[modules] When merging class definitions, make the retained definition visible
if the merged definition is visible, and perform lookups into all merged copies
of the definition (not just for special members) so that we can complete the
redecl chains for members of the class.

llvm-svn: 233420
diff --git a/clang/test/Modules/Inputs/submodules-merge-defs/module.modulemap b/clang/test/Modules/Inputs/submodules-merge-defs/module.modulemap
index 5c7ee8a..82abdb0 100644
--- a/clang/test/Modules/Inputs/submodules-merge-defs/module.modulemap
+++ b/clang/test/Modules/Inputs/submodules-merge-defs/module.modulemap
@@ -9,3 +9,8 @@
   // Do not re-export stuff.use
   use "stuff"
 }
+
+module "merged-defs" {
+  header "merged-defs.h"
+  use "stuff"
+}