Today I noticed that GHC is more concerned (when using -Wall) about uninitialized fields when those fields have names: data A = A {a::Integer} data B = B Integer x :: A x = A{} -- Gives a nice warning: "Fields of `A' not initialised: a" y :: B y = B{} -- No warning! Is this on purpose? If so, what is the rationale? The context in which I encountered this boils down to the following: {-# LANGUAGE RecordWildCards #-} data C = C {c::Integer} f :: C -> C f C{..} = C{..} g :: C -> Integer g (C i) = i main :: IO () main = print (g (f (C 3))) This code worked fine (and printed "3"), until I made C's Integer nameless. This made it crash with following runtime error instead: T: T.hs:6:11-15: Missing field in record construction The crash and error are perfectly understandable, but it would have been more helpful if GHC had warned about this at compile-time! The reason it didn't, though, is because of its aforementioned cavalier attitude towards uninitialized fields that don't have names... :-) (I'm using GHC 7.0.4.) Cheers, Eelis