Occurrence typing: Advanced filters (e.g. for `positive?`) kept secret

When looking at a function type, (some?) filters which can't be expressed with just : are not shown without warning, making it hard to understand how occurrence typing works. This is also not documented, so I'm not sure if there's any rationale, but I can only imagine verbosity or complexity of the signature.

However, such filters are never shown, even when using #:verbose, and I'm confident that's bad — how can I understand what the typechecker is doing if signatures are hidden?

Moreover, even if you want to hide part of a type by default, there should be some warning to the user. So for positive?, Typed Racket shouldn't show (-> Real Boolean) but sth. like (-> Real Boolean ...), and docs should explain that ... means "there's more you're not seeing". (No clue if ... is a decent idea as concrete syntax, you can figure that out).

> string?
- : (-> Any Boolean : String)
#<procedure:string?>
> positive?
- : (-> Real Boolean)
#<procedure:positive?>
> (:type (-> Real Boolean : #:+ Positive-Real #:- Nonpositive-Real))
(-> Real Boolean)
[can expand further: Boolean Real]
> (:type #:verbose (-> Real Boolean : #:+ Positive-Real #:- Nonpositive-Real))
(-> (U 0
       1
       Byte-Larger-Than-One
       Positive-Index-Not-Byte
       Positive-Fixnum-Not-Index
       Negative-Fixnum
       Positive-Integer-Not-Fixnum
       Negative-Integer-Not-Fixnum
       Positive-Rational-Not-Integer
       Negative-Rational-Not-Integer
       Float-Nan
       Float-Positive-Zero
       Float-Negative-Zero
       Positive-Float-No-NaN
       Negative-Float-No-NaN
       Single-Flonum-Nan
       Single-Flonum-Positive-Zero
       Single-Flonum-Negative-Zero
       Positive-Single-Flonum-No-Nan
       Negative-Single-Flonum-No-Nan)
    (U #f #t))

Start with the REPL examples for string? and positive?, comparing the default and #:verbose output for occurrence filters. Determine how advanced filters should be surfaced or warned about, then document the meaning of any hidden-filter notation and verify that the examples expose the relevant type information.