Remove the deriving Show bits

Useful for debugging, but kind of scary because they all hinge on an
`unsafePerformIO`

compiler/src/Type/Occurs.hs

@@ -18,7 +18,7 @@ import qualified Type.UnionFind as UF
 
 
 occurs :: Type.Variable -> IO Bool
-occurs var = 
+occurs var =
   occursHelp [] var False
 
 

compiler/src/Type/Type.hs

@@ -64,7 +64,6 @@ data Constraint
       , _headerCon :: Constraint
       , _bodyCon :: Constraint
       }
-  deriving Show
 
 
 exists :: [Variable] -> Constraint -> Constraint
@@ -87,7 +86,6 @@ data FlatType
     | Record1 (Map.Map Name.Name Variable) Variable
     | Unit1
     | Tuple1 Variable Variable (Maybe Variable)
-    deriving Show
 
 
 data Type
@@ -100,7 +98,6 @@ data Type
     | RecordN (Map.Map Name.Name Type) Type
     | UnitN
     | TupleN Type Type (Maybe Type)
-    deriving Show
 
 
 
@@ -114,7 +111,6 @@ data Descriptor =
     , _mark :: Mark
     , _copy :: Maybe Variable
     }
-    deriving Show
 
 
 data Content
@@ -125,15 +121,14 @@ data Content
     | Structure FlatType
     | Alias ModuleName.Canonical Name.Name [(Name.Name,Variable)] Variable
     | Error
-    deriving Show
 
 
 data SuperType
   = Number
   | Comparable
   | Appendable
   | CompAppend
-  deriving (Eq, Show)
+  deriving (Eq)
 
 
 makeDescriptor :: Content -> Descriptor
@@ -160,7 +155,7 @@ outermostRank =
 
 
 newtype Mark = Mark Word32
-  deriving (Eq, Ord, Show)
+  deriving (Eq, Ord)
 
 
 noMark :: Mark

compiler/src/Type/Unify.hs

@@ -135,7 +135,6 @@ data Context =
     , _second :: Variable
     , _secondDesc :: Descriptor
     }
-    deriving Show
 
 
 reorient :: Context -> Context

compiler/src/Type/UnionFind.hs

@@ -40,16 +40,12 @@ import GHC.IO (unsafePerformIO)
 
 newtype Point a =
   Pt (IORef (PointInfo a))
-  deriving (Eq, Show)
-
-instance (Show a) => Show (IORef a) where
-  show a = show (unsafePerformIO (readIORef a))
+  deriving Eq
 
 
 data PointInfo a
   = Info {-# UNPACK #-} !(IORef Word32) {-# UNPACK #-} !(IORef a)
   | Link {-# UNPACK #-} !(Point a)
-  deriving Show