc: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
---
 qapi/ui.json | 30 ++++++++++++++++++++++++++++--
 1 file changed, 28 insertions(+), 2 deletions(-)

diff --git a/qapi/ui.json b/qapi/ui.json
index b2cf7a6759..9e04f9d65d 100644
--- a/qapi/ui.json
+++ b/qapi/ui.json
@@ -824,6 +824,30 @@
             'ac_home', 'ac_back', 'ac_forward', 'ac_refresh', 'ac_bookmarks',
             'lang1', 'lang2' ] }
 
+##
+# @KeyValueKind:
+#
+# Since: 1.3
+##
+{ 'enum': 'KeyValueKind',
+  'data': [ 'number', 'qcode' ] }
+
+##
+# @IntWrapper:
+#
+# Since: 1.3
+##
+{ 'struct': 'IntWrapper',
+  'data': { 'data': 'int' } }
+
+##
+# @QKeyCodeWrapper:
+#
+# Since: 1.3
+##
+{ 'struct': 'QKeyCodeWrapper',
+  'data': { 'data': 'QKeyCode' } }
+
 ##
 # @KeyValue:
 #
@@ -832,9 +856,11 @@
 # Since: 1.3
 ##
 { 'union': 'KeyValue',
+  'base': { 'type': 'KeyValueKind' },
+  'discriminator': 'type',
   'data': {
-    'number': 'int',
-    'qcode': 'QKeyCode' } }
+    'number': 'IntWrapper',
+    'qcode': 'QKeyCodeWrapper' } }
 
 ##
 # @send-key:
-- 
2.31.1