+
+(9) DONE -
+ Make the error locations fine-grained, particularly so they point to
+ individual fields, not the whole match.
+
+(10) Cross-module, persistent, named patterns, see:
+ http://caml.inria.fr/pub/ml-archives/caml-list/2008/04/25992c9c9fa999fe1d35d961dd9917a2.en.html