Tracking Issue for `#![feature(const_io_structs)]`

[a1phyr]

This is a tracking issue for #![feature(const_io_structs)]

New const functions are:

• io::Cursor::new
• io::Cursor::get_ref
• io::Cursor::position
• io::empty
• io::repeat
• io::sink

About tracking issues

Tracking issues are used to record the overall progress of implementation.
They are also used as hubs connecting to other relevant issues, e.g., bugs or open design questions.
A tracking issue is however not meant for large scale discussion, questions, or bug reports about a feature.
Instead, open a dedicated issue for the specific matter and add the relevant feature gate label.

Steps

• Implementation (Make some std::io functions const #78811)
• FCP
• Stabilization PR

[jhpratt]

Are there any blockers for these? They appear to all have straightforward implementations that should work on stable.

CC @dtolnay who r+'d the original PR

[Stebalien]

Hey, I'd love to have this if we can make it stable. This would make it possible to, e.g., create "global" spooled temporary files without lazy_static:

static BUFFER: Mutex<SpooledTempFile> = Mutex::new(tempfile::SpooledTempFile::new(1024 * 1024));

[dtolnay]

@rust-lang/libs-api:
@rfcbot fcp merge

const for the following already-stable functions:

• https://doc.rust-lang.org/nightly/std/io/struct.Cursor.html#method.new
• https://doc.rust-lang.org/nightly/std/io/struct.Cursor.html#method.get_ref
• https://doc.rust-lang.org/nightly/std/io/struct.Cursor.html#method.position
• https://doc.rust-lang.org/nightly/std/io/fn.empty.html
• https://doc.rust-lang.org/nightly/std/io/fn.repeat.html
• https://doc.rust-lang.org/nightly/std/io/fn.sink.html

[rfcbot]

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

• @Amanieu
• @BurntSushi
• @dtolnay
• @joshtriplett
• @m-ou-se

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.