#4175: GHCi support for type/data families should match that of related features ---------------------------------+------------------------------------------ Reporter: claus | Owner: Type: bug | Status: patch Priority: low | Milestone: 7.6.2 Component: GHCi | Version: 6.12.3 Keywords: FD TF | Os: Unknown/Multiple Architecture: Unknown/Multiple | Failure: None/Unknown Difficulty: | Testcase: Blockedby: | Blocking: Related: | ---------------------------------+------------------------------------------ Changes (by parcs): * status: new => patch Comment: I've attached a patch that implements support for showing type family instances through `:info`. Examples: {{{ {-# LANGUAGE TypeFamilies #-} type family A a b type instance A Int Int = () type instance A (Maybe a) a = a data family B a data instance B () = MkB class C a where type D a b instance C Int where type D Int () = String instance C () where type D () () = Bool type family E a type instance where E () = Bool E Int = String }}} {{{ Main> :i A type family A a b :: * -- Defined at tf.hs:3:13 type instance A (Maybe a) a -- Defined at tf.hs:5:15 type instance A Int Int -- Defined at tf.hs:4:15 }}} {{{ *Main> :i B data family B a -- Defined at tf.hs:7:13 data instance B () -- Defined at tf.hs:8:15 }}} {{{ *Main> :i D class C a where type family D a b :: * -- Defined at tf.hs:11:10 type D () () -- Defined at tf.hs:17:10 type D Int () -- Defined at tf.hs:14:10 }}} {{{ Main> :i E type family E a :: * -- Defined at tf.hs:23:13 type instance where E () -- Defined at tf.hs:26:5 E Int -- Defined at tf.hs:27:5 }}} {{{ *Main> :i () data () = () -- Defined in ‛GHC.Tuple’ instance C () -- Defined at tf.hs:16:10 ... data instance B () -- Defined at tf.hs:8:15 type D () () -- Defined at tf.hs:17:10 type D Int () -- Defined at tf.hs:14:10 type instance where E () -- Defined at tf.hs:26:5 E Int -- Defined at tf.hs:27:5 }}} {{{ *Main> :i Maybe data Maybe a = Nothing | Just a -- Defined in ‛Data.Maybe’ ... type instance A (Maybe a) a -- Defined at tf.hs:5:15 }}} {{{ *Main> :i Int data Int = GHC.Types.I# GHC.Prim.Int# -- Defined in ‛GHC.Types’ instance C Int -- Defined at tf.hs:13:10 ... type instance A Int Int -- Defined at tf.hs:4:15 type D Int () -- Defined at tf.hs:14:10 type instance where E () -- Defined at tf.hs:26:5 E Int -- Defined at tf.hs:27:5 }}} The patch causes a trivial testsuite failure: {{{ Unexpected failures: ghci/scripts T5417 [bad stdout] (ghci) }}} -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/4175#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler