Enum Where 

#[non_exhaustive]
pub enum Where<'a> {
    Polling(PollingCtx<'a>),
    PreSolve(PreSolveCtx<'a>),
    Simplex(SimplexCtx<'a>),
    MIP(MIPCtx<'a>),
    MIPSol(MIPSolCtx<'a>),
    MIPNode(MIPNodeCtx<'a>),
    Message(MessageCtx<'a>),
    Barrier(BarrierCtx<'a>),
    IIS(IISCtx<'a>),
}

TODO: (medium) add MultiObj ctx The argument given to callbacks.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

Polling(PollingCtx<'a>)

PreSolve(PreSolveCtx<'a>)

Simplex(SimplexCtx<'a>)

MIP(MIPCtx<'a>)

MIPSol(MIPSolCtx<'a>)

MIPNode(MIPNodeCtx<'a>)

Message(MessageCtx<'a>)

Barrier(BarrierCtx<'a>)

IIS(IISCtx<'a>)