Index: lib/Sema/Sema.cpp
===================================================================
--- lib/Sema/Sema.cpp
+++ lib/Sema/Sema.cpp
@@ -721,8 +721,15 @@
     if (WeakID.second.getUsed())
       continue;
 
-    Diag(WeakID.second.getLocation(), diag::warn_weak_identifier_undeclared)
-        << WeakID.first;
+    Decl *PrevDecl = LookupSingleName(TUScope, WeakID.first, SourceLocation(),
+                                      LookupOrdinaryName);
+    if (PrevDecl != nullptr &&
+        !(isa<FunctionDecl>(PrevDecl) || isa<VarDecl>(PrevDecl)))
+      Diag(WeakID.second.getLocation(), diag::warn_attribute_wrong_decl_type)
+          << "weak" << ExpectedVariableOrFunction;
+    else
+      Diag(WeakID.second.getLocation(), diag::warn_weak_identifier_undeclared)
+          << WeakID.first;
   }
 
   if (LangOpts.CPlusPlus11 &&
Index: lib/Sema/SemaDecl.cpp
===================================================================
--- lib/Sema/SemaDecl.cpp
+++ lib/Sema/SemaDecl.cpp
@@ -14530,7 +14530,7 @@
                                     LookupOrdinaryName);
   WeakInfo W = WeakInfo(Name, NameLoc);
 
-  if (PrevDecl) {
+  if (PrevDecl && (isa<FunctionDecl>(PrevDecl) || isa<VarDecl>(PrevDecl))) {
     if (!PrevDecl->hasAttr<AliasAttr>())
       if (NamedDecl *ND = dyn_cast<NamedDecl>(PrevDecl))
         DeclApplyPragmaWeak(TUScope, ND, W);
Index: test/CodeGen/pragma-weak.c
===================================================================
--- test/CodeGen/pragma-weak.c
+++ test/CodeGen/pragma-weak.c
@@ -53,12 +53,14 @@
 #pragma weak unused // expected-warning {{weak identifier 'unused' never declared}}
 #pragma weak unused_alias = __unused_alias  // expected-warning {{weak identifier '__unused_alias' never declared}}
 
-#pragma weak td // expected-warning {{weak identifier 'td' never declared}}
+#pragma weak td // expected-warning {{weak attribute only applies to variables and functions}}
 typedef int td;
 
-#pragma weak td2 = __td2 // expected-warning {{weak identifier '__td2' never declared}}
+#pragma weak td2 = __td2 // expected-warning {{weak attribute only applies to variables and functions}}
 typedef int __td2;
 
+typedef int __td3;
+#pragma weak td3 = __td3 // expected-warning {{weak attribute only applies to variables and functions}}
 
 ///// test weird cases