Document overrides of clone_from() in core/std
#122201
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Specifically, when an override doesn't just forward to an inner type, document the behavior and that it's preferred over simply assigning a clone of source. Also, change instances where the second parameter is "other" to "source".
clone_from()clone_from() in core/std
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r? libs-api |
dtolnay
requested changes
Mar 31, 2024
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| /// as it avoids reallocation if possible. Additionally, if the element type | ||
| /// `T` overrides `clone_from()`, this will reuse the resources of `self`'s | ||
| /// elements as well. |
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It doesn't do this currently. All existing elements are dropped.
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@rust-lang/libs-api: Please take a skim through the added documentation and decide whether these are all commitments we can make. Some of them are in the form of "This method is preferred over simply assigning Other ones are stronger commitments. Deliberate new commitments:
"Commitments":
@rfcbot fcp merge |
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Team member @dtolnay has proposed to merge this. The next step is review by the rest of the tagged team members: No concerns currently listed. Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up! See this document for info about what commands tagged team members can give me. |
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🔔 This is now entering its final comment period, as per the review above. 🔔 |
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It seems to me "avoids allocations if possible" could also be interpreted to sound like a much more affirmative "we will do this if there is any possible interpretation of our data structure that will avoid allocations here". That may prove to be a bit of a peculiar thing to promise, especially when there's nothing stopping you from using clone_from for cloning a larger data structure "into" a smaller one, which will force new allocations.
It is possible that we may wish to say "reduces allocations" instead, as reducing the number of allocations by some N can validly be 0.
I am most concerned about this in the case of the types like BinaryHeap, LinkedList, and the Map/Set types, which have a somewhat more ambiguous internal representation, and in some cases are direly under-loved.
riking
reviewed
Apr 5, 2024
library/core/src/cell.rs
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| @@ -1276,8 +1276,8 @@ impl<T: Clone> Clone for RefCell<T> { | |||
| /// Panics if `other` is currently mutably borrowed. | |||
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nit: parameter rename missed in the comment.
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I'm unsure of how the FCP interacts with reviews - should I address the nits/review comments while the FCP is active? |
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The final comment period, with a disposition to merge, as per the review above, is now complete. As the automated representative of the governance process, I would like to thank the author for their work and everyone else who contributed. This will be merged soon. |
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Please address the review comments at your leisure. It doesn't make a difference whether that happens while the FCP is active or afterward, unless some team member's approval is contingent on seeing the resolution of some concern (usually with "@rfcbot concern"). |
dtolnay
approved these changes
Apr 17, 2024
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Thank you! This looks good to me.
I think this wording is all right, but I would be interested to evaluate a followup PR if someone wants to address #122201 (review). The reason I think the current wording in the PR is all right is I don't see "avoids reallocation if possible" being interpreted as "does not allocate if there is any possible interpretation of our data structure that could implement this operation without allocating". It instead just means "avoids those allocations which are possible to avoid per this manifestation of the data structure". The more interesting guarantees being committed to are the ones listed in #122201 (comment).
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@bors r+ |
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@bors ping |
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@bors ping |
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😪 I'm awake I'm awake |
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@bors r+ |
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…iaskrgr Rollup of 9 pull requests Successful merges: - rust-lang#116957 (meta: notify #t-rustdoc Zulip stream on backport nominations) - rust-lang#122201 (Document overrides of `clone_from()` in core/std) - rust-lang#122723 (Use same file permissions for ar_archive_writer as the LLVM archive writer) - rust-lang#124030 (interpret: pass MemoryKind to adjust_alloc_base_pointer) - rust-lang#124037 (Don't ascend into parent bodies when collecting stmts for possible return suggestion) - rust-lang#124049 (Stabilize `const_io_structs`) - rust-lang#124062 (Add another expression to weird-exprs.rs) - rust-lang#124066 (Don't error on subtyping of equal types) - rust-lang#124073 (Remove libc from rust_get_test_int uses) r? `@ghost` `@rustbot` modify labels: rollup
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Rollup merge of rust-lang#122201 - coolreader18:doc-clone_from, r=dtolnay Document overrides of `clone_from()` in core/std As mentioned in rust-lang#96979 (comment) Specifically, when an override doesn't just forward to an inner type, document the behavior and that it's preferred over simply assigning a clone of source. Also, change instances where the second parameter is "other" to "source". I reused some of the wording over and over for similar impls, but I'm not sure that the wording is actually *good*. Would appreciate feedback about that. Also, now some of these seem to provide pretty specific guarantees about behavior (e.g. will reuse the exact same allocation iff the len is the same), but I was basing it off of the docs for [`Box::clone_from`](https://doc.rust-lang.org/1.75.0/std/boxed/struct.Box.html#method.clone_from-1) - I'm not sure if providing those strong guarantees is actually good or not.
