[steveklabnik]

That's because of `Box::new`, I'd think. If you use the box keyword, you should get the placement new effect.

[mkishi]

Thank you! I thought the box keyword was simply a syntactic sugar -- I'm not that familiar with placement new, even in C++.

Note for the interested: the optimization works right now, even though the keyword is behind the box_syntax feature gate.

Updated test: https://play.rust-lang.org/?code=%23!%5Bfeature(core)%5D%0A%...