Emit nested unused enum types with -fno-eliminate-unused-debug-types (#137818)

Unused types are retained in the debug info when
-fno-eliminate-unused-debug-types is specified.
However, unused nested enums were not being emitted even with this
option.
This patch fixes the missing emission of unused nested enums with
-fno-eliminate-unused-debug-types

Author: ykhatav

clang/lib/CodeGen/CodeGenModule.cpp

@@ -7119,7 +7119,7 @@ void CodeGenModule::EmitTopLevelDecl(Decl *D) {
     }
     // Emit any static data members, they may be definitions.
     for (auto *I : CRD->decls())
-      if (isa<VarDecl>(I) || isa<CXXRecordDecl>(I))
+      if (isa<VarDecl>(I) || isa<CXXRecordDecl>(I) || isa<EnumDecl>(I))
         EmitTopLevelDecl(I);
     break;
   }

clang/test/CodeGen/unused_nested_enump.cpp

@@ -0,0 +1,23 @@
+// RUN: %clang_cc1 -debug-info-kind=unused-types  -emit-llvm -o - %s | FileCheck %s
+// RUN: %clang_cc1 -debug-info-kind=limited -emit-llvm -o - %s | FileCheck --check-prefix=NOUNUSEDTYPE %s
+
+struct Type {
+    enum { Unused };
+    int value = 0;
+};
+int main() {
+    Type t;
+    return t.value;
+}
+
+// CHECK:  !DICompositeType(tag: DW_TAG_enumeration_type
+// CHECK-SAME: scope: ![[STRUCT:[0-9]+]]
+// CHECK-SAME: elements: ![[ELEMENTS:[0-9]+]]
+
+// CHECK: ![[STRUCT]] = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "Type"
+
+// CHECK: ![[ELEMENTS]] = !{![[ENUMERATOR:[0-9]+]]}
+// CHECK: ![[ENUMERATOR]] = !DIEnumerator(name: "Unused", value: 0
+
+
+// NOUNUSEDTYPE-NOT: !DIEnumerator(name: "Unused"