[masklinn]

It didn't, actually. Instead go 1.15 has a static array of the first 256 positive integers, and when it needs to box one for an interface it gets a pointer into that array instead: https://go-review.googlesource.com/c/go/+/216401/4/src/runti...

This array is also used for single-byte strings (which previously had its own array): https://go-review.googlesource.com/c/go/+/221979/3/src/runti...

[ominous_prime]

It didn't, do what? I would consider the first 256 integers to be "small integers" ;)

> Converting a small integer value into an interface value no longer causes allocation

I forgot that it can also be used for single byte strings, That's not an optimization I ever encountered being useful, but it's there!

[masklinn]

> It didn't, do what?

Reintroduce “packing into interfaces”.

It did a completely different thing. Small integers remain not inlined.