apply changes from code review

Author: Vipul-Cariappa

lib/Interpreter/CppInterOp.cpp

@@ -3078,27 +3078,18 @@ namespace Cpp {
   }
 
   void GetEnums(TCppScope_t scope, std::vector<std::string>& Result) {
-    auto *D = (clang::Decl *)scope;
-    clang::DeclContext *DC;
-    clang::DeclContext::decl_iterator decl;
-
-    llvm::SmallVector<clang::DeclContext*, 4> DCs;
+    auto* D = (clang::Decl*)scope;
 
-    if (auto *TD = dyn_cast_or_null<TagDecl>(D)) {
-      DC = clang::TagDecl::castToDeclContext(TD);
-      DCs.push_back(DC);
-    } else if (auto *ND = dyn_cast_or_null<NamespaceDecl>(D)) {
-      DC = clang::NamespaceDecl::castToDeclContext(ND);
-      DC->collectAllContexts(DCs);
-    } else if (auto *TUD = dyn_cast_or_null<TranslationUnitDecl>(D)) {
-      DC = clang::TranslationUnitDecl::castToDeclContext(TUD);
-      DC->collectAllContexts(DCs);
-    } else {
+    if (!llvm::isa_and_nonnull<clang::DeclContext>(D))
       return;
-    }
+
+    clang::DeclContext* DC = llvm::dyn_cast<clang::DeclContext>(D);
+
+    llvm::SmallVector<clang::DeclContext*, 4> DCs;
+    DC->collectAllContexts(DCs);
 
     for (auto* DC : DCs) {
-      for (decl = DC->decls_begin(); decl != DC->decls_end(); decl++) {
+      for (auto decl = DC->decls_begin(); decl != DC->decls_end(); decl++) {
         if (auto* ND = llvm::dyn_cast_or_null<EnumDecl>(*decl)) {
           Result.push_back(ND->getNameAsString());
         }