std: Derive `Default` for `io::Cursor`#60234

tesaguri · 2019-04-24T12:04:59Z

I think this change is quite obvious, so made it insta-stable, but I won't insist on that.

rust-highfive · 2019-04-24T12:05:03Z

(rust_highfive has picked a reviewer for you, use r? to override)

jonas-schievink · 2019-04-24T12:12:27Z

Unfortunately trait impls can't be made unstable, so this can only be landed as an insta-stable impl

hellow554 · 2019-04-24T12:23:06Z

So this would make Cursor::<Vec<u8>>::default() possible, but is that really something one would do? Don't you rather want to wrap an existing Vec, because you want that content?

tesaguri · 2019-04-24T13:05:25Z

I'm dealing with a S: futures::Stream, so the content is not immediately available and I need a placeholder. I could just write Cursor::new(/* ... */) if S::Item were a concrete type (Cursor), but actually that is a type parameter with a trait bound S::Item: bytes::Buf + Default.

erikdesjardins · 2019-04-24T20:17:17Z

You should be able to use Cursor::new(Default::default()) anywhere Cursor::default() would work.
(not that I think this change shouldn't be made; I'm ambivalent)

Centril · 2019-04-28T12:11:53Z

r? @Amanieu

Amanieu · 2019-04-29T01:06:38Z

I think this is fine, but just in case anyone has objections...

@rfcbot fcp merge

rfcbot · 2019-04-29T01:06:39Z

Team member @Amanieu has proposed to merge this. The next step is review by the rest of the tagged team members:

No concerns currently listed.

Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

See this document for info about what commands tagged team members can give me.

rfcbot · 2019-04-29T17:28:04Z

🔔 This is now entering its final comment period, as per the review above. 🔔

rfcbot · 2019-05-09T17:30:24Z

The final comment period, with a disposition to merge, as per the review above, is now complete.

As the automated representative of the governance process, I would like to thank the author for their work and everyone else who contributed.

The RFC will be merged soon.

Centril · 2019-05-09T17:32:47Z

@bors r=Amanieu rollup

bors · 2019-05-09T17:32:49Z

📌 Commit 902904a has been approved by Amanieu

std: Derive `Default` for `io::Cursor` I think this change is quite obvious, so made it insta-stable, but I won't insist on that.

@ghost

Rollup of 8 pull requests Successful merges: - #59348 (Clean up and add tests for slice drop shims) - #60188 (Identify when a stmt could have been parsed as an expr) - #60234 (std: Derive `Default` for `io::Cursor`) - #60618 (Comment ext::tt::transcribe) - #60648 (Skip codegen for one UI test with long file path) - #60671 (remove unneeded `extern crate`s from build tools) - #60675 (Remove the old await! macro) - #60676 (Fix async desugaring providing wrong input to procedural macros.) Failed merges: r? @ghost

