[modules] When determining the visible module set during template
instantiation, use the set of modules visible from the template definition, not
from whichever declaration the specialization was instantiated from.

llvm-svn: 241662
diff --git a/clang/lib/AST/DeclCXX.cpp b/clang/lib/AST/DeclCXX.cpp
index b00b8a0..d905fcf 100644
--- a/clang/lib/AST/DeclCXX.cpp
+++ b/clang/lib/AST/DeclCXX.cpp
@@ -1272,7 +1272,7 @@
           break;
         CTD = NewCTD;
       }
-      return CTD->getTemplatedDecl();
+      return CTD->getTemplatedDecl()->getDefinition();
     }
     if (auto *CTPSD =
             From.dyn_cast<ClassTemplatePartialSpecializationDecl *>()) {
@@ -1281,7 +1281,7 @@
           break;
         CTPSD = NewCTPSD;
       }
-      return CTPSD;
+      return CTPSD->getDefinition();
     }
   }
 
@@ -1290,7 +1290,7 @@
       const CXXRecordDecl *RD = this;
       while (auto *NewRD = RD->getInstantiatedFromMemberClass())
         RD = NewRD;
-      return RD;
+      return RD->getDefinition();
     }
   }
 
diff --git a/clang/test/Modules/Inputs/merge-template-pattern-visibility/a.h b/clang/test/Modules/Inputs/merge-template-pattern-visibility/a.h
new file mode 100644
index 0000000..7f9b649
--- /dev/null
+++ b/clang/test/Modules/Inputs/merge-template-pattern-visibility/a.h
@@ -0,0 +1,5 @@
+template<typename, typename = int> struct A;
+template<typename T> struct B;
+
+template<typename, typename> struct A {};
+template<typename T> struct B : A<T> {};
diff --git a/clang/test/Modules/Inputs/merge-template-pattern-visibility/b.h b/clang/test/Modules/Inputs/merge-template-pattern-visibility/b.h
new file mode 100644
index 0000000..5ed18e7
--- /dev/null
+++ b/clang/test/Modules/Inputs/merge-template-pattern-visibility/b.h
@@ -0,0 +1,9 @@
+template<typename, typename = int> struct A;
+template<typename T> struct B;
+
+template<typename, typename> struct A {};
+template<typename T> struct B : A<T> {};
+
+inline void f() {
+  B<int> bi;
+}
diff --git a/clang/test/Modules/Inputs/merge-template-pattern-visibility/module.modulemap b/clang/test/Modules/Inputs/merge-template-pattern-visibility/module.modulemap
new file mode 100644
index 0000000..ba97abb
--- /dev/null
+++ b/clang/test/Modules/Inputs/merge-template-pattern-visibility/module.modulemap
@@ -0,0 +1,4 @@
+module X {
+  module A { header "a.h" }
+  module B { header "b.h" }
+}
diff --git a/clang/test/Modules/merge-template-pattern-visibility.cpp b/clang/test/Modules/merge-template-pattern-visibility.cpp
new file mode 100644
index 0000000..db759b5
--- /dev/null
+++ b/clang/test/Modules/merge-template-pattern-visibility.cpp
@@ -0,0 +1,4 @@
+// RUN: rm -rf %t
+// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t -fno-modules-error-recovery \
+// RUN:            -fmodule-name=X -emit-module %S/Inputs/merge-template-pattern-visibility/module.modulemap -x c++ \
+// RUN:            -fmodules-local-submodule-visibility