id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	os	architecture	failure	difficulty	testcase	blockedby	blocking	related
4175	GHCi support for type/data families should match that of related features	claus		"Currently, GHCi queries are not as helpful with type and data families as they are with type synonyms or class instances. Consider this module:
{{{
{-# LANGUAGE FunctionalDependencies #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE TypeFamilies #-}

type family TF a
type instance TF Bool = Char
type instance TF Int  = Bool

data family DF a
data instance DF Bool = DFC Char
data instance DF Int  = DFB Bool

class FD a b | a -> b
instance FD Bool Char
instance FD Int  Bool

type TS a = (a,a)
}}}
and compare the output of `:info` for these items:
{{{
*Main> :i TS
type TS a = (a, a)
        -- Defined at C:\Users\claus\Desktop\tmp\fd-tf\tf-df-info.hs:17:5-6
*Main> :i TF
type family TF a :: *
        -- Defined at C:\Users\claus\Desktop\tmp\fd-tf\tf-df-info.hs:5:12-13
*Main> :i FD
class FD a b | a -> b
        -- Defined at C:\Users\claus\Desktop\tmp\fd-tf\tf-df-info.hs:13:6-7
instance FD Bool Char
  -- Defined at C:\Users\claus\Desktop\tmp\fd-tf\tf-df-info.hs:14:9-20
instance FD Int Bool
  -- Defined at C:\Users\claus\Desktop\tmp\fd-tf\tf-df-info.hs:15:9-20
*Main> :i DF
data family DF a
        -- Defined at C:\Users\claus\Desktop\tmp\fd-tf\tf-df-info.hs:9:12-13
}}}
Neither the type family definition nor the data family instances are listed. If we try `:browse` instead
{{{
*Main> :browse
type family TF a :: *
data family DF a
data instance Main.R:DFBool Bool = DFC Char
data instance Main.R:DFInt Int = DFB Bool
class FD a b | a -> b
type TS a = (a, a)
}}}
we get some form of info about the data family instances, though no instances are listed for the plain old class, and the data family instance info shows internal encoding details."	bug	closed	low	7.6.2	GHCi	6.12.3	fixed	FD TF	shelarcy@…	Unknown/Multiple	Unknown/Multiple	None/Unknown	Unknown	ghci/scripts/T4175