Remove `#[rustc_allow_const_fn_ptr]` and add `#![feature(const_fn_fn_ptr_basics)]` #77170

ecstatic-morse · 2020-09-24T23:31:46Z

rustc_allow_const_fn_ptr was a hack to work around the lack of an escape hatch for the "min const fn" checks in const-stable functions. Now that we have co-opted allow_internal_unstable for this purpose, we no longer need a bespoke attribute.

Now this functionality is gated under const_fn_fn_ptr_basics (how concise!), and #[allow_internal_unstable(const_fn_fn_ptr_basics)] replaces #[rustc_allow_const_fn_ptr]. const_fn_fn_ptr_basics allows function pointer types to appear in the arguments and locals of a const fn as well as function pointer casts to be performed inside a const fn. Both of these were allowed in constants and statics already. Notably, this does not allow users to invoke function pointers in a const context. Presumably, we will use a nicer name for that (const_fn_ptr?).

r? @oli-obk

bors · 2020-09-25T04:54:03Z

☔ The latest upstream changes (presumably #77172) made this pull request unmergeable. Please resolve the merge conflicts.

Note that reviewers usually do not review pull requests until merge conflicts are resolved! Once you resolve the conflicts, you should change the labels applied by bors to indicate that your PR is ready for review. Post this as a comment to change the labels:

@rustbot modify labels: +S-waiting-on-review -S-waiting-on-author

oli-obk · 2020-09-25T10:22:11Z

Oh this is a wondeful fix.

Presumably, we will use a nicer name for that (const_fn_ptr?).

we could add an unsound feature like that if you want it for experimentation (though it would probably be better to just allow it via unleash and not a gate). We'll need to figure out the details around that together with trait objects and method calls in general.

Note that you don't really need to fix the old min_const_fn check here, as that is just used by clippy now. We could in fact remove all feature gating logic from min_const_fn and just move it to clippy. this way it's removed from rustc and we'll just have to figure out whether we want to not just permit trivial const fns (so we'll have to adjust the logic in clippy instead of reusing the rustc logic)

ecstatic-morse · 2020-09-25T16:46:10Z

we could add an unsound feature like that if you want it for experimentation.

Oh nothing like that. I was trying to explain the reason I chose a verbose name here (const_fn_fn_ptr_basics). const_fn_fn_ptr or const_fn_ptr imply that you can actually do stuff with them besides move them around, and I think we would want to use const_fn_ptr for const fn() -> i32 (or whatever form it takes).

oli-obk · 2020-09-25T17:17:47Z

right. So this PR lgtm, r=me after a rebase

ecstatic-morse · 2020-09-25T17:56:19Z

@bors r=oli-obk rollup

bors · 2020-09-25T17:56:20Z

📌 Commit 6d91b11a29a3d14f71bdef7383aeecc0e0fa1149 has been approved by oli-obk

Rollup of 12 pull requests Successful merges: - rust-lang#75454 (Explicitly document the size guarantees that Option makes.) - rust-lang#76631 (Add `x.py setup`) - rust-lang#77076 (Add missing code examples on slice iter types) - rust-lang#77093 (merge `need_type_info_err(_const)`) - rust-lang#77122 (Add `#![feature(const_fn_floating_point_arithmetic)]`) - rust-lang#77127 (Update mdBook) - rust-lang#77161 (Remove TrustedLen requirement from BuilderMethods::switch) - rust-lang#77166 (update Miri) - rust-lang#77181 (Add doc alias for pointer primitive) - rust-lang#77204 (Remove stray word from `ClosureKind::extends` docs) - rust-lang#77207 (Rename `whence` to `span`) - rust-lang#77211 (Remove unused #[allow(...)] statements from compiler/) Failed merges: - rust-lang#77170 (Remove `#[rustc_allow_const_fn_ptr]` and add `#![feature(const_fn_fn_ptr_basics)]`) r? `@ghost`

bors · 2020-09-26T20:23:03Z

☔ The latest upstream changes (presumably #77224) made this pull request unmergeable. Please resolve the merge conflicts.

