&gt; I&#x27;d love an implementation of a Lisp with a Hindley Milner-esque type system.<p>I am not certain of whether it is more Hindley-Milner or more &quot;esque&quot;, but you may find something of interest in Shen [0].<p>[0] <a href="http:&#x2F;&#x2F;shenlanguage.org&#x2F;" rel="nofollow">http:&#x2F;&#x2F;shenlanguage.org&#x2F;</a><p>Edit: I submitted this reply an hour or so after opening the tab, during which interval several others mentioned Shen (which is good, as it deserves a bit of exposure).