diff options
Diffstat (limited to 'compiler/GHC/Tc/Solver/Monad.hs')
| -rw-r--r-- | compiler/GHC/Tc/Solver/Monad.hs | 24 |
1 files changed, 11 insertions, 13 deletions
diff --git a/compiler/GHC/Tc/Solver/Monad.hs b/compiler/GHC/Tc/Solver/Monad.hs index 80f6e7f3a8..76d9316bf6 100644 --- a/compiler/GHC/Tc/Solver/Monad.hs +++ b/compiler/GHC/Tc/Solver/Monad.hs @@ -90,7 +90,7 @@ module GHC.Tc.Solver.Monad ( -- Irreds foldIrreds, - -- The flattening cache + -- The family application cache lookupFamAppInert, lookupFamAppCache, extendFamAppCache, pprKicked, @@ -124,7 +124,7 @@ module GHC.Tc.Solver.Monad ( -- if the whole instance matcher simply belongs -- here - breakTyVarCycle, flattenView + breakTyVarCycle, rewriterView ) where #include "HsVersions.h" @@ -1193,7 +1193,7 @@ old inert, because a [D] can rewrite a [WD]. inert: [D] F v ~ alpha (CEqCan) Can't make progress on this work item either (although GHC tries by -decomposing the cast and reflattening... but that doesn't make a difference), +decomposing the cast and rewriting... but that doesn't make a difference), which is still hetero. Emit a new kind equality and add to inert set. But, critically, we split the Irred. @@ -1215,7 +1215,7 @@ We decompose the cast, yielding [D] a ~ beta -We then flatten the kinds. The lhs kind is F v, which flattens to alpha. +We then rewrite the kinds. The lhs kind is F v, which flattens to alpha. co' :: F v ~ alpha [D] (a |> co') ~ beta @@ -1782,7 +1782,7 @@ kickOutAfterUnification new_tv ; setInertCans ics2 ; return n_kicked } --- See Wrinkle (2a) in Note [Equalities with incompatible kinds] in GHC.Tc.Solver.Canonical +-- See Wrinkle (2) in Note [Equalities with incompatible kinds] in GHC.Tc.Solver.Canonical kickOutAfterFillingCoercionHole :: CoercionHole -> Coercion -> TcS () kickOutAfterFillingCoercionHole hole filled_co = do { ics <- getInertCans @@ -2230,7 +2230,6 @@ type family applications? (Examples are below the explanation.) To allow flexibility in how type family applications unify we use the Core flattener. See Note [Flattening type-family applications when matching instances] in GHC.Core.Unify. -This is *distinct* from the flattener in GHC.Tc.Solver.Flatten. The Core flattener replaces all type family applications with fresh variables. The next question: should we allow these fresh variables in the domain of a unifying substitution? @@ -2445,7 +2444,7 @@ lookupFamAppCache fam_tc tys Nothing -> return Nothing } extendFamAppCache :: TyCon -> [Type] -> (TcCoercion, TcType) -> TcS () --- NB: co :: rhs ~ F tys, to match expectations of flattener +-- NB: co :: rhs ~ F tys, to match expectations of rewriter extendFamAppCache tc xi_args stuff@(_, ty) = do { dflags <- getDynFlags ; when (gopt Opt_FamAppCache dflags) $ @@ -2728,7 +2727,6 @@ data TcSEnv tcs_inerts :: IORef InertSet, -- Current inert set - -- The main work-list and the flattening worklist -- See Note [WorkList priorities] and tcs_worklist :: IORef WorkList -- Current worklist } @@ -3577,7 +3575,7 @@ breakTyVarCycle :: CtLoc -- This could be considerably more efficient. See Detail (5) of Note. breakTyVarCycle loc = go where - go ty | Just ty' <- flattenView ty = go ty' + go ty | Just ty' <- rewriterView ty = go ty' go (Rep.TyConApp tc tys) | isTypeFamilyTyCon tc = do { let (fun_args, extra_args) = splitAt (tyConArity tc) tys @@ -3621,9 +3619,9 @@ restoreTyVarCycles is -- Unwrap a type synonym only when either: -- The type synonym is forgetful, or -- the type synonym mentions a type family in its expansion --- See Note [Flattening synonyms] in GHC.Tc.Solver.Flatten. -flattenView :: TcType -> Maybe TcType -flattenView ty@(Rep.TyConApp tc _) +-- See Note [Rewriting synonyms] in GHC.Tc.Solver.Rewrite. +rewriterView :: TcType -> Maybe TcType +rewriterView ty@(Rep.TyConApp tc _) | isForgetfulSynTyCon tc || (isTypeSynonymTyCon tc && not (isFamFreeTyCon tc)) = tcView ty -flattenView _other = Nothing +rewriterView _other = Nothing |