Iterating over services until one returns a value

const readFiles = (files: FileNode[]) => Effect.gen(function* () {
  return yield* Option.firstSomeOf([
    Option.gen(function* () { // <-- Typescript error
      const md = yield* MarkdownFileTranscoder;
      const result = yield* md.discover(files);

      return Option.some(result);
    }),

    Option.gen(function* () { // <-- Typescript error
      const img = yield* ImageFileTranscoder;
      const result = yield* img.discover(files);

      return Option.some(result);
    }),
  ]);
});

export const PipelineTranscodeService = (selection: FileNode[]) => pipe(
  selection,
  discoverFiles,
  Effect.map(readFiles),
);