Use the most recent redecl to decide if it is needed.

This fixes pr14691, which I think is a regression from r168519.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@171077 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Sema/Sema.cpp

@@ -328,7 +328,7 @@ CastKind Sema::ScalarTypeToBooleanCastKind(QualType ScalarTy) {
 
 /// \brief Used to prune the decls of Sema's UnusedFileScopedDecls vector.
 static bool ShouldRemoveFromUnused(Sema *SemaRef, const DeclaratorDecl *D) {
-  if (D->isUsed())
+  if (D->getMostRecentDecl()->isUsed())
     return true;
 
   if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {

test/SemaCXX/warn-func-not-needed.cpp

+// RUN: %clang_cc1 -fsyntax-only -verify -Wall %s
+
+namespace test1 {
+  static void f() {} // expected-warning {{is not needed and will not be emitted}}
+  static void f();
+  template <typename T>
+  void foo() {
+    f();
+  }
+}
+
+namespace test2 {
+  static void f() {}
+  static void f();
+  static void g() { f(); }
+  void h() { g(); }
+}