The current style (A) for records is:

data Foo
  = Foo
      { bar :: Bar,
        baz :: Baz
      }

I propose the following style (B) for single-constructor records:

data Foo = Foo
  { bar :: Bar,
    baz :: Baz
  }

Pros

• The most common style, according to Hackage grep.

• One-constructor records seem to stay one-constructor records so git diffs don't get worse. (Not sure about this one. Feedback welcome.)

• Slightly better use of horizontal space.

• Much better use of vertical space for data-heavy modules – important for people who split their screens horizontally instead of vertically.

Cons

• Still, some diffs are inevitable. Especially annoying when the fields were heavily commented and you have to rewrap the comments.

Unresolved questions

• Should (A) be reformatted into (B)? "Yes" seems like a good answer, but it would be slightly unfortunate if it was impossible to break a data ReallyReallyReallyReallyLongName = ReallyReallyReallyReallyLongName ... even when requested by the programmerr.