I feel like I must be missing something, or my TR intuition is seriously
broken. This piece of code:
#lang typed/racket
(define sounds
(for/list : (Listof String) ([i : Index (in-range (ann 7 Index))])
"abc”))
… fails to type-check with this error:
Type Checker: type mismatch
expected: Index
given: Integer in: (for/list : (Listof String) ((i : Index (in-range (ann 7
Index)))) "abc”)
… and unfortunately, the whole ‘for’ is highlighted.
I checked the type of “in-range”, and it suggests that if you give it an an
Index, it can return a (Sequenceof Index). Finally, in a fit of desperation, I
manually annotated the call to “in-range” with the (Sequenceof Index) type …
and it worked.
Does it make sense that this kind of annotation should be required, or is this
a bug?
John
P.S.: this is a simplification of code whose body does in fact require that i
be of type Index….
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