Custom Query

Reported by Ashley Yakeley <ashley@…>, 6 years ago.

Try compiling this:

{-# OPTIONS -fglasgow-exts #-}
module Bug where
	data T a = MkT

	out :: forall a. T a -> ()
	out MkT = ()

	inHoisted :: forall r. () -> (forall a. T a -> r) -> r
	inHoisted _ foo = foo MkT

	inUnhoisted :: () -> forall r. (forall a. T a -> r) -> r
	inUnhoisted _ foo = foo MkT
	
	testHoisted :: ()
	testHoisted = inHoisted () out
	
	testUnhoisted :: ()
	testUnhoisted = inUnhoisted () out

Results:

Bug.hs:18:17:
    Couldn't match expected type `T a -> ()'
           against inferred type `forall a1. T a1 -> r'
      Expected type: (T a -> ()) -> ()
      Inferred type: (forall a1. T a1 -> r) -> r
    In the expression: inUnhoisted () out
    In the definition of `testUnhoisted':
        testUnhoisted = inUnhoisted () out

Expected: testUnhoisted to compile, just like testHoisted

Reported by Ashley Yakeley <ashley@…>, 6 years ago.

Try compiling this:

{-# OPTIONS -fglasgow-exts #-}
module Bug where
	f :: () -> (?p :: ()) => () -> ()
	f _ _ = ();

	g :: (?p :: ()) => ()
	g = f () ()

Results:

Bug.hs:7:10:
    Couldn't match expected type `{?p::()}' against inferred type `()'
    In the second argument of `f', namely `()'
    In the expression: f () ()
    In the definition of `g': g = f () ()

Expected: to compile.

Reported by Athas, 2 years ago.

getArgs is implemented as simply dereferencing argv and returning a list of the octets passed as arguments, resulting in unexpected results for multibyte characters. I think it would be more natural if getArgs performed locale-relevant decoding, and a more low-level function (perhaps returning ByteStrings?) was available for when you really want the raw arguments.