Comment by eru

Well as I have pointed out before, I am still learning but there are few interesting propositions here.

core.typed - Type Clojure, but still not complete

Shen - despite its questionable licensing scheme, it is a derivative of Qi. Qi and Shen are very powerful types systems (not just Haskell, but think even more complex like Idris, Coq, Agda, etc). The original implementations, if you want irony, are Common Lisp. The caveat is Shen has been ported to other runtimes, namely, Python and Ruby. But SBCL is the preferred runtime layer for Shen's crazy type system.

Typed Racket - It is a Scheme, and people will throw things at me, but I think it safe to say static types for this subset prove Lisp family languages have the potential for robust static typing systems you hint at.

TL;DR: Strong static typing is not common (pun intended), but it is possible. I think what we want to see is Shen with a good license: a very robust type system with a Lisp, separate or library. Then, Lisp will be the one ring-language to rule them all.

Perhaps we can call this library or Lisp variant Precious, and its hipster vote can go through the charts.

Common Lisp already features strong static typing (the example below uses SBCL):

  * (defun foo (x) x)

  FOO
  * (declaim (ftype (function (fixnum)) foo))

  * (defun bar (y) (declare (string y)) (foo y))
  ; in: DEFUN BAR
  ;     (FOO Y)
  ; 
  ; caught WARNING:
  ;   Derived type of Y is
  ;     (VALUES STRING &OPTIONAL),
  ;   conflicting with its asserted type
  ;     FIXNUM.
  ;   See also:
  ;     The SBCL Manual, Node "Handling of Types"
  ; 
  ; compilation unit finished
  ;   caught 1 WARNING condition

  BAR

One could also declare the function signature first (perhaps in skeleton code generated by modelling tools). Then, if someone implements it incorrectly, the compiler will throw an error (again, SBCL):

  * (declaim (ftype (function (fixnum)) qux))

  * (defun qux (z) (car z))
  ; in: DEFUN QUX
  ;     (CAR Z)
  ; 
  ; caught WARNING:
  ;   Derived type of Z is
  ;     (VALUES FIXNUM &OPTIONAL),
  ;   conflicting with its asserted type
  ;     LIST.
  ;   See also:
  ;     The SBCL Manual, Node "Handling of Types"
  ; 
  ; compilation unit finished
  ;   caught 1 WARNING condition

  QUX

So, what else do you think Common Lisp lacks compare to more "modern" languages? ;)