X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcRnTypes.lhs;h=1e03afd5a383bba6f30d3c10acdb3ceb26471b3a;hb=d8f6f78cd8342fcfcb4a2789d7f9629123778f54;hp=4138c00a187ee1ab84b5f3f2dfe2ce4350201563;hpb=5822cb8d13aa3c05d2b46b4510c13d94b902eb21;p=ghc-hetmet.git

diff --git a/compiler/typecheck/TcRnTypes.lhs b/compiler/typecheck/TcRnTypes.lhs
index 4138c00..1e03afd 100644
--- a/compiler/typecheck/TcRnTypes.lhs
+++ b/compiler/typecheck/TcRnTypes.lhs
@@ -3,6 +3,13 @@
 % (c) The GRASP Project, Glasgow University, 1992-2002
 %
 \begin{code}
+{-# OPTIONS -w #-}
+-- The above warning supression flag is a temporary kludge.
+-- While working on this module you are encouraged to remove it and fix
+-- any warnings in the module. See
+--     http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
+-- for details
+
 module TcRnTypes(
 	TcRnIf, TcRn, TcM, RnM,	IfM, IfL, IfG, -- The monad is opaque outside this module
 	TcRef,
@@ -463,7 +470,7 @@ data RefinementVisibility
 					-- GADT refinement
 
 instance Outputable TcTyThing where	-- Debugging only
-   ppr (AGlobal g)      = ppr g
+   ppr (AGlobal g)      = pprTyThing g
    ppr elt@(ATcId {})   = text "Identifier" <> 
 			  ifPprDebug (brackets (ppr (tct_id elt) <> dcolon <> ppr (tct_type elt) <> comma
 				 <+> ppr (tct_level elt) <+> ppr (tct_co elt)))
@@ -628,6 +635,17 @@ In addition to the basic Haskell variants of 'Inst's, they can now also
 represent implication constraints 'forall tvs. (reft, given) => wanted'
 and equality constraints 'co :: ty1 ~ ty2'.
 
+NB: Equalities occur in two flavours:
+
+  (1) Dict {tci_pred = EqPred ty1 ty2}
+  (2) EqInst {tci_left = ty1, tci_right = ty2, tci_co = coe}
+
+The former arises from equalities in contexts, whereas the latter is used
+whenever the type checker introduces an equality (e.g., during deferring
+unification).
+
+I am not convinced that this duplication is necessary or useful! -=chak
+
 \begin{code}
 data Inst
   = Dict {