Pkgsrc changes: * NetBSD/sparc64 disabling of "packed" removed ("packed" removed upstream) * Adapt src_libstd_build.rs patch, update sed'ing of .cargo-checksum.json Build verified on NetBSD 8.0/amd64. Upstream changes: Version 1.36.0 (2019-07-04) ========================== Language -------- - [Non-Lexical Lifetimes are now enabled on the 2015 edition.][59114] - [The order of traits in trait objects no longer affects the semantics of that object.][59445] e.g. `dyn Send + fmt::Debug` is now equivalent to `dyn fmt::Debug + Send`, where this was previously not the case. Libraries --------- - [`HashMap`'s implementation has been replaced with `hashbrown::HashMap` implem entation.][58623] - [`TryFromSliceError` now implements `From<Infallible>`.][60318] - [`mem::needs_drop` is now available as a const fn.][60364] - [`alloc::Layout::from_size_align_unchecked` is now available as a const fn.][6 0370] - [`String` now implements `BorrowMut<str>`.][60404] - [`io::Cursor` now implements `Default`.][60234] - [Both `NonNull::{dangling, cast}` are now const fns.][60244] - [The `alloc` crate is now stable.][59675] `alloc` allows you to use a subset of `std` (e.g. `Vec`, `Box`, `Arc`) in `#![no_std]` environments if the environment has access to heap memory allocation. - [`String` now implements `From<&String>`.][59825] - [You can now pass multiple arguments to the `dbg!` macro.][59826] `dbg!` will return a tuple of each argument when there is multiple arguments. - [`Result::{is_err, is_ok}` are now `#[must_use]` and will produce a warning if not used.][59648] Stabilized APIs --------------- - [`VecDeque::rotate_left`] - [`VecDeque::rotate_right`] - [`Iterator::copied`] - [`io::IoSlice`] - [`io::IoSliceMut`] - [`Read::read_vectored`] - [`Write::write_vectored`] - [`str::as_mut_ptr`] - [`mem::MaybeUninit`] - [`pointer::align_offset`] - [`future::Future`] - [`task::Context`] - [`task::RawWaker`] - [`task::RawWakerVTable`] - [`task::Waker`] - [`task::Poll`] Cargo ----- - [Cargo will now produce an error if you attempt to use the name of a required dependency as a feature.][cargo/6860] - [You can now pass the `--offline` flag to run cargo without accessing the netw ork.][cargo/6934] You can find further change's in [Cargo's 1.36.0 release notes][cargo-1-36-0]. Clippy ------ There have been numerous additions and fixes to clippy, see [Clippy's 1.36.0 rel ease notes][clippy-1-36-0] for more details. Misc ---- Compatibility Notes ------------------- - [`std::arch::x86::_rdtsc` returns `u64` instead of `i64`][stdsimd/559] - [`std::arch::x86_64::_mm_shuffle_ps` takes an `i32` instead of `u32` for `mask `][stdsimd/522] - With the stabilisation of `mem::MaybeUninit`, `mem::uninitialized` use is no longer recommended, and will be deprecated in 1.38.0. [60318]: rust-lang/rust#60318 [60364]: rust-lang/rust#60364 [60370]: rust-lang/rust#60370 [60404]: rust-lang/rust#60404 [60234]: rust-lang/rust#60234 [60244]: rust-lang/rust#60244 [58623]: rust-lang/rust#58623 [59648]: rust-lang/rust#59648 [59675]: rust-lang/rust#59675 [59825]: rust-lang/rust#59825 [59826]: rust-lang/rust#59826 [59445]: rust-lang/rust#59445 [59114]: rust-lang/rust#59114 [cargo/6860]: rust-lang/cargo#6860 [cargo/6934]: rust-lang/cargo#6934 [`VecDeque::rotate_left`]: https://doc.rust-lang.org/std/collections/struct.VecDeque.html#method.rotate_left [`VecDeque::rotate_right`]: https://doc.rust-lang.org/std/collections/struct.VecDeque.html#method.rotate_right [`Iterator::copied`]: https://doc.rust-lang.org/std/iter/trait.Iterator.html#tymethod.copied [`io::IoSlice`]: https://doc.rust-lang.org/std/io/struct.IoSlice.html [`io::IoSliceMut`]: https://doc.rust-lang.org/std/io/struct.IoSliceMut.html [`Read::read_vectored`]: https://doc.rust-lang.org/std/io/trait.Read.html#method.read_vectored [`Write::write_vectored`]: https://doc.rust-lang.org/std/io/trait.Write.html#method.write_vectored [`str::as_mut_ptr`]: https://doc.rust-lang.org/std/primitive.str.html#method.as_mut_ptr [`mem::MaybeUninit`]: https://doc.rust-lang.org/std/mem/union.MaybeUninit.html [`pointer::align_offset`]: https://doc.rust-lang.org/std/primitive.pointer.html#method.align_offset [`future::Future`]: https://doc.rust-lang.org/std/future/trait.Future.html [`task::Context`]: https://doc.rust-lang.org/beta/std/task/struct.Context.html [`task::RawWaker`]: https://doc.rust-lang.org/beta/std/task/struct.RawWaker.html [`task::RawWakerVTable`]: https://doc.rust-lang.org/beta/std/task/struct.RawWakerVTable.html [`task::Waker`]: https://doc.rust-lang.org/beta/std/task/struct.Waker.html [`task::Poll`]: https://doc.rust-lang.org/beta/std/task/enum.Poll.html [clippy-1-36-0]: https://github.com/rust-lang/rust-clippy/blob/master/CHANGELOG.md#rust-136 [cargo-1-36-0]: https://github.com/rust-lang/cargo/blob/master/CHANGELOG.md#cargo-136-2019-07-04 [stdsimd/522]: rust-lang/stdarch#522 [stdsimd/559]: rust-lang/stdarch#559

std: Derive Default for io::Cursor

902904a

rust-highfive assigned withoutboats Apr 24, 2019

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Apr 24, 2019

jonas-schievink added T-libs-api Relevant to the library API team, which will review and decide on the PR/issue. needs-fcp This change is insta-stable, or significant enough to need a team FCP to proceed. labels Apr 24, 2019

Centril added the relnotes Marks issues that should be documented in the release notes of the next release. label Apr 25, 2019

Centril added this to the 1.36 milestone Apr 25, 2019

rust-highfive assigned Amanieu and unassigned withoutboats Apr 28, 2019

rfcbot added proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. disposition-merge This issue / PR is in PFCP or FCP with a disposition to merge it. labels Apr 29, 2019

rfcbot added final-comment-period In the final comment period and will be merged soon unless new substantive objections are raised. and removed proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. labels Apr 29, 2019

rfcbot added finished-final-comment-period The final comment period is finished for this PR / Issue. and removed final-comment-period In the final comment period and will be merged soon unless new substantive objections are raised. labels May 9, 2019

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 May 9, 2019

Centril added a commit to Centril/rust that referenced this pull request May 9, 2019

Rollup merge of rust-lang#60234 - tesaguri:cursor-default, r=Amanieu

bd17b5c

std: Derive `Default` for `io::Cursor` I think this change is quite obvious, so made it insta-stable, but I won't insist on that.

Centril mentioned this pull request May 9, 2019

Rollup of 8 pull requests #60683

Merged

bors merged commit 902904a into rust-lang:master May 10, 2019

tesaguri deleted the cursor-default branch May 10, 2019 04:36

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std: Derive `Default` for `io::Cursor`#60234