Syntax Modelled by Set-builder notation

[CSDUMMI]

I think your idea is great.
But I believe, that your Syntax,
apparently modeled on Python decorators may not be the best one to use.
I believe, it could be very much worth it to think about modelling
the Syntax on Set-builder notation.

An example:

dividedBy : Int\{0} -> Int -> Int
dividedBy a b = b // a

This extends the perspective on types as sets.
Another example using a predicate:

not_null : Int -> Bool
not_null = (/=) 0

dividedBy : { x <- Int | not_null x } -> Int -> Int
dividedBy a b = b // a

What do you think?