racket / racket/typed-racket

Inference for `for/fold` should not be helped by annotation of `Any`

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Dominant language
Racket
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106
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2h 1m
Merged PRs (30d)
2

Description

#lang typed/racket/base
(define z
  (for/fold ([x (read (open-input-string "x"))])
            ([y : Any (build-list 10 (λ _ (random 1)))])
    (cons x y)))

does not type check, but annotating x with Any makes it work.

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First steps

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  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by reproducing the typed Racket example in the issue and compare inference with and without the x annotation. Trace the for/fold inference path and add a regression test; done means the unannotated form type-checks consistently with the intended inference behavior.

Written by the indexing model from the issue text.

Assessment

Domain
compilers
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
38/100

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