[project @ 2002-10-11 16:45:16 by simonpj]

[ghc-hetmet.git] / ghc / compiler / typecheck / TcRules.lhs

diff --git a/ghc/compiler/typecheck/TcRules.lhs b/ghc/compiler/typecheck/TcRules.lhs
index 6f9890b..fb3464d 100644 (file)
--- a/ghc/compiler/typecheck/TcRules.lhs
+++ b/ghc/compiler/typecheck/TcRules.lhs
@@ -8,21 +8,20 @@ module TcRules ( tcRules ) where
 
 #include "HsVersions.h"
 
-import HsSyn           ( RuleDecl(..), RuleBndr(..), HsExpr(..), collectRuleBndrSigTys )
+import HsSyn           ( RuleDecl(..), RuleBndr(..), collectRuleBndrSigTys )
 import CoreSyn         ( CoreRule(..) )
 import RnHsSyn         ( RenamedRuleDecl )
-import TcHsSyn         ( TypecheckedRuleDecl, TcExpr, mkHsLet )
+import TcHsSyn         ( TypecheckedRuleDecl, mkHsLet )
 import TcRnMonad
 import TcSimplify      ( tcSimplifyToDicts, tcSimplifyInferCheck )
 import TcMType         ( newTyVarTy )
-import TcType          ( TcTyVarSet, tyVarsOfTypes, openTypeKind )
+import TcType          ( tyVarsOfTypes, openTypeKind )
 import TcIfaceSig      ( tcCoreExpr, tcCoreLamBndrs, tcVar )
 import TcMonoType      ( tcHsSigType, UserTypeCtxt(..), tcAddScopedTyVars )
 import TcExpr          ( tcMonoExpr )
 import TcEnv           ( tcExtendLocalValEnv )
 import Inst            ( instToId )
 import Id              ( idType, mkLocalId )
-import VarSet
 import Outputable
 \end{code}
 
@@ -87,12 +86,10 @@ tcRule (HsRule name act vars lhs rhs src_loc)
        --      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
@@ -114,34 +111,6 @@ tcRule (HsRule name act vars lhs rhs src_loc)
     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}