import TcRnMonad
import TcSimplify ( tcSimplifyToDicts, tcSimplifyInferCheck )
import TcMType ( newTyVarTy )
-import TcType ( TcTyVarSet, tyVarsOfTypes, openTypeKind )
+import TcType ( TcTyVarSet, tyVarsOfTypes, tyVarsOfType, openTypeKind )
import TcIfaceSig ( tcCoreExpr, tcCoreLamBndrs, tcVar )
import TcMonoType ( tcHsSigType, UserTypeCtxt(..), tcAddScopedTyVars )
import TcExpr ( tcMonoExpr )
-- RULE: forall v. fst (ss v) = fst v
-- The type of the rhs of the rule is just a, but v::(a,(b,c))
--
- -- We also need to get the free tyvars of the LHS; see notes
- -- below with ruleLhsTvs.
+ -- We also need to get the free tyvars of the LHS; but we do that
+ -- during zonking (see TcHsSyn.zonkRule)
--
forall_tvs = tyVarsOfTypes (rule_ty : map idType tpl_ids)
- `unionVarSet`
- ruleLhsTvs lhs'
in
-- RHS can be a bit more lenient. In particular,
-- we let constant dictionaries etc float outwards
new_id (RuleBndrSig var rn_ty) = tcHsSigType (RuleSigCtxt var) rn_ty `thenM` \ ty ->
returnM (mkLocalId var ty)
-ruleLhsTvs :: TcExpr -> TcTyVarSet
--- We need to gather the type variables mentioned on the LHS so we can
--- quantify over them. Example:
--- data T a = C
---
--- foo :: T a -> Int
--- foo C = 1
---
--- {-# RULES "myrule" foo C = 1 #-}
---
--- After type checking the LHS becomes (foo a (C a))
--- and we do not want to zap the unbound tyvar 'a' to (), because
--- that limits the applicability of the rule. Instead, we
--- want to quantify over it!
---
--- Fortunately the form of the LHS is pretty limited (see RnSource.validRuleLhs)
--- so we don't need to deal with the whole of HsSyn.
---
-ruleLhsTvs (OpApp e1 op _ e2)
- = ruleLhsTvs e1 `unionVarSet` ruleLhsTvs op `unionVarSet` ruleLhsTvs e2
-ruleLhsTvs (HsApp e1 e2)
- = ruleLhsTvs e1 `unionVarSet` ruleLhsTvs e2
-ruleLhsTvs (HsVar v) = emptyVarSet -- I don't think we need the tyvars of the Id
-ruleLhsTvs (TyApp e1 tys)
- = ruleLhsTvs e1 `unionVarSet` tyVarsOfTypes tys
-ruleLhsTvs e = pprPanic "ruleLhsTvs" (ppr e)
-
-
ruleCtxt name = ptext SLIT("When checking the transformation rule") <+>
doubleQuotes (ftext name)
\end{code}