[Modules] Cope better with top-level declarations loaded after being declared in the current translation unit <rdar://problem/13189985>.

These two related tweaks to keep the information associated with a
given identifier correct when the identifier has been given some
top-level information (say, a top-level declaration) and more
information is then loaded from a module. The first ensures that an
identifier that was "interesting" before being loaded from an AST is
considered to be different from its on-disk counterpart. Otherwise, we
lose such changes when writing the current translation unit as a
module.

Second, teach the code that injects AST-loaded names into the
identifier chain for name lookup to keep the most recent declaration,
so that we don't end up confusing our declaration chains by having a
different declaration in there.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@174895 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 8 insertions, 0 deletions

diff --git a/lib/Sema/IdentifierResolver.cpp b/lib/Sema/IdentifierResolver.cpp
index 6f5ddca20b..d44c1fb926 100644
--- a/lib/Sema/IdentifierResolver.cpp
+++ b/lib/Sema/IdentifierResolver.cpp
@@ -302,6 +302,14 @@ static DeclMatchKind compareDeclarations(NamedDecl *Existing, NamedDecl *New) {
 
   // If the declarations are redeclarations of each other, keep the newest one.
   if (Existing->getCanonicalDecl() == New->getCanonicalDecl()) {
+    // If either of these is the most recent declaration, use it.
+    Decl *MostRecent = Existing->getMostRecentDecl();
+    if (Existing == MostRecent)
+      return DMK_Ignore;
+
+    if (New == MostRecent)
+      return DMK_Replace;
+
     // If the existing declaration is somewhere in the previous declaration
     // chain of the new declaration, then prefer the new declaration.
     for (Decl::redecl_iterator RD = New->redecls_begin(),