[Utilities] Fix method invalidation

[odow]

The existing method was pretty terrible for inference.

[blegat]

So if I understand correctly:

Base.promote_rule(::Type{F}, ::Type{T}) where {T,F<:TypedScalarLike{T}} = F

is bad,

Base.promote_rule(::Type{F}, ::Type{T}) where {T,F<:MOI.ScalarAffineFunction{T}} = F

is bad but

Base.promote_rule(::Type{MOI.ScalarAffineFunction{T}}, ::Type{T}) where {T} = MOI.ScalarAffineFunction{T}

is good ?

[odow]

The underlying issue is

julia> Union{} <: MOI.Utilities.TypedScalarLike{Float64}
true

which conflicts with

julia> @which promote_type(Union{}, Float64)
promote_type(::Type{Union{}}, ::Type{T}) where T in Base at promotion.jl:224

[odow]

Why do we even need these methods? Coverage didn't hit them.

[blegat]

I see, I didn't think about Union{} ^^

Why do we even need these methods? Coverage didn't hit them.

Maybe because they are inlined ? I don't remember why they were added though.

[odow]

Let's see if anything breaks.

[odow]

I guess that's a false negative on the codecov then!