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Oct 13, 2024
This is based on the pkgsrc-wip rust180 package, retaining the main pkgsrc changes as best as I could. Pkgsrc changes: * Adapt checksums and patches. * Make this work again on big-endian aarch64 (at least on NetBSD). * Make the choice of GCC = 12 work for sparc64 by testing options after options.mk is included (which is required...). Makes this work on NetBSD/sparc64 10.0 again. Upstream chnages: Version 1.80.1 (2024-08-08) =========================== - [Fix miscompilation in the jump threading MIR optimization when comparing floats] (rust-lang/rust#128271) - [Revert changes to the `dead_code` lint from 1.80.0] (rust-lang/rust#128618) Version 1.80.0 (2024-07-25) ========================== Language -------- - [Document maximum allocation size] (rust-lang/rust#116675) - [Allow zero-byte offsets and ZST read/writes on arbitrary pointers] (rust-lang/rust#117329) - [Support C23's variadics without a named parameter] (rust-lang/rust#124048) - [Stabilize `exclusive_range_pattern` feature] (rust-lang/rust#124459) - [Guarantee layout and ABI of `Result` in some scenarios] (rust-lang/rust#124870) Compiler -------- - [Update cc crate to v1.0.97 allowing additional spectre mitigations on MSVC targets] (rust-lang/rust#124892) - [Allow field reordering on types marked `repr(packed(1))`] (rust-lang/rust#125360) - [Add a lint against never type fallback affecting unsafe code] (rust-lang/rust#123939) - [Disallow cast with trailing braced macro in let-else] (rust-lang/rust#125049) - [Expand `for_loops_over_fallibles` lint to lint on fallibles behind references.] (rust-lang/rust#125156) - [self-contained linker: retry linking without `-fuse-ld=lld` on CCs that don't support it] (rust-lang/rust#125417) - [Do not parse CVarArgs (`...`) as a type in trait bounds] (rust-lang/rust#125863) - Improvements to LLDB formatting [#124458] (rust-lang/rust#124458) [#124500] (rust-lang/rust#124500) - [For the wasm32-wasip2 target default to PIC and do not use `-fuse-ld=lld`] (rust-lang/rust#124858) - [Add x86_64-unknown-linux-none as a tier 3 target] (rust-lang/rust#125023) - [Lint on `foo.into_iter()` resolving to `&Box<[T]>: IntoIterator`] (rust-lang/rust#124097) Libraries --------- - [Add `size_of` and `size_of_val` and `align_of` and `align_of_val` to the prelude] (rust-lang/rust#123168) - [Abort a process when FD ownership is violated] (rust-lang/rust#124210) - [io::Write::write_fmt: panic if the formatter fails when the stream does not fail] (rust-lang/rust#125012) - [Panic if `PathBuf::set_extension` would add a path separator] (rust-lang/rust#125070) - [Add assert_unsafe_precondition to unchecked_{add,sub,neg,mul,shl,shr} methods] (rust-lang/rust#121571) - [Update `c_char` on AIX to use the correct type] (rust-lang/rust#122986) - [`offset_of!` no longer returns a temporary] (rust-lang/rust#124484) - [Handle sigma in `str.to_lowercase` correctly] (rust-lang/rust#124773) - [Raise `DEFAULT_MIN_STACK_SIZE` to at least 64KiB] (rust-lang/rust#126059) Stabilized APIs --------------- - [`impl Default for Rc<CStr>`] (https://doc.rust-lang.org/beta/alloc/rc/struct.Rc.html#impl-Default-for-Rc%3CCStr%3E) - [`impl Default for Rc<str>`] (https://doc.rust-lang.org/beta/alloc/rc/struct.Rc.html#impl-Default-for-Rc%3Cstr%3E) - [`impl Default for Rc<[T]>`] (https://doc.rust-lang.org/beta/alloc/rc/struct.Rc.html#impl-Default-for-Rc%3C%5BT%5D%3E) - [`impl Default for Arc<str>`] (https://doc.rust-lang.org/beta/alloc/sync/struct.Arc.html#impl-Default-for-Arc%3Cstr%3E) - [`impl Default for Arc<CStr>`] (https://doc.rust-lang.org/beta/alloc/sync/struct.Arc.html#impl-Default-for-Arc%3CCStr%3E) - [`impl Default for Arc<[T]>`] (https://doc.rust-lang.org/beta/alloc/sync/struct.Arc.html#impl-Default-for-Arc%3C%5BT%5D%3E) - [`impl IntoIterator for Box<[T]>`] (https://doc.rust-lang.org/beta/alloc/boxed/struct.Box.html#impl-IntoIterator-for-Box%3C%5BI%5D,+A%3E) - [`impl FromIterator<String> for Box<str>`] (https://doc.rust-lang.org/beta/alloc/boxed/struct.Box.html#impl-FromIterator%3CString%3E-for-Box%3Cstr%3E) - [`impl FromIterator<char> for