Detect {-# LANGUAGE UnboxedTuples #-} automatically

[jmcarthur]

Completed checklist

• I've checked the issue tracker for similar issues.
• I am not creating an issue about adding more configuration options for the styling/layout of hindent, because hindent is not about customizing style.

Problem description

In #419, it is explained that UnboxedTuples is intentionally unsupported by default because it would be mutually exclusive with handling lens operators. Makes sense, but it would be nice if this behavior would be altered by LANGUAGE pragmas so that it doesn't have to be overridden in the command manually.

Proposed solution

If the file contains the UnboxedTuples language extension, behave as though passing -XUnboxedTuples on the command line.

Alternatives

I can't think of an alternative.

[toku-sa-n]

Seems like HIndent 6.0.1 can detect the language extension. Could you give me an example that HIndent can't format?

Input

{-# LANGUAGE MagicHash #-}
{-# LANGUAGE UnboxedTuples #-}

f :: (# Int, Int #) -> Int
f t = case t of
    (# x, _ #) -> x

Output

{-# LANGUAGE MagicHash #-}
{-# LANGUAGE UnboxedTuples #-}

f :: (# Int, Int #) -> Int
f t =
  case t of
    (# x, _ #) -> x

[jmcarthur]

It works in patterns but not in expressions, so I guess it's actually a bug. Perhaps I was wrong that this has anything to do with #419.

Input

f :: (# Int, Int #) -> (# Int, Int #)
f t = case t of
    (# x, y #) -> (# x, y #)

Output

f :: (# Int, Int #) -> (# Int, Int #)
f t =
  case t of
    (# x, y #) -> (x, y)

[toku-sa-n]

Thanks for the code. I can reproduce it, and I am fixing it now.