<p><pre><code>  But [Lisp] won&#x27;t enforce those things at compilation time
  in the type system, because it doesn&#x27;t have one.
</code></pre>
What Lisp implementation do you have in mind?  I ask because Common Lisp has type system that includes compile-time type checking.  For example, SBCL:<p><a href="http:&#x2F;&#x2F;sbcl.org&#x2F;manual&#x2F;index.html#Handling-of-Types" rel="nofollow">http:&#x2F;&#x2F;sbcl.org&#x2F;manual&#x2F;index.html#Handling-of-Types</a>