Update stdlib to the 2021 edition

[rukai]

progress towards #88638

I couldnt find a way to run the 2018 style panic tests against 2018 so I just deleted them, maybe theres a way to do it that I missed though?

[rust-highfive]

r? @kennytm

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[rukai]

Oh, seeing as theres a whole lint against it, maybe this needs more ceremony then some random person coming along and bumping to 2021.

rust/src/tools/tidy/src/edition.rs

Lines 26 to 35 in f410bc7

	// Library crates are not yet ready to migrate to 2021.
	if path.components().any(|c| c.as_os_str() == "library"){
	let has = contents.lines().any(is_edition_2018);
	if !has {
	tidy_error!(
	bad,
	"{} doesn't have `edition = \"2018\"` on a separate line",
	file.display()
	);
	}

[jyn514]

@m-ou-se do you happen to know why there's a lint against upgrading libstd to 2021?

@rukai please don't just delete the tests completely - you should be able to tell rustdoc to run them with an old edition using the edition2018 language string.

[jyn514]

Oh hmm, those are unit tests, not doctests - I'm not sure how to make them use a different edition :/ maybe they need to be UI tests instead so they're in a separate crate?

[rukai]

ah, replacing them with ui tests makes sense!
I'll do that.

[jyn514]

Hmm, this looks related to macro spans? Not sure what the bugs @Mark-Simulacrum referred to were.

#89103:

It excludes a migration of the library crates for now (see tidy diff) because we have some pending bugs around macro spans to fix there.

[m-ou-se]

ah, replacing them with ui tests makes sense! I'll do that.

There's no need for that. You can still panic with arbitrary payloads in Rust 2021. You just need to use panic_any instead of the panic (or assert) macro.

[m-ou-se]

No need to use format!() to format the argument to a format string. So instead of adding "{}", just remove the format!() macro:

Suggested change

	Err(ref err) => assert!(
	err.raw_os_error() == Some($s),
	"{}",
	format!("`{}` did not have a code of `{}`", err, $s)
	),
	Err(ref err) => assert!(err.raw_os_error() == Some($s),"`{}` did not have a code of `{}`", err, $s),

[m-ou-se]

Same here.

[m-ou-se]

There's no need to remove these tests. Just replace panic!() by panic_any().

[m-ou-se]

@m-ou-se do you happen to know why there's a lint against upgrading libstd to 2021?

That lint was originally checking that everything is using Rust 2018 rather than 2015. For most of the crates it's been changed to check for 2021 instead. So it's not meant as a lint against upgrading, more a lint against not using 2015. We can change it to accept either 2018 or 2021 for now, or to require 2021 for std specifically as well.

[rukai]

Thanks for the feedback!
Should be all addressed now.
I opted to special case std in the lint so that we remember to remove the lint when everything is moved to 2021.

[m-ou-se]

There's a typo in TODO.

(Maybe just say 'Not all library crate are ..' in the existing comment? We're force to update this anyway when another library crate moves to 2021, so it's not like we can forget anything here.)

[m-ou-se]

@bors r+

[bors]

📌 Commit b656384 has been approved by m-ou-se