diff options
Diffstat (limited to 'compiler/typecheck/TcType.hs')
| -rw-r--r-- | compiler/typecheck/TcType.hs | 46 |
1 files changed, 31 insertions, 15 deletions
diff --git a/compiler/typecheck/TcType.hs b/compiler/typecheck/TcType.hs index 83d491f3dc..230c5626fb 100644 --- a/compiler/typecheck/TcType.hs +++ b/compiler/typecheck/TcType.hs @@ -851,13 +851,14 @@ allBoundVariabless = mapUnionVarSet allBoundVariables * * ********************************************************************* -} -data TcDepVars -- See note [Dependent type variables] - = DV { dv_kvs :: TyCoVarSet -- "kind" variables (dependent) - , dv_tvs :: TyVarSet -- "type" variables (non-dependent) - -- The two are disjoint sets +data TcDepVars -- See Note [Dependent type variables] + -- See Note [TcDepVars determinism] + = DV { dv_kvs :: DTyCoVarSet -- "kind" variables (dependent) + , dv_tvs :: DTyVarSet -- "type" variables (non-dependent) + -- The two are disjoint sets } -depVarsTyVars :: TcDepVars -> TyVarSet +depVarsTyVars :: TcDepVars -> DTyVarSet depVarsTyVars = dv_tvs instance Outputable TcDepVars where @@ -895,13 +896,26 @@ Note that (k1 :: k2), (k2 :: *) The "type variables" do not depend on each other; if one did, it'd be classified as a kind variable! + +Note [TcDepVars determinism] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +When we quantify over type variables we decide the order in which they +appear in the final type. Because the order of type variables in the type +can end up in the interface file and affects some optimizations like +worker-wrapper we want this order to be deterministic. + +To achieve that we use deterministic sets of variables that can be converted to +lists in a deterministic order. + +For more information about deterministic sets see +Note [Deterministic UniqFM] in UniqDFM. -} splitDepVarsOfType :: Type -> TcDepVars -- See Note [Dependent type variables] splitDepVarsOfType ty = DV { dv_kvs = dep_vars - , dv_tvs = nondep_vars `minusVarSet` dep_vars } + , dv_tvs = nondep_vars `minusDVarSet` dep_vars } where Pair dep_vars nondep_vars = split_dep_vars ty @@ -910,28 +924,30 @@ splitDepVarsOfTypes :: [Type] -> TcDepVars -- See Note [Dependent type variables] splitDepVarsOfTypes tys = DV { dv_kvs = dep_vars - , dv_tvs = nondep_vars `minusVarSet` dep_vars } + , dv_tvs = nondep_vars `minusDVarSet` dep_vars } where Pair dep_vars nondep_vars = foldMap split_dep_vars tys -- | Worker for 'splitDepVarsOfType'. This might output the same var -- in both sets, if it's used in both a type and a kind. -split_dep_vars :: Type -> Pair TyCoVarSet -- Pair kvs tvs +-- See Note [TcDepVars determinism] +split_dep_vars :: Type -> Pair DTyCoVarSet -- Pair kvs tvs split_dep_vars = go where - go (TyVarTy tv) = Pair (tyCoVarsOfType $ tyVarKind tv) - (unitVarSet tv) + go (TyVarTy tv) = Pair (tyCoVarsOfTypeDSet $ tyVarKind tv) + (unitDVarSet tv) go (AppTy t1 t2) = go t1 `mappend` go t2 go (TyConApp _ tys) = foldMap go tys go (ForAllTy (Anon arg) res) = go arg `mappend` go res go (ForAllTy (Named tv _) ty) = let Pair kvs tvs = go ty in - Pair (kvs `delVarSet` tv `unionVarSet` tyCoVarsOfType (tyVarKind tv)) - (tvs `delVarSet` tv) + Pair (kvs `delDVarSet` tv + `extendDVarSetList` tyCoVarsOfTypeList (tyVarKind tv)) + (tvs `delDVarSet` tv) go (LitTy {}) = mempty - go (CastTy ty co) = go ty `mappend` Pair (tyCoVarsOfCo co) - emptyVarSet - go (CoercionTy co) = Pair (tyCoVarsOfCo co) emptyVarSet + go (CastTy ty co) = go ty `mappend` Pair (tyCoVarsOfCoDSet co) + emptyDVarSet + go (CoercionTy co) = Pair (tyCoVarsOfCoDSet co) emptyDVarSet {- ************************************************************************ |