[-fms-extensions] Permit incomplete types in dynamic exception specifications

Microsoft headers, comdef.h and comutil.h, assume that this is an OK
thing to do.  Downgrade the hard error to a warning if we are in
-fms-extensions mode.

This fixes PR28080.

llvm-svn: 272412

1 files changed, 5 insertions, 1 deletions

diff --git a/clang/test/SemaCXX/ms-exception-spec.cpp b/clang/test/SemaCXX/ms-exception-spec.cpp
index 1be8ec29369..81e04dd54df 100644
--- a/clang/test/SemaCXX/ms-exception-spec.cpp
+++ b/clang/test/SemaCXX/ms-exception-spec.cpp
@@ -1,4 +1,8 @@
 // RUN: %clang_cc1 %s -fsyntax-only -verify -fms-extensions
-// expected-no-diagnostics
 
 void f() throw(...) { }
+
+namespace PR28080 {
+struct S; // expected-note {{forward declaration}}
+void fn() throw(S); // expected-warning {{incomplete type}}
+}