Derive Macro Lattice 

#[derive(Lattice)]

#[derive(Lattice)] Macro

A struct of multiple lattices can form a product lattice. The simplest case of this is the Pair lattice, which is a product of two sub-lattices. For more than two lattices, and/or to improve readability, users can create their own product lattice structs, where each field is a sub-lattice, and use the #[derive(Lattice)] macro to automatically derive the lattice traits.

Derives Merge, PartialEq, PartialOrd, LatticeOrd, IsBot, IsTop, and LatticeFrom, and therefore Lattice too. Alternatively, individual traits can be derived: #[derive(Merge, LatticeOrd, IsBot, IsTop, LatticeFrom)]. Note that LatticeOrd also derives PartialEq and PartialOrd.

Note that all fields must be lattice types. If any field cannot be a lattice type then the where clauses prevent the trait impl from compiling.

These derive macros will create a second set of generics to allow conversion and merging between varying types. For example, given this struct:

#[derive(Lattice)]
struct MyLattice<KeySet, Epoch>
where
    KeySet: Collection,
    Epoch: Ord,
{
    keys: SetUnion<KeySet>,
    epoch: Max<Epoch>,
}

Will create derive macros impls in the form:

impl<KeySet, Epoch, KeySetOther, EpochOther>
    Merge<MyLattice<KeySetOther, EpochOther>> for MyLattice<KeySet, Epoch>
where
    KeySet: Collection,
    Epoch: Ord,
    KeySetOther: Collection,
    EpochOther: Ord,
{
    // ...
}