Another Lennart, last name Spitzner, creates another genie that turns type signatures into programs. Unlike Djinn, Exference makes no promises over termination. "Your wish is my command even at the expense of closure."

Like Agda? You can now enjoy the hole-driven development style in Haskell, brought to you courtesy of Mote by Izaak Meckler. Discussion here.

Relevant addendum:

Ever use 'undefined' when writing definition stubs? Ever wished you had a type-level 'undefined' too? Thomas Winant explains advanced stubbing using GHC 7.10's new PartialTypeSignatures extension. Three years later, Dan Burton's wish is granted.

Thanks to Dominique Devriese for prompting inclusion.

And speaking of granting wishes, stub-driven development in your favorite editor jetpacked with type-to-term genies is tantalizingly within grasp. Visual Studio, eat your heart out.

-- Kim-Ee