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update patterns.md for const pattern RFC #1456

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merged 3 commits into from
May 27, 2024

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@RalfJung RalfJung commented Jan 26, 2024

Updates the reference for rust-lang/rfcs#3535.
Tracking issue: rust-lang/rust#120362.

This is not 100% implemented yet:

matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request Feb 3, 2024
make matching on NaN a hard error, and remove the rest of illegal_floating_point_literal_pattern

These arms would never be hit anyway, so the pattern makes little sense. We have had a future-compat lint against float matches in general for a *long* time, so I hope we can get away with immediately making this a hard error.

This is part of implementing rust-lang/rfcs#3535.

Closes rust-lang#41620 by removing the lint.

rust-lang/reference#1456 updates the reference to match.
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request Feb 3, 2024
make matching on NaN a hard error, and remove the rest of illegal_floating_point_literal_pattern

These arms would never be hit anyway, so the pattern makes little sense. We have had a future-compat lint against float matches in general for a *long* time, so I hope we can get away with immediately making this a hard error.

This is part of implementing rust-lang/rfcs#3535.

Closes rust-lang#41620 by removing the lint.

rust-lang/reference#1456 updates the reference to match.
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request Feb 5, 2024
make matching on NaN a hard error, and remove the rest of illegal_floating_point_literal_pattern

These arms would never be hit anyway, so the pattern makes little sense. We have had a future-compat lint against float matches in general for a *long* time, so I hope we can get away with immediately making this a hard error.

This is part of implementing rust-lang/rfcs#3535.

Closes rust-lang#41620 by removing the lint.

rust-lang/reference#1456 updates the reference to match.
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request Feb 5, 2024
make matching on NaN a hard error, and remove the rest of illegal_floating_point_literal_pattern

These arms would never be hit anyway, so the pattern makes little sense. We have had a future-compat lint against float matches in general for a *long* time, so I hope we can get away with immediately making this a hard error.

This is part of implementing rust-lang/rfcs#3535.

Closes rust-lang#41620 by removing the lint.

rust-lang/reference#1456 updates the reference to match.
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request Feb 5, 2024
make matching on NaN a hard error, and remove the rest of illegal_floating_point_literal_pattern

These arms would never be hit anyway, so the pattern makes little sense. We have had a future-compat lint against float matches in general for a *long* time, so I hope we can get away with immediately making this a hard error.

This is part of implementing rust-lang/rfcs#3535.

Closes rust-lang#41620 by removing the lint.

rust-lang/reference#1456 updates the reference to match.
rust-timer added a commit to rust-lang-ci/rust that referenced this pull request Feb 5, 2024
Rollup merge of rust-lang#116284 - RalfJung:no-nan-match, r=cjgillot

make matching on NaN a hard error, and remove the rest of illegal_floating_point_literal_pattern

These arms would never be hit anyway, so the pattern makes little sense. We have had a future-compat lint against float matches in general for a *long* time, so I hope we can get away with immediately making this a hard error.

This is part of implementing rust-lang/rfcs#3535.

Closes rust-lang#41620 by removing the lint.

rust-lang/reference#1456 updates the reference to match.
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ehuss commented Feb 5, 2024

@RalfJung Is this ready to merge? Were there any changes since this was written?

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RalfJung commented Feb 5, 2024

We are slowly staging the deployment of this in rustc. Not sure how closely the reference wants to match that.

If you are okay with the reference stating things as required that are just future-compat lints in rustc (rather than hard errors), then this is ready to go, yes.

flip1995 pushed a commit to flip1995/rust-clippy that referenced this pull request Feb 8, 2024
make matching on NaN a hard error, and remove the rest of illegal_floating_point_literal_pattern

These arms would never be hit anyway, so the pattern makes little sense. We have had a future-compat lint against float matches in general for a *long* time, so I hope we can get away with immediately making this a hard error.

This is part of implementing rust-lang/rfcs#3535.

