X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcExpr.lhs;h=e2f1d0cd5ea2ba4fbacde26712fe6ba18e87d805;hb=365ab3dad0f9a77e01758a14bf3817dea0ee2a31;hp=e6ab82b2636a4765b478facf57835c98c64904fa;hpb=e6d057711f4d6d6ff6342c39fa2b9e44d25447f1;p=ghc-hetmet.git

diff --git a/compiler/typecheck/TcExpr.lhs b/compiler/typecheck/TcExpr.lhs
index e6ab82b..e2f1d0c 100644
--- a/compiler/typecheck/TcExpr.lhs
+++ b/compiler/typecheck/TcExpr.lhs
@@ -21,7 +21,7 @@ import qualified DsMeta
 #endif
 
 import HsSyn		( HsExpr(..), LHsExpr, ArithSeqInfo(..), recBindFields,
-			  HsMatchContext(..), HsRecordBinds, mkHsWrap,
+			  HsMatchContext(..), HsRecordBinds, mkHsWrap, hsExplicitTvs,
 			  mkHsApp, mkLHsWrap )
 import TcHsSyn		( hsLitType )
 import TcRnMonad
@@ -32,7 +32,7 @@ import BasicTypes	( Arity, isMarkedStrict )
 import Inst		( newMethodFromName, newIPDict, instCall,
 			  newMethodWithGivenTy, instStupidTheta )
 import TcBinds		( tcLocalBinds )
-import TcEnv		( tcLookup, tcLookupDataCon, tcLookupField )
+import TcEnv		( tcLookup, tcLookupDataCon, tcLookupField, tcExtendTyVarEnv2 )
 import TcArrows		( tcProc )
 import TcMatches	( tcMatchesCase, tcMatchLambda, tcDoStmts, tcBody,
 			  TcMatchCtxt(..) )
@@ -45,7 +45,7 @@ import TcType		( TcType, TcSigmaType, TcRhoType, TvSubst,
 			  mkTyVarTys, mkFunTys, 
 			  tcMultiSplitSigmaTy, tcSplitFunTysN,
 			  tcSplitTyConApp_maybe, 
-			  isSigmaTy, mkFunTy, mkTyConApp, isLinearPred,
+			  isSigmaTy, mkFunTy, mkTyConApp, 
 			  exactTyVarsOfType, exactTyVarsOfTypes, 
 			  zipTopTvSubst, zipOpenTvSubst, substTys, substTyVar
 			)
@@ -111,7 +111,7 @@ tcPolyExpr expr res_ty
 
 tcPolyExprNC expr res_ty 
   | isSigmaTy res_ty
-  = do	{ (gen_fn, expr') <- tcGen res_ty emptyVarSet (tcPolyExprNC expr)
+  = do	{ (gen_fn, expr') <- tcGen res_ty emptyVarSet (\_ -> tcPolyExprNC expr)
 		-- Note the recursive call to tcPolyExpr, because the
 		-- type may have multiple layers of for-alls
 	; return (mkLHsWrap gen_fn expr') }
@@ -208,9 +208,14 @@ tcExpr (HsLam match) res_ty
 
 tcExpr in_expr@(ExprWithTySig expr sig_ty) res_ty
  = do	{ sig_tc_ty <- tcHsSigType ExprSigCtxt sig_ty
-	; expr' <- tcPolyExpr expr sig_tc_ty
+
+	-- Remember to extend the lexical type-variable environment
+	; (gen_fn, expr') <- tcGen sig_tc_ty emptyVarSet (\ skol_tvs res_ty ->
+		             tcExtendTyVarEnv2 (hsExplicitTvs sig_ty `zip` mkTyVarTys skol_tvs) $
+			     tcPolyExprNC expr res_ty)
+
 	; co_fn <- tcSubExp sig_tc_ty res_ty
-	; return (mkHsWrap co_fn (ExprWithTySigOut expr' sig_ty)) }
+	; return (mkHsWrap co_fn (ExprWithTySigOut (mkLHsWrap gen_fn expr') sig_ty)) }
 
 tcExpr (HsType ty) res_ty
   = failWithTc (text "Can't handle type argument:" <+> ppr ty)
@@ -796,19 +801,9 @@ instFun orig fun subst tv_theta_prs
 	= do { co_fn <- instCall orig tys theta
 	     ; go False (HsWrap co_fn fun) prs }
 
-	-- 	Hack Alert (want_method_inst)!
 	-- See Note [No method sharing]
-	-- If 	f :: (%x :: T) => Int -> Int
-	-- Then if we have two separate calls, (f 3, f 4), we cannot
-	-- make a method constraint that then gets shared, thus:
-	--	let m = f %x in (m 3, m 4)
-	-- because that loses the linearity of the constraint.
-	-- The simplest thing to do is never to construct a method constraint
-	-- in the first place that has a linear implicit parameter in it.
-    want_method_inst theta =  not (null theta)			-- Overloaded
-			   && not (any isLinearPred theta)	-- Not linear
+    want_method_inst theta =  not (null theta)	-- Overloaded
 		   	   && not opt_NoMethodSharing
-		-- See Note [No method sharing] below
 \end{code}
 
 Note [Multiple instantiation]