qapi: Fix broken discriminator error messages

check_union() checks the discriminator exists in base and makes sense.
Two error messages mention the base.  These are broken for anonymous
bases, as demonstrated by tests flat-union-invalid-discriminator and
flat-union-invalid-if-discriminator.err.  The third one doesn't
bother.

First broken when commit ac4338f8eb "qapi: Allow anonymous base for
flat union" (v2.6.0) neglected to adjust the "not a member of base"
error message.  Commit ccadd6bcba "qapi: Add 'if' to implicit struct
members" (v4.0.0) then cloned the flawed error message.

Dumb them down not to mention the base.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20190914153506.2151-11-armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>

1 files changed, 4 insertions, 5 deletions

diff --git a/scripts/qapi/common.py b/scripts/qapi/common.py
index ef7c7be4fd..a58e904978 100644
--- a/scripts/qapi/common.py
+++ b/scripts/qapi/common.py
@@ -877,14 +877,13 @@ def check_union(expr, info):
         discriminator_value = base_members.get(discriminator)
         if not discriminator_value:
             raise QAPISemError(info,
-                               "Discriminator '%s' is not a member of base "
-                               "struct '%s'"
-                               % (discriminator, base))
+                               "Discriminator '%s' is not a member of 'base'"
+                               % discriminator)
         if discriminator_value.get('if'):
             raise QAPISemError(
                 info,
-                "The discriminator %s.%s for union %s must not be conditional"
-                % (base, discriminator, name))
+                "The discriminator '%s' for union %s must not be conditional"
+                % (discriminator, name))
         enum_define = enum_types.get(discriminator_value['type'])
         # Do not allow string discriminator
         if not enum_define: