[MLton] Bug report

[Matthew Fluet]

> The attached causes the compiler typechecker to through an exception (see
> below).  I know there is a problem with the program (a value restriction issue)
> but I generally expect a friendlier error message :).  If you need more info
> let me know.

The bug is already fixed in the latest experimental MLton release (which
should be followed up by a stable release in a month or so).  The error
message now directly referes to the inability to generalize type
variables:

[fluet@tiger temp 9]% ~/mlton/mlton-20040819/build/bin/mlton s.cm
Error: queue.sml 1.19:
   Variable type in structure disagrees with signature.
   variable: foldl
   unable to generalize: 'b, 'a
   signature: (('a * 'b) -> 'b)
              -> ('b
                  -> ({back: int ref,
                       count: int ref,
                       front: int ref,
                       v: 'a option array ref}
                      -> 'b))
Error: queue.sml 1.19:
   Variable type in structure disagrees with signature.
   variable: foldr
   unable to generalize: 'b, 'a
   signature: (('a * 'b) -> 'b)
              -> ('b
                  -> ({back: int ref,
                       count: int ref,
                       front: int ref,
                       v: 'a option array ref}
                      -> 'b))
compilation aborted: parseAndElaborate reported errors