Thanks, I'm relieved if that's a bug. Although, if it is a bug, it's a
showstopper for me until fixed, as problems like this exhibit throughout
some list-processing-intensive code I'm trying to convert to Typed Racket.
Carl Eastlund wrote at 12/22/2010 03:42 PM:
I believe your intermediate expression there, the one with two
"ann"otations in it, is a Typed Racket bug. You should definitely not
be able to take something with the type (Listof Symbol) and coerce it
to (List Symbol Symbol).
...yet the following does get errors when trying to do the same coercion
from "(Listof Symbol)" to "(List Symbol Symbol)":
(cons 'a (cons 'b '()))
- : (Listof (U 'a 'b))
(a b)
(ann (cons 'a (cons 'b '())) (Listof Symbol))
- : (Listof Symbol)
(a b)
(ann (cons 'a (cons 'b '())) (List Symbol Symbol))
. . Type Checker: Polymorphic function cons could not be applied to
arguments:
Types: a (Listof a) -> (Listof a)
a b -> (Pairof a b)
Arguments: 'a (Listof 'b)
Expected result: (List Symbol Symbol)
in: (cons (quote a) (cons (quote b) (quote ())))
(ann (ann (cons 'a (cons 'b '())) (Listof Symbol)) (List Symbol Symbol))
. . Type Checker: Polymorphic function cons could not be applied to
arguments:
Types: a (Listof a) -> (Listof a)
a b -> (Pairof a b)
Arguments: 'a (Listof 'b)
Expected result: (List Symbol Symbol)
in: (cons (quote a) (cons (quote b) (quote ())))
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