Require stable/unstable annotations for the constness of all stable fns with a const modifier #67136

oli-obk · 2019-12-08T01:33:53Z

Every #[stable] const fn now needs either a #[rustc_const_unstable] attribute or a #[rustc_const_stable] attribute. You can't silently stabilize the constness of a function anymore.

src/librustc/ty/constness.rs

src/librustc_feature/builtin_attrs.rs

RalfJung · 2019-12-08T21:38:38Z

src/librustc/ty/constness.rs

@@ -83,15 +88,36 @@ impl<'tcx> TyCtxt<'tcx> {
        }

        if self.features().staged_api {


The function this is in is called is_min_const_fn, but the body comments make it sounds more like "is the fn required to conform to min_const_fn restrictions", which is not reflected in the function name. Maybe must_be_min_const_fn?

well... it's both :D We call is_min_const_fn to check whether a function can be called from other min const fn. When checking a function we call is_min_const_fn to check if we are callable from other min const fn and thus must conform.

RalfJung · 2019-12-08T21:39:47Z

src/librustc/ty/constness.rs

+                    // Note: this is an arbitrary choice that does not affect stability or const
+                    // safety or anything, it just changes whether we need to annotate some
+                    // internal functions with `rustc_const_stable` or with `rustc_const_unstable`
+                    true


So internal unannounced functions are more restricted than stable functions with #[rustc_const_unstable]? That seems odd.

Ah I see @Centril asked for this. Well I think this is somewhat silly and would prefer to treat functions without staging attributes the same as unstable functions, but I won't fight over this.^^

RalfJung · 2019-12-08T21:41:34Z

I'm strongly in favor of the general approach! However, I am unfamiliar with how stability checking is implemented, so I'll have to pass on the review.

r? @Centril

Centril

r=me with comments addressed

src/libcore/sync/atomic.rs

src/librustc/ty/constness.rs

Centril · 2019-12-11T04:50:50Z

src/libsyntax/attr/builtin.rs

    find_stability_generic(sess, attrs.iter(), item_sp)
 }

 fn find_stability_generic<'a, I>(sess: &ParseSess,
                                 attrs_iter: I,
                                 item_sp: Span)
-                                 -> Option<Stability>
+                                 -> (Option<Stability>, Option<ConstStability>)


I have a feeling this function is doing way too much but let's not overhaul it here; making a note-to-self for now tho. I think the right structure would be to look for each attribute form independently and then do a post-processing step to merge information.

src/libsyntax_expand/base.rs

src/librustc/ty/constness.rs

oli-obk · 2019-12-12T09:55:51Z

@bors r=Centril

bors · 2019-12-12T09:55:53Z

📌 Commit 50bc0d2f72babab9d9038274a0ba1e93ebcca85c has been approved by Centril

bors · 2019-12-12T19:20:51Z

⌛ Testing commit 50bc0d2f72babab9d9038274a0ba1e93ebcca85c with merge 49c221ca4e14ea4210101b3be94ee74be1e6b444...

rust-highfive · 2019-12-12T19:50:37Z

The job x86_64-apple of your PR failed (pretty log, raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

