Index: lib/Sema/SemaDeclCXX.cpp
===================================================================
--- lib/Sema/SemaDeclCXX.cpp
+++ lib/Sema/SemaDeclCXX.cpp
@@ -615,7 +615,8 @@
       << New << New->isConstexpr();
     Diag(Old->getLocation(), diag::note_previous_declaration);
     Invalid = true;
-  } else if (!Old->isInlined() && New->isInlined() && Old->isDefined(Def)) {
+  } else if (!Old->getMostRecentDecl()->isInlined() && New->isInlined() &&
+             Old->isDefined(Def)) {
     // C++11 [dcl.fcn.spec]p4:
     //   If the definition of a function appears in a translation unit before its
     //   first declaration as inline, the program is ill-formed.
Index: test/SemaTemplate/friend.cpp
===================================================================
--- test/SemaTemplate/friend.cpp
+++ test/SemaTemplate/friend.cpp
@@ -31,3 +31,16 @@
     friend class f1; // expected-error{{'friend' used outside of class}}
   }
 }
+
+namespace friend_redecl_inline {
+// We had a bug where instantiating the foo friend declaration would check the
+// defined-ness of the most recent decl while checking if the canonical decl was
+// inlined.
+void foo();
+template <typename T>
+class C {
+  friend void foo();
+};
+inline void foo() {}
+C<int> c;
+}