it's unlikely to be used in any law, and likely to be cause for confusion.
best of all, the new operator has a different return type, which
ensures no inconsistency with the change can get overlooked.
Normally I would make sure this is not by default, or at leat disableable; but
here the code we print may contain utf8 anyway, so the terminal really needs to
support it. Anyway, it's just a little fancier, doesn't add much.
a quick fix for now, ideally we want an option for editor-friendly output.
But for now this is a very cheap way to at least have clickable error messages
which are a big time-saver.
These are just variable renumberings, and type error message changes but still
pointing to the same information; the latter are slightly better in general,
pointing to actual expressions rather than scope declarations.
The issue was coming from Bindlib: it stores variable bindings as closures, so
`Bindlib.box_apply f bx` actually delays the application of `f` until the term
is substituted or unboxed (likely long after we are out of the `try..with`
block).
The proposed fix is to make sure we run the wrapper outside of bindlib
applications, on explicitely unboxed terms.
