Tracking issue for RFC#1685: Deprecate anonymous parameters #41686

aturon · 2017-05-01T22:05:35Z

This is a tracking issue for the RFC "Deprecate anonymous parameters " (rust-lang/rfcs#1685).

Steps:

Implement the RFC (cc @rust-lang/compiler -- can anyone write up mentoring instructions?)
Adjust documentation (see instructions on forge)

Unresolved questions:

The precise deprecation strategy

est31 · 2017-05-01T22:43:01Z

I could work on this. From reading the RFC discussion, I think the "soft" deprecation strategy has been chosen? So on the compiler side, we'll need an allow by default (deprecation) lint for anonymous parameters, right?

aturon · 2017-05-01T22:48:48Z

@est31 Awesome! And yes, that's correct. This will be most effective if we add the lint to Clippy as well.

(The open question is around the criteria for moving to a warn-by-default strategy in the future.)

Removes occurences of anonymous parameters from the rustc codebase, as they are to be deprecated. See issue rust-lang#41686 and RFC 1685.

est31 · 2017-05-02T04:55:51Z

About the clippy lint, I'll leave that to someone else. Given #41692, it should be mostly copy paste, but maybe with official rust claiming the lint name one has to chose another one. No idea.

Add a lint to disallow anonymous parameters Adds a (allow by default) lint to disallow anonymous parameters, like it was decided in RFC 1685 (rust-lang/rfcs#1685). cc tracking issue rust-lang#41686

@frewsxcv

Removal pass for anonymous parameters Removes occurences of anonymous parameters from the rustc codebase, as they are to be deprecated. See issue rust-lang#41686 and RFC 1685. r? @frewsxcv

matklad · 2017-05-05T09:25:15Z

IJR inspection: intellij-rust/intellij-rust#1211

I'll try to add an automatic fix to rustfmt as well. Not sure it's a great idea, but I want to try :)

Accept interpolated patterns in trait method parameters Permit this, basically ```rust macro_rules! m { ($pat: pat) => { trait Tr { fn f($pat: u8) {} } } } ``` it previously caused a parsing error during expansion because trait methods accept only very restricted set of patterns during parsing due to ambiguities caused by [anonymous parameters](#41686), and this set didn't include interpolated patterns. Some outdated messages from "no patterns allowed" errors are also removed. Addresses #35203 (comment)

mark-i-m · 2018-02-17T23:20:47Z

It doesn't appear that this is linting: https://play.rust-lang.org/?gist=b818c6024acb95add60b339e7708d132&version=nightly

Also, we might want to try to finish this for the 2018 epoch, so we should start linting now

mark-i-m · 2018-02-17T23:24:46Z

Oh, duh 🤦‍

It's an allow by default lint.

mark-i-m · 2018-02-17T23:29:39Z

Sorry for the multiple rapid posts.

After having read a bit more of the discussion that I can find, I propose a more aggressive deprecation strategy:

We make the lint warn-by-default as soon as possible
We make anon parameters a hard error at the epoch boundary

cc @matklad @est31 @aturon

SimonSapin · 2018-02-18T22:05:57Z

Should this also apply to fn(Foo) function pointer types?

matklad · 2018-02-18T22:59:02Z

@SimonSapin I would say no, because the situation for function pointers is just the opposite: nontrivial patterns are forbidden:

error[E0561]: patterns aren't allowed in function pointer types
 --> main.rs:1:13
  |
1 | type F = fn(&x: &i32);
  |             ^^

mark-i-m · 2018-02-18T23:38:08Z

Also, I think the original RFC doesn't mention fn pointers...

petrochenkov · 2018-02-19T07:46:46Z

@SimonSapin
The problem solved by this RFC is unique to trait methods - they may have or not have body, so they may need or not need the full power of patterns in parameters (and full pattern support is incompatible with anonymous parameters).
Function pointers never have body, so they never need non-trivial patterns, so they can freely use anonymous parameters as well.

vi · 2018-05-27T00:53:53Z

Shall it be addressed before Rust 2018?

Maybe there should be a Github label like "rust-2018-checklist"? Or it should be a Github milestone?

mark-i-m · 2018-05-27T20:59:38Z

Do the current plan is to make this warn by default starting at the edition and deprecate it in a later edition. (See #48309)

@matklad

Make anon params lint warn-by-default This is intended as a followup on anonymous parameters deprecation. Cross-posting from #41686: > After having read a bit more of the discussion that I can find, I propose a more aggressive deprecation strategy: > - We make the lint warn-by-default as soon as possible > - We make anon parameters a hard error at the epoch boundary cc @matklad @est31 @aturon

cramertj · 2018-08-31T18:54:02Z

@mark-i-m The forge has a section on updating documentation, but I don't think there's much to do here for deprecations other than to make sure that the book / reference / RBE aren't using the feature.