Closes rust-lang/rust#41620 by removing the lint.

rust-lang/reference#1456 updates the reference to match.
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RalfJung commented May 3, 2024

FYI, when rust-lang/rust#124661 lands rustc will fully behave as documented here. I hope to land that in this release cycle.

src/patterns.md Outdated
Comment on lines 789 to 790
In particular, the value of `C` must be known at pattern-building time (which is pre-monomorphization).
This means that associated consts cannot be used as patterns.
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I don't understand this part. Path patterns can be associated consts. Can you clarify what it is referring to?

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@RalfJung RalfJung May 6, 2024

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This is intended to explain why this code does not compile:

trait Trait {
    const C: i32;
}

fn f<T: Trait>(x: i32) -> bool {
    matches!(x, T::C) //~ERROR: associated consts cannot be referenced in patterns
}

src/patterns.md Outdated
When a constant `C` of type `T` is used as a pattern, we first check that `T: PartialEq`.
Furthermore we require that the value of `C` *has (recursive) structural equality*, which is defined recursively as follows:

- Integers as well as `bool` and `char` values always have structural equality.
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And strings?

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Ah right, they should also be added here, good catch.

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Thanks!

@ehuss ehuss added this pull request to the merge queue May 27, 2024
Merged via the queue into rust-lang:master with commit 0e07fc5 May 27, 2024
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compiler-errors added a commit to compiler-errors/rust that referenced this pull request Jun 4, 2024
Update books

## rust-lang/book

6 commits in 85442a608426d3667f1c9458ad457b241a36b569..5228bfac8267ad24659a81b92ec5417976b5edbc
2024-05-29 20:55:49 UTC to 2024-05-27 17:22:03 UTC

- Fix typo in ch10-03 (rust-lang/book#3539)
- Backport changes to ch 9 and 10 (rust-lang/book#3946)
- infra: correctly support preprocessors for nostarch (rust-lang/book#3944)
- Use `<kbd>` instead of `<span class="keystroke">` (rust-lang/book#3945)
- infra: Fix clippy warning in remove_markup (rust-lang/book#3943)
- fix: ch10-03 - misleading use of expect on .split (rust-lang/book#3939)

## rust-lang/edition-guide

2 commits in 0c68e90acaae5a611f8f5098a3c2980de9845ab2..bbaabbe088e21a81a0d9ae6757705020d5d7b416
2024-05-24 19:07:18 UTC to 2024-05-21 22:40:52 UTC

- 2024: Document reserving `gen` keyword (rust-lang/edition-guide#300)
- 2024: Document cargo changes (rust-lang/edition-guide#301)

## rust-embedded/book

1 commits in dd962bb82865a5284f2404e5234f1e3222b9c022..b10c6acaf0f43481f6600e95d4b5013446e29f7a
2024-05-31 08:51:50 UTC to 2024-05-31 08:51:50 UTC

- Add some explanations as to why exception re-entrancy may still be an issue in a multicore-environment. (rust-embedded/book#367)

## rust-lang/reference

6 commits in e356977fceaa8591c762312d8d446769166d4b3e..6019b76f5b28938565b251bbba0bf5cc5c43d863
2024-06-03 15:58:57 UTC to 2024-05-25 18:35:54 UTC

- Add Apple `target_abi` values to the example values (rust-lang/reference#1507)
- this needs a space (rust-lang/reference#1506)
- Mention Variadics With No Fixed Parameter (rust-lang/reference#1494)
- Add "scopes" chapter. (rust-lang/reference#1040)
- update patterns.md for const pattern RFC (rust-lang/reference#1456)
- document guarantee about evaluation of associated consts and const blocks (rust-lang/reference#1497)

## rust-lang/rust-by-example

3 commits in 20482893d1a502df72f76762c97aed88854cdf81..4840dca06cadf48b305d3ce0aeafde7f80933f80
2024-05-28 13:56:12 UTC to 2024-05-27 11:51:10 UTC

