Add as_str() to string::Drain. #76525

m-ou-se · 2020-09-09T16:08:11Z

Vec's Drain recently had its .as_slice() stabilized, but String's Drain was still missing the analogous .as_str(). This adds that.

Also improves the Debug implementation, which now shows the remaining data instead of just "Drain { .. }".

rust-highfive · 2020-09-09T16:08:14Z

r? @kennytm

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kennytm · 2020-09-09T16:35:22Z

r? @dtolnay

kennytm · 2020-09-09T16:36:02Z

🤔 Actually those two AsRef impls are insta-stable

Trait implementations effectively can't be #[unstable].

m-ou-se · 2020-09-09T17:10:56Z

thinking Actually those two AsRef impls are insta-stable

Ah, I was unaware of this unstable-trait-impl problem. That's unfortunate. Marked them as stable for now.

kennytm · 2020-09-09T17:33:13Z

Or perhaps you could skip the AsRef impls for now so we don't need to invoke FCP on this (similar to the treatment in #58924 → #72584)

Since trait implementations cannot be unstable, we should only add them when the as_str feature gets stabilized. Until then, only `.as_str()` is available (behind a feature gate).

…ess-unstable-trait-impl, r=lcnr Warn for #[unstable] on trait impls when it has no effect. Earlier today I sent a PR with an `#[unstable]` attribute on a trait `impl`, but was informed that this attribute has no effect there. (comment: rust-lang#76525 (comment), issue: rust-lang#55436) This PR adds a warning for this situation. Trait `impl` blocks with `#[unstable]` where both the type and the trait are stable will result in a warning: ``` warning: An `#[unstable]` annotation here has no effect. See issue rust-lang#55436 <rust-lang#55436> for more information. --> library/std/src/panic.rs:235:1 | 235 | #[unstable(feature = "integer_atomics", issue = "32976")] | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ``` --- It detects three problems in the existing code: 1. A few `RefUnwindSafe` implementations for the atomic integer types in `library/std/src/panic.rs`. Example: https://github.com/rust-lang/rust/blob/d92155bf6ae0b7d79fc83cbeeb0cc0c765353471/library/std/src/panic.rs#L235-L236 2. An implementation of `Error` for `LayoutErr` in `library/std/srd/error.rs`: https://github.com/rust-lang/rust/blob/d92155bf6ae0b7d79fc83cbeeb0cc0c765353471/library/std/src/error.rs#L392-L397 3. `From` implementations for `Waker` and `RawWaker` in `library/alloc/src/task.rs`. Example: https://github.com/rust-lang/rust/blob/d92155bf6ae0b7d79fc83cbeeb0cc0c765353471/library/alloc/src/task.rs#L36-L37 Case 3 interesting: It has a bound with an `#[unstable]` trait (`W: Wake`), so appears to have much effect on stable code. It does however break similar blanket implementations. It would also have immediate effect if `Wake` was implemented for any stable type. (Which is not the case right now, but there are no warnings in place to prevent it.) Whether this case is a problem or not is not clear to me. If it isn't, adding a simple `c.visit_generics(..);` to this PR will stop the warning for this case.

…s-unstable-trait-impl, r=lcnr Warn for #[unstable] on trait impls when it has no effect. Earlier today I sent a PR with an `#[unstable]` attribute on a trait `impl`, but was informed that this attribute has no effect there. (comment: rust-lang#76525 (comment), issue: rust-lang#55436) This PR adds a warning for this situation. Trait `impl` blocks with `#[unstable]` where both the type and the trait are stable will result in a warning: ``` warning: An `#[unstable]` annotation here has no effect. See issue rust-lang#55436 <rust-lang#55436> for more information. --> library/std/src/panic.rs:235:1 | 235 | #[unstable(feature = "integer_atomics", issue = "32976")] | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ``` --- It detects three problems in the existing code: 1. A few `RefUnwindSafe` implementations for the atomic integer types in `library/std/src/panic.rs`. Example: https://github.com/rust-lang/rust/blob/d92155bf6ae0b7d79fc83cbeeb0cc0c765353471/library/std/src/panic.rs#L235-L236 2. An implementation of `Error` for `LayoutErr` in `library/std/srd/error.rs`: https://github.com/rust-lang/rust/blob/d92155bf6ae0b7d79fc83cbeeb0cc0c765353471/library/std/src/error.rs#L392-L397 3. `From` implementations for `Waker` and `RawWaker` in `library/alloc/src/task.rs`. Example: https://github.com/rust-lang/rust/blob/d92155bf6ae0b7d79fc83cbeeb0cc0c765353471/library/alloc/src/task.rs#L36-L37 Case 3 interesting: It has a bound with an `#[unstable]` trait (`W: Wake`), so appears to have much effect on stable code. It does however break similar blanket implementations. It would also have immediate effect if `Wake` was implemented for any stable type. (Which is not the case right now, but there are no warnings in place to prevent it.) Whether this case is a problem or not is not clear to me. If it isn't, adding a simple `c.visit_generics(..);` to this PR will stop the warning for this case.

