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| author | Simon Peyton Jones <simonpj@microsoft.com> | 2018-07-24 08:57:34 +0100 |
|---|---|---|
| committer | Simon Peyton Jones <simonpj@microsoft.com> | 2018-07-24 08:57:34 +0100 |
| commit | e1b5a1174e42e390855b153015ce5227b3251d89 (patch) | |
| tree | fde15f0774013eb06559da5a5173ec53b0b7803f /compiler/types/Type.hs | |
| parent | f0d27f515ffbc476144d1d1dd1a71bf9fa93c94b (diff) | |
| download | haskell-e1b5a1174e42e390855b153015ce5227b3251d89.tar.gz | |
Fix a nasty bug in piResultTys
I was failing to instantiate vigorously enough in Type.piResultTys
and in the very similar function ToIface.toIfaceAppArgsX
This caused Trac #15428. The fix is easy.
See Note [Care with kind instantiation] in Type.hs
Diffstat (limited to 'compiler/types/Type.hs')
| -rw-r--r-- | compiler/types/Type.hs | 43 |
1 files changed, 35 insertions, 8 deletions
diff --git a/compiler/types/Type.hs b/compiler/types/Type.hs index e96188f218..a38bd1f0a6 100644 --- a/compiler/types/Type.hs +++ b/compiler/types/Type.hs @@ -1038,13 +1038,12 @@ piResultTys ty orig_args@(arg:args) | ForAllTy (TvBndr tv _) res <- ty = go (extendVarEnv tv_env tv arg) res args - | TyVarTy tv <- ty - , Just ty' <- lookupVarEnv tv_env tv - -- Deals with piResultTys (forall a. a) [forall b.b, Int] - = piResultTys ty' all_args - - | otherwise - = pprPanic "piResultTys2" (ppr ty $$ ppr orig_args $$ ppr all_args) + | otherwise -- See Note [Care with kind instantiation] + = ASSERT2( not (isEmptyVarEnv tv_env) + , ppr ty $$ ppr orig_args $$ ppr all_args ) + go emptyTvSubstEnv + (substTy (mkTvSubst in_scope tv_env) ty) + all_args applyTysX :: [TyVar] -> Type -> [Type] -> Type -- applyTyxX beta-reduces (/\tvs. body_ty) arg_tys @@ -1058,7 +1057,35 @@ applyTysX tvs body_ty arg_tys pp_stuff = vcat [ppr tvs, ppr body_ty, ppr arg_tys] n_tvs = length tvs -{- + + +{- Note [Care with kind instantiation] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Suppose we have + T :: forall k. k +and we are finding the kind of + T (forall b. b -> b) * Int +Then + T (forall b. b->b) :: k[ k :-> forall b. b->b] + :: forall b. b -> b +So + T (forall b. b->b) * :: (b -> b)[ b :-> *] + :: * -> * + +In other words wwe must intantiate the forall! + +Similarly (Trac #154218) + S :: forall k f. k -> f k +and we are finding the kind of + S * (* ->) Int Bool +We have + S * (* ->) :: (k -> f k)[ k :-> *, f :-> (* ->)] + :: * -> * -> * +So again we must instantiate. + +The same thing happens in ToIface.toIfaceAppArgsX. + + --------------------------------------------------------------------- TyConApp ~~~~~~~~ |