"A[:] = ..." allocates memory

[stevengj]

It seems like this construct should operate in-place, but it apparently doesn't:

function foo(A)
    for i = 1:10^6
        A[:] = 0
    end
end
@time foo([3,4,5])

gives

0.021217 seconds (1.00 M allocations: 15.259 MB, 23.12% gc time)

Notice that it is apparently allocating something on each loop iteration. (Same on 0.4 and 0.5.)

[yuyichao]

The allocation is caused by the vararg call.

[stevengj]

We should have a specialized setindex method for this case that just calls fill!.

[yuyichao]

Ref #13459 (comment) , maybe .... It looks like we are getting close to fix #13359 though....