[Haskell-cafe] ANN: Important lambabot update ( release)

Bertram Felgenhauer bertram.felgenhauer at googlemail.com
Thu May 7 21:12:08 UTC 2015


> Generally, lambdabot relies on SafeHaskell and not running user-supplied
> IO actions for safety. This is unlikely to be bullet-proof, so it's
> advisable to sandbox mueval. However, the @check command violated this
> basic principle, and allowed running arbitrary IO actions.

This was deliberately vague. The point is that @check took an arbitrary
value of type Property, and ran it. That type is based on IO, and there
are actually direct ways of incorporating an IO action into a Property:

 * ioProperty (alias morallyDubiousIOProperty)
 * whenFail, whenFail'

In the end, rather than trying to control whether these functions are
imported (which would be a fool's errand, because Test.QuickCheck is a
Safe module, and can be reexported from other modules), I came up with
the QuickCheck-safe design whose SProperty type does not embed IO



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