[racket] Module Availability

I'm trying to understand why TR requires a module that it doesn't actually
use in the file that requires it.

The requirement is unstable/contract in typed-racket/type-racket.rkt.
Without it tests/typed-racket/succeed/succed-cnt.rkt fails. But when I try
to reduce the test case to not use TR, I cannot replicate it.

The error message:

link: namespace mismatch;
 reference to a module that is not available
  reference phase: 0
  referenced module:
"/Users/endobson/proj/racket/plt/collects/unstable/contract.rkt"
  referenced phase level: 0
  reference in module:
"/Users/endobson/proj/racket/plt/collects/tests/typed-racket/succeed/succeed-cnt2.rkt"
  in: provide/contract-contract-id-sequence/c.24

Can someone explain what this error means/how to write a simple program
which triggers it?
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