pub trait Effect4 {
type Fixed1;
type Fixed2;
type Fixed3;
type HktWitness: HKT4<Self::Fixed1, Self::Fixed2, Self::Fixed3> + HKT;
}Expand description
Effect4: The Bridge Trait for Arity 4 Type Constructors.
Similar to Effect3, this trait is implemented by a user-defined System Witness
to partially apply (fix) three of the four generic parameters of an HKT4 type.
It is used for effect systems that need to track three distinct fixed effect types
(e.g., Error, Warning, and a Counter) alongside the primary value type.