OK but the original question was "Why don't Smalltalk or Smalltalklike languages have checked interfaces?��� and my mail was an answer to that.
You are correct, I did not read carefully and made the mistake to assume that it was about not being possible.��
"�� I think there was Lisp for Squeak (and also Prolog). And port to Pharo should not be���� difficult. "
Ah yes thanks for reminding , my intention was to do it from scratch mainly as an opportunity to understand the basics of parsers, AST and compilers etc but still could really help to see those examples.