From 3343fad1f1ec81af43674b76eddbe9ab10e344eb Mon Sep 17 00:00:00 2001
From: Richard Smith <richard-llvm@metafoo.co.uk>
Date: Fri, 23 Mar 2012 23:09:08 +0000
Subject: [PATCH] When defining a forward-declared enum, don't try to attach
 the definition to a previous declaration if the redeclaration is invalid.
 That way lies madness. Fixes a crash-on-invalid reported by Abramo.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@153349 91177308-0d34-0410-b5e6-96231b3b80d8
---
 docs/ReleaseNotes.html                     |  1 +
 include/clang/Basic/DiagnosticSemaKinds.td |  2 ++
 lib/Sema/SemaDecl.cpp                      |  5 +++--
 lib/Sema/SemaTemplateInstantiate.cpp       |  3 ++-
 test/SemaCXX/enum-scoped.cpp               | 11 +++++++++++
 www/cxx_status.html                        |  2 +-
 6 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/docs/ReleaseNotes.html b/docs/ReleaseNotes.html
index 628079978e..64c6acb25a 100644
--- a/docs/ReleaseNotes.html
+++ b/docs/ReleaseNotes.html
@@ -125,6 +125,7 @@ following are now considered to be of production quality:
   <li>Generalized initializers</li>
   <li>Unrestricted unions</li>
   <li>User-defined literals</li>
+  <li>Forward-declared enumerations</li>
 </ul>
 
 <!-- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = -->
diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index 36232b1e98..405ae906e5 100644
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -1276,6 +1276,8 @@ def err_enum_class_reference : Error<
   "not 'enum class'">;
 def err_only_enums_have_underlying_types : Error<
   "only enumeration types have underlying types">;
+def err_unscoped_enum_defined_out_of_class : Error<
+  "out-of-line definition of unscoped enumeration member is not supported">;
 
 // C++11 delegating constructors
 def err_delegating_ctor : Error<
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 71f567f47a..68b27ef1f9 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -8260,10 +8260,11 @@ Decl *Sema::ActOnTag(Scope *S, unsigned TagSpec, TagUseKind TUK,
             EnumUnderlyingTy = QualType(T, 0);
 
           // All conflicts with previous declarations are recovered by
-          // returning the previous declaration.
+          // returning the previous declaration, unless this is a definition,
+          // in which case we want the caller to bail out.
           if (CheckEnumRedeclaration(NameLoc.isValid() ? NameLoc : KWLoc,
                                      ScopedEnum, EnumUnderlyingTy, PrevEnum))
-            return PrevTagDecl;
+            return TUK == TUK_Declaration ? PrevTagDecl : 0;
         }
 
         if (!Invalid) {
diff --git a/lib/Sema/SemaTemplateInstantiate.cpp b/lib/Sema/SemaTemplateInstantiate.cpp
index afa65ea9ee..307cccce8b 100644
--- a/lib/Sema/SemaTemplateInstantiate.cpp
+++ b/lib/Sema/SemaTemplateInstantiate.cpp
@@ -1848,7 +1848,8 @@ Sema::InstantiateClass(SourceLocation PointOfInstantiation,
         // specialization causes the implicit instantiation of the definitions
         // of unscoped member enumerations.
         // Record a point of instantiation for this implicit instantiation.
-        if (TSK == TSK_ImplicitInstantiation && !Enum->isScoped()) {
+        if (TSK == TSK_ImplicitInstantiation && !Enum->isScoped() &&
+            Enum->isCompleteDefinition()) {
           MemberSpecializationInfo *MSInfo =Enum->getMemberSpecializationInfo();
           assert(MSInfo && "no spec info for member enum specialization");
           MSInfo->setTemplateSpecializationKind(TSK_ImplicitInstantiation);
diff --git a/test/SemaCXX/enum-scoped.cpp b/test/SemaCXX/enum-scoped.cpp
index 31190bebaa..44394296e3 100644
--- a/test/SemaCXX/enum-scoped.cpp
+++ b/test/SemaCXX/enum-scoped.cpp
@@ -189,3 +189,14 @@ namespace test7 {
   enum class E { e = (struct S*)0 == (struct S*)0 };
   S *p;
 }
+
+namespace test8 {
+  template<typename T> struct S {
+    enum A : int; // expected-note {{here}}
+    enum class B; // expected-note {{here}}
+    enum class C : int; // expected-note {{here}}
+  };
+  template<typename T> enum S<T>::A { a }; // expected-error {{previously declared with fixed underlying type}}
+  template<typename T> enum class S<T>::B : char { b }; // expected-error {{redeclared with different underlying}}
+  template<typename T> enum S<T>::C : int { c }; // expected-error {{previously declared as scoped}}
+}
diff --git a/www/cxx_status.html b/www/cxx_status.html
index 28da5f096b..8305b73ec6 100644
--- a/www/cxx_status.html
+++ b/www/cxx_status.html
@@ -158,7 +158,7 @@ with clang; other versions have not been tested.</p>
       <td>Forward declarations for enums</td>
       <td><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2764.pdf">N2764</a>
       <br><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#1206">DR1206</a></td>
-      <td class="none" align="center">No</td>
+      <td class="svn" align="center">SVN</td>
     </tr>
     <tr>
       <td>Generalized attributes</td>
-- 
2.50.1