update patterns.md for const pattern RFC #1456
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matthiaskrgr
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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
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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
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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
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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
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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
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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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@RalfJung Is this ready to merge? Were there any changes since this was written? |
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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
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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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FYI, when rust-lang/rust#124661 lands rustc will fully behave as documented here. I hope to land that in this release cycle. |
RalfJung
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May 3, 2024
ehuss
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May 6, 2024
src/patterns.md
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| 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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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
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| 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: | ||
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| - Integers as well as `bool` and `char` values always have structural equality. |
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Ah right, they should also be added here, good catch.
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Updates the reference for rust-lang/rfcs#3535.
Tracking issue: rust-lang/rust#120362.
This is not 100% implemented yet:
T: PartialEqcurrently also just give a future-compat lint, not a hard error