PR13433: In Microsoft mode, don't require function calls within decltype

expressions to have complete return types (or accessible destructors). If the
return type is required to be complete for some other reason (for instance, if
it is needed by overload resolution), then it will still be required to be
complete. This is apparently required in order to parse a MSVC11 header.

llvm-svn: 160924

clang/lib/Sema/SemaExprCXX.cpp

@@ -4783,6 +4783,11 @@ ExprResult Sema::ActOnDecltypeExpression(Expr *E) {
   // Disable the special decltype handling now.
   Rec.IsDecltype = false;
 
+  // In MS mode, don't perform any extra checking of call return types within a
+  // decltype expression.
+  if (getLangOpts().MicrosoftMode)
+    return Owned(E);
+
   // Perform the semantic checks we delayed until this point.
   CallExpr *TopCall = dyn_cast<CallExpr>(E);
   for (unsigned I = 0, N = Rec.DelayedDecltypeCalls.size(); I != N; ++I) {

clang/test/SemaCXX/microsoft-cxx0x.cpp

@@ -1,4 +1,5 @@
 // RUN: %clang_cc1 %s -triple i686-pc-win32 -fsyntax-only -Wc++11-narrowing -Wmicrosoft -verify -fms-extensions -std=c++11
+// RUN: %clang_cc1 %s -triple i686-pc-win32 -fsyntax-only -Wc++11-narrowing -Wmicrosoft -verify -fms-extensions -std=c++11 -fms-compatibility -DMS_COMPAT
 
 
 struct A {
@@ -6,3 +7,16 @@ struct A {
 };
 int b = 3;
 A var = {  b }; // expected-warning {{ cannot be narrowed }} expected-note {{override}}
+
+
+namespace PR13433 {
+  struct S;
+  S make();
+
+  template<typename F> auto x(F f) -> decltype(f(make()));
+#ifndef MS_COMPAT
+// expected-error@-2{{calling 'make' with incomplete return type 'PR13433::S'}}
+// expected-note@-5{{'make' declared here}}
+// expected-note@-7{{forward declaration of 'PR13433::S'}}
+#endif
+}