Make printing of binding results optional in GHCi, and document it

[ghc-hetmet.git] / compiler / typecheck / TcType.lhs

diff --git a/compiler/typecheck/TcType.lhs b/compiler/typecheck/TcType.lhs
index 94ea3f9..21375a9 100644 (file)
--- a/compiler/typecheck/TcType.lhs
+++ b/compiler/typecheck/TcType.lhs
@@ -1,4 +1,4 @@
-
+%
 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
 %
 \section[TcType]{Types used in the typechecker}
@@ -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}
@@ -399,6 +399,7 @@ mkKindName unique = mkSystemName unique kind_var_occ
 
 kindVarRef :: KindVar -> IORef MetaDetails
 kindVarRef tc = 
+  ASSERT ( isTcTyVar tc )
   case tcTyVarDetails tc of
     MetaTv TauTv ref -> ref
     other            -> pprPanic "kindVarRef" (ppr tc)
@@ -472,7 +473,8 @@ pprSkolTvBinding :: TcTyVar -> SDoc
 -- Print info about the binding of a skolem tyvar, 
 -- or nothing if we don't have anything useful to say
 pprSkolTvBinding tv
-  = ppr_details (tcTyVarDetails tv)
+  = ASSERT ( isTcTyVar tv )
+    ppr_details (tcTyVarDetails tv)
   where
     ppr_details (MetaTv TauTv _)   = quotes (ppr tv) <+> ptext SLIT("is a meta type variable")
     ppr_details (MetaTv BoxTv _)   = quotes (ppr tv) <+> ptext SLIT("is a boxy type variable")
@@ -696,10 +698,14 @@ tcMultiSplitSigmaTy sigma
 
 -----------------------
 tcTyConAppTyCon :: Type -> TyCon
-tcTyConAppTyCon ty = fst (tcSplitTyConApp ty)
+tcTyConAppTyCon ty = case tcSplitTyConApp_maybe ty of
+                       Just (tc, _) -> tc
+                       Nothing      -> pprPanic "tcTyConAppTyCon" (pprType ty)
 
 tcTyConAppArgs :: Type -> [Type]
-tcTyConAppArgs ty = snd (tcSplitTyConApp ty)
+tcTyConAppArgs ty = case tcSplitTyConApp_maybe ty of
+                       Just (_, args) -> args
+                       Nothing        -> pprPanic "tcTyConAppArgs" (pprType ty)
 
 tcSplitTyConApp :: Type -> (TyCon, [Type])
 tcSplitTyConApp ty = case tcSplitTyConApp_maybe ty of