[clang][Parse] Add parsing support for C++ attributes on using-declarations

This is a re-application of dc67299 which was reverted in f63adf5b because
it broke the build. The issue should now be fixed.

Attribution note: The original author of this patch is Erik Pilkington.
I'm only trying to land it after rebasing.

Differential Revision: https://reviews.llvm.org/D91630

1 files changed, 7 insertions, 0 deletions

diff --git a/clang/lib/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp
index fda4275..76d031b 100644
--- a/clang/lib/Parse/ParseDecl.cpp
+++ b/clang/lib/Parse/ParseDecl.cpp
@@ -1650,6 +1650,13 @@ void Parser::ProhibitCXX11Attributes(ParsedAttributesWithRange &Attrs,
   }
 }
 
+void Parser::DiagnoseCXX11AttributeExtension(ParsedAttributesWithRange &Attrs) {
+  for (const ParsedAttr &PA : Attrs) {
+    if (PA.isCXX11Attribute() || PA.isC2xAttribute())
+      Diag(PA.getLoc(), diag::ext_cxx11_attr_placement) << PA << PA.getRange();
+  }
+}
+
 // Usually, `__attribute__((attrib)) class Foo {} var` means that attribute
 // applies to var, not the type Foo.
 // As an exception to the rule, __declspec(align(...)) before the