New (?) ObjC SemA regression

I'm pretty sure clang used to be able to -fsyntax-only WebKit.h, but
it certainly can't on the trunk, on Leopard:

CookieJar:Desktop keith$ cat test.m
#import <WebKit/WebKit.h>
CookieJar:Desktop keith$ clang -arch ppc -fsyntax-only test.m
Assertion failed: (0 && "Sema::ActOnField(): Unknown TagDecl"),
function ActOnField, file SemaDecl.cpp, line 1770.
0 clang 0x001f0485
_ZN40_GLOBAL__N_Signals.cpp_00000000_8827448115PrintStackTraceEv + 45
1 clang 0x001f082b
_ZN40_GLOBAL__N_Signals.cpp_00000000_8827448113SignalHandlerEi + 323
2 libSystem.B.dylib 0x92abc97b _sigtramp + 43
3 ??? 0xffffffff 0x0 + 4294967295
4 libSystem.B.dylib 0x92b35782 raise + 26
5 libSystem.B.dylib 0x92b44d3f abort + 73
6 libSystem.B.dylib 0x92b36923 __assert_rtn + 101
7 clang 0x00068675
_ZN5clang4Sema10ActOnFieldEPNS_5ScopeEPvNS_14SourceLocationERNS_10DeclaratorES3_
+ 509
8 clang 0x000cbabf
_ZN5clang6Parser22ParseStructDeclarationEPvRN4llvm15SmallVectorImplIS1_EE
+ 489
9 clang 0x000d33de
_ZN5clang6Parser21ParseObjCPropertyDeclEPvNS_14SourceLocationE + 206
10 clang 0x000d5dd5
_ZN5clang6Parser26ParseObjCInterfaceDeclListEPvNS_3tok15ObjCKeywordKindE
+ 361
11 clang 0x000d67f0
_ZN5clang6Parser31ParseObjCAtInterfaceDeclarationENS_14SourceLocationEPNS_13AttributeListE
+ 948
12 clang 0x000d6bd4
_ZN5clang6Parser21ParseObjCAtDirectivesEv + 224
13 clang 0x000ddbfa
_ZN5clang6Parser24ParseExternalDeclarationEv + 336
14 clang 0x000ddcd7
_ZN5clang6Parser17ParseTopLevelDeclERPv + 61
15 clang 0x00061578
_ZN37_GLOBAL__N__ZN5clang11ASTConsumerD2Ev11ASTStreamer16ReadTopLevelDeclEv
+ 96
16 clang 0x00061736
_ZN5clang8ParseASTERNS_12PreprocessorEjPNS_11ASTConsumerEb + 272
17 clang 0x00021fd2
_ZNSsC1IN9__gnu_cxx17__normal_iteratorIPcSsEEEET_S4_RKSaIcE + 1676
18 clang 0x00023e7e main + 966
19 clang 0x000022ea start + 54
Abort trap
CookieJar:Desktop keith$

The regression is specific to properties (a new feature in ObjC2).

Here is a minimal test case that exposes the bug...

[steve-naroffs-imac:llvm/tools/clang] snaroff% cat web.m

@class WebScriptObject;

@interface DOMObject : WebScriptObject
@end

@interface DOMObject (DOMLinkStyle)
@property(readonly, retain) DOMStyleSheet *sheet;
@end

Thanks,

snaroff