:info for record pattern synonyms

At present, when :info is used for a pattern synonym field selector, GHCi prints the type of the selector function. For example:

GHCi, version 9.1.20210216: https://www.haskell.org/ghc/  :? for help
ghci> :set -XPatternSynonyms
ghci> pattern P{x,y} = (x,y)
ghci> :info x
x :: (a,b) -> a 	-- Defined at <interactive>:2:11

However, this doesn't make sense if the pattern synonym was defined when NoFieldSelectors was enabled, because no such function exists. (At the moment I think HEAD will show some nonsense like $sel:x:P :: (), but I don't have a build available to test right now.) What should it show instead?

Using :info on the pattern synonym itself shows the type of the builder (without field names).

ghci> :info P
pattern P :: a -> b -> (a, b) 	-- Defined at <interactive>:2:1

For comparison, using :info on a normal field selector shows a condensed version of the datatype to which it belongs, which is more informative and makes sense even when NoFieldSelectors is in use:

ghci> data Pair a b = MkPair { x :: a, y :: b }
ghci> :info x
type Pair :: * -> * -> *
data Pair a b = MkPair {x :: a, ...}
  	-- Defined at <interactive>:4:26
ghci> :info Pair
type Pair :: * -> * -> *
data Pair a b = MkPair {x :: a, y :: b}
  	-- Defined at <interactive>:4:1
ghci> :info MkPair
type Pair :: * -> * -> *
data Pair a b = MkPair {...}
  	-- Defined at <interactive>:4:17

(In the last case it seems odd to elide the fields of MkPair, but it isn't really a problem.)

Perhaps we should do something similar in the pattern synonym case, and show the full definition? That is, :info on a pattern synonym or one of its fields could yield something like:

pattern P :: a -> b -> (a, b)
pattern P{x,y} = (x,y)

This would convey more information and be valid even when NoFieldSelectors is in use.