public ImmutableArray <CompletionProvider> GetProviders(ImmutableHashSet <string> roles, Project?project)
                {
                    using var _ = ArrayBuilder <CompletionProvider> .GetInstance(out var providers);

                    providers.AddRange(_providerManager.GetImportedAndBuiltInProviders(roles));
                    providers.AddRange(GetProjectCompletionProviders(project));
                    return(providers.ToImmutable());
                }