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allow unannotated lambdas

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in cases where the expected type has enough information, and propagate
the expected type in those cases.
This commit is contained in:
AlexKnauth 2016-05-02 15:11:12 -04:00
parent 95a7fb87f8
commit 59b0ad3d3a
1 changed files with 12 additions and 3 deletions
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15
tapl/mlish.rkt
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@ -670,13 +670,22 @@
; all λs have type (∀ (X ...) (→ τ_in ... τ_out)), even monomorphic fns
(define-typed-syntax liftedλ #:export-as λ
[(_ (y:id x:id ...) . body)
(type-error #:src stx #:msg "λ parameters must have type annotations")]
[(_ (x:id ...+) body)
#:with (~?∀ Xs expected) (get-expected-type stx)
#:do [(unless (→? #'expected)
(type-error #:src stx #:msg "λ parameters must have type annotations"))]
#:with (~ext-stlc:→ arg-ty ... body-ty) #'expected
#:do [(unless (stx-length=? #'[x ...] #'[arg-ty ...])
(type-error #:src stx #:msg
(format "expected a function of ~a arguments, got one with ~a arguments"
(stx-length #'[arg-ty ...] #'[x ...]))))]
#`(Λ Xs (ext-stlc:λ ([x : arg-ty] ...) #,(add-expected-ty #'body #'body-ty)))]
[(_ args body)
#:with (~∀ () (~ext-stlc:→ arg-ty ... body-ty)) (get-expected-type stx)
#:with (~?∀ () (~ext-stlc:→ arg-ty ... body-ty)) (get-expected-type stx)
#`(Λ () (ext-stlc:λ args #,(add-expected-ty #'body #'body-ty)))]
[(_ (~and x+tys ([_ (~datum :) ty] ...)) . body)
#:with Xs (compute-tyvars #'(ty ...))
;; TODO is there a way to have λs that refer to ids defined after them?
#'(Λ Xs (ext-stlc:λ x+tys . body))])