https://github.com/rust-lang/rust http://git.dreamy.place/mirrors/rust/atom?h=automation/bors/try 2024-10-25T18:31:40+00:00 2024-10-25T18:31:40+00:00 Ralf Jung post@ralfj.de 2024-10-06T17:59:19+00:00 urn:sha1:a0215d8e46aab41219dea0bb1cbaaf97dafe2f89 Fundamentally, we have *three* disjoint categories of functions: 1. const-stable functions 2. private/unstable functions that are meant to be callable from const-stable functions 3. functions that can make use of unstable const features This PR implements the following system: - `#[rustc_const_stable]` puts functions in the first category. It may only be applied to `#[stable]` functions. - `#[rustc_const_unstable]` by default puts functions in the third category. The new attribute `#[rustc_const_stable_indirect]` can be added to such a function to move it into the second category. - `const fn` without a const stability marker are in the second category if they are still unstable. They automatically inherit the feature gate for regular calls, it can now also be used for const-calls. Also, several holes in recursive const stability checking are being closed. There's still one potential hole that is hard to avoid, which is when MIR building automatically inserts calls to a particular function in stable functions -- which happens in the panic machinery. Those need to *not* be `rustc_const_unstable` (or manually get a `rustc_const_stable_indirect`) to be sure they follow recursive const stability. But that's a fairly rare and special case so IMO it's fine. The net effect of this is that a `#[unstable]` or unmarked function can be constified simply by marking it as `const fn`, and it will then be const-callable from stable `const fn` and subject to recursive const stability requirements. If it is publicly reachable (which implies it cannot be unmarked), it will be const-unstable under the same feature gate. Only if the function ever becomes `#[stable]` does it need a `#[rustc_const_unstable]` or `#[rustc_const_stable]` marker to decide if this should also imply const-stability. Adding `#[rustc_const_unstable]` is only needed for (a) functions that need to use unstable const lang features (including intrinsics), or (b) `#[stable]` functions that are not yet intended to be const-stable. Adding `#[rustc_const_stable]` is only needed for functions that are actually meant to be directly callable from stable const code. `#[rustc_const_stable_indirect]` is used to mark intrinsics as const-callable and for `#[rustc_const_unstable]` functions that are actually called from other, exposed-on-stable `const fn`. No other attributes are required. 2024-02-08T08:10:43+00:00 Oli Scherer git-spam-no-reply9815368754983@oli-obk.de 2024-02-01T22:45:00+00:00 urn:sha1:eab2adb6607d94fd0c70de93abf546ae9282afaa 2023-11-24T18:15:52+00:00 Nilstrieb 48135649+Nilstrieb@users.noreply.github.com 2023-11-21T15:44:16+00:00 urn:sha1:41e8d152dc5abb5a706999ada8b059d3420af8f3 Co-authored-by: Adrian <adrian.iosdev@gmail.com> 2023-02-08T15:09:11+00:00 David Wood david.wood@huawei.com 2023-02-08T13:25:38+00:00 urn:sha1:912783402fe2f0d1fff41b047b0918e7e58e18ae Extend support for `implies_by` (from `#[stable]` and `#[unstable]`) to `#[rustc_const_stable]` and `#[rustc_const_unstable]`. Signed-off-by: David Wood <david.wood@huawei.com>