dtolnay

Thanks, looks good. Please file a tracking issue for the new method and mention the pending AsRef impls.

dtolnay · 2020-09-19T06:26:56Z

@bors r+

bors · 2020-09-19T06:26:57Z

📌 Commit 15eb638 has been approved by dtolnay

Rollup of 14 pull requests Successful merges: - rust-lang#73963 (deny(unsafe_op_in_unsafe_fn) in libstd/path.rs) - rust-lang#75099 (lint/ty: move fns to avoid abstraction violation) - rust-lang#75502 (Use implicit (not explicit) rules for promotability by default in `const fn`) - rust-lang#75580 (Add test for checking duplicated branch or-patterns) - rust-lang#76310 (Add `[T; N]: TryFrom<Vec<T>>` (insta-stable)) - rust-lang#76400 (Clean up vec benches bench_in_place style) - rust-lang#76434 (do not inline black_box when building for Miri) - rust-lang#76492 (Add associated constant `BITS` to all integer types) - rust-lang#76525 (Add as_str() to string::Drain.) - rust-lang#76636 (assert ScalarMaybeUninit size) - rust-lang#76749 (give *even better* suggestion when matching a const range) - rust-lang#76757 (don't convert types to the same type with try_into (clippy::useless_conversion)) - rust-lang#76796 (Give a better error message when x.py uses the wrong stage for CI) - rust-lang#76798 (Build fixes for RISC-V 32-bit Linux support) Failed merges: r? `@ghost`

m-ou-se added 3 commits September 9, 2020 17:50

Add as_str() and AsRef to string::Drain.

daa62d9

Show remaining data in string::Drain's Debug impl.

6732840

Add AsRef<[u8]> for String's Drain.

f5bb523

rust-highfive assigned kennytm Sep 9, 2020

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Sep 9, 2020

rust-highfive assigned dtolnay and unassigned kennytm Sep 9, 2020

kennytm added the T-libs-api Relevant to the library API team, which will review and decide on the PR/issue. label Sep 9, 2020

Mark AsRef impls for String's Drain as stable.

f2a3290

Trait implementations effectively can't be #[unstable].

kennytm added the needs-fcp This change is insta-stable, so needs a completed FCP to proceed. label Sep 9, 2020

kennytm removed the needs-fcp This change is insta-stable, so needs a completed FCP to proceed. label Sep 9, 2020

Disable AsRef implementations for String's Drain.

829019d

Since trait implementations cannot be unstable, we should only add them when the as_str feature gets stabilized. Until then, only `.as_str()` is available (behind a feature gate).

m-ou-se force-pushed the string-drain branch from e21da9a to 829019d Compare September 9, 2020 17:58

m-ou-se mentioned this pull request Sep 9, 2020

Warn for #[unstable] on trait impls when it has no effect. #76538

Merged

dtolnay approved these changes Sep 19, 2020

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m-ou-se mentioned this pull request Sep 19, 2020

Tracking Issue for feature(string_drain_as_str) - string::Drain::as_str() #76905

Closed

Add tracking issue number for string_drain_as_str.

15eb638

dtolnay approved these changes Sep 19, 2020

View reviewed changes

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 19, 2020

kennytm changed the title ~~Add as_str() and AsRef to string::Drain.~~ Add as_str() to string::Drain. Sep 19, 2020

RalfJung mentioned this pull request Sep 19, 2020

Rollup of 14 pull requests #76912

Merged

bors merged commit 46bb884 into rust-lang:master Sep 19, 2020

rustbot added this to the 1.48.0 milestone Sep 19, 2020

m-ou-se deleted the string-drain branch June 23, 2021 16:45

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Add as_str() to string::Drain. #76525

Add as_str() to string::Drain. #76525

m-ou-se commented Sep 9, 2020

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bors commented Sep 19, 2020

Add as_str() to string::Drain. #76525

Add as_str() to string::Drain. #76525

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