From e6a9521238a12d8bbee47fcf74dd8db389095bf0 Mon Sep 17 00:00:00 2001
From: Richard Smith <richard-llvm@metafoo.co.uk>
Date: Thu, 5 May 2016 19:16:15 +0000
Subject: [PATCH] Add a FixItHint for the new diagnostic for a non-class-scope
 using-declaration that names a class-scope enumerator.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@268664 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/clang/Basic/DiagnosticSemaKinds.td    |  4 +--
 lib/Sema/SemaDeclCXX.cpp                      | 14 ++++++++++
 .../namespace.udecl/p8-cxx0x.cpp              | 27 +++++++++++++++++++
 3 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index b0b6004ac0..c5bf16ba6d 100644
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -393,8 +393,8 @@ def note_using_decl_constructor_ellipsis : Note<
 def err_using_decl_can_not_refer_to_class_member : Error<
   "using declaration cannot refer to class member">;
 def note_using_decl_class_member_workaround : Note<
-  "use %select{an alias declaration|a typedef declaration|a reference}0 "
-  "instead">;
+  "use %select{an alias declaration|a typedef declaration|a reference|"
+  "a const variable|a constexpr variable}0 instead">;
 def err_using_decl_can_not_refer_to_namespace : Error<
   "using declaration cannot refer to a namespace">;
 def err_using_decl_can_not_refer_to_scoped_enum : Error<
diff --git a/lib/Sema/SemaDeclCXX.cpp b/lib/Sema/SemaDeclCXX.cpp
index f478f0419b..95f10f8ccc 100644
--- a/lib/Sema/SemaDeclCXX.cpp
+++ b/lib/Sema/SemaDeclCXX.cpp
@@ -8421,6 +8421,20 @@ bool Sema::CheckUsingDeclQualifier(SourceLocation UsingLoc,
         Diag(UsingLoc, diag::note_using_decl_class_member_workaround)
           << 2 // reference declaration
           << FixIt;
+      } else if (R.getAsSingle<EnumConstantDecl>()) {
+        // Don't provide a fixit outside C++11 mode; we don't want to suggest
+        // repeating the type of the enumeration here, and we can't do so if
+        // the type is anonymous.
+        FixItHint FixIt;
+        if (getLangOpts().CPlusPlus11) {
+          // Convert 'using X::Y;' to 'auto &Y = X::Y;'.
+          FixIt = FixItHint::CreateReplacement(
+              UsingLoc, "constexpr auto " + NameInfo.getName().getAsString() + " = ");
+        }
+
+        Diag(UsingLoc, diag::note_using_decl_class_member_workaround)
+          << (getLangOpts().CPlusPlus11 ? 4 : 3) // const[expr] variable
+          << FixIt;
       }
       return true;
     }
diff --git a/test/CXX/dcl.dcl/basic.namespace/namespace.udecl/p8-cxx0x.cpp b/test/CXX/dcl.dcl/basic.namespace/namespace.udecl/p8-cxx0x.cpp
index ebe5388d65..6c63f061ab 100644
--- a/test/CXX/dcl.dcl/basic.namespace/namespace.udecl/p8-cxx0x.cpp
+++ b/test/CXX/dcl.dcl/basic.namespace/namespace.udecl/p8-cxx0x.cpp
@@ -7,14 +7,41 @@
 struct X {
   int i;
   static int a;
+  enum E { e };
 };
 
 using X::i; // expected-error{{using declaration cannot refer to class member}}
 using X::s; // expected-error{{using declaration cannot refer to class member}}
+using X::e; // expected-error{{using declaration cannot refer to class member}}
+using X::E::e; // expected-error{{using declaration cannot refer to class member}} expected-warning 0-1{{C++11}}
+#if __cplusplus < 201103L
+// expected-note@-3 {{use a const variable}}
+// expected-note@-3 {{use a const variable}}
+// CXX98-NOT: fix-it:"{{.*}}":{[[@LINE-5]]:
+// CXX98-NOT: fix-it:"{{.*}}":{[[@LINE-5]]:
+#else
+// expected-note@-8 {{use a constexpr variable}}
+// expected-note@-8 {{use a constexpr variable}}
+// CXX11: fix-it:"{{.*}}":{[[@LINE-10]]:1-[[@LINE-10]]:6}:"constexpr auto e = "
+// CXX11: fix-it:"{{.*}}":{[[@LINE-10]]:1-[[@LINE-10]]:6}:"constexpr auto e = "
+#endif
 
 void f() {
   using X::i; // expected-error{{using declaration cannot refer to class member}}
   using X::s; // expected-error{{using declaration cannot refer to class member}}
+  using X::e; // expected-error{{using declaration cannot refer to class member}}
+  using X::E::e; // expected-error{{using declaration cannot refer to class member}} expected-warning 0-1{{C++11}}
+#if __cplusplus < 201103L
+  // expected-note@-3 {{use a const variable}}
+  // expected-note@-3 {{use a const variable}}
+  // CXX98-NOT: fix-it:"{{.*}}":{[[@LINE-5]]:
+  // CXX98-NOT: fix-it:"{{.*}}":{[[@LINE-5]]:
+#else
+  // expected-note@-8 {{use a constexpr variable}}
+  // expected-note@-8 {{use a constexpr variable}}
+  // CXX11: fix-it:"{{.*}}":{[[@LINE-10]]:3-[[@LINE-10]]:8}:"constexpr auto e = "
+  // CXX11: fix-it:"{{.*}}":{[[@LINE-10]]:3-[[@LINE-10]]:8}:"constexpr auto e = "
+#endif
 }
 
 template <typename T>
-- 
2.40.0