Cannot push to a vector after applying a 3-arg ldiv!

[simonbyrne]

using LinearAlgebra
u = rand(2)
A = rand(2,2)
b = rand(2)

push!(b,3.0) # works
u = rand(3)
A = rand(3,3)
ldiv!(u,lu(A),b)

push!(b,4.0) # Error: cannot resize array with shared data

Originally posted by @ChrisRackauckas in JuliaLang/julia#33143 (comment)

[KristofferC]

3-arg ldiv!, right?

[simonbyrne]

The problem are the views, which trigger JuliaLang/julia#33143:
https://github.com/JuliaLang/julia/blob/4b0d6c9407e337c249498185b146f80141c492ca/stdlib/LinearAlgebra/src/factorization.jl#L117-L128

The rationale was to handle factorizations (e.g. QR) of non-square matrices (#25810).

[simonbyrne]

Honestly, by putting a copy in the first branch, it seems a bit self-defeating to define a 3-arg ldiv! to begin with (you might as well use /). But I don't get the rationale for the view in the 2nd branch (which is what triggers the problem above)? @andreasnoack any ideas?

[simonbyrne]

ah, it seems to be for matrix args: in that case, it probably makes sense to split them out into separate methods.