Multiplying JuMP expression with UniformScaling absorbs the matrix about jump.jl HOT 7 CLOSED

Could this give a better error message? For example,

Base.:-(a::Matrix, b::Union{JuMP.GenericVariableRef, JuMP.GenericAffExpr}) = error(
   "Subtraction between a Matrix and a JuMP variable is not supported: instead of A - x, " *
   "do A .- x for element-wise subtraction, or if you are modifying the diagonal entries of the matrix " *
   " do A - x * LinearAlgebra.I(n), where n is the diagonal length."
)

from jump.jl.

I don't know what we can or should do here. The answer is to force people to use I(2).

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I don't really want to add MutableArithmetics.UniformScaling{<:AbstractMutable} and have to deal with all the consequences?

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Yes it seems like a rabbit hole. Maybe we could try to convince LinearAlgebra to accept Any instead of Number. I think they thought that they are only implementing * with Number. This is fine but they can still allow Any in the constructor when it's called explicitly. In a Matrix they didn't force the entries to be Number so why do it in UniformScaling ?

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Perhaps open an issue? This will be easier with upgradable stdlibs.

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Closing as too hard to fix. It can't be a common issue, because I don't remember it coming up on Discourse.

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Yes, I think such error message for :+(::Matrix, ::AbstractJuMPScalar) would be useful

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