[modules] Follow the C++ standard's rule for linkage of enumerators: they have

the linkage of the enumeration. For enumerators of unnamed enumerations, extend
the -Wmodules-ambiguous-internal-linkage extension to allow selecting an
arbitrary enumerator (but only if they all have the same value, otherwise it's
ambiguous).

llvm-svn: 253010

1 files changed, 37 insertions, 22 deletions

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index a23d9debb86..e7c10d18a66 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -1880,7 +1880,8 @@ bool Sema::isIncompatibleTypedef(TypeDecl *Old, TypedefNameDecl *New) {
 /// how to resolve this situation, merging decls or emitting
 /// diagnostics as appropriate. If there was an error, set New to be invalid.
 ///
-void Sema::MergeTypedefNameDecl(TypedefNameDecl *New, LookupResult &OldDecls) {
+void Sema::MergeTypedefNameDecl(Scope *S, TypedefNameDecl *New,
+                                LookupResult &OldDecls) {
   // If the new decl is known invalid already, don't bother doing any
   // merging checks.
   if (New->isInvalidDecl()) return;
@@ -1961,6 +1962,19 @@ void Sema::MergeTypedefNameDecl(TypedefNameDecl *New, LookupResult &OldDecls) {
 
       // Make the old tag definition visible.
       makeMergedDefinitionVisible(Hidden, NewTag->getLocation());
+
+      // If this was an unscoped enumeration, yank all of its enumerators
+      // out of the scope.
+      if (isa<EnumDecl>(NewTag)) {
+        Scope *EnumScope = getNonFieldDeclScope(S);
+        for (auto *D : NewTag->decls()) {
+          auto *ED = cast<EnumConstantDecl>(D);
+          assert(EnumScope->isDeclScope(ED));
+          EnumScope->RemoveDecl(ED);
+          IdResolver.RemoveDecl(ED);
+          ED->getLexicalDeclContext()->removeDecl(ED);
+        }
+      }
     }
   }
 
@@ -5212,7 +5226,7 @@ Sema::ActOnTypedefNameDecl(Scope *S, DeclContext *DC, TypedefNameDecl *NewTD,
   filterNonConflictingPreviousTypedefDecls(*this, NewTD, Previous);
   if (!Previous.empty()) {
     Redeclaration = true;
-    MergeTypedefNameDecl(NewTD, Previous);
+    MergeTypedefNameDecl(S, NewTD, Previous);
   }
 
   // If this is the C FILE type, notify the AST context.
@@ -13994,12 +14008,27 @@ Decl *Sema::ActOnEnumConstant(Scope *S, Decl *theEnumDecl, Decl *lastEnumConst,
     PrevDecl = nullptr;
   }
 
+  // C++ [class.mem]p15:
+  // If T is the name of a class, then each of the following shall have a name 
+  // different from T:
+  // - every enumerator of every member of class T that is an unscoped 
+  // enumerated type
+  if (!TheEnumDecl->isScoped())
+    DiagnoseClassNameShadow(TheEnumDecl->getDeclContext(),
+                            DeclarationNameInfo(Id, IdLoc));
+  
+  EnumConstantDecl *New =
+    CheckEnumConstant(TheEnumDecl, LastEnumConst, IdLoc, Id, Val);
+  if (!New)
+    return nullptr;
+
   if (PrevDecl) {
     // When in C++, we may get a TagDecl with the same name; in this case the
     // enum constant will 'hide' the tag.
     assert((getLangOpts().CPlusPlus || !isa<TagDecl>(PrevDecl)) &&
            "Received TagDecl when not in C++!");
-    if (!isa<TagDecl>(PrevDecl) && isDeclInScope(PrevDecl, CurContext, S)) {
+    if (!isa<TagDecl>(PrevDecl) && isDeclInScope(PrevDecl, CurContext, S) &&
+        shouldLinkPossiblyHiddenDecl(PrevDecl, New)) {
       if (isa<EnumConstantDecl>(PrevDecl))
         Diag(IdLoc, diag::err_redefinition_of_enumerator) << Id;
       else
@@ -14009,26 +14038,12 @@ Decl *Sema::ActOnEnumConstant(Scope *S, Decl *theEnumDecl, Decl *lastEnumConst,
     }
   }
 
-  // C++ [class.mem]p15:
-  // If T is the name of a class, then each of the following shall have a name 
-  // different from T:
-  // - every enumerator of every member of class T that is an unscoped 
-  // enumerated type
-  if (!TheEnumDecl->isScoped())
-    DiagnoseClassNameShadow(TheEnumDecl->getDeclContext(),
-                            DeclarationNameInfo(Id, IdLoc));
-  
-  EnumConstantDecl *New =
-    CheckEnumConstant(TheEnumDecl, LastEnumConst, IdLoc, Id, Val);
-
-  if (New) {
-    // Process attributes.
-    if (Attr) ProcessDeclAttributeList(S, New, Attr);
+  // Process attributes.
+  if (Attr) ProcessDeclAttributeList(S, New, Attr);
 
-    // Register this decl in the current scope stack.
-    New->setAccess(TheEnumDecl->getAccess());
-    PushOnScopeChains(New, S);
-  }
+  // Register this decl in the current scope stack.
+  New->setAccess(TheEnumDecl->getAccess());
+  PushOnScopeChains(New, S);
 
   ActOnDocumentableDecl(New);