Centril · 2018-08-31T19:40:02Z

@cramertj @mark-i-m We should probably note this in the edition guide as well.

Centril · 2018-09-15T12:49:01Z

Triage: We still need to update the documentation.
ping @mark-i-m

mark-i-m · 2018-09-17T23:15:31Z

Sorry for the delay. I have been a bit swamped lately and mostly keeping up from my phone, so not much opportunity to write PRs 😛.

Reference: rust-lang/reference#420
Edition Guide: rust-lang/edition-guide#105

I did a brief search through the nomicon, book, RBE sections on traits and didn't see any other anon params, but please let me know if I missed one.

steveklabnik · 2018-09-18T16:18:28Z

Docs have all been merged. This is good to go.

Centril · 2018-09-18T16:32:59Z

Before we close the tracking issue; we still need to update the reference with notes about the actual edition-breaking change.

mark-i-m · 2018-09-18T17:55:09Z

@Centril @steveklabnik I opened rust-lang/reference#421

Does this look like what you were thinking of?

Centril · 2018-09-18T17:59:41Z

@mark-i-m I was thinking of specifying somewhat more formally (BNF, etc.) but this is good in the interim :)

mark-i-m · 2018-09-18T23:02:46Z

@Centril I didn't realize there was a BNF spec of rust anywhere. Could you point me to it so I can update it?

Centril · 2018-09-18T23:07:20Z

@mark-i-m I don't think there is a BNF spec of Rust anywhere that covers all of Rust and is up to date;

However, we do specify some parts of the language in BNF; for example: https://doc.rust-lang.org/reference/expressions/literal-expr.html.

I think the most up-to-date specification is in parser-lalr.y but it isn't fully updated either.

We don't need to spec it in BNF right now; but as a long term goal it would be good to do so.

mark-i-m · 2018-09-21T19:35:10Z

@Centril Perhaps we can spin that off into its own specific issue?

Currently, I think the last piece of documentation that is mandatory for this issue would be rust-lang/reference#421. Right?

Centril · 2018-09-21T19:38:52Z

@mark-i-m nah; no issue needed; we should define a canonical grammar for Rust at some point, hopefully soon.

Once the reference PR lands we can close this issue.

Centril · 2018-09-22T19:15:29Z

The reference PR has been merged, so I am closing this.

From the warning: anonymous parameters are deprecated and will be removed in the next edition. this was previously accepted by the compiler but is being phased out; it will become a hard error in the 2018 edition! for more information, see issue #41686 <rust-lang/rust#41686> Signed-off-by: Moritz Hoffmann <[email protected]>

For more info, see: rust-lang/rust#41686

Otherwise we get this and the appveyor build fails: ``` warning: anonymous parameters are deprecated and will be removed in the next edition. --> tests\tests.rs:68:18 | 68 | fn from_vecs(CsvVecs) -> Self; | ^^^^^^^ help: try naming the parameter or explicitly ignoring it: `_: CsvVecs` | = note: `#[warn(anonymous_parameters)]` on by default = warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2018! = note: for more information, see issue #41686 <rust-lang/rust#41686> error: linking with `i686-w64-mingw32-gcc` failed: exit code: 1 ```

=== stdout === === stderr === warning: anonymous parameters are deprecated and will be removed in the next edition --> <anon>:16:19 | 16 | fn parse_mode(&Self, Self::PartialState) {} | ^^^^^ help: try naming the parameter or explicitly ignoring it: `_: &Self` | = note: `#[warn(anonymous_parameters)]` on by default = warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2018! = note: for more information, see issue #41686 <rust-lang/rust#41686> warning: anonymous parameters are deprecated and will be removed in the next edition --> <anon>:16:26 | 16 | fn parse_mode(&Self, Self::PartialState) {} | ^^^^^^^^^^^^^^^^^^ help: try naming the parameter or explicitly ignoring it: `_: Self::PartialState` | = warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2018! = note: for more information, see issue #41686 <rust-lang/rust#41686> warning: function is never used: `expr` --> <anon>:26:4 | 26 | fn expr<A>() -> impl Parser | ^^^^ | = note: `#[warn(dead_code)]` on by default warning: function is never used: `parse_mode_impl` --> <anon>:32:4 | 32 | fn parse_mode_impl<A>() | ^^^^^^^^^^^^^^^ warning: 4 warnings emitted ==============

