diff options
Diffstat (limited to 'compiler')
| -rw-r--r-- | compiler/ghci/RtClosureInspect.hs | 25 | ||||
| -rw-r--r-- | compiler/typecheck/TcErrors.lhs | 13 | ||||
| -rw-r--r-- | compiler/typecheck/TcType.lhs | 12 |
3 files changed, 24 insertions, 26 deletions
diff --git a/compiler/ghci/RtClosureInspect.hs b/compiler/ghci/RtClosureInspect.hs index b281695985..5d74dc92c2 100644 --- a/compiler/ghci/RtClosureInspect.hs +++ b/compiler/ghci/RtClosureInspect.hs @@ -571,17 +571,24 @@ liftTcM = id newVar :: Kind -> TR TcType newVar = liftTcM . newFlexiTyVarTy -type RttiInstantiation = [(TyVar, TcTyVar)] - -- Assoicates the debugger-world type variables (which are skolems) - -- to typechecker-world meta type variables (which are mutable, - -- and may be refined) +type RttiInstantiation = [(TcTyVar, TyVar)] + -- Associates the typechecker-world meta type variables + -- (which are mutable and may be refined), to their + -- debugger-world RuntimeUnkSkol counterparts. + -- If the TcTyVar has not been refined by the runtime type + -- elaboration, then we want to turn it back into the + -- original RuntimeUnkSkol -- | Returns the instantiated type scheme ty', and the --- mapping from old to new (instantiated) type variables +-- mapping from new (instantiated) -to- old (skolem) type variables +-- We want this mapping just for old RuntimeUnkSkols, to avoid +-- gratuitously changing their unique on every trip instScheme :: QuantifiedType -> TR (TcType, RttiInstantiation) instScheme (tvs, ty) = liftTcM $ do { (tvs', _, subst) <- tcInstTyVars tvs - ; return (substTy subst ty, tvs `zip` tvs') } + ; let rtti_inst = [(tv',tv) | (tv',tv) <- tvs' `zip` tvs + , isRuntimeUnkSkol tv] + ; return (substTy subst ty, rtti_inst) } applyRevSubst :: RttiInstantiation -> TR () -- Apply the *reverse* substitution in-place to any un-filled-in @@ -589,7 +596,7 @@ applyRevSubst :: RttiInstantiation -> TR () -- unless it has been refined by new information from the heap applyRevSubst pairs = liftTcM (mapM_ do_pair pairs) where - do_pair (rtti_tv, tc_tv) + do_pair (tc_tv, rtti_tv) = do { tc_ty <- zonkTcTyVar tc_tv ; case tcGetTyVar_maybe tc_ty of Just tv | isMetaTyVar tv -> writeMetaTyVar tv (mkTyVarTy rtti_tv) @@ -1131,6 +1138,10 @@ zonkRttiType = zonkType (mkZonkTcTyVar zonk_unbound_meta) zonk_unbound_meta tv = ASSERT( isTcTyVar tv ) do { tv' <- skolemiseUnboundMetaTyVar RuntimeUnkSkol tv + -- This is where RuntimeUnkSkols are born: + -- otherwise-unconstrained unification variables are + -- turned into RuntimeUnkSkols as they leave the + -- typechecker's monad ; return (mkTyVarTy tv') } -------------------------------------------------------------------------------- diff --git a/compiler/typecheck/TcErrors.lhs b/compiler/typecheck/TcErrors.lhs index c8f624f6ea..28fc91bcd2 100644 --- a/compiler/typecheck/TcErrors.lhs +++ b/compiler/typecheck/TcErrors.lhs @@ -640,17 +640,8 @@ warnDefaulting wanteds default_ty Note [Runtime skolems] ~~~~~~~~~~~~~~~~~~~~~~ We want to give a reasonably helpful error message for ambiguity -arising from *runtime* skolems in the debugger. Mostly these -are created by in RtClosureInspec.zonkRTTIType. However at a -breakpoint we return Ids from the CoreExpr, whose types may have -free type variables bound by some enclosing 'forall'. These are -UnkSkols, created ty TcType.zonkQuantifiedTyVar. - -These UnkSkols should never show up as ambiguous type variables in -normal typechecking, so we hackily emit the debugger-related message -both for RuntimeUnkSkols and UnkSkols. Hence the two cases in -TcType.isRuntimeUnkSkol. Yuk. The rest of the debugger is such -a mess that I don't feel motivated to clean up this bit. +arising from *runtime* skolems in the debugger. These +are created by in RtClosureInspect.zonkRTTIType. %************************************************************************ diff --git a/compiler/typecheck/TcType.lhs b/compiler/typecheck/TcType.lhs index 74100920bb..47bb554e86 100644 --- a/compiler/typecheck/TcType.lhs +++ b/compiler/typecheck/TcType.lhs @@ -673,14 +673,10 @@ isIndirect _ = False isRuntimeUnkSkol :: TyVar -> Bool -- Called only in TcErrors; see Note [Runtime skolems] there -isRuntimeUnkSkol x - | isTcTyVar x - , SkolemTv info <- tcTyVarDetails x - = case info of - UnkSkol -> True - RuntimeUnkSkol -> True - _ -> False - | otherwise = False +isRuntimeUnkSkol x | isTcTyVar x + , SkolemTv RuntimeUnkSkol <- tcTyVarDetails x + = True + | otherwise = False isUnkSkol :: TyVar -> Bool isUnkSkol x | isTcTyVar x |