[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, 17 insertions, 0 deletions

diff --git a/clang/test/Modules/template-default-args.cpp b/clang/test/Modules/template-default-args.cpp
index 9d16cbf4342..c51cb284088 100644
--- a/clang/test/Modules/template-default-args.cpp
+++ b/clang/test/Modules/template-default-args.cpp
@@ -44,3 +44,20 @@ H<> h; // expected-error {{default argument of 'H' must be imported from module
 I<> i;
 L<> *l;
 END
+
+namespace DeferredLookup {
+  template<typename T, typename U = T> using X = U;
+  template<typename T> void f() { (void) X<T>(); }
+  template<typename T> int n = X<T>(); // expected-warning {{extension}}
+  template<typename T> struct S { X<T> xt; enum E : int; };
+  template<typename T> enum S<T>::E : int { a = X<T>() };
+
+  void test() {
+    f<int>();
+    n<int> = 1;
+    S<int> s;
+    S<int>::E e = S<int>::E::a;
+
+    Indirect::B<int>::C<int> indirect;
+  }
+}