[racket] TR predicate documentation, typo?

In http://docs.racket-lang.org/ts-reference/type-ref.html

1.6 Other Type Constructors

"The filter specifies that when (string? x) evaluates to a true value,
the variable x can be assumed to have type String. Likewise, if the
expression evaluates to #f, the variable has type String."

I think there must be a typo here, what exactly happens if the
expression evaluates to #f?

-- 
Anthony Carrico

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