Simon Peyton Jones wrote:
anywhere, I think.  You might want a new HsSyn data type for "list with possible leading or trailing commas":

  data HsCommadList a
    = HCL
         Int -- Number of leading commas
         [a]
         Int -- Number of trailing commas

If we're going to go to the trouble of supporting extra leading and trailing commas, why not also support extra commas in the middle? That way,

    #include "theseexports"
    ,
    #include "thoseexports"

doesn't have to worry about how these and those exports are listed.

David