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[ghc-hetmet.git] / compiler / basicTypes / DataCon.lhs

diff --git a/compiler/basicTypes/DataCon.lhs b/compiler/basicTypes/DataCon.lhs
index 851bf66..0c6e3c5 100644 (file)
--- a/compiler/basicTypes/DataCon.lhs
+++ b/compiler/basicTypes/DataCon.lhs
@@ -87,15 +87,20 @@ differently, as follows.
 
 Note [Data Constructor Naming]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-Each data constructor C has two, and possibly three, Names associated with it:
+Each data constructor C has two, and possibly up to four, Names associated with it:
 
-                            OccName    Name space      Used for
+                            OccName    Name space      Name of
   ---------------------------------------------------------------------------
-  * The "source data con"      C       DataName        The DataCon itself
-  * The "real data con"                C       VarName         Its worker Id
-  * The "wrapper data con"     $WC     VarName         Wrapper Id (optional)
-
-Each of these three has a distinct Unique.  The "source data con" name
+  * The "data con itself"      C       DataName        DataCon
+  * The "worker data con"      C       VarName         Id (the worker)
+  * The "wrapper data con"     $WC     VarName         Id (the wrapper)
+  * The "newtype coercion"      :CoT    TcClsName      TyCon
+ 
+EVERY data constructor (incl for newtypes) has the former two (the
+data con itself, and its worker.  But only some data constructors have a
+wrapper (see Note [The need for a wrapper]).
+
+Each of these three has a distinct Unique.  The "data con itself" name
 appears in the output of the renamer, and names the Haskell-source
 data constructor.  The type checker translates it into either the wrapper Id
 (if it exists) or worker Id (otherwise).
@@ -129,6 +134,8 @@ The "wrapper Id", $WC, goes as follows
   nothing for the wrapper to do.  That is, if its defn would be
        $wC = C
 
+Note [The need for a wrapper]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 Why might the wrapper have anything to do?  Two reasons:
 
 * Unboxing strict fields (with -funbox-strict-fields)
@@ -152,6 +159,8 @@ Why might the wrapper have anything to do?  Two reasons:
   The third argument is a coerion
        [a] :: [a]:=:[a]
 
+INVARIANT: the dictionary constructor for a class
+          never has a wrapper.
 
 
 A note about the stupid context