/span> <span>&#45;&gt;</span> <a href="index.html#type-t">t</a></code></dt></dl></details></div></div></div><dl><dt class="spec value" id="val-is_top"><a href="#val-is_top" class="anchor"></a><code><span class="keyword">val</span> is_top : <a href="index.html#type-t">t</a> <span>&#45;&gt;</span> bool</code></dt><dt class="spec value" id="val-subst"><a href="#val-subst" class="anchor"></a><code><span class="keyword">val</span> subst : <span>ret_id:<a href="../../../IR/Ident/index.html#type-t">IR.Ident.t</a><