[project @ 1997-03-14 07:52:06 by simonpj]

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

diff --git a/ghc/compiler/types/TyCon.lhs b/ghc/compiler/types/TyCon.lhs
index d473ea4..0460e6e 100644 (file)
--- a/ghc/compiler/types/TyCon.lhs
+++ b/ghc/compiler/types/TyCon.lhs
@@ -34,7 +34,7 @@ module TyCon(
        getSynTyConDefn,
 
         maybeTyConSingleCon,
-       isEnumerationTyCon,
+       isEnumerationTyCon, isTupleTyCon,
        derivedFor
 ) where
 
@@ -79,6 +79,11 @@ data TyCon
                [TyVar]
                [(Class,Type)]  -- Its context
                [Id]            -- Its data constructors, with fully polymorphic types
+                               --      This list can be empty, when we import a data type abstractly,
+                               --      either (a) the interface is hand-written and doesn't give
+                               --                 the constructors, or
+                               --             (b) in a quest for fast compilation we don't import 
+                               --                 the constructors
                [Class]         -- Classes which have derived instances
                NewOrData
 
@@ -275,6 +280,13 @@ isEnumerationTyCon (TupleTyCon _ _ arity)
   = arity == 0
 isEnumerationTyCon (DataTyCon _ _ _ _ _ data_cons _ _)
   = not (null data_cons) && all isNullaryDataCon data_cons
+
+
+isTupleTyCon (TupleTyCon _ _ arity) = arity >= 2    -- treat "0-tuple" specially
+isTupleTyCon (SpecTyCon tc tys)     = isTupleTyCon tc
+isTupleTyCon other                 = False
+
+
 \end{code}
 
 @derivedFor@ reports if we have an {\em obviously}-derived instance