ScaledMap issue for Unitful scaling factors

[JeffFessler]

Some of this package works fine with Unitful values thanks to its support for Numbers.
But maybe it hasn't actually been tested with Unitful values.
Now I am trying to use it with some and hit my first issue:

M = ones(3,2) * m
L = LinearMap(M)
Matrix(L) # works fine
S = 1s * L # runs, but has wrong eltype
Matrix(S) # throws

I think the issue is here:

LinearMaps.jl/src/scaledmap.jl

Line 17 in 50f5bf9

ScaledMap{Base.promote_op(*, typeof(λ), eltype(lmap))}(λ, lmap)

I may know how to fix so I'll aim for a PR.

FWIW, the docstring for promote_op says "Due to its fragility, use of promote_op should be avoided."

[JeffFessler]

Actually it is more subtle than I thought at first. Because Unitful values are Numbers but not Real, it is using the "non-commuting" constructor rather than a ScaledMap here:

LinearMaps.jl/src/composition.jl

Line 80 in 50f5bf9

function Base.:(*)(α::Number, A::LinearMap)

Still working on it...