Index: clang/lib/Sema/SemaLookup.cpp
===================================================================
--- clang/lib/Sema/SemaLookup.cpp
+++ clang/lib/Sema/SemaLookup.cpp
@@ -2578,6 +2578,8 @@
 
     bool addClassTransitive(CXXRecordDecl *RD) {
       Classes.insert(RD);
+      if (InstantiationLoc.isInvalid())
+        InstantiationLoc = RD->getLocation();
       return ClassesTransitive.insert(RD);
     }
 
@@ -2723,8 +2725,10 @@
   if (!Result.addClassTransitive(Class))
     return;
 
-  // Only recurse into base classes for complete types.
-  if (!Result.S.isCompleteType(Result.InstantiationLoc,
+  // Only recurse into base classes for complete types and for class templates
+  // that that have been instantiated.
+  if (!Result.InstantiationLoc.isValid() ||
+      !Result.S.isCompleteType(Result.InstantiationLoc,
                                Result.S.Context.getRecordType(Class)))
     return;
 
Index: clang/test/SemaCXX/class-argument-lookup.cpp
===================================================================
--- /dev/null
+++ clang/test/SemaCXX/class-argument-lookup.cpp
@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -verify -fsyntax-only -fopenmp %s
+
+// expected-no-diagnostics
+
+template <typename T>
+struct z {
+  static void aj() {
+    T f;
+#pragma omp target map(f)
+    ;
+  }
+};
+
+template <typename> class ar {};
+template <int> struct as {};
+
+template class z<ar<as<4>>>;