[modules] Properly look up the owning module for an instantiation of a merged template.

When looking for the template instantiation pattern of a templated entity,
consistently select the definition of the pattern if there is one. This means
we'll pick the same owning module when we start instantiating a template that
we'll later pick when determining which modules are visible during that
instantiation.

This reinstates r300650, reverted in r300659, with a fix for a regression
reported by Chandler after commit.

llvm-svn: 300938

1 files changed, 7 insertions, 0 deletions

diff --git a/clang/test/Modules/Inputs/template-default-args/d.h b/clang/test/Modules/Inputs/template-default-args/d.h
index 5961c91a82e..07ececc1f41 100644
--- a/clang/test/Modules/Inputs/template-default-args/d.h
+++ b/clang/test/Modules/Inputs/template-default-args/d.h
@@ -4,3 +4,10 @@ struct FriendL {
   template<typename T> friend struct L;
 };
 END
+
+namespace DeferredLookup {
+  namespace Indirect {
+    template<typename, bool = true> struct A {};
+    template<typename> struct B { template<typename T> using C = A<T>; };
+  }
+}