Look through using decls when classifying implicit member access

Clang will now accept this valid C++11 code:
  struct A { int field; };
  struct B : A {
    using A::field;
    enum { TheSize = sizeof(field) };
  };

Previously we would classify the 'field' reference as something other
than a field, and then forget to apply the C++11 rule to allow
non-static data member references in unevaluated contexts.

This usually arises in class templates that want to reference fields of
a dependent base in an unevaluated context outside of an instance
method. Such contexts do not allow references to 'this', so the only way
to access the field is with a using decl and an implicit member
reference.

llvm-svn: 250839

1 files changed, 13 insertions, 0 deletions

diff --git a/clang/test/SemaCXX/using-decl-1.cpp b/clang/test/SemaCXX/using-decl-1.cpp
index ca532692c1c..5afd15f8b50 100644
--- a/clang/test/SemaCXX/using-decl-1.cpp
+++ b/clang/test/SemaCXX/using-decl-1.cpp
@@ -327,3 +327,16 @@ namespace PR24033 {
     using PR24033::st; // expected-error {{target of using declaration conflicts with declaration already in scope}}
   }
 }
+
+namespace field_use {
+struct A { int field; };
+struct B : A {
+  // Previously Clang rejected this valid C++11 code because it didn't look
+  // through the UsingShadowDecl.
+  using A::field;
+#if __cplusplus < 201103L
+  // expected-error@+2 {{invalid use of non-static data member 'field'}}
+#endif
+  enum { X = sizeof(field) };
+};
+}