2019-12-12T19:47:45.0485160Z [RUSTC-TIMING] build_script_build test:false 0.920
2019-12-12T19:47:52.7953620Z error: `sync::atomic::AtomicI128::new` is not yet stable as a const fn
2019-12-12T19:47:52.7954470Z     --> src/libcore/sync/atomic.rs:1221:48
2019-12-12T19:47:52.7955030Z      |
2019-12-12T19:47:52.7955660Z 1180 | / macro_rules! atomic_int {
2019-12-12T19:47:52.7956260Z 1181 | |     ($cfg_cas:meta,
2019-12-12T19:47:52.7956880Z 1182 | |      $stable:meta,
2019-12-12T19:47:52.7957540Z 1183 | |      $stable_cxchg:meta,
2019-12-12T19:47:52.7958090Z ...    |
2019-12-12T19:47:52.7958730Z 1221 | |         pub const $atomic_init: $atomic_type = $atomic_type::new(0);
2019-12-12T19:47:52.7959980Z ...    |
2019-12-12T19:47:52.7960570Z 1973 | |     }
2019-12-12T19:47:52.7961130Z 1974 | | }
2019-12-12T19:47:52.7961760Z      | |_- in this expansion of `atomic_int!`
2019-12-12T19:47:52.7961760Z      | |_- in this expansion of `atomic_int!`
2019-12-12T19:47:52.7962420Z ...
2019-12-12T19:47:52.7963000Z 2121 | / atomic_int! {
2019-12-12T19:47:52.7964480Z 2122 | |     cfg(target_has_atomic = "128"),
2019-12-12T19:47:52.7965220Z 2123 | |     unstable(feature = "integer_atomics", issue = "32976"),
2019-12-12T19:47:52.7965940Z 2124 | |     unstable(feature = "integer_atomics", issue = "32976"),
2019-12-12T19:47:52.7966510Z ...    |
2019-12-12T19:47:52.7967140Z 2136 | |     i128 AtomicI128 ATOMIC_I128_INIT
2019-12-12T19:47:52.7968370Z      | |_- in this macro invocation
2019-12-12T19:47:52.7968900Z      |
2019-12-12T19:47:52.7969530Z      = help: add `#![feature(const_integer_atomics)]` to the crate attributes to enable
2019-12-12T19:47:52.7969830Z 
2019-12-12T19:47:52.7969830Z 
2019-12-12T19:47:52.8354650Z error: `sync::atomic::AtomicU128::new` is not yet stable as a const fn
2019-12-12T19:47:52.8355400Z     --> src/libcore/sync/atomic.rs:1221:48
2019-12-12T19:47:52.8355950Z      |
2019-12-12T19:47:52.8356570Z 1180 | / macro_rules! atomic_int {
2019-12-12T19:47:52.8357180Z 1181 | |     ($cfg_cas:meta,
2019-12-12T19:47:52.8357810Z 1182 | |      $stable:meta,
2019-12-12T19:47:52.8358460Z 1183 | |      $stable_cxchg:meta,
2019-12-12T19:47:52.8359040Z ...    |
2019-12-12T19:47:52.8359720Z 1221 | |         pub const $atomic_init: $atomic_type = $atomic_type::new(0);
2019-12-12T19:47:52.8360980Z ...    |
2019-12-12T19:47:52.8361560Z 1973 | |     }
2019-12-12T19:47:52.8362170Z 1974 | | }
2019-12-12T19:47:52.8362820Z      | |_- in this expansion of `atomic_int!`
2019-12-12T19:47:52.8362820Z      | |_- in this expansion of `atomic_int!`
2019-12-12T19:47:52.8363340Z ...
2019-12-12T19:47:52.8363950Z 2139 | / atomic_int! {
2019-12-12T19:47:52.8364590Z 2140 | |     cfg(target_has_atomic = "128"),
2019-12-12T19:47:52.8365280Z 2141 | |     unstable(feature = "integer_atomics", issue = "32976"),
2019-12-12T19:47:52.8365960Z 2142 | |     unstable(feature = "integer_atomics", issue = "32976"),
2019-12-12T19:47:52.8366520Z ...    |
2019-12-12T19:47:52.8367160Z 2154 | |     u128 AtomicU128 ATOMIC_U128_INIT
2019-12-12T19:47:52.8368700Z      | |_- in this macro invocation
2019-12-12T19:47:52.8369250Z      |
2019-12-12T19:47:52.8369860Z      = help: add `#![feature(const_integer_atomics)]` to the crate attributes to enable
2019-12-12T19:47:52.8369960Z 
---
2019-12-12T19:49:01.4101010Z   local time: Thu Dec 12 19:49:01 UTC 2019
2019-12-12T19:49:01.4654960Z   network time: Thu, 12 Dec 2019 19:49:01 GMT
2019-12-12T19:49:01.4656250Z == end clock drift check ==
2019-12-12T19:49:01.4702650Z 
2019-12-12T19:49:01.4830100Z ##[error]Bash exited with code '1'.
2019-12-12T19:49:01.4873710Z ##[section]Starting: Checkout
2019-12-12T19:49:01.4876260Z ==============================================================================
2019-12-12T19:49:01.4876370Z Task         : Get sources
2019-12-12T19:49:01.4876450Z Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

