X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Ftypes%2FTypeRep.lhs;h=db41403a4b46b009779dbc5e342d579b63e19cfb;hp=0f400fadcd9d77b3efed8f5d76f3d7badd25c7c3;hb=914e415702a25a6e52ab1eaaf2aea233d6c6097e;hpb=b855273185a7b86c65172c10674c98bab1052e2c

diff --git a/compiler/types/TypeRep.lhs b/compiler/types/TypeRep.lhs
index 0f400fa..db41403 100644
--- a/compiler/types/TypeRep.lhs
+++ b/compiler/types/TypeRep.lhs
@@ -145,11 +145,12 @@ data Type
 	                --    can appear as the right hand side of a type synonym.
 
   | FunTy
-	Type
+	Type		
 	Type		-- ^ Special case of 'TyConApp': @TyConApp FunTyCon [t1, t2]@
+			-- See Note [Equality-constrained types]
 
   | ForAllTy
-	TyCoVar         -- ^ Type *or* coercion variable; see Note [Equality-constrained types]
+	TyCoVar         -- Type variable
 	Type	        -- ^ A polymorphic type
 
   | PredTy
@@ -183,21 +184,9 @@ The type   forall ab. (a ~ [b]) => blah
 is encoded like this:
 
    ForAllTy (a:*) $ ForAllTy (b:*) $
-   ForAllTy (wild_co : a ~ [b]) $
+   FunTy (PredTy (EqPred a [b]) $
    blah
 
-That is, the "(a ~ [b]) =>" part is encode as a for-all
-type with a coercion variable that is never mentioned.
-
-We could instead have used a FunTy with an EqPred on the 
-left.  But we want 
-
-  * FunTy to mean RUN-TIME abstraction,
-    passing a real value at runtime, 
-
-  * ForAllTy to mean COMPILE-TIME abstraction, 
-    erased at runtime
-
 -------------------------------------
  		Note [PredTy]