Note that reviewers usually do not review pull requests until merge conflicts are resolved! Once you resolve the conflicts, you should change the labels applied by bors to indicate that your PR is ready for review. Post this as a comment to change the labels:

@rustbot modify labels: +S-waiting-on-review -S-waiting-on-author

ecstatic-morse · 2020-09-26T21:44:41Z

This will conflict with #77231. Better to let that one go through first.

jonas-schievink · 2020-09-27T16:36:21Z

@bors r- failed in #77269

This was a hack to work around the lack of an escape hatch for the "min `const fn`" checks in const-stable functions. Now that we have co-opted `allow_internal_unstable` for this purpose, we no longer need the bespoke attribute.

ecstatic-morse · 2020-09-27T18:06:04Z

@jonas-schievink Any idea where I can find the logs for the failing rollup? A stage 1 build works and all UI tests pass for me locally on the latest master.

jonas-schievink · 2020-09-27T18:08:41Z

Logs should be here: https://github.com/rust-lang/rust/runs/1173085918

ecstatic-morse · 2020-09-27T19:26:46Z

Seems to be working now. I removed the old failing gate test for rustc_allow_const_fn_ptr, since it's not covering anything unique now.

@bors r=oli-obk

bors · 2020-09-27T19:26:58Z

📌 Commit 807260b has been approved by oli-obk

@oli-obk

Remove `#[rustc_allow_const_fn_ptr]` and add `#![feature(const_fn_fn_ptr_basics)]` `rustc_allow_const_fn_ptr` was a hack to work around the lack of an escape hatch for the "min `const fn`" checks in const-stable functions. Now that we have co-opted `allow_internal_unstable` for this purpose, we no longer need a bespoke attribute. Now this functionality is gated under `const_fn_fn_ptr_basics` (how concise!), and `#[allow_internal_unstable(const_fn_fn_ptr_basics)]` replaces `#[rustc_allow_const_fn_ptr]`. `const_fn_fn_ptr_basics` allows function pointer types to appear in the arguments and locals of a `const fn` as well as function pointer casts to be performed inside a `const fn`. Both of these were allowed in constants and statics already. Notably, this does **not** allow users to invoke function pointers in a const context. Presumably, we will use a nicer name for that (`const_fn_ptr`?). r? @oli-obk

@oli-obk

Remove `#[rustc_allow_const_fn_ptr]` and add `#![feature(const_fn_fn_ptr_basics)]` `rustc_allow_const_fn_ptr` was a hack to work around the lack of an escape hatch for the "min `const fn`" checks in const-stable functions. Now that we have co-opted `allow_internal_unstable` for this purpose, we no longer need a bespoke attribute. Now this functionality is gated under `const_fn_fn_ptr_basics` (how concise!), and `#[allow_internal_unstable(const_fn_fn_ptr_basics)]` replaces `#[rustc_allow_const_fn_ptr]`. `const_fn_fn_ptr_basics` allows function pointer types to appear in the arguments and locals of a `const fn` as well as function pointer casts to be performed inside a `const fn`. Both of these were allowed in constants and statics already. Notably, this does **not** allow users to invoke function pointers in a const context. Presumably, we will use a nicer name for that (`const_fn_ptr`?). r? @oli-obk

Rollup of 7 pull requests Successful merges: - rust-lang#76454 (UI to unit test for those using Cell/RefCell/UnsafeCell) - rust-lang#76474 (Add option to pass a custom codegen backend from a driver) - rust-lang#76711 (diag: improve closure/generic parameter mismatch) - rust-lang#77170 (Remove `#[rustc_allow_const_fn_ptr]` and add `#![feature(const_fn_fn_ptr_basics)]`) - rust-lang#77194 (Add doc alias for iterator fold) - rust-lang#77288 (fix building libstd for Miri on macOS) - rust-lang#77295 (Update unstable-book: Fix ABNF in inline assembly docs) Failed merges: r? `@ghost`

