diff options
Diffstat (limited to 'compiler/GHC/Core/Coercion/Axiom.hs')
| -rw-r--r-- | compiler/GHC/Core/Coercion/Axiom.hs | 42 |
1 files changed, 28 insertions, 14 deletions
diff --git a/compiler/GHC/Core/Coercion/Axiom.hs b/compiler/GHC/Core/Coercion/Axiom.hs index 409acea036..5e6b456081 100644 --- a/compiler/GHC/Core/Coercion/Axiom.hs +++ b/compiler/GHC/Core/Coercion/Axiom.hs @@ -39,7 +39,7 @@ import GHC.Prelude import Language.Haskell.Syntax.Basic (Role(..)) import {-# SOURCE #-} GHC.Core.TyCo.Rep ( Type ) -import {-# SOURCE #-} GHC.Core.TyCo.Ppr ( pprType ) +import {-# SOURCE #-} GHC.Core.TyCo.Ppr ( pprType, pprTyVar ) import {-# SOURCE #-} GHC.Core.TyCon ( TyCon ) import GHC.Utils.Outputable import GHC.Data.FastString @@ -278,7 +278,6 @@ coAxiomArity ax index = length tvs + length cvs where CoAxBranch { cab_tvs = tvs, cab_cvs = cvs } = coAxiomNthBranch ax index - coAxiomName :: CoAxiom br -> Name coAxiomName = co_ax_name @@ -334,7 +333,7 @@ placeHolderIncomps = panic "placeHolderIncomps" Note [CoAxBranch type variables] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ In the case of a CoAxBranch of an associated type-family instance, -we use the *same* type variables (where possible) as the +we use the *same* type variables in cab_tvs (where possible) as the enclosing class or instance. Consider instance C Int [z] where @@ -344,8 +343,11 @@ In the CoAxBranch in the instance decl (F Int [z]) we use the same 'z', so that it's easy to check that that type is the same as that in the instance header. -So, unlike FamInsts, there is no expectation that the cab_tvs -are fresh wrt each other, or any other CoAxBranch. +However, I believe that the cab_tvs of any CoAxBranch are distinct +from the cab_tvs of other CoAxBranches in the same CoAxiom. This is +important when checking for compatiblity and apartness; e.g. see +GHC.Core.FamInstEnv.compatibleBranches. (The story seems a bit wobbly +here, but it seems to work.) Note [CoAxBranch roles] ~~~~~~~~~~~~~~~~~~~~~~~ @@ -461,6 +463,12 @@ See also: * Note [RoughMap and rm_empty] for how this complicates the RoughMap implementation slightly. -} +{- ********************************************************************* +* * + Instances, especially pretty-printing +* * +********************************************************************* -} + instance Eq (CoAxiom br) where a == b = getUnique a == getUnique b a /= b = getUnique a /= getUnique b @@ -468,9 +476,6 @@ instance Eq (CoAxiom br) where instance Uniquable (CoAxiom br) where getUnique = co_ax_unique -instance Outputable (CoAxiom br) where - ppr = ppr . getName - instance NamedThing (CoAxiom br) where getName = co_ax_name @@ -480,13 +485,22 @@ instance Typeable br => Data.Data (CoAxiom br) where gunfold _ _ = error "gunfold" dataTypeOf _ = mkNoRepType "CoAxiom" +instance Outputable (CoAxiom br) where + -- You may want GHC.Core.Coercion.pprCoAxiom instead + ppr = ppr . getName + instance Outputable CoAxBranch where - ppr (CoAxBranch { cab_loc = loc - , cab_lhs = lhs - , cab_rhs = rhs }) = - text "CoAxBranch" <+> parens (ppr loc) <> colon - <+> brackets (pprWithCommas pprType lhs) - <+> text "=>" <+> pprType rhs + -- This instance doesn't know the name of the type family + -- If possible, use GHC.Core.Coercion.pprCoAxBranch instead + ppr (CoAxBranch { cab_tvs = tvs, cab_cvs = cvs + , cab_lhs = lhs_tys, cab_rhs = rhs, cab_incomps = incomps }) + = text "CoAxBranch" <+> braces payload + where + payload = hang (text "forall" <+> pprWithCommas pprTyVar (tvs ++ cvs) <> dot) + 2 (vcat [ text "<tycon>" <+> sep (map pprType lhs_tys) + , nest 2 (text "=" <+> ppr rhs) + , ppUnless (null incomps) $ + text "incomps:" <+> vcat (map ppr incomps) ]) {- ************************************************************************ |