- Update mdbook-i18n-helpers to 0.3.3 (rust-lang/rust-by-example#1857)
- Fix CI failure (rust-lang/rust-by-example#1856)
- Add precision on From/Into asymmetry to from_into.md (rust-lang/rust-by-example#1855)

## rust-lang/rustc-dev-guide

4 commits in b6d4a49..6a7374b
2024-05-31 00:27:28 UTC to 2024-05-21 09:56:12 UTC

- Flesh out the "representing types" chapter (rust-lang/rustc-dev-guide#1985)
- sync the stage0 filename (rust-lang/rustc-dev-guide#1979)
- Add Rust for Linux notification group entry (rust-lang/rustc-dev-guide#1984)
- fix some typos (rust-lang/rustc-dev-guide#1983)
GuillaumeGomez added a commit to GuillaumeGomez/rust that referenced this pull request Jun 4, 2024
Update books

## rust-lang/book

6 commits in 85442a608426d3667f1c9458ad457b241a36b569..5228bfac8267ad24659a81b92ec5417976b5edbc
2024-05-29 20:55:49 UTC to 2024-05-27 17:22:03 UTC

- Fix typo in ch10-03 (rust-lang/book#3539)
- Backport changes to ch 9 and 10 (rust-lang/book#3946)
- infra: correctly support preprocessors for nostarch (rust-lang/book#3944)
- Use `<kbd>` instead of `<span class="keystroke">` (rust-lang/book#3945)
- infra: Fix clippy warning in remove_markup (rust-lang/book#3943)
- fix: ch10-03 - misleading use of expect on .split (rust-lang/book#3939)

## rust-lang/edition-guide

2 commits in 0c68e90acaae5a611f8f5098a3c2980de9845ab2..bbaabbe088e21a81a0d9ae6757705020d5d7b416
2024-05-24 19:07:18 UTC to 2024-05-21 22:40:52 UTC

- 2024: Document reserving `gen` keyword (rust-lang/edition-guide#300)
- 2024: Document cargo changes (rust-lang/edition-guide#301)

## rust-embedded/book

1 commits in dd962bb82865a5284f2404e5234f1e3222b9c022..b10c6acaf0f43481f6600e95d4b5013446e29f7a
2024-05-31 08:51:50 UTC to 2024-05-31 08:51:50 UTC

- Add some explanations as to why exception re-entrancy may still be an issue in a multicore-environment. (rust-embedded/book#367)

## rust-lang/reference

6 commits in e356977fceaa8591c762312d8d446769166d4b3e..6019b76f5b28938565b251bbba0bf5cc5c43d863
2024-06-03 15:58:57 UTC to 2024-05-25 18:35:54 UTC

- Add Apple `target_abi` values to the example values (rust-lang/reference#1507)
- this needs a space (rust-lang/reference#1506)
- Mention Variadics With No Fixed Parameter (rust-lang/reference#1494)
- Add "scopes" chapter. (rust-lang/reference#1040)
- update patterns.md for const pattern RFC (rust-lang/reference#1456)
- document guarantee about evaluation of associated consts and const blocks (rust-lang/reference#1497)

## rust-lang/rust-by-example

3 commits in 20482893d1a502df72f76762c97aed88854cdf81..4840dca06cadf48b305d3ce0aeafde7f80933f80
2024-05-28 13:56:12 UTC to 2024-05-27 11:51:10 UTC

- Update mdbook-i18n-helpers to 0.3.3 (rust-lang/rust-by-example#1857)
- Fix CI failure (rust-lang/rust-by-example#1856)
- Add precision on From/Into asymmetry to from_into.md (rust-lang/rust-by-example#1855)

