Say I have an n x m `Matrix`

, and an n-length `Vector`

that I want to copy to, say, column 2 of my matrix. My first try was to do `copyto!`

using `CartesianIndices`

.

```
m = rand(3,3)
v = rand(3)
copyto!(m, CartesianIndices((1:3, 2:2)), v, CartesianIndices(1:3))
```

But that fails. `copyto!`

only works to copy a slice of an `AbstractArray{T1,N}`

to another slice of an `AbstractArray{T2,N}`

, i.e. between tensors with the same number of indices, despite the API very elegantly allows to express the more general case with `N1 != N2`

as above. What is the proper way to do this (for arbitrary `N1`

, `N2`

) in v1.0? Is there a reason why we would not want a more general `copyto!`

?