1 files changed, 34 insertions, 6 deletions

diff --git a/clang/lib/Sema/SemaLookup.cpp b/clang/lib/Sema/SemaLookup.cpp
index e15e532be19..0b406184058 100644
--- a/clang/lib/Sema/SemaLookup.cpp
+++ b/clang/lib/Sema/SemaLookup.cpp
@@ -3021,17 +3021,45 @@ static void LookupVisibleDecls(DeclContext *Ctx, LookupResult &Result,
   if (Visited.visitedContext(Ctx->getPrimaryContext()))
     return;
 
+  // Outside C++, lookup results for the TU live on identifiers.
+  if (isa<TranslationUnitDecl>(Ctx) &&
+      !Result.getSema().getLangOpts().CPlusPlus) {
+    auto &S = Result.getSema();
+    auto &Idents = S.Context.Idents;
+
+    // Ensure all external identifiers are in the identifier table.
+    if (IdentifierInfoLookup *External = Idents.getExternalIdentifierLookup()) {
+      std::unique_ptr<IdentifierIterator> Iter(External->getIdentifiers());
+      for (StringRef Name = Iter->Next(); !Name.empty(); Name = Iter->Next())
+        Idents.get(Name);
+    }
+
+    // Walk all lookup results in the TU for each identifier.
+    for (const auto &Ident : Idents) {
+      for (auto I = S.IdResolver.begin(Ident.getValue()),
+                E = S.IdResolver.end();
+           I != E; ++I) {
+        if (S.IdResolver.isDeclInScope(*I, Ctx)) {
+          if (NamedDecl *ND = Result.getAcceptableDecl(*I)) {
+            Consumer.FoundDecl(ND, Visited.checkHidden(ND), Ctx, InBaseClass);
+            Visited.add(ND);
+          }
+        }
+      }
+    }
+
+    return;
+  }
+
   if (CXXRecordDecl *Class = dyn_cast<CXXRecordDecl>(Ctx))
     Result.getSema().ForceDeclarationOfImplicitMembers(Class);
 
   // Enumerate all of the results in this context.
   for (const auto &R : Ctx->lookups()) {
-    for (auto *I : R) {
-      if (NamedDecl *ND = dyn_cast<NamedDecl>(I)) {
-        if ((ND = Result.getAcceptableDecl(ND))) {
-          Consumer.FoundDecl(ND, Visited.checkHidden(ND), Ctx, InBaseClass);
-          Visited.add(ND);
-        }
+    for (auto *D : R) {
+      if (auto *ND = Result.getAcceptableDecl(D)) {
+        Consumer.FoundDecl(ND, Visited.checkHidden(ND), Ctx, InBaseClass);
+        Visited.add(ND);
       }
     }
   }