You need to allocate A in such a way that it can hold elements of typeof(v), for example something like this
function f(v::AbstractVector{T}, xtrue) where T
A = Matrix{T}(undef, 3, 3)
# ...
end
You need to allocate A in such a way that it can hold elements of typeof(v), for example something like this
function f(v::AbstractVector{T}, xtrue) where T
A = Matrix{T}(undef, 3, 3)
# ...
end