Data-first twin of TaskClass#mapErr — the adapter edge, receiver-first.

import { define } from '../result/failure.ts';
const Classified = define('Classified', (d: { op: string }) => `failed: ${d.op}`);

const t = Task.mapErr(Task(() => 'ok'), (cause) => Classified({ op: 'io' }, { cause }));
await t; // 'ok' — success passes through untouched