Consider Union{Nothing, in LazyBridgeOptimizer

[odow]

A key problem in LazyBridgeOptimizer is things like

MathOptInterface.jl/src/Bridges/lazy_bridge_optimizer.jl

Line 27 in 7923c60

variable_map::Variable.Map

Two important definitions are

MathOptInterface.jl/src/Bridges/lazy_bridge_optimizer.jl

Lines 79 to 81 in 7923c60

	function Variable.bridges(bridge::LazyBridgeOptimizer)
	return bridge.variable_map
	end

MathOptInterface.jl/src/Bridges/Variable/map.jl

Line 281 in 7923c60

has_bridges(map::Map) = !isempty(map.info)

So in methods like

MathOptInterface.jl/src/Bridges/bridge_optimizer.jl

Lines 328 to 343 in 7923c60

	function MOI.empty!(b::AbstractBridgeOptimizer)
	MOI.empty!(b.model)
	if Variable.has_bridges(Variable.bridges(b))
	empty!(b.var_to_name)
	b.name_to_var = nothing
	end
	if Variable.has_bridges(Variable.bridges(b)) ||
	Constraint.has_bridges(Constraint.bridges(b))
	empty!(b.con_to_name)
	b.name_to_con = nothing
	end
	empty!(Variable.bridges(b))
	empty!(Constraint.bridges(b))
	empty!(Objective.bridges(b))
	return
	end

the compiler has to do a run-time check to see if there are bridges.

If we made the field ::Union{Nothing,Map}, the compiler may be clever enough to compile away the branches based on the Nothing. As an alternative, we could pass map as a function argument to force it to specialize.

[odow]

Closing. We should implement this at the JuMP-level. I'll make a PR with some ideas.