span> <span class="type-var">'b</span>)</span> <span class="arrow">&#45;&gt;</span></span>
  <span><span class="label">write</span>:<span>(<span><span class="type-var">'b</span> <span class="arrow">&#45;&gt;</span></span> <span class="type-var">'a</span>)</span> <span class="arrow">&#45;&gt;</span></span>
  <span><span><span class="type-var">'a</span> <a href="#type-typ">typ</a></span> <span class="arrow">&#45;&gt;</span></span>
  <span><span class="type-var">'b</span> <a href="#type-typ">typ</a></span></sp