Partially ordered unique closures

from blog baby steps, | ↗ original
On a call with other Rust developers, I realized that I was thinking about unique closures all wrong. I had in mind a total ordering: fn[send] but of course this is not necessary. What is desirable is a partial ordering: fn[send] just as ~ and @ pointers can both be aliased using a reference. Ironically, this is precisely what I proposed in...