Remove code that handles #<undefined> in TR
TR no longer needs to handle #<undefined> because the value no longer leaks out from uninitialized variables. However, uses of uninitialized variables are not caught by TR (they are treated like errors from the `error` function).
This commit is contained in:
Asumu Takikawa
parent
d4c60e8608
commit
715d596e47
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@ -35,26 +35,21 @@
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;; Checks that the body has the expected type when names are bound to the types spcified by results.
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;; The exprs are also typechecked by using expr->type.
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;; TODO: make this function sane.
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(define/cond-contract (do-check expr->type namess results expected-results exprs body expected)
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(define/cond-contract (do-check expr->type namess expected-results exprs body expected)
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((syntax? tc-results/c . -> . any/c)
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(listof (listof identifier?)) (listof tc-results/c) (listof tc-results/c)
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(listof syntax?) syntax? (or/c #f tc-results/c)
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. -> .
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tc-results/c)
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(with-cond-contract t/p ([types (listof (listof Type/c))] ; types that may contain undefined (letrec)
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[expected-types (listof (listof Type/c))] ; types that may not contain undefined (what we got from the user)
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(with-cond-contract t/p ([expected-types (listof (listof Type/c))]
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[props (listof (listof Filter?))])
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(define-values (types expected-types props)
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(for/lists (t e p)
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([r (in-list results)]
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[e-r (in-list expected-results)]
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(define-values (expected-types props)
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(for/lists (e p)
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([e-r (in-list expected-results)]
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[names (in-list namess)])
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(match* (r e-r)
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[((tc-results: ts (FilterSet: fs+ fs-) os) (tc-results: e-ts _ _)) ; rest should be the same
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;(printf "f+: ~a\n" fs+)
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;(printf "f-: ~a\n" fs-)
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(values ts
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e-ts
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(match e-r
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[(tc-results: e-ts (FilterSet: fs+ fs-) os)
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(values e-ts
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(apply append
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(for/list ([n (in-list names)]
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[f+ (in-list fs+)]
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@ -63,35 +58,27 @@
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(list)
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(list (-imp (-not-filter (-val #f) n) f+)
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(-imp (-filter (-val #f) n) f-))))))]
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[((tc-results: ts (NoFilter:) _) (tc-results: e-ts (NoFilter:) _))
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(values ts e-ts null)]))))
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[(tc-results: e-ts (NoFilter:) _)
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(values e-ts null)]))))
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(with-cond-contract append-region ([p1 (listof Filter?)]
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[p2 (listof Filter?)])
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(define-values (p1 p2)
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(combine-props (apply append props) (env-props (lexical-env)) (box #t))))
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;; extend the lexical environment for checking the body
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(with-lexical-env/extend/props
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;; the list of lists of name
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namess
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;; the types
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types
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expected-types
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(append p1 p2)
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;; type-check the rhs exprs
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(for-each expr->type
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exprs
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expected-results)
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(with-lexical-env/extend/props
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;; we typechecked the rhss with the lhss having types that potentially contain undefined
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;; if undefined can actually show up, a type error will have been triggered
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;; it is therefore safe to typecheck the body with the original types the user gave us
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;; any undefined-related problems have been caught already
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namess
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expected-types ; types w/o undefined
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(append p1 p2)
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;; typecheck the body
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(replace-names (get-names+objects namess expected-results)
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(replace-names
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(get-names+objects namess expected-results)
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(if expected
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(tc-body/check body (erase-filter expected))
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(tc-body body))))))
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(tc-body body)))))
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(define (tc-expr/maybe-expected/t e names)
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(syntax-parse names
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@ -159,30 +146,7 @@
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(define flat-names (apply append remaining-names))
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(do-check tc-expr/check
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remaining-names
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;; compute set of variables that can't be undefined. see below.
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(let-values
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([(safe-bindings _)
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(for/fold ([safe-bindings '()] ; includes transitively-safe
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[transitively-safe-bindings '()])
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([names (in-list remaining-names)]
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[expr (in-list remaining-exprs)])
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(case (safe-letrec-values-clause? expr transitively-safe-bindings flat-names)
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;; transitively safe -> safe to mention in a subsequent rhs
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[(transitively-safe) (values (append names safe-bindings)
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(append names transitively-safe-bindings))]
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;; safe -> safe by itself, but may not be safe to use in a subsequent rhs
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[(safe) (values (append names safe-bindings)
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transitively-safe-bindings)]
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;; unsafe -> could be undefined
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[(unsafe) (values safe-bindings transitively-safe-bindings)]))])
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(map (λ (l) (let ([types-from-user (map get-type l)])
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(ret (if (andmap (λ (x) ; are all the lhs vars safe?
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(member x safe-bindings bound-identifier=?))
