X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcDeriv.lhs;h=2563b0979dcf9b116e297244868e27d88f3f658d;hb=8053aac536c96dabdc06e9f068852f5481474a29;hp=b77796831a97f9d29cb0e078e8a171efcef86b1b;hpb=ad4a18b179fbe4ad314b3accf32e806cf00f2a0b;p=ghc-hetmet.git

diff --git a/compiler/typecheck/TcDeriv.lhs b/compiler/typecheck/TcDeriv.lhs
index b777968..2563b09 100644
--- a/compiler/typecheck/TcDeriv.lhs
+++ b/compiler/typecheck/TcDeriv.lhs
@@ -42,8 +42,7 @@ import NameSet		( duDefs )
 import Type		( splitKindFunTys )
 import TyCon		( tyConTyVars, tyConDataCons, tyConArity, tyConHasGenerics,
 			  tyConStupidTheta, isProductTyCon, isDataTyCon, newTyConRhs,
-			  isEnumerationTyCon, isRecursiveTyCon, TyCon, isNewTyCon,
-                          newTyConCo
+			  isEnumerationTyCon, isRecursiveTyCon, TyCon, isNewTyCon
 			)
 import TcType		( TcType, ThetaType, mkTyVarTys, mkTyConApp, tcTyConAppTyCon,
 			  isUnLiftedType, mkClassPred, tyVarsOfType,
@@ -333,8 +332,9 @@ not just use the Num one.  The instance we want is something like:
      instance (Num a, Show (Foo a), Eq (Foo a)) => Num (Foo a) where
      	(+) = ((+)@a)
      	...etc...
-There's no 'corece' needed because after the type checker newtypes
-are transparent.
+There may be a coercion needed which we get from the tycon for the newtype
+when the dict is constructed in TcInstDcls.tcInstDecl2
+
 
 \begin{code}
 makeDerivEqns :: OverlapFlag
@@ -464,7 +464,7 @@ makeDerivEqns overlap_flag tycl_decls
 		-- If there are no tyvars, there's no need
 		-- to abstract over the dictionaries we need
 	dict_tvs = deriv_tvs ++ tc_tvs
-	dict_args | null dict_tvs = []
+	dict_args -- | null dict_tvs = []
 		  | otherwise     = rep_pred : sc_theta
 
 		-- Finally! Here's where we build the dictionary Id