[C++20] [Modules] Handle reachability for enum class

In previous reachability patch, we missed the case for enum class.
Trying to handle it in this patch and add the corresponding tests.

clang/lib/Sema/SemaType.cpp

@@ -8669,12 +8669,13 @@ bool Sema::hasAcceptableDefinition(NamedDecl *D, NamedDecl **Suggested,
       // of it will do.
       *Suggested = nullptr;
       for (auto *Redecl : ED->redecls()) {
-        if (isVisible(Redecl))
+        if (isAcceptable(Redecl, Kind))
           return true;
         if (Redecl->isThisDeclarationADefinition() ||
             (Redecl->isCanonicalDecl() && !*Suggested))
           *Suggested = Redecl;
       }
+
       return false;
     }
     D = ED->getDefinition();

clang/test/Modules/enum-class.cppm

@@ -0,0 +1,26 @@
+// Checks for reachability for C++11 enum class properly
+//
+// RUN: rm -rf %t
+// RUN: mkdir -p %t
+// RUN: split-file %s %t
+//
+// RUN: %clang_cc1 -std=c++20 %t/A.cppm -emit-module-interface -o %t/A.pcm
+// RUN: %clang_cc1 -std=c++20 -fprebuilt-module-path=%t %t/Use.cpp -verify -fsyntax-only
+
+//--- foo.h
+enum class foo {
+    a, b, c
+};
+
+//--- A.cppm
+module;
+#include "foo.h"
+export module A;
+export foo func();
+
+//--- Use.cpp
+// expected-no-diagnostics
+import A;
+void bar() {
+    auto f = func();
+}