Error when using the name "unit" for something in a class

[hashimmm]

What version of Racket are you using?

Racket CS 7.9

What program did you run?

 #lang typed/racket
 
 (define foo%
   (class object%
     (init [unit : String])
     (super-new)
     (: _unit String)
     (define _unit unit)
     (: get-unit (-> String))
     (define/public (get-unit) _unit)))

 (new foo% [unit "kg"])

What should have happened?

The above should work the same as this:

 #lang racket
 
 (define foo%
   (class object%
     (init unit)
     (super-new)
     (define _unit unit)
     (define/public (get-unit) _unit)))
 
 (new foo% [unit "kg"])

If you got an error message, please include it here.

unit: bad syntax in: unit

More info:

Renaming unit to bar works in the typed/racket version.
Switching to typed/racket/base also works.

[yjqww6]

Another example of same bug (early local expansion from method-procedure? in class-prims.rkt):

#lang typed/racket
(define foo%
  (class object%
    (init [case-lambda : (-> String)])
    (super-new)
    (: _unit String)
    (define _unit (case-lambda))))

(new foo% [case-lambda (λ () "kg")])

got

chaperone-procedure: contract violation
  expected: procedure?
  given: "kg"

Replacing case-lambda with a safe name or changed to untyped racket would have the expected behavior:
(object:foo% ...)