bors · 2019-12-12T19:50:44Z

💔 Test failed - checks-azure

…unctions with a `const` modifier

oli-obk · 2019-12-13T12:15:21Z

@bors r=Centril

bors · 2019-12-13T12:15:22Z

📌 Commit f12affe has been approved by Centril

oli-obk · 2019-12-13T12:21:46Z

@bors r-

… atomics

oli-obk · 2019-12-13T12:29:10Z

@bors r=Centril

bors · 2019-12-13T12:29:11Z

📌 Commit 0b47ba7 has been approved by Centril

@RalfJung

Require stable/unstable annotations for the constness of all stable fns with a const modifier r? @RalfJung @Centril Every `#[stable]` const fn now needs either a `#[rustc_const_unstable]` attribute or a `#[rustc_const_stable]` attribute. You can't silently stabilize the constness of a function anymore.

bors · 2019-12-14T10:21:39Z

⌛ Testing commit 0b47ba7 with merge c8ea4ac...

@RalfJung

Require stable/unstable annotations for the constness of all stable fns with a const modifier r? @RalfJung @Centril Every `#[stable]` const fn now needs either a `#[rustc_const_unstable]` attribute or a `#[rustc_const_stable]` attribute. You can't silently stabilize the constness of a function anymore.

bors · 2019-12-14T13:22:33Z

☀️ Test successful - checks-azure
Approved by: Centril
Pushing c8ea4ac to master...

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oli-obk force-pushed the const_stability branch from 0dacbac to 50bc0d2 Compare December 12, 2019 09:55

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oli-obk added 5 commits December 13, 2019 11:27

Reuse the staged_api feature for rustc_const_unstable

d75c753

Require stable/unstable annotations for the constness of all stable f…

5e17e39

…unctions with a `const` modifier

Compiler internal error codes need no documentation

c7471ad

Elaborate internal const fn comment

8c83264

Fix rustdoc test

395a789

oli-obk added 3 commits December 13, 2019 11:27

Change the const stab default for internal const fns

83b8a56

Consistently name min_const_fn

3abc727

Address review comments

f12affe

oli-obk force-pushed the const_stability branch from 50bc0d2 to f12affe Compare December 13, 2019 11:33

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Dec 13, 2019

bors added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Dec 13, 2019

The constness of 128 bit atomics will be stabilized together with the…

0b47ba7

… atomics

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Dec 13, 2019

Centril mentioned this pull request Dec 13, 2019

Rollup of 5 pull requests #67288

Closed

bors added the merged-by-bors This PR was explicitly merged by bors. label Dec 14, 2019

bors merged commit 0b47ba7 into rust-lang:master Dec 14, 2019

This was referenced Dec 14, 2019

Split up ptr/mod.rs in libcore... #67163

Merged

Improve Style #67221

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Centril mentioned this pull request Dec 14, 2019

Enforce min_const_fn by default in staged_api with opt-out #64285

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tbu- mentioned this pull request Feb 14, 2021

str::as_bytes and friends have incorrect const stabilization version annotation #82085

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oli-obk deleted the const_stability branch March 16, 2021 12:13

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Require stable/unstable annotations for the constness of all stable fns with a const modifier #67136

Require stable/unstable annotations for the constness of all stable fns with a const modifier #67136

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bors commented Dec 14, 2019

		@@ -83,15 +88,36 @@ impl<'tcx> TyCtxt<'tcx> {
		}

		if self.features().staged_api {

Require stable/unstable annotations for the constness of all stable fns with a const modifier #67136

Require stable/unstable annotations for the constness of all stable fns with a const modifier #67136

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