Lookup rules associated with functions/values in GHCI

It would be nice to have a way to look up in GHCi what rules can fire for a certain constant as the outmost symbol on the LHS. For example, something like

ghci> :pragmas map
{-# RULE "map"         [~1] forall f xs. map f xs = build (\c n -> foldr (mapFB c f) n xs) #-}
{-# RULE "map/coerce"  [1]               map coerce = coerce #-}

As the name suggests, I think we would also want to list applicable NOINLINE, INLINE, INLINABLE, CONLIKE, SPECIALIZE, etc pragmas too. This would simplify the process of debugging mis-firing rules.

If this isn't too difficult, I'd love to try implementing it. I've been looking for some way of contributing to GHC.

This initially came up here http://stackoverflow.com/q/38651602/3072788.

Trac metadata

Trac field	Value
Version	8.0.1
Type	FeatureRequest
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	GHCi
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