Re: [racket-users] type mismatch: given (Listof Error)
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? I know that the current behavior of Error types causes at least one soundness bug in the top-level. Cheers, Asumu -- 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 racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [racket-users] type mismatch: given (Listof Error)
I think we should at least make `(Listof Error)` turn into `Error`. That would eliminate the error message than Ben reported. Sam On Mon, May 11, 2015 at 4:01 PM, Asumu Takikawa as...@ccs.neu.edu 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? I know that the current behavior of Error types causes at least one soundness bug in the top-level. Cheers, Asumu -- 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 racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout. -- 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 racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [racket-users] type mismatch: given (Listof Error)
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 racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
