import TcType ( Type, Kind, SourceType(..), ThetaType, TyVarDetails(..),
TcTyVar, TcKind, TcThetaType, TcTauType,
mkTyVarTy, mkTyVarTys, mkFunTy,
- hoistForAllTys, zipFunTys,
+ zipFunTys, mkForAllTys, mkFunTys, tcEqType, isPredTy,
mkSigmaTy, mkPredTy, mkGenTyConApp, mkTyConApp, mkAppTys,
liftedTypeKind, unliftedTypeKind, mkArrowKind,
- mkArrowKinds, tcSplitFunTy_maybe
+ mkArrowKinds, tcSplitFunTy_maybe, tcSplitForAllTys
)
import Inst ( Inst, InstOrigin(..), newMethodWithGivenTy, instToId )
import Class ( classTyCon )
import Name ( Name )
import NameSet
+import Subst ( deShadowTy )
import TysWiredIn ( mkListTy, mkPArrTy, mkTupleTy, genUnitTyCon )
import BasicTypes ( Boxity(..) )
import SrcLoc ( SrcLoc )
import Util ( lengthIs )
import Outputable
-
+import List ( nubBy )
\end{code}
\end{code}
+%************************************************************************
+%* *
+\subsection{Errors and contexts}
+%* *
+%************************************************************************
+
+
+\begin{code}
+hoistForAllTys :: Type -> Type
+-- Used for user-written type signatures only
+-- Move all the foralls and constraints to the top
+-- e.g. T -> forall a. a ==> forall a. T -> a
+-- T -> (?x::Int) -> Int ==> (?x::Int) -> T -> Int
+--
+-- We want to 'look through' type synonyms when doing this
+-- so it's better done on the Type than the HsType
+
+hoistForAllTys ty
+ = let
+ no_shadow_ty = deShadowTy ty
+ -- Running over ty with an empty substitution gives it the
+ -- no-shadowing property. This is important. For example:
+ -- type Foo r = forall a. a -> r
+ -- foo :: Foo (Foo ())
+ -- Here the hoisting should give
+ -- foo :: forall a a1. a -> a1 -> ()
+ --
+ -- What about type vars that are lexically in scope in the envt?
+ -- We simply rely on them having a different unique to any
+ -- binder in 'ty'. Otherwise we'd have to slurp the in-scope-tyvars
+ -- out of the envt, which is boring and (I think) not necessary.
+ in
+ case hoist no_shadow_ty of
+ (tvs, theta, body) -> mkForAllTys tvs (mkFunTys (nubBy tcEqType theta) body)
+ -- The 'nubBy' eliminates duplicate constraints
+ where
+ hoist ty
+ | (tvs1, body_ty) <- tcSplitForAllTys ty,
+ not (null tvs1)
+ = case hoist body_ty of
+ (tvs2,theta,tau) -> (tvs1 ++ tvs2, theta, tau)
+
+ | Just (arg, res) <- tcSplitFunTy_maybe ty
+ = let
+ arg' = hoistForAllTys arg -- Don't forget to apply hoist recursively
+ in -- to the argument type
+ if (isPredTy arg') then
+ case hoist res of
+ (tvs,theta,tau) -> (tvs, arg':theta, tau)
+ else
+ case hoist res of
+ (tvs,theta,tau) -> (tvs, theta, mkFunTy arg' tau)
+
+ | otherwise = ([], [], ty)
+\end{code}
+
%************************************************************************
%* *
---------------------------------
-- Misc type manipulators
- hoistForAllTys, deNoteType,
+ deNoteType,
namesOfType, namesOfDFunHead,
getDFunTyKey,
%************************************************************************
\begin{code}
-hoistForAllTys :: Type -> Type
--- Used for user-written type signatures only
--- Move all the foralls and constraints to the top
--- e.g. T -> forall a. a ==> forall a. T -> a
--- T -> (?x::Int) -> Int ==> (?x::Int) -> T -> Int
---
--- We want to 'look through' type synonyms when doing this
--- so it's better done on the Type than the HsType
-
-hoistForAllTys ty
- = case hoist ty ty of
- (tvs, theta, body) -> mkForAllTys tvs (mkFunTys theta body)
- where
- hoist orig_ty (ForAllTy tv ty) = case hoist ty ty of
- (tvs,theta,tau) -> (tv:tvs,theta,tau)
- hoist orig_ty (FunTy arg res)
- | isPredTy arg' = case hoist res res of
- (tvs,theta,tau) -> (tvs,arg':theta,tau)
- | otherwise = case hoist res res of
- (tvs,theta,tau) -> (tvs,theta,mkFunTy arg' tau)
- where
- arg' = hoistForAllTys arg -- Don't forget to apply hoist recursively
- -- to the argument type
-
- hoist orig_ty (NoteTy _ ty) = hoist orig_ty ty
- hoist orig_ty ty = ([], [], orig_ty)
-\end{code}
-
-
-\begin{code}
deNoteType :: Type -> Type
-- Remove synonyms, but not source types
deNoteType ty@(TyVarTy tyvar) = ty