Boolean refinements "weak"

The title sucks, I know 😃

The following is an annoying thing refined allows but should probably not be allowed. I also think that some kind of type bound or self-typing may be able to solve this, although I have not looked into it at all.

Imagine this code:

type Foo = String Refined NonEmpty And MaxSize[W.`10`.T]

Looks fine until you realize it makes no sense at all (but compiles!).

typeOf[Foo].dealias.toString 
res23: String = "eu.timepit.refined.boolean.And[eu.timepit.refined.api.Refined[String,eu.timepit.refined.collection.NonEmpty],eu.timepit.refined.collection.MaxSize[Int(10)]]"

So we have an And[Refined[String, NonEmpty], MaxSize[10]]. Is there an actual use case for Refined being a type parameter to any of the boolean operators? I can’t think of one.

What I actually would want is this:

type Foo = String Refined (NonEmpty And MaxSize[W.`10`.T])
 typeOf[Foo].dealias.toString 
res21: String = "eu.timepit.refined.api.Refined[String,eu.timepit.refined.boolean.And[eu.timepit.refined.collection.NonEmpty,eu.timepit.refined.collection.MaxSize[Int(10)]]]"

To my understanding, there is no way we can make Refined “weaker”. But this should at least be a compile error without the parentheses, should it not?

[fthomas]

We could introduce a marker trait Predicate, let every predicate extends that, and then use a type bound in And: class And[A <: Predicate, B <: Predicate]. Refined would not be a Predicate and And[Refined, ...] would be a compile error.

[NeQuissimus]

Yeah, I don’t think we can do this with what we currently have. I have sort of given up since I’ve run into lots of different issues whenever I tried… Not sure how to solve this…