## rust-lang/rustc-dev-guide

4 commits in b6d4a49..6a7374b
2024-05-31 00:27:28 UTC to 2024-05-21 09:56:12 UTC

- Flesh out the "representing types" chapter (rust-lang/rustc-dev-guide#1985)
- sync the stage0 filename (rust-lang/rustc-dev-guide#1979)
- Add Rust for Linux notification group entry (rust-lang/rustc-dev-guide#1984)
- fix some typos (rust-lang/rustc-dev-guide#1983)
rust-timer added a commit to rust-lang-ci/rust that referenced this pull request Jun 4, 2024
Rollup merge of rust-lang#125933 - rustbot:docs-update, r=ehuss

Update books

## rust-lang/book

6 commits in 85442a608426d3667f1c9458ad457b241a36b569..5228bfac8267ad24659a81b92ec5417976b5edbc
2024-05-29 20:55:49 UTC to 2024-05-27 17:22:03 UTC

- Fix typo in ch10-03 (rust-lang/book#3539)
- Backport changes to ch 9 and 10 (rust-lang/book#3946)
- infra: correctly support preprocessors for nostarch (rust-lang/book#3944)
- Use `<kbd>` instead of `<span class="keystroke">` (rust-lang/book#3945)
- infra: Fix clippy warning in remove_markup (rust-lang/book#3943)
- fix: ch10-03 - misleading use of expect on .split (rust-lang/book#3939)

## rust-lang/edition-guide

2 commits in 0c68e90acaae5a611f8f5098a3c2980de9845ab2..bbaabbe088e21a81a0d9ae6757705020d5d7b416
2024-05-24 19:07:18 UTC to 2024-05-21 22:40:52 UTC

- 2024: Document reserving `gen` keyword (rust-lang/edition-guide#300)
- 2024: Document cargo changes (rust-lang/edition-guide#301)

## rust-embedded/book

1 commits in dd962bb82865a5284f2404e5234f1e3222b9c022..b10c6acaf0f43481f6600e95d4b5013446e29f7a
2024-05-31 08:51:50 UTC to 2024-05-31 08:51:50 UTC

- Add some explanations as to why exception re-entrancy may still be an issue in a multicore-environment. (rust-embedded/book#367)

## rust-lang/reference

6 commits in e356977fceaa8591c762312d8d446769166d4b3e..6019b76f5b28938565b251bbba0bf5cc5c43d863
2024-06-03 15:58:57 UTC to 2024-05-25 18:35:54 UTC

- Add Apple `target_abi` values to the example values (rust-lang/reference#1507)
- this needs a space (rust-lang/reference#1506)
- Mention Variadics With No Fixed Parameter (rust-lang/reference#1494)
- Add "scopes" chapter. (rust-lang/reference#1040)
- update patterns.md for const pattern RFC (rust-lang/reference#1456)
- document guarantee about evaluation of associated consts and const blocks (rust-lang/reference#1497)

## rust-lang/rust-by-example

3 commits in 20482893d1a502df72f76762c97aed88854cdf81..4840dca06cadf48b305d3ce0aeafde7f80933f80
2024-05-28 13:56:12 UTC to 2024-05-27 11:51:10 UTC

- Update mdbook-i18n-helpers to 0.3.3 (rust-lang/rust-by-example#1857)
- Fix CI failure (rust-lang/rust-by-example#1856)
- Add precision on From/Into asymmetry to from_into.md (rust-lang/rust-by-example#1855)

## rust-lang/rustc-dev-guide

4 commits in b6d4a49..6a7374b
2024-05-31 00:27:28 UTC to 2024-05-21 09:56:12 UTC

- Flesh out the "representing types" chapter (rust-lang/rustc-dev-guide#1985)
- sync the stage0 filename (rust-lang/rustc-dev-guide#1979)
- Add Rust for Linux notification group entry (rust-lang/rustc-dev-guide#1984)
- fix some typos (rust-lang/rustc-dev-guide#1983)
@RalfJung RalfJung deleted the const-pattern branch July 22, 2024 09:50
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