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Leverage core::marker::Freeze #941

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jswrenn opened this issue Feb 23, 2024 · 1 comment
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Leverage core::marker::Freeze #941

jswrenn opened this issue Feb 23, 2024 · 1 comment

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@jswrenn
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jswrenn commented Feb 23, 2024 •
edited by joshlf
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With rust-lang/rust#121501, Rust may expose and subsequently stabilize the Freeze trait, which is automatically implemented for all types free of UnsafeCell (excluding by indirection such as &UnsafeCell). This is analogous to our NoCell trait, but our trait must be explicitly derived.

Once Freeze is stabilized, we should first emit a

where
     Self: Freeze

bound on the definition of NoCell when zerocopy is compiled with sufficiently-recent toolchains.

Then, we should consider whether to eliminate our NoCell trait altogether in favor of re-exporting Freeze as NoCell.
@oli-obk oli-obk mentioned this issue Feb 23, 2024
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@joshlf joshlf mentioned this issue Feb 28, 2024
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@oli-obk oli-obk mentioned this issue Mar 1, 2024
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jhpratt added a commit to jhpratt/rust that referenced this issue Mar 10, 2024
@jhpratt
Rollup merge of rust-lang#121840 - oli-obk:freeze, r=dtolnay
5d75182 
Expose the Freeze trait again (unstably) and forbid implementing it manually

non-emoji version of rust-lang#121501

cc rust-lang#60715

This trait is useful for generic constants (associated consts of generic traits). See the test (`tests/ui/associated-consts/freeze.rs`) added in this PR for a usage example. The builtin `Freeze` trait is the only way to do it, users cannot work around this issue.

It's also a useful trait for building some very specific abstrations, as shown by the usage by the `zerocopy` crate: google/zerocopy#941

cc `@RalfJung`

T-lang signed off on reexposing this unstably: rust-lang#121501 (comment)
jhpratt added a commit to jhpratt/rust that referenced this issue Mar 11, 2024
@jhpratt
Rollup merge of rust-lang#121840 - oli-obk:freeze, r=dtolnay
61ff631 
Expose the Freeze trait again (unstably) and forbid implementing it manually

non-emoji version of rust-lang#121501

cc rust-lang#60715

This trait is useful for generic constants (associated consts of generic traits). See the test (`tests/ui/associated-consts/freeze.rs`) added in this PR for a usage example. The builtin `Freeze` trait is the only way to do it, users cannot work around this issue.

It's also a useful trait for building some very specific abstrations, as shown by the usage by the `zerocopy` crate: google/zerocopy#941

cc ``@RalfJung``

T-lang signed off on reexposing this unstably: rust-lang#121501 (comment)
jhpratt added a commit to jhpratt/rust that referenced this issue Mar 11, 2024
@jhpratt
Rollup merge of rust-lang#121840 - oli-obk:freeze, r=dtolnay
05f22c3 
Expose the Freeze trait again (unstably) and forbid implementing it manually

non-emoji version of rust-lang#121501

cc rust-lang#60715

This trait is useful for generic constants (associated consts of generic traits). See the test (`tests/ui/associated-consts/freeze.rs`) added in this PR for a usage example. The builtin `Freeze` trait is the only way to do it, users cannot work around this issue.

It's also a useful trait for building some very specific abstrations, as shown by the usage by the `zerocopy` crate: google/zerocopy#941

cc ```@RalfJung```

T-lang signed off on reexposing this unstably: rust-lang#121501 (comment)
rust-timer added a commit to rust-lang-ci/rust that referenced this issue Mar 11, 2024
@rust-timer
Unrolled build for rust-lang#121840
e94c1ca 
Rollup merge of rust-lang#121840 - oli-obk:freeze, r=dtolnay

Expose the Freeze trait again (unstably) and forbid implementing it manually

non-emoji version of rust-lang#121501

cc rust-lang#60715

This trait is useful for generic constants (associated consts of generic traits). See the test (`tests/ui/associated-consts/freeze.rs`) added in this PR for a usage example. The builtin `Freeze` trait is the only way to do it, users cannot work around this issue.

It's also a useful trait for building some very specific abstrations, as shown by the usage by the `zerocopy` crate: google/zerocopy#941

cc ```@RalfJung```

T-lang signed off on reexposing this unstably: rust-lang#121501 (comment)
github-actions bot pushed a commit to rust-lang/miri that referenced this issue Mar 12, 2024
@jhpratt
Rollup merge of #121840 - oli-obk:freeze, r=dtolnay
96ec563 
Expose the Freeze trait again (unstably) and forbid implementing it manually

non-emoji version of rust-lang/rust#121501

cc #60715

This trait is useful for generic constants (associated consts of generic traits). See the test (`tests/ui/associated-consts/freeze.rs`) added in this PR for a usage example. The builtin `Freeze` trait is the only way to do it, users cannot work around this issue.

It's also a useful trait for building some very specific abstrations, as shown by the usage by the `zerocopy` crate: google/zerocopy#941

cc ```@RalfJung```

T-lang signed off on reexposing this unstably: rust-lang/rust#121501 (comment)
bjorn3 pushed a commit to rust-lang/rustc_codegen_cranelift that referenced this issue Mar 16, 2024
@jhpratt
Rollup merge of #121840 - oli-obk:freeze, r=dtolnay
221402e 
Expose the Freeze trait again (unstably) and forbid implementing it manually

non-emoji version of rust-lang/rust#121501

cc #60715

This trait is useful for generic constants (associated consts of generic traits). See the test (`tests/ui/associated-consts/freeze.rs`) added in this PR for a usage example. The builtin `Freeze` trait is the only way to do it, users cannot work around this issue.

It's also a useful trait for building some very specific abstrations, as shown by the usage by the `zerocopy` crate: google/zerocopy#941

cc ```@RalfJung```

T-lang signed off on reexposing this unstably: rust-lang/rust#121501 (comment)
GuillaumeGomez pushed a commit to GuillaumeGomez/rustc_codegen_gcc that referenced this issue Mar 26, 2024
@jhpratt
Rollup merge of #121840 - oli-obk:freeze, r=dtolnay
a6202e2 
Expose the Freeze trait again (unstably) and forbid implementing it manually

non-emoji version of rust-lang/rust#121501

cc #60715

This trait is useful for generic constants (associated consts of generic traits). See the test (`tests/ui/associated-consts/freeze.rs`) added in this PR for a usage example. The builtin `Freeze` trait is the only way to do it, users cannot work around this issue.

It's also a useful trait for building some very specific abstrations, as shown by the usage by the `zerocopy` crate: google/zerocopy#941

cc ```@RalfJung```

T-lang signed off on reexposing this unstably: rust-lang/rust#121501 (comment)
@joshlf
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joshlf commented May 3, 2024

We've decided that our Immutable will need to have slightly different semantics than stdlib Freeze - namely, it bans interior mutability recursively (ie, even via reference/pointer indirection), while Freeze does not. See #1155.

@joshlf joshlf closed this as completed May 3, 2024
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