type checker bug

[guest]

This causes a type error:

    foo :: forall b. (b -> String, Int)
    foo = (const "hi", 0)
 
    bar :: (forall b. b -> String, Int)
    bar = foo

This should compile fine since the types are equivalent.

[guest]

Sorry about bad formatting before...

This produces a type error:

    foo :: forall b. (b -> String, Int)
    foo = (const "hi", 0)
 
    bar :: (forall b. b -> String, Int)
    bar = foo

But the types are equivalent.

[igloo]

Thanks for the report! However, the types are not equivalent, e.g. this fails to typecheck:

foo :: forall b. (b -> String, Int)
foo = undefined

x :: (String, String)
x = case foo of
    (f, _) -> (f 'a', f True)

with:

    Couldn't match expected type `Char' against inferred type `Bool'
    In the first argument of `f', namely `True'
    In the expression: f True
    In the expression: (f 'a', f True)

but this does typecheck:

bar :: (forall b. b -> String, Int)
bar = undefined

x :: (String, String)
x = case bar of
    (f, _) -> (f 'a', f True)

(with -XImpredicativeTypes -XRank2Types)