On 3 May 2018 at 15:56, Glenn Linderman <v+python@g.nevcal.com> wrote:

On 5/2/2018 8:56 PM, Gregory Szorc wrote:

Nobody in the project is seriously talking about a complete rewrite in Rust. Contributors to the project have varying opinions on how aggressively Rust should be utilized. People who contribute to the C code, low-level primitives (like storage, deltas, etc), and those who care about performance tend to want more Rust. One thing we almost universally agree on is that we want to rewrite all of Mercurial's C code in Rust. I anticipate that figuring out the balance between Rust and Python in Mercurial will be an ongoing conversation/process for the next few years.

Have you considered simply rewriting CPython in Rust?

And yes, the 4th word in that question was intended to produce peals of shocked laughter. But why Rust? Why not Go?

Trying to get two different garbage collection engines to play nice with each other is a recipe for significant pain, since you can easily end up with uncollectable cycles that neither GC system has complete visibility into (all it needs is a loop from PyObject A -> Go Object B -> back to PyObject A).

Combining Python and Rust can still get into that kind of trouble when using reference counting on the Rust side, but it's a lot easier to avoid than it is in runtimes with mandatory GC.

Cheers,

Nick.