I opted to keep the space in data type declarations. It just feels weird somehow:

data Foo = Foo {fooX :: Int, fooY :: Int}
data Foo = Foo{fooX :: Int, fooY :: Int}

Anyway, in general, the major reason for preferring not to have the space, is to underline the fact that record update/construction binds even more tightly than function composition, and that isn't relevant here.

I'm open to changing it if anyone has an opinion.

Edit: Come to think of it, I don't think I ever define record types on a single line, so this shouldn't actually bother me.