tituting each occurrence of identifier <code>id</code> by identifier <code>phi id</code></p></div></div><div class="odoc-spec"><div class="spec value anchored" id="val-subst_param_type_expr"><a href="#val-subst_param_type_expr" class="anchor"></a><code><span><span class="keyword">val</span> subst_param_type_expr : <span><span><a href="#type-expr">expr</a> <a href="../../../../../Subst/index.html#type-t">Subst.t</a></span> <span class="arrow">&#45;&gt;</span></span> <span><a href="#type-type_expr">type_expr<