On Mon, May 11, 2015 at 04:01:15PM -0400, Asumu Takikawa wrote: > On 2015-05-11 14:33:51 -0400, Benjamin Greenman wrote: > > This program gives a confusing error message. Does anyone know why the > > "xs" in the body doesn't have type "(List Foo)"? > > It's because the type `Foo` is not defined, so it cannot have a sensible > representation. Erroneous types like this `Foo` are turned into `Error` > (unless > the error stops the type-checker). > > Error does not propagate (i.e., (Listof Error) != Error) so you can get weird > error messages like this. > > ;;; > > Maybe we should consider just terminating the typechecker when it hits > undefined types (or other malformed types) instead of trying to continue?
No. Don't terminate the type checker -- it can still be useful to find *other* errors that do not depend on the malformed type. I think the answer needs to be a little more subtle. For example, if Foo is an undefined type, it can still be useful to report an error if one tries to multiply a list of Foo by 7. But once the undefinedness of Foo has been reported, it probably isn't useful to flag as an error an attempt multiply a Foo by 7. -- hendrik -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
