[racket-dev] Is this a type error?

From: Danny Yoo (dyoo at hashcollision.org)
Date: Tue Oct 23 20:41:48 EDT 2012

>> (: current-defined-name (Parameterof (U Symbol False LamPositionalName)))
>> (define current-defined-name (make-parameter UNKNOWN))
> That looks to me like a problem with the inferencer.

There's some interaction with the structure in the union.  If I
simplify the type definition to:

    (: current-defined-name (Parameterof (U Symbol)))

then the type system seems to be happy to accept 'unknown as an
acceptable symbol.

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