Disable CSOUND, same issue as on powerpc64*: error[E0433]: failed to resolve: use of undeclared crate or module `imp` --> /wrkdirs/usr/ports/multimedia/gstreamer1-plugins-rust/work/gst-plugins-rs-d0466b3eee114207f851b37cae0015c0e718f021/cargo-crates/va_list-0.1.3/src/lib.rs:77:15 | 77 | internal: imp::VaList, | ^^^ use of undeclared crate or module `imp` error[E0433]: failed to resolve: use of undeclared crate or module `imp` --> /wrkdirs/usr/ports/multimedia/gstreamer1-plugins-rust/work/gst-plugins-rs-d0466b3eee114207f851b37cae0015c0e718f021/cargo-crates/va_list-0.1.3/src/lib.rs:93:24 | 93 | unsafe fn get(&mut imp::VaList) -> Self; | ^^^ use of undeclared crate or module `imp` warning: anonymous parameters are deprecated and will be removed in the next edition. --> /wrkdirs/usr/ports/multimedia/gstreamer1-plugins-rust/work/gst-plugins-rs-d0466b3eee114207f851b37cae0015c0e718f021/cargo-crates/va_list-0.1.3/src/lib.rs:93:19 | 93 | unsafe fn get(&mut imp::VaList) -> Self; | ^^^^^^^^^^^^^^^^ help: try naming the parameter or explicitly ignoring it: `_: &mut imp::VaList` | = note: `#[warn(anonymous_parameters)]` on by default = warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2018! = note: for more information, see issue #41686 <rust-lang/rust#41686> For more information about this error, try `rustc --explain E0433`. warning: `va_list` (lib) generated 1 warning Error: CliError { error: Some(could not compile `va_list` due to 2 previous errors; 1 warning emitted Also patch crossbeam-utils crate for no atomics on powerpc. Building dav1d segfaults, so disable it as well: process didn't exit successfully: `/wrkdirs/usr/ports/multimedia/gstreamer1-plugins-rust/work/gst-plugins-rs-d0466b3eee114207f851b37cae0015c0e718f021/_build/target/release/build/dav1d-sys-3a3db191566872b8/build-script-build` (signal: 11, SIGSEGV: invalid memory reference)

aturon added B-RFC-approved T-lang labels May 1, 2017

aturon mentioned this issue May 1, 2017

Deprecate anonymous parameters rust-lang/rfcs#1685

Merged

est31 mentioned this issue May 2, 2017

Add a lint to disallow anonymous parameters #41692

Merged

est31 mentioned this issue May 2, 2017

Removal pass for anonymous parameters #41693

Merged

Mark-Simulacrum added the C-tracking-issue label Jul 27, 2017

petrochenkov mentioned this issue Nov 5, 2017

Accept interpolated patterns in trait method parameters #45775

Merged

mjadczak mentioned this issue Feb 17, 2018

[API Design] [II] Get rid of unnamed parameters in traits gfx-rs/gfx#1829

Closed

mark-i-m mentioned this issue Feb 17, 2018

Make anon params lint warn-by-default #48309

Merged

petrochenkov mentioned this issue May 9, 2018

Slice patterns cannot be used in trait methods #50571

Closed

varkor mentioned this issue Aug 3, 2018

Allow destructuring parameters in trait function declarations #53046

Open

Centril mentioned this issue Sep 15, 2018

Note anon params as hard error in 2018 in guide rust-lang/edition-guide#103

Closed

This was referenced Sep 17, 2018

Document deprecation of anon params rust-lang/edition-guide#105

Merged

No more anonymous trait fn parameters rust-lang/reference#420

Merged

mark-i-m mentioned this issue Sep 18, 2018

Add note about anon params rust-lang/reference#421

Merged

Centril closed this as completed Sep 22, 2018

Centril mentioned this issue Oct 7, 2018

require argument names in trait method signatures? rust-lang/rfcs#1351

Closed

paddyhoran mentioned this issue Nov 29, 2018

ARROW-3878: [Rust] Improve primitive types apache/arrow#3031

Closed

antiguru mentioned this issue Jul 2, 2021

Fix compiler warning on Rust 1.53 TimelyDataflow/differential-dataflow#329

Merged

fwip pushed a commit to fwip/miniz_oxide that referenced this issue Aug 9, 2021

Remove deprecated anonymous parameter

b0f6915

For more info, see: rust-lang/rust#41686

est31 mentioned this issue Nov 14, 2022

Non-unique argument names should not be allowed in a trait method #104374

Closed

github-actions bot mentioned this issue Apr 9, 2024

rust/1.77.2 package update wolfi-dev/os#16567

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devzing mentioned this issue Feb 11, 2025

docker-compose up fails bloxberg-org/bloxberg-validator-node#2

Open

Tracking issue for RFC#1685: Deprecate anonymous parameters #41686

Tracking issue for RFC#1685: Deprecate anonymous parameters #41686

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