[modules] Retain multiple using-directives in the same scope even if they name the same namespace.

They might have different visibility, and thus discarding all but one of them
can result in rejecting valid code. Also fix name lookup to cope with multiple
using-directives being found that denote the same namespace, where some are not
visible -- don't cache an "already visited" state for a using-directive that we
didn't visit because it was hidden.

llvm-svn: 316965

1 files changed, 37 insertions, 0 deletions

diff --git a/clang/test/Modules/using-directive-redecl.cpp b/clang/test/Modules/using-directive-redecl.cpp
new file mode 100644
index 00000000000..94772f30a3d
--- /dev/null
+++ b/clang/test/Modules/using-directive-redecl.cpp
@@ -0,0 +1,37 @@
+// RUN: %clang_cc1 -fmodules -fmodules-local-submodule-visibility -verify %s
+// expected-no-diagnostics
+#pragma clang module build M
+module M { module TDFNodes {} module TDFInterface {} }
+#pragma clang module contents
+  // TDFNodes
+  #pragma clang module begin M.TDFNodes
+  namespace Detail {
+     namespace TDF {
+        class TLoopManager {};
+     }
+  }
+  namespace Internal {
+     namespace TDF {
+        using namespace Detail::TDF;
+     }
+  }
+  #pragma clang module end
+
+  // TDFInterface
+  #pragma clang module begin M.TDFInterface
+    #pragma clang module import M.TDFNodes
+      namespace Internal {
+        namespace TDF {
+          using namespace Detail::TDF;
+        }
+      }
+  #pragma clang module end
+
+#pragma clang module endbuild
+
+#pragma clang module import M.TDFNodes
+namespace Internal {
+  namespace TDF {
+    TLoopManager * use;
+  }
+}