diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -360,8 +360,9 @@
   "%select{function|variable}0 %1 is not needed and will not be emitted">,
   InGroup<UnneededInternalDecl>, DefaultIgnore;
 def warn_unneeded_static_internal_decl : Warning<
-  "'static' function %0 declared in header file "
-  "should be declared 'static inline'">,
+  "function %0 declared in header file should "
+  "%select{be declared 'inline' instead of|not be declared}1 "
+  "%select{in an anonymous namespace|'static'}2">,
   InGroup<UnneededInternalDecl>, DefaultIgnore;
 def warn_unneeded_member_function : Warning<
   "member function %0 is not needed and will not be emitted">,
diff --git a/clang/lib/Sema/Sema.cpp b/clang/lib/Sema/Sema.cpp
--- a/clang/lib/Sema/Sema.cpp
+++ b/clang/lib/Sema/Sema.cpp
@@ -1211,13 +1211,12 @@
             Diag(DiagD->getLocation(), diag::warn_unneeded_member_function)
                 << DiagD;
           else {
-            if (FD->getStorageClass() == SC_Static &&
-                !FD->isInlineSpecified() &&
-                !SourceMgr.isInMainFile(
-                   SourceMgr.getExpansionLoc(FD->getLocation())))
+            if (!SourceMgr.isInMainFile(
+                    SourceMgr.getExpansionLoc(FD->getLocation())))
               Diag(DiagD->getLocation(),
                    diag::warn_unneeded_static_internal_decl)
-                  << DiagD;
+                  << DiagD << FD->isInlineSpecified()
+                  << (FD->getStorageClass() == SC_Static);
             else
               Diag(DiagD->getLocation(), diag::warn_unneeded_internal_decl)
                   << /*function*/ 0 << DiagD;
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -1697,10 +1697,6 @@
     if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(FD)) {
       if (MD->isVirtual() || IsDisallowedCopyOrAssign(MD))
         return false;
-    } else {
-      // 'static inline' functions are defined in headers; don't warn.
-      if (FD->isInlined() && !isMainFileLoc(*this, FD->getLocation()))
-        return false;
     }
 
     if (FD->doesThisDeclarationHaveABody() &&
diff --git a/clang/test/SemaCXX/warn-static-function-inheader.h b/clang/test/SemaCXX/warn-static-function-inheader.h
--- a/clang/test/SemaCXX/warn-static-function-inheader.h
+++ b/clang/test/SemaCXX/warn-static-function-inheader.h
@@ -1,3 +1,13 @@
-static void thing(void) { // expected-warning {{'static' function 'thing' declared in header file should be declared 'static inline'}}
+static void thing(void) { // expected-warning {{function 'thing' declared in header file should be declared 'inline' instead of 'static'}}
 }
 
+static inline void inline_thing(void) { // expected-warning {{function 'inline_thing' declared in header file should not be declared 'static'}}
+}
+
+namespace {
+void anon_thing(void) { // expected-warning {{function 'anon_thing' declared in header file should be declared 'inline' instead of in an anonymous namespace}}
+}
+
+inline void anon_inline_thing(void) { // expected-warning {{function 'anon_inline_thing' declared in header file should not be declared in an anonymous namespace}}
+}
+} // namespace
diff --git a/clang/test/SemaCXX/warn-static-function-inheader.cpp b/clang/test/SemaCXX/warn-static-function-inheader.cpp
--- a/clang/test/SemaCXX/warn-static-function-inheader.cpp
+++ b/clang/test/SemaCXX/warn-static-function-inheader.cpp
@@ -7,6 +7,9 @@
 
 template <typename T>
 void foo(void) {
-        thing();
-	another();
+  thing();
+  inline_thing();
+  anon_thing();
+  anon_inline_thing();
+  another();
 }
diff --git a/clang/test/SemaCXX/warn-unused-filescoped.cpp b/clang/test/SemaCXX/warn-unused-filescoped.cpp
--- a/clang/test/SemaCXX/warn-unused-filescoped.cpp
+++ b/clang/test/SemaCXX/warn-unused-filescoped.cpp
@@ -5,26 +5,26 @@
 #ifdef HEADER
 
 static void headerstatic() {} // expected-warning{{unused function 'headerstatic'}}
-static inline void headerstaticinline() {}
+static inline void headerstaticinline() {} // expected-warning{{unused function 'headerstaticinline'}}
 
 namespace {
 void headeranon() {} // expected-warning{{unused function 'headeranon'}}
-inline void headerinlineanon() {}
+inline void headerinlineanon() {} // expected-warning{{unused function 'headerinlineanon'}}
 }
 
 namespace test7
 {
   template<typename T>
-  static inline void foo(T) { }
+  static inline void foo(T) { } // expected-warning{{unused function template 'foo'}}
 
-  // This should not emit an unused-function warning since it inherits
+  // This should emit an unused-function warning since it inherits
   // the static storage type from the base template.
   template<>
-  inline void foo(int) {  }
+  inline void foo(int) {  } // expected-warning{{unused function 'foo<int>'}}
 
   // Partial specialization
   template<typename T, typename U>
-  static inline void bar(T, U) { }
+  static inline void bar(T, U) { } // expected-warning{{unused function template 'bar'}}
 
   template<typename U>
   inline void bar(int, U) { }
@@ -35,7 +35,7 @@
 
 namespace pr19713 {
 #if __cplusplus >= 201103L
-  static constexpr int constexpr1() { return 1; }
+  static constexpr int constexpr1() { return 1; } // expected-warning{{unused function 'constexpr1'}}
   constexpr int constexpr2() { return 2; }
 #endif
 }