GHCi display visible type application

Similar to #8751, have a way to get GHCi to dump which types an expression is applied to:

ghci> :tyapp length [1,2,3]
length @[] @Integer [1,2,3]

It could also function as the :all-types, :type-at commands where we can specify a region of code (from Combining Deep and Shallow Embedding of Domain-Specific Languages)

  fromFunC :: FunC (m (Internal a)) -> Mon m a
  fromFunC m = M $ \k -> fromFunC Bind m k

displays

  fromFunC :: FunC (m (Internal a)) -> Mon m a
  fromFunC m = M @m @a $ \(k :: a -> FunC (m b)) -> fromFunC @(FunC (m (Internal a)) -> (a -> FunC (m b)) -> FunC (m b)) (Bind @m @(Internal a) @b) m k

Would be great to get this feature as an IDE support.

changed weight to 5

added Tfeature request Trac import labels

changed the description

assigned to @Icelandjack

TODO See if you can easily generate a dependency tree of type class instances used for an expression. Quite often I delete instances to check which instance they make use of (especially with indirect dependencies). A famous case where this would help is view _Just Nothing which has a Monoid constraint and the connection is contrived (I haven't considered how this could be visualised):

ghci> :whichInst view _Just Nothing

instance Monoid m => Applicative (Const m)
...

This should be a separate ticket if anyone is interested.

I really like this idea. But please submit as a ghc-proposal. Thanks!

mentioned in issue #15762

Trac metadata

Trac field	Value
Related	#8751 → #8751, #15762

added Pnormal label