Big tidy-up of deriving code

[ghc-hetmet.git] / compiler / types / TyCon.lhs

diff --git a/compiler/types/TyCon.lhs b/compiler/types/TyCon.lhs
index d91effe..9595759 100644 (file)
--- a/compiler/types/TyCon.lhs
+++ b/compiler/types/TyCon.lhs
@@ -1,7 +1,9 @@
 %
+% (c) The University of Glasgow 2006
 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
 %
-\section[TyCon]{The @TyCon@ datatype}
+
+The @TyCon@ datatype
 
 \begin{code}
 module TyCon(
@@ -11,7 +13,7 @@ module TyCon(
        tyConPrimRep,
 
        AlgTyConRhs(..), visibleDataCons, 
-        AlgTyConParent(..), hasParent,
+        AlgTyConParent(..), 
        SynTyConRhs(..),
 
        isFunTyCon, isUnLiftedTyCon, isProductTyCon, 
@@ -66,13 +68,12 @@ module TyCon(
 import {-# SOURCE #-} TypeRep ( Kind, Type, PredType )
 import {-# SOURCE #-} DataCon ( DataCon, isVanillaDataCon )
 
-import Var             ( TyVar, Id )
-import Class           ( Class )
-import BasicTypes      ( Arity, RecFlag(..), Boxity(..), isBoxed )
-import Name            ( Name, nameUnique, NamedThing(getName) )
-import PrelNames       ( Unique, Uniquable(..) )
-import Maybe           ( isJust )
-import Maybes          ( orElse )
+import Var
+import Class
+import BasicTypes
+import Name
+import PrelNames
+import Maybes
 import Outputable
 import FastString
 \end{code}
@@ -113,6 +114,8 @@ data TyCon
                                        -- argument list (starting from 0).
                                        -- NB: Length is less than tyConArity
                                        --     if higher kind signature.
+                                       -- NB: Just _ <=> associated (not
+                                       --                toplevel) family
        
        algTcSelIds :: [Id],            -- Its record selectors (empty if none)
 
@@ -171,7 +174,8 @@ data TyCon
        tyConUnique   :: Unique,
        tyConName     :: Name,
        tyConKind     :: Kind,
-       tyConArity    :: Arity,
+       tyConArity    :: Arity,         -- SLPJ Oct06: I'm not sure what the significance
+                                       --             of the arity of a primtycon is!
 
        primTyConRep  :: PrimRep,
                        -- Many primitive tycons are unboxed, but some are
@@ -277,10 +281,6 @@ data AlgTyConParent = -- An ordinary type constructor has no parent.
                                                -- the representation type
                                                -- with the type instance
 
-hasParent :: AlgTyConParent -> Bool
-hasParent NoParentTyCon = False
-hasParent _other        = True
-
 data SynTyConRhs
   = OpenSynTyCon Kind  -- Type family: *result* kind given
   | SynonymTyCon Type   -- Mentioning head type vars.  Acts as a template for
@@ -543,8 +543,8 @@ isAlgTyCon (TupleTyCon {}) = True
 isAlgTyCon other          = False
 
 isDataTyCon :: TyCon -> Bool
--- isDataTyCon returns True for data types that are represented by
--- heap-allocated constructors.
+-- isDataTyCon returns True for data types that are definitely
+-- represented by heap-allocated constructors.
 -- These are srcutinised by Core-level @case@ expressions, and they
 -- get info tables allocated for them.
 --     True for all @data@ types
@@ -556,7 +556,7 @@ isDataTyCon tc@(AlgTyCon {algTcRhs = rhs})
        DataTyCon {}  -> True
        OpenNewTyCon  -> False
        NewTyCon {}   -> False
-       AbstractTyCon -> pprPanic "isDataTyCon" (ppr tc)
+       AbstractTyCon -> False  -- We don't know, so return False
 isDataTyCon (TupleTyCon {tyConBoxed = boxity}) = isBoxed boxity
 isDataTyCon other = False
 
@@ -672,11 +672,24 @@ isCoercionTyCon :: TyCon -> Bool
 isCoercionTyCon (CoercionTyCon {}) = True
 isCoercionTyCon other              = False
 
+-- Identifies implicit tycons that, in particular, do not go into interface
+-- files (because they are implicitly reconstructed when the interface is
+-- read).
+--
+-- Note that 
+--
+-- * associated families are implicit, as they are re-constructed from
+--   the class declaration in which they reside, and 
+-- * family instances are *not* implicit as they represent the instance body
+--   (similar to a dfun does that for a class instance).
+--
 isImplicitTyCon :: TyCon -> Bool
-isImplicitTyCon SynTyCon{}                     = False
-isImplicitTyCon AlgTyCon{algTcParent = parent} = hasParent parent
-isImplicitTyCon other                          = True
-        -- catches: FunTyCon, TupleTyCon, PrimTyCon, 
+isImplicitTyCon tycon | isTyConAssoc tycon           = True
+                     | isSynTyCon tycon             = False
+                     | isAlgTyCon tycon             = isClassTyCon tycon ||
+                                                      isTupleTyCon tycon
+isImplicitTyCon _other                               = True
+        -- catches: FunTyCon, PrimTyCon, 
         -- CoercionTyCon, SuperKindTyCon
 \end{code}
 
@@ -824,7 +837,7 @@ isClassTyCon other_tycon                         = False
 
 tyConClass_maybe :: TyCon -> Maybe Class
 tyConClass_maybe (AlgTyCon {algTcParent = ClassTyCon clas}) = Just clas
-tyConClass_maybe ther_tycon                                = Nothing
+tyConClass_maybe other_tycon                               = Nothing
 
 isFamInstTyCon :: TyCon -> Bool
 isFamInstTyCon (AlgTyCon {algTcParent = FamilyTyCon _ _ _ }) = True
@@ -833,13 +846,13 @@ isFamInstTyCon other_tycon                                     = False
 tyConFamInst_maybe :: TyCon -> Maybe (TyCon, [Type])
 tyConFamInst_maybe (AlgTyCon {algTcParent = FamilyTyCon fam instTys _}) = 
   Just (fam, instTys)
-tyConFamInst_maybe ther_tycon                                          = 
+tyConFamInst_maybe other_tycon                                         = 
   Nothing
 
 tyConFamilyCoercion_maybe :: TyCon -> Maybe TyCon
 tyConFamilyCoercion_maybe (AlgTyCon {algTcParent = FamilyTyCon _ _ coe}) = 
   Just coe
-tyConFamilyCoercion_maybe ther_tycon                                    = 
+tyConFamilyCoercion_maybe other_tycon                                   = 
   Nothing
 \end{code}