21 lines
874 B
Racket
21 lines
874 B
Racket
#lang scheme
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(provide/contract (find-referenced-locals ((listof identifier?) syntax? . -> . (listof identifier?))))
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(define (find-referenced-locals env-ids stx)
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(local ([define id-hash (make-custom-hash free-identifier=?
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(λ (v) (equal-hash-code (syntax->datum v)))
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(λ (v) (equal-secondary-hash-code (syntax->datum v))))]
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[define (find stx)
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(syntax-case stx ()
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[(head . tail)
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(begin
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(find #'head)
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(find #'tail))]
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[id (identifier? stx)
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(begin
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(unless (dict-ref id-hash stx false)
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(dict-set! id-hash stx true)))]
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[_ (void)])])
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(find stx)
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(filter (λ (env-id) (dict-ref id-hash env-id false)) env-ids)))
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