Bug 1505891 - Allow XPIDL CEnums to be infallible; r=froydnj

They're just integers, so there's no reason they need to be fallible
since they're basically a built-in anyways.

Differential Revision: https://phabricator.services.mozilla.com/D11363

--HG--
extra : moz-landing-system : lando

xpcom/idl-parser/xpidl/header.py

@@ -414,7 +414,7 @@ def write_interface(iface, fd):
             realtype = a.realtype.nativeType('in')
             tmpl = attr_builtin_infallible_tmpl
 
-            if a.realtype.kind != 'builtin':
+            if a.realtype.kind != 'builtin' and a.realtype.kind != 'cenum':
                 assert realtype.endswith(' *'), "bad infallible type"
                 tmpl = attr_refcnt_infallible_tmpl
                 realtype = realtype[:-2]  # strip trailing pointer

xpcom/idl-parser/xpidl/xpidl.py

@@ -1041,9 +1041,10 @@ class Attribute(object):
         if self.infallible and self.realtype.kind not in ['builtin',
                                                           'interface',
                                                           'forward',
-                                                          'webidl']:
+                                                          'webidl',
+                                                          'cenum']:
             raise IDLError('[infallible] only works on interfaces, domobjects, and builtin types '
-                           '(numbers, booleans, and raw char types)',
+                           '(numbers, booleans, cenum, and raw char types)',
                            self.location)
         if self.infallible and not iface.attributes.builtinclass:
             raise IDLError('[infallible] attributes are only allowed on '