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l)
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types-from-user
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(map (λ (x) (Un x -Undefined)) types-from-user)))))
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remaining-names))
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;; types the user gave. check against that to error if we could get undefined
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;; types the user gave.
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(map (λ (l) (ret (map get-type l))) remaining-names)
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remaining-exprs body expected)])))))
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@ -267,37 +231,6 @@
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(cons names env-ids)
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(cons results env-types)))])))
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;; determines whether any of the variables bound in the given clause can have an undefined value
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;; in this case, we cannot trust the type the user gave us and must union it with undefined
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;; for example, the following code:
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;; (letrec: ([x : Float x]) x)
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;; should not typecheck with type Float, even though the user said so, because the actual value
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;; is undefined.
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;; this implements a conservative analysis.
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;; we identify 3 kinds of bindings:
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;; - safe bindings cannot be undefined
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;; - transitively safe bindings are safe and can safely be used in subsequent rhss
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;; - unsafe bindings may be undefined
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;; x is transitively safe if for all its free variables, they are either transitively safe and
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;; earlier in the letrec or they are bound outside the letrec
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;; x is safe if it is transitively safe or if its rhs is a lambda
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;; otherwise, x is unsafe
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;; this function returns either 'transitively-safe, 'safe or 'unsafe
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;; Note: In some cases (such as the example on the bottom of page 6 of Ghuloum and Dybvig's
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;; Fixing Letrec (reloaded) paper), we are more conservative than a fully-connected component
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;; based approach. On the other hand, our algorithm should cover most interesting cases and
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;; is much simpler than Tarjan's.
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(define (safe-letrec-values-clause? expr transitively-safe-bindings letrec-bound-ids)
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(cond [(andmap (lambda (fv)
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(or (not (member fv letrec-bound-ids bound-identifier=?)) ; from outside
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(member fv transitively-safe-bindings bound-identifier=?)))
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(free-vars expr))
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'transitively-safe]
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[else
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(syntax-parse expr #:literal-sets (kernel-literals)
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[(#%plain-lambda _ ...) 'safe]
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[else 'unsafe])]))
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;; this is so match can provide us with a syntax property to
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;; say that this binding is only called in tail position
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(define ((tc-expr-t/maybe-expected expected) e)
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@ -322,4 +255,4 @@
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[types (for/list ([name (in-list names)] [e (in-list exprs)])
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(get-type/infer name e (tc-expr-t/maybe-expected expected)
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tc-expr/check))])
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(do-check void names types types exprs body expected)))
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(do-check void names types exprs body expected)))
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@ -1,8 +1,9 @@
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#;
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(exn-pred 2)
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(exn-pred "x:.*cannot use before initialization")
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#lang typed/racket
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;; make sure letrec takes into account that some bindings may be undefined
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;; This test previously tested TR's static analysis of undefined
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;; variables, but it now just delegates to Racket's dynamic checks.
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(+ (letrec: ([x : Float x]) x) 1) ; PR 11511
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@ -1,7 +1,10 @@
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#;
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(exn-pred "Undefined")
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(exn-pred "x:.*cannot use before initialization")
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#lang scheme/load
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;; This test used to fail due to a type error, but TR no longer
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;; tracks undefined statically, so it is just a dynamic error.
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(module A scheme
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(define (f x) (add1 x))
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@ -846,15 +846,36 @@
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[tc-e (letrec: ([x : Number (values 1)]) (add1 x)) -Number]
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;; This test case used to test Undefined, but the `x` is now Bottom because
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;; cyclic definitions can be given *any* type. This is ok since cyclic definitions
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;; are just errors that TR does not handle (because #<undefined> no longer leaks out
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;; in such cases).
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[tc-e (let ()
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(: complicated Boolean)
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(define complicated #f)
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(: undefined Undefined)
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(define undefined (letrec: ((x : Undefined x)) x))
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(letrec: ((x : Undefined (if complicated undefined undefined))
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(y : Undefined (if complicated x undefined)))
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(: undefined (Un))
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(define undefined (letrec: ((x : (Un) x)) x))
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(letrec: ((x : (Un) (if complicated undefined undefined))
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(y : (Un) (if complicated x undefined)))
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y))
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-Undefined]
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-Bottom]
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;; This case fails, unlike the last one, since the types in the
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;; cycle are inconsistent. Note that this will error (if it typechecked)
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;; because of the uninitialized variables.
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[tc-err (let ()
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(: x String)
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(define x y)
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(: y Symbol)
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(define y x)
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y)
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#:ret (ret -Symbol)
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#:msg #rx"expected: String|expected: Symbol"]
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;; Test ill-typed code in letrec RHS
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[tc-err (let () (: x String) (define x 'foo) x)
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#:ret (ret -String)
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#:msg #rx"expected: String.*given: 'foo"]
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[tc-err (let ([x (add1 5)])
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(set! x "foo")
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