Stabilisation Report
Summary
This PR will stabilise inline_const feature in expression position. inline_const_pat is still unstable and will not be stabilised.
The feature will allow code like this...
What I’m curious about - this function was already const, so for stuff like this, I’d think there’s basically a 100% chance the compiler would optimize this too, just implicitly.
AFAIK this new feature is just for times when it isn’t an optimization, but more your own domain invariants. E.g. assertions.
But I could be wrong. I wonder if this can be used for actual optimizations in some places that the compiler couldn’t figure out by itself.
Maybe at some point I can append to it at compile time too. I’d love to be able to put a const {} and have allocations that resolve down to a 'static, and this seems to be a step toward that.
I guess I’m just excited that Vec::new() is the example they picked, since the next obvious question is, “can I push?”
Huh, this is awesome! From the link, this now works:
I’m going to have to play with this to see how far it goes.
What I’m curious about - this function was already const, so for stuff like this, I’d think there’s basically a 100% chance the compiler would optimize this too, just implicitly.
AFAIK this new feature is just for times when it isn’t an optimization, but more your own domain invariants. E.g. assertions.
But I could be wrong. I wonder if this can be used for actual optimizations in some places that the compiler couldn’t figure out by itself.
Wouldn’t this just prevent you from allocating more memory (than zero)?
Ah, apparently for now you’re not allowed to allocate. But
vec::new_in(allocator)looks interesting. This works in nightly today:#![feature(allocator_api)] use std::alloc::Global; fn main() { const MY_VEC: Vec<i32> = const { Vec::new_in(Global) }; println!("{:?}", MY_VEC); }Maybe at some point I can append to it at compile time too. I’d love to be able to put a
const {}and have allocations that resolve down to a'static, and this seems to be a step toward that.I guess I’m just excited that
Vec::new()is the example they picked, since the next obvious question is, “can I push?”