Feature request: Lazy @something macro

[jeffreyesun]

For performance reasons, we usually do not need to evaluate the second argument of the something function. For example, in this pattern I sometimes use for propagating default arguments:

function foo(; bar=nothing)
   bar = something(bar, defaultbar())
   ...
end

I propose a lazy version of this, @something:

macro something(valornothing, ex)
    return valornothing == :nothing ? ex : valornothing
end

to be used as follows:

function foo(; bar=nothing)
   bar = @something(bar, defaultbar())
   ...
end

so that defaultbar() need not be called when it is not needed.

[DilumAluthge]

Don't we already have this on master?

https://docs.julialang.org/en/v1.7-dev/base/base/#Base.@something

(Added in #40729.)

[jeffreyesun]

My bad, this is indeed already going to be in 1.7. Sorry for wasting your time.