[GHC] #15762: ghci command: report function's inferred visible type applications

[GHC]

#15762: ghci command: report function's inferred visible type applications
-------------------------------------+-------------------------------------
        Reporter:  Iceland_jack      |                Owner:  (none)
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  GHCi              |              Version:  8.6.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #15610 #15613     |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------
Description changed by Iceland_jack:

Old description:

> Example inspired by #40.
>
> ghci already has a
> [https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/ghci.html
> #ghci-cmd-:type-at :type-at] command for reporting a type in a range
>
> {{{
> >> :type-at X.hs 6 6 6 7 f
> Int -> Int
> }}}
>
> A similar thing (for integrating into IDEs) is doing the same for visible
> type applications. An innocent expression like `x y` has a lot going on
> under the surface
>
> {{{#!hs
> {-# Language RankNTypes     #-}
> {-# Language PolyKinds      #-}
> {-# Language KindSignatures #-}
>
> import Data.Kind
>
> f :: forall res
>    . (forall k (f :: k    -> Type) (a :: k). f a -> res)
>   -> (forall   (f :: Type -> Type)         . f res)
>   -> res
> f x y = x y
> }}}
>
> How hard would it be to expand that to `(x @Type @f @res) (y @f)` or (x
> @Type @Any @res) (y @Any)
>
> {{{#!hs
> f :: forall res (f :: Type -> Type)
>    . (forall k (f :: k    -> Type) (a :: k). f a -> res)
>   -> (forall   (f :: Type -> Type)         . f res)
>   -> res
> f x y = (x @Type @f @res) (y @f)
> }}}
>
> ----
>
> Other ghci ideas: #15610, #15613

New description:

 Example inspired by #40.

 ghci already has a
 [https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/ghci.html
 #ghci-cmd-:type-at :type-at] command for reporting a type in a range

 {{{
 >> :type-at X.hs 6 6 6 7 f
 Int -> Int
 }}}

 A similar thing (for integrating into IDEs) is doing the same for visible
 type applications. An innocent expression like `x y` has a lot going on
 under the surface

 {{{#!hs
 {-# Language RankNTypes     #-}
 {-# Language PolyKinds      #-}
 {-# Language KindSignatures #-}

 import Data.Kind

 f :: forall res
    . (forall k (f :: k    -> Type) (a :: k). f a -> res)
   -> (forall   (f :: Type -> Type)         . f res)
   -> res
 f x y = x y
 }}}

 How hard would it be to expand that to `(x @Type @f @res) (y @f)` (or `(x
 @Type @Any @res) (y @Any)`)

 {{{#!hs
 f :: forall res (f :: Type -> Type)
    . (forall k (f :: k    -> Type) (a :: k). f a -> res)
   -> (forall   (f :: Type -> Type)         . f res)
   -> res
 f x y = (x @Type @f @res) (y @f)
 }}}

 ----

 Other ghci ideas: #15610, #15613

--

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15762#comment:1>
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