When merging redeclaration chains across modules, if a declaration is visible

in one module but is only declared as a friend in another module, keep it
visible in the result of the merge.

This is incomplete on two axes:

1) Our handling of local extern declarations is basically broken (we put them
in the wrong decl context, and don't find them in redeclaration lookup, unless
they've previously been declared), and this results in them making friends
visible after a merge.

2) Eventually we'll need to mark that this has happened, and more carefully
check whether a declaration should be visible if it was only visible in some
of the modules in which it was declared. Fortunately it's rare for the
identifier namespace of a declaration to change along its redeclaration chain.

llvm-svn: 187639

1 files changed, 12 insertions, 6 deletions

diff --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
index 99d6eaa3a03..122865b4686 100644
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -2003,6 +2003,17 @@ void ASTDeclReader::attachPreviousDecl(Decl *D, Decl *previous) {
     RedeclarableTemplateDecl *TD = cast<RedeclarableTemplateDecl>(D);
     TD->RedeclLink.setNext(cast<RedeclarableTemplateDecl>(previous));
   }
+
+  // If the declaration was visible in one module, a redeclaration of it in
+  // another module remains visible even if it wouldn't be visible by itself.
+  //
+  // FIXME: In this case, the declaration should only be visible if a module
+  //        that makes it visible has been imported.
+  // FIXME: This is not correct in the case where previous is a local extern
+  //        declaration and D is a friend declaraton.
+  D->IdentifierNamespace |=
+      previous->IdentifierNamespace &
+      (Decl::IDNS_Ordinary | Decl::IDNS_Tag | Decl::IDNS_Type);
 }
 
 void ASTDeclReader::attachLatestDecl(Decl *D, Decl *Latest) {
@@ -2063,11 +2074,6 @@ ASTReader::combineStoredMergedDecls(Decl *Canon, GlobalDeclID CanonID) {
   return Pos;
 }
 
-void ASTReader::loadAndAttachPreviousDecl(Decl *D, serialization::DeclID ID) {
-  Decl *previous = GetDecl(ID);
-  ASTDeclReader::attachPreviousDecl(D, previous);
-}
-
 /// \brief Read the declaration at the given offset from the AST file.
 Decl *ASTReader::ReadDeclRecord(DeclID ID) {
   unsigned Index = ID - NUM_PREDEF_DECL_IDS;
@@ -2499,7 +2505,7 @@ void ASTReader::loadPendingDeclChain(serialization::GlobalDeclID ID) {
   for (unsigned I = 0, N = Chain.size(); I != N; ++I) {
     if (Chain[I] == CanonDecl)
       continue;
-    
+
     ASTDeclReader::attachPreviousDecl(Chain[I], MostRecent);
     MostRecent = Chain[I];
   }