Optimization for strong zeros and broadcasting

[antoine-levitt]

It'd be helpful to have x .+ false recognize that false is a strong zero and therefore the expression can be optimized to x. Use case is something like

if cond
    to_add = some_array
else
    to_add = false
end
# lots of code including to_add .+ some_other_array

Currently one has to put the lot of code in the if branch, which can be annoying.

[martinholters]

For correctness, it should probably return copy(x) which drastically reduces the optimization potential.