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

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Merged
merged 6 commits into from
Sep 19, 2020
Merged

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

merged 6 commits into from
Sep 19, 2020

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m-ou-se
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@m-ou-se m-ou-se commented Sep 9, 2020

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 { .. }".

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r? @kennytm

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

r? @dtolnay

@rust-highfive rust-highfive assigned dtolnay and unassigned kennytm Sep 9, 2020
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kennytm commented Sep 9, 2020 •
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🤔 Actually those two AsRef impls are insta-stable

@kennytm 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
@m-ou-se
Mark AsRef impls for String's Drain as stable.
f2a3290 
Trait implementations effectively can't be #[unstable].
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m-ou-se commented Sep 9, 2020

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 kennytm added the needs-fcp This change is insta-stable, or significant enough to need a team FCP to proceed. label Sep 9, 2020
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kennytm commented Sep 9, 2020 •
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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)

@kennytm kennytm removed the needs-fcp This change is insta-stable, or significant enough to need a team FCP to proceed. label Sep 9, 2020
@m-ou-se
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 m-ou-se mentioned this pull request Sep 9, 2020
Merged
Dylan-DPC-zz pushed a commit to Dylan-DPC-zz/rust that referenced this pull request Sep 12, 2020
@Dylan-DPC
Rollup merge of rust-lang#76538 - fusion-engineering-forks:check-usel…
a493e97 
…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.
bors added a commit to rust-lang-ci/rust that referenced this pull request Sep 12, 2020
@bors
Auto merge of rust-lang#76538 - fusion-engineering-forks:check-useles…
9891908 
…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
dtolnay approved these changes Sep 19, 2020
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Thanks, looks good. Please file a tracking issue for the new method and mention the pending AsRef impls.

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

@bors r+

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bors commented Sep 19, 2020

📌 Commit 15eb638 has been approved by dtolnay

@bors 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 kennytm changed the title Add as_str() and AsRef to string::Drain. Add as_str() to string::Drain. Sep 19, 2020
@RalfJung RalfJung mentioned this pull request Sep 19, 2020
Merged
bors added a commit to rust-lang-ci/rust that referenced this pull request Sep 19, 2020
@bors
Auto merge of rust-lang#76912 - RalfJung:rollup-q9ur56h, r=RalfJung
8e9d5db 
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`
@bors bors merged commit 46bb884 into rust-lang:master Sep 19, 2020
@rustbot rustbot added this to the 1.48.0 milestone Sep 19, 2020
@m-ou-se m-ou-se deleted the string-drain branch June 23, 2021 16:45
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