Comments only

[ghc-hetmet.git] / compiler / hsSyn / HsDecls.lhs

diff --git a/compiler/hsSyn/HsDecls.lhs b/compiler/hsSyn/HsDecls.lhs
index 049f597..09d8d0a 100644 (file)
--- a/compiler/hsSyn/HsDecls.lhs
+++ b/compiler/hsSyn/HsDecls.lhs
@@ -344,11 +344,6 @@ Interface file code:
 
 
 \begin{code}
--- TyClDecls are precisely the kind of declarations that can 
--- appear in interface files; or (internally) in GHC's interface
--- for a module.  That's why (despite the misnomer) IfaceSig and ForeignType
--- are both in TyClDecl
-
 -- Representation of indexed types
 -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 -- Kind signatures of indexed types come in two flavours:
@@ -386,12 +381,21 @@ data TyClDecl name
   | TyData {   tcdND     :: NewOrData,
                tcdCtxt   :: LHsContext name,           -- Context
                tcdLName  :: Located name,              -- Type constructor
+
                tcdTyVars :: [LHsTyVarBndr name],       -- Type variables
+                       
                tcdTyPats :: Maybe [LHsType name],      -- Type patterns
-               tcdKindSig:: Maybe Kind,                -- Optional kind sig; 
-                                                       -- (only for the 
-                                                       -- 'where' form and
-                                                       -- indexed type sigs)
+                       -- Just [t1..tn] for data instance T t1..tn = ...
+                       --      in this case tcdTyVars = fv( tcdTyPats )
+                       -- Nothing for everything else
+
+               tcdKindSig:: Maybe Kind,                -- Optional kind sig 
+                       -- (Just k) for a
+                       --      (a) GADT-style 'data', or 'data instance' decl 
+                       --              with explicit kind sig
+                       --      (b) 'data family' decl, whether or not 
+                       --              there is an explicit kind sig
+                       --              (this is how we distinguish a data family decl)
 
                tcdCons   :: [LConDecl name],           -- Data constructors
                        -- For data T a = T1 | T2 a          the LConDecls all have ResTyH98
@@ -405,6 +409,12 @@ data TyClDecl name
                        -- Typically the foralls and ty args are empty, but they
                        -- are non-empty for the newtype-deriving case
     }
+       -- data family:   tcdPats = Nothing, tcdCons = [], tcdKindSig = Just k
+       --
+       -- data instance: tcdPats = Just tys
+       --
+       -- data:          tcdPats = Nothing, 
+       --                tcdCons is non-empty *or* tcdKindSig = Nothing
 
   | TyFunction {tcdLName  :: Located name,             -- type constructor
                tcdTyVars :: [LHsTyVarBndr name],       -- type variables
@@ -415,8 +425,9 @@ data TyClDecl name
   | TySynonym {        tcdLName  :: Located name,              -- type constructor
                tcdTyVars :: [LHsTyVarBndr name],       -- type variables
                tcdTyPats :: Maybe [LHsType name],      -- Type patterns
-                                                       -- 'Nothing' => vanilla
-                                                       --   type synonym
+                       -- See comments for tcdTyPats in TyData
+                       -- 'Nothing' => vanilla type synonym
+
                tcdSynRhs :: LHsType name               -- synonym expansion
     }
 
@@ -745,12 +756,11 @@ instDeclATs (InstDecl _ _ _ ats) = ats
 \begin{code}
 type LDerivDecl name = Located (DerivDecl name)
 
-data DerivDecl name
-  = DerivDecl (LHsType name) (Located name)
+data DerivDecl name = DerivDecl (LHsType name)
 
 instance (OutputableBndr name) => Outputable (DerivDecl name) where
-    ppr (DerivDecl ty n) 
-        = hsep [ptext SLIT("deriving"), ppr ty, ptext SLIT("for"), ppr n]
+    ppr (DerivDecl ty) 
+        = hsep [ptext SLIT("derived instance"), ppr ty]
 \end{code}
 
 %************************************************************************