Automatically insert lifetimes

[MilesCranmer]

Using https://docs.julialang.org/en/v1.12-dev/devdocs/EscapeAnalysis/ it might be possible to avoid the explicit @lifetime scope and instead have lifetimes get inserted by the compiler automatically.

e.g.,

@do_magic function foo(x::Array, y)
    @own :mut x y

    @ref rx = x
    @own result = my_sum(rx)
    
    push!(x, result)
end

You would want it to generate this:

function foo(x::Array, y)
    @own :mut x y

    lt1 = Lifetime()
    @ref ~lt1 rx = x
    @own result = my_sum(rx)
    cleanup!(lt1)
    
    push!(x, result)
end

based on detecting that rx is last used at the line my_sum(rx). However, I'm not sure if EscapeAnalysis is smart enough to figure this out or not?

@MasonProtter interested in your thoughts.

If we figure this out, we could even allow for @ref x which could be really nice. Then it's basically the same as &x in Rust.