1 files changed, 57 insertions, 0 deletions

diff --git a/clang/lib/Sema/SemaLookup.cpp b/clang/lib/Sema/SemaLookup.cpp
index 04350831c68..c5b579a4b2e 100644
--- a/clang/lib/Sema/SemaLookup.cpp
+++ b/clang/lib/Sema/SemaLookup.cpp
@@ -1326,6 +1326,62 @@ bool Sema::CppLookupName(LookupResult &R, Scope *S) {
   return !R.empty();
 }
 
+Module *Sema::getOwningModule(Decl *Entity) {
+  // If it's imported, grab its owning module.
+  Module *M = Entity->getImportedOwningModule();
+  if (M || !isa<NamedDecl>(Entity) || !cast<NamedDecl>(Entity)->isHidden())
+    return M;
+  assert(!Entity->isFromASTFile() &&
+         "hidden entity from AST file has no owning module");
+
+  if (!getLangOpts().ModulesLocalVisibility) {
+    // If we're not tracking visibility locally, the only way a declaration
+    // can be hidden and local is if it's hidden because it's parent is (for
+    // instance, maybe this is a lazily-declared special member of an imported
+    // class).
+    auto *Parent = cast<NamedDecl>(Entity->getDeclContext());
+    assert(Parent->isHidden() && "unexpectedly hidden decl");
+    return getOwningModule(Parent);
+  }
+
+  // It's local and hidden; grab or compute its owning module.
+  M = Entity->getLocalOwningModule();
+  if (M)
+    return M;
+
+  if (auto *Containing =
+          PP.getModuleContainingLocation(Entity->getLocation())) {
+    M = Containing;
+  } else if (Entity->isInvalidDecl() || Entity->getLocation().isInvalid()) {
+    // Don't bother tracking visibility for invalid declarations with broken
+    // locations.
+    cast<NamedDecl>(Entity)->setHidden(false);
+  } else {
+    // We need to assign a module to an entity that exists outside of any
+    // module, so that we can hide it from modules that we textually enter.
+    // Invent a fake module for all such entities.
+    if (!CachedFakeTopLevelModule) {
+      CachedFakeTopLevelModule =
+          PP.getHeaderSearchInfo().getModuleMap().findOrCreateModule(
+              "<top-level>", nullptr, false, false).first;
+
+      auto &SrcMgr = PP.getSourceManager();
+      SourceLocation StartLoc =
+          SrcMgr.getLocForStartOfFile(SrcMgr.getMainFileID());
+      auto &TopLevel = ModuleScopes.empty()
+                           ? VisibleModules
+                           : ModuleScopes[0].OuterVisibleModules;
+      TopLevel.setVisible(CachedFakeTopLevelModule, StartLoc);
+    }
+
+    M = CachedFakeTopLevelModule;
+  }
+
+  if (M)
+    Entity->setLocalOwningModule(M);
+  return M;
+}
+
 void Sema::makeMergedDefinitionVisible(NamedDecl *ND) {
   if (auto *M = getCurrentModule())
     Context.mergeDefinitionIntoModule(ND, M);
@@ -1464,6 +1520,7 @@ bool LookupResult::isVisibleSlow(Sema &SemaRef, NamedDecl *D) {
   if (SemaRef.getLangOpts().ModulesLocalVisibility) {
     DeclModule = SemaRef.getOwningModule(D);
     if (!DeclModule) {
+      // getOwningModule() may have decided the declaration should not be hidden.
       assert(!D->isHidden() && "hidden decl not from a module");
       return true;
     }