Implement TypeSystemSwiftTypeRef::GetTypeInf() (NFC)

This should enable a lot of additional functionality.

(cherry picked from commit 5873328)

Author: adrian-prantl

lldb/source/Plugins/Language/Swift/SwiftLanguage.cpp

@@ -774,6 +774,10 @@ SwiftLanguage::GetHardcodedSynthetics() {
       CompilerType type(valobj.GetCompilerType());
       Flags type_flags(type.GetTypeInfo());
       if (type_flags.AllSet(eTypeIsSwift | eTypeIsEnumeration)) {
+        // FIXME: The classification of clang-imported enums may
+        // change based on whether a Swift module is present or not.
+        if (!valobj.GetValueAsCString())
+          return nullptr;
         if (!swift_enum_synth)
           swift_enum_synth = lldb::SyntheticChildrenSP(new CXXSyntheticChildren(
               SyntheticChildren::Flags()

lldb/source/Symbol/SwiftASTContext.cpp

@@ -5508,19 +5508,22 @@ SwiftASTContext::GetTypeInfo(opaque_compiler_type_t type,
     LLVM_FALLTHROUGH;
   case swift::TypeKind::Enum: {
     SwiftEnumDescriptor *cached_enum_info = GetCachedEnumInfo(type);
-    if (cached_enum_info) {
-      if (cached_enum_info->GetNumElementsWithPayload() == 0)
-        swift_flags |= eTypeHasValue | eTypeIsEnumeration;
-      else
-        swift_flags |= eTypeHasValue | eTypeIsEnumeration | eTypeHasChildren;
-    } else
+    if (cached_enum_info)
+      swift_flags |= eTypeHasValue | eTypeIsEnumeration | eTypeHasChildren;
+    else
       swift_flags |= eTypeIsEnumeration;
   } break;
 
   case swift::TypeKind::BoundGenericStruct:
     swift_flags |= eTypeIsGeneric | eTypeIsBound;
     LLVM_FALLTHROUGH;
   case swift::TypeKind::Struct:
+    if (auto *ndecl = swift_can_type.getAnyNominal())
+      if (llvm::dyn_cast_or_null<clang::EnumDecl>(ndecl->getClangDecl())) {
+        swift_flags |= eTypeHasChildren | eTypeIsEnumeration | eTypeHasValue;
+        break;
+      }
+
     swift_flags |= eTypeHasChildren | eTypeIsStructUnion;
     break;