href="#type-t">t</a></span> <span class="arrow">&#45;&gt;</span></span> <span><span class="label">f</span>:<span>(<span><a href="#type-key">key</a> <span class="arrow">&#45;&gt;</span></span> <span><span class="type-var">'a</span> <span class="arrow">&#45;&gt;</span></span> <span><span>(<span class="type-var">'b</span>, <span class="type-var">'c</span>)</span> <span class="xref-unresolved">Either</span>.t</span>)</span> <span class="arrow">&#45;&gt;</span></span> <span><span class="type-var">'b</span> <a hr