rust-highfive assigned oli-obk Sep 24, 2020

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Sep 24, 2020

ecstatic-morse changed the title ~~Remove rustc_allow_const_fn_ptr and add #![feature(const_fn_fn_ptr_basics)]~~ Remove #[rustc_allow_const_fn_ptr] and add #![feature(const_fn_fn_ptr_basics)] Sep 24, 2020

ecstatic-morse force-pushed the const-fn-ptr branch from 915f5bb to c02170d Compare September 25, 2020 00:10

jyn514 added A-const-fn Area: const fn foo(..) {..}. Pure functions which can be applied at compile time. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Sep 25, 2020

oli-obk mentioned this pull request Sep 25, 2020

Add speculative const-checking and remove qualify_min_const_fn.rs #77128

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ecstatic-morse force-pushed the const-fn-ptr branch from c02170d to 6d91b11 Compare September 25, 2020 17:19

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 Sep 25, 2020

jonas-schievink mentioned this pull request Sep 25, 2020

Rollup of 14 pull requests #77206

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RalfJung mentioned this pull request Sep 26, 2020

Rollup of 10 pull requests #77222

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RalfJung mentioned this pull request Sep 26, 2020

Rollup of 12 pull requests #77224

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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 Sep 26, 2020

ecstatic-morse force-pushed the const-fn-ptr branch 3 times, most recently from aa2e362 to 7a5ab4b Compare September 26, 2020 21:43

ecstatic-morse added the S-blocked Status: Marked as blocked ❌ on something else such as an RFC or other implementation work. label Sep 26, 2020

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 Sep 27, 2020

jonas-schievink mentioned this pull request Sep 27, 2020

Rollup of 8 pull requests #77269

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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 Sep 27, 2020

ecstatic-morse added 5 commits September 27, 2020 10:46

Add a feature gate for basic function pointer use in const fn

1ff1431

Remove rustc_allow_const_fn_ptr

3cbd17f

This was a hack to work around the lack of an escape hatch for the "min `const fn`" checks in const-stable functions. Now that we have co-opted `allow_internal_unstable` for this purpose, we no longer need the bespoke attribute.

Update tests with new feature gate

e2622b9

Bless tests

54d3329

Mark min_const_fn_fn_ptr test as gate test

368502c

Remove feature gate test for rustc_allow_const_fn_ptr

807260b

ecstatic-morse force-pushed the const-fn-ptr branch from 16f36db to 807260b Compare September 27, 2020 18:51

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 Sep 27, 2020

RalfJung mentioned this pull request Sep 28, 2020

Rollup of 7 pull requests #77297

Closed

Dylan-DPC-zz mentioned this pull request Sep 28, 2020

Rollup of 9 pull requests #77301

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RalfJung mentioned this pull request Sep 28, 2020

Rollup of 7 pull requests #77302

Merged

bors merged commit 85a59d4 into rust-lang:master Sep 28, 2020

rustbot added this to the 1.48.0 milestone Sep 28, 2020

bjorn3 mentioned this pull request Oct 1, 2020

Comments for "https://os.phil-opp.com/minimal-rust-kernel/" phil-opp/blog_os#403

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ecstatic-morse deleted the const-fn-ptr branch October 6, 2020 01:42

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Remove `#[rustc_allow_const_fn_ptr]` and add `#![feature(const_fn_fn_ptr_basics)]` #77170

Remove `#[rustc_allow_const_fn_ptr]` and add `#![feature(const_fn_fn_ptr_basics)]` #77170

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bors commented Sep 27, 2020

Remove #[rustc_allow_const_fn_ptr] and add #![feature(const_fn_fn_ptr_basics)] #77170

Remove #[rustc_allow_const_fn_ptr] and add #![feature(const_fn_fn_ptr_basics)] #77170

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Remove `#[rustc_allow_const_fn_ptr]` and add `#![feature(const_fn_fn_ptr_basics)]` #77170

Remove `#[rustc_allow_const_fn_ptr]` and add `#![feature(const_fn_fn_ptr_basics)]` #77170

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