Simon's big boxy-type commit

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

diff --git a/ghc/compiler/typecheck/TcRules.lhs b/ghc/compiler/typecheck/TcRules.lhs
index 704f2f9..5017533 100644 (file)
--- a/ghc/compiler/typecheck/TcRules.lhs
+++ b/ghc/compiler/typecheck/TcRules.lhs
@@ -11,10 +11,10 @@ module TcRules ( tcRules ) where
 import HsSyn           ( RuleDecl(..), LRuleDecl, RuleBndr(..), mkHsDictLet )
 import TcRnMonad
 import TcSimplify      ( tcSimplifyToDicts, tcSimplifyInferCheck )
-import TcMType         ( newTyFlexiVarTy, zonkQuantifiedTyVar )
-import TcType          ( tyVarsOfTypes, openTypeKind )
+import TcMType         ( newFlexiTyVarTy, zonkQuantifiedTyVar, tcSkolSigTyVars )
+import TcType          ( tyVarsOfTypes, openTypeKind, SkolemInfo(..), substTyWith, mkTyVarTys )
 import TcHsType                ( UserTypeCtxt(..), tcHsPatSigType )
-import TcExpr          ( tcCheckRho )
+import TcExpr          ( tcMonoExpr )
 import TcEnv           ( tcExtendIdEnv, tcExtendTyVarEnv )
 import Inst            ( instToId )
 import Id              ( idType, mkLocalId )
@@ -32,13 +32,13 @@ tcRule (HsRule name act vars lhs rhs)
   = addErrCtxt (ruleCtxt name)                 $
     traceTc (ptext SLIT("---- Rule ------")
                 <+> ppr name)                  `thenM_` 
-    newTyFlexiVarTy openTypeKind               `thenM` \ rule_ty ->
+    newFlexiTyVarTy openTypeKind               `thenM` \ rule_ty ->
 
        -- Deal with the tyvars mentioned in signatures
     tcRuleBndrs vars (\ ids ->
                -- Now LHS and RHS
-       getLIE (tcCheckRho lhs rule_ty) `thenM` \ (lhs', lhs_lie) ->
-       getLIE (tcCheckRho rhs rule_ty) `thenM` \ (rhs', rhs_lie) ->
+       getLIE (tcMonoExpr lhs rule_ty) `thenM` \ (lhs', lhs_lie) ->
+       getLIE (tcMonoExpr rhs rule_ty) `thenM` \ (rhs', rhs_lie) ->
        returnM (ids, lhs', rhs', lhs_lie, rhs_lie)
     )                          `thenM` \ (ids, lhs', rhs', lhs_lie, rhs_lie) ->
 
@@ -90,14 +90,20 @@ tcRule (HsRule name act vars lhs rhs)
 
 tcRuleBndrs [] thing_inside = thing_inside []
 tcRuleBndrs (RuleBndr var : vars) thing_inside
-  = do         { ty <- newTyFlexiVarTy openTypeKind
+  = do         { ty <- newFlexiTyVarTy openTypeKind
        ; let id = mkLocalId (unLoc var) ty
        ; tcExtendIdEnv [id] $
          tcRuleBndrs vars (\ids -> thing_inside (id:ids)) }
 tcRuleBndrs (RuleBndrSig var rn_ty : vars) thing_inside
-  = do { (tyvars, ty) <- tcHsPatSigType (RuleSigCtxt (unLoc var)) rn_ty
-       ; let id = mkLocalId (unLoc var) ty
-       ; tcExtendTyVarEnv tyvars $
+--  e.g        x :: a->a
+--  The tyvar 'a' is brought into scope first, just as if you'd written
+--             a::*, x :: a->a
+  = do { let ctxt = RuleSigCtxt (unLoc var)
+       ; (tyvars, ty) <- tcHsPatSigType ctxt rn_ty
+       ; let skol_tvs = tcSkolSigTyVars (SigSkol ctxt) tyvars
+             id_ty = substTyWith tyvars (mkTyVarTys skol_tvs) ty
+             id = mkLocalId (unLoc var) id_ty
+       ; tcExtendTyVarEnv skol_tvs $
          tcExtendIdEnv [id] $
          tcRuleBndrs vars (\ids -> thing_inside (id:ids)) }