Comment-only: Fix a typo, and note that the PredTy case on SplitTyConApp_maybe was...

diff --git a/compiler/typecheck/TcType.lhs b/compiler/typecheck/TcType.lhs
index 888452b..c10c2eb 100644 (file)
--- a/compiler/typecheck/TcType.lhs
+++ b/compiler/typecheck/TcType.lhs
@@ -10,7 +10,7 @@ compiler.  These parts
                newtypes, and predicates are meaningful. 
        * look through usage types
 
-The "tc" prefix is for "typechechecker", because the type checker
+The "tc" prefix is for "TypeChecker", because the type checker
 is the principal client.
 
 \begin{code}
@@ -713,10 +713,16 @@ tcSplitTyConApp_maybe ty | Just ty' <- tcView ty = tcSplitTyConApp_maybe ty'
 tcSplitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys)
 tcSplitTyConApp_maybe (FunTy arg res)   = Just (funTyCon, [arg,res])
 tcSplitTyConApp_maybe (AppTy arg res)   = Just (funTyCon, [arg,res])
-tcSplitTyConApp_maybe (PredTy (ClassP _ [ty']))   = tcSplitTyConApp_maybe ty'
        -- Newtypes are opaque, so they may be split
        -- However, predicates are not treated
        -- as tycon applications by the type checker
+
+-- XXX - 2006-09-24: This case is hard-coded in (rendering predicates opaque as well)
+--       to make the newly reworked newtype-deriving work on the trivial case:
+--              newtype T = T () deriving (Eq, Ord)
+--       Please remove this if the newtype-deriving scheme no longer produces a PredTy.
+tcSplitTyConApp_maybe (PredTy (ClassP _ [ty']))   = tcSplitTyConApp_maybe ty'
+
 tcSplitTyConApp_maybe other            = Nothing
 
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