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.