Box<str>`] (https://doc.rust-lang.org/beta/alloc/boxed/struct.Box.html#impl-FromIterator%3Cchar%3E-for-Box%3Cstr%3E) - [`LazyCell`] (https://doc.rust-lang.org/beta/core/cell/struct.LazyCell.html) - [`LazyLock`] (https://doc.rust-lang.org/beta/std/sync/struct.LazyLock.html) - [`Duration::div_duration_f32`] (https://doc.rust-lang.org/beta/std/time/struct.Duration.html#method.div_duration_f32) - [`Duration::div_duration_f64`] (https://doc.rust-lang.org/beta/std/time/struct.Duration.html#method.div_duration_f64) - [`Option::take_if`] (https://doc.rust-lang.org/beta/std/option/enum.Option.html#method.take_if) - [`Seek::seek_relative`] (https://doc.rust-lang.org/beta/std/io/trait.Seek.html#method.seek_relative) - [`BinaryHeap::as_slice`] (https://doc.rust-lang.org/beta/std/collections/struct.BinaryHeap.html#method.as_slice) - [`NonNull::offset`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.offset) - [`NonNull::byte_offset`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.byte_offset) - [`NonNull::add`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.add) - [`NonNull::byte_add`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.byte_add) - [`NonNull::sub`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.sub) - [`NonNull::byte_sub`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.byte_sub) - [`NonNull::offset_from`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.offset_from) - [`NonNull::byte_offset_from`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.byte_offset_from) - [`NonNull::read`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.read) - [`NonNull::read_volatile`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.read_volatile) - [`NonNull::read_unaligned`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.read_unaligned) - [`NonNull::write`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.write) - [`NonNull::write_volatile`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.write_volatile) - [`NonNull::write_unaligned`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.write_unaligned) - [`NonNull::write_bytes`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.write_bytes) - [`NonNull::copy_to`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.copy_to) - [`NonNull::copy_to_nonoverlapping`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.copy_to_nonoverlapping) - [`NonNull::copy_from`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.copy_from) - [`NonNull::copy_from_nonoverlapping`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.copy_from_nonoverlapping) - [`NonNull::replace`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.replace) - [`NonNull::swap`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.swap) - [`NonNull::drop_in_place`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.drop_in_place) - [`NonNull::align_offset`] (https://doc.rust-lang.org/beta/std/ptr/struct.NonNull.html#method.align_offset) - [`<[T]>::split_at_checked`] (https://doc.rust-lang.org/beta/std/primitive.slice.html#method.split_at_checked) - [`<[T]>::split_at_mut_checked`] (https://doc.rust-lang.org/beta/std/primitive.slice.html#method.split_at_mut_checked) - [`str::split_at_checked`] (https://doc.rust-lang.org/beta/std/primitive.str.html#method.split_at_checked) - [`str::split_at_mut_checked`] (https://doc.rust-lang.org/beta/std/primitive.str.html#method.split_at_mut_checked) - [`str::trim_ascii`] (https://doc.rust-lang.org/beta/std/primitive.str.html#method.trim_ascii) - [`str::trim_ascii_start`] (https://doc.rust-lang.org/beta/std/primitive.str.html#method.trim_ascii_start) - [`str::trim_ascii_end`] (https://doc.rust-lang.org/beta/std/primitive.str.html#method.trim_ascii_end) - [`<[u8]>::trim_ascii`] (https://doc.rust-lang.org/beta/core/primitive.slice.html#method.trim_ascii) - [`<[u8]>::trim_ascii_start`] (https://doc.rust-lang.org/beta/core/primitive.slice.html#method.trim_ascii_start) - [`<[u8]>::trim_ascii_end`] (https://doc.rust-lang.org/beta/core/primitive.slice.html#method.trim_ascii_end) - [`Ipv4Addr::BITS`] (https://doc.rust-lang.org/beta/core/net/struct.Ipv4Addr.html#associatedconstant.BITS) - [`Ipv4Addr::to_bits`] (https://doc.rust-lang.org/beta/core/net/struct.Ipv4Addr.html#method.to_bits) - [`Ipv4Addr::from_bits`] (https://doc.rust-lang.org/beta/core/net/struct.Ipv4Addr.html#method.from_bits) - [`Ipv6Addr::BITS`] (https://doc.rust-lang.org/beta/core/net/struct.Ipv6Addr.html#associatedconstant.BITS) - [`Ipv6Addr::to_bits`] (https://doc.rust-lang.org/beta/core/net/struct.Ipv6Addr.html#method.to_bits) - [`Ipv6Addr::from_bits`] (https://doc.rust-lang.org/beta/core/net/struct.Ipv6Addr.html#method.from_bits) - [`Vec::<[T; N]>::into_flattened`] (https://doc.rust-lang.org/beta/alloc/vec/struct.Vec.html#method.into_flattened) - [`<[[T; N]]>::as_flattened`] (https://doc.rust-lang.org/beta/core/primitive.slice.html#method.as_flattened) - [`<[[T; N]]>::as_flattened_mut`] (https://doc.rust-lang.org/beta/core/primitive.slice.html#method.as_flattened_mut) These APIs are now stable in const contexts: - [`<[T]>::last_chunk`] (https://doc.rust-lang.org/beta/core/primitive.slice.html#method.last_chunk) - [`BinaryHeap::new`] (https://doc.rust-lang.org/beta/std/collections/struct.BinaryHeap.html#method.new) Cargo ----- - [Stabilize `-Zcheck-cfg` as always enabled] (rust-lang/cargo#13571) - [Warn, rather than fail publish, if a target is excluded] (rust-lang/cargo#13713) - [Add special `check-cfg` lint config for the `unexpected_cfgs` lint] (rust-lang/cargo#13913) - [Stabilize `cargo update --precise <yanked>`] (rust-lang/cargo#13974) - [Don't change file permissions on `Cargo.toml` when using `cargo add`] (rust-lang/cargo#13898) - [Support using `cargo fix` on IPv6-only networks] (rust-lang/cargo#13907) Rustdoc ----- - [Allow searching for references] (rust-lang/rust#124148) - [Stabilize `custom_code_classes_in_docs` feature] (rust-lang/rust#124577) - [fix: In cross-crate scenarios show enum variants on type aliases of enums] (rust-lang/rust#125300) Compatibility Notes ------------------- - [rustfmt estimates line lengths differently when using non-ascii characters] (rust-lang/rustfmt#6203) - [Type aliases are now handled correctly in orphan check] (rust-lang/rust#117164) - [Allow instructing rustdoc to read from stdin via `-`] (rust-lang/rust#124611) - [`std::env::{set_var, remove_var}` can no longer be converted to safe function pointers and no longer implement the `Fn` family of traits] (rust-lang/rust#124636) - [Warn (or error) when `Self` constructor from outer item is referenced in inner nested item] (rust-lang/rust#124187) - [Turn `indirect_structural_match` and `pointer_structural_match` lints into hard errors] (rust-lang/rust#124661) - [Make `where_clause_object_safety` lint a regular object safety violation] (rust-lang/rust#125380) - [Turn `proc_macro_back_compat` lint into a hard error.] (rust-lang/rust#125596) - [Detect unused structs even when implementing private traits] (rust-lang/rust#122382) - [`std::sync::ReentrantLockGuard<T>` is no longer `Sync` if `T: !Sync`] (rust-lang/rust#125527) which means [`std::io::StdoutLock` and `std::io::StderrLock` are no longer Sync] (rust-lang/rust#127340) Internal Changes ---------------- These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools. - Misc improvements to size of generated html by rustdoc e.g. [#124738] (rust-lang/rust#124738) and [#123734] (rust-lang/rust#123734) - [MSVC targets no longer depend on libc] (rust-lang/rust#124050) Version 1.79.0 (2024-06-13) ========================== Language -------- - [Stabilize inline `const {}` expressions.] (rust-lang/rust#104087) - [Prevent opaque types being instantiated twice with different regions within the same function.] (rust-lang/rust#116935) - [Stabilize WebAssembly target features that are in phase 4 and 5.] (rust-lang/rust#117457) - [Add the `redundant_lifetimes` lint to detect lifetimes which are semantically redundant.] (rust-lang/rust#118391) - [Stabilize the `unnameable_types` lint for public types that can't be named.] (rust-lang/rust#120144) - [Enable debuginfo in macros, and stabilize `-C collapse-macro-debuginfo` and `#[collapse_debuginfo]`.] (rust-lang/rust#120845) - [Propagate temporary lifetime extension into `if` and `match` expressions.] (rust-lang/rust#121346) - [Restrict promotion of `const fn` calls.] (rust-lang/rust#121557) - [Warn against refining impls of crate-private traits with `refining_impl_trait` lint.] (rust-lang/rust#121720) - [Stabilize associated type bounds (RFC 2289).] (rust-lang/rust#122055) - [Stabilize importing `main` from other modules or crates.] (rust-lang/rust#122060) - [Check return types of function types for well-formedness] (rust-lang/rust#115538) - [Rework `impl Trait` lifetime inference] (rust-lang/rust#116891) - [Change inductive trait solver cycles to be ambiguous] (rust-lang/rust#122791) Compiler -------- - [Define `-C strip` to only affect binaries, not artifacts like `.pdb`.] (rust-lang/rust#115120) - [Stabilize `-Crelro-level` for controlling runtime link hardening.] (rust-lang/rust#121694) - [Stabilize checking of `cfg` names and values at compile-time with `--check-cfg`.] (rust-lang/rust#123501) *Note that this only stabilizes the compiler part, the Cargo part is still unstable in this release.* - [Add `aarch64-apple-visionos` and `aarch64-apple-visionos-sim` tier 3 targets.] (rust-lang/rust#121419) - [Add `riscv32ima-unknown-none-elf` tier 3 target.] (rust-lang/rust#122696) - [Promote several Windows targets to tier 2] (rust-lang/rust#121712): `aarch64-pc-windows-gnullvm`, `i686-pc-windows-gnullvm`, and `x86_64-pc-windows-gnullvm`. Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support. Libraries --------- - [Implement `FromIterator` for `(impl Default + Extend, impl Default + Extend)`.] (rust-lang/rust#107462) - [Implement `{Div,Rem}Assign<NonZero<X>>` on `X`.] (rust-lang/rust#121952) - [Document overrides of `clone_from()` in core/std.] (rust-lang/rust#122201) - [Link MSVC default lib in core.] (rust-lang/rust#122268) - [Caution against using `transmute` between pointers and integers.] (rust-lang/rust#122379) - [Enable frame pointers for the standard library.] (rust-lang/rust#122646) Stabilized APIs --------------- - [`{integer}::unchecked_add`] (https://doc.rust-lang.org/stable/core/primitive.i32.html#method.unchecked_add) - [`{integer}::unchecked_mul`] (https://doc.rust-lang.org/stable/core/primitive.i32.html#method.unchecked_mul) - [`{integer}::unchecked_sub`] (https://doc.rust-lang.org/stable/core/primitive.i32.html#method.unchecked_sub) - [`<[T]>::split_at_unchecked`] (https://doc.rust-lang.org/stable/core/primitive.slice.html#method.split_at_unchecked) - [`<[T]>::split_at_mut_unchecked`] (https://doc.rust-lang.org/stable/core/primitive.slice.html#method.split_at_mut_unchecked) - [`<[u8]>::utf8_chunks`] (https://doc.rust-lang.org/stable/core/primitive.slice.html#method.utf8_chunks) - [`str::Utf8Chunks`] (https://doc.rust-lang.org/stable/core/str/struct.Utf8Chunks.html) - [`str::Utf8Chunk`] (https://doc.rust-lang.org/stable/core/str/struct.Utf8Chunk.html) - [`<*const T>::is_aligned`] (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.is_aligned) - [`<*mut T>::is_aligned`] (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.is_aligned-1) - [`NonNull::is_aligned`] (https://doc.rust-lang.org/stable/core/ptr/struct.NonNull.html#method.is_aligned) - [`<*const [T]>::len`] (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.len) - [`<*mut [T]>::len`] (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.len-1) - [`<*const [T]>::is_empty`] (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.is_empty) - [`<*mut [T]>::is_empty`] (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.is_empty-1) - [`NonNull::<[T]>::is_empty`] (https://doc.rust-lang.org/stable/core/ptr/struct.NonNull.html#method.is_empty) - [`CStr::count_bytes`] (https://doc.rust-lang.org/stable/core/ffi/c_str/struct.CStr.html#method.count_bytes) - [`io::Error::downcast`] (https://doc.rust-lang.org/stable/std/io/struct.Error.html#method.downcast) - [`num::NonZero<T>`] (https://doc.rust-lang.org/stable/core/num/struct.NonZero.html) - [`path::absolute`] (https://doc.rust-lang.org/stable/std/path/fn.absolute.html) - [`proc_macro::Literal::byte_character`] (https://doc.rust-lang.org/stable/proc_macro/struct.Literal.html#method.byte_character) - [`proc_macro::Literal::c_string`] (https://doc.rust-lang.org/stable/proc_macro/struct.Literal.html#method.c_string) These APIs are now stable in const contexts: - [`Atomic*::into_inner`] (https://doc.rust-lang.org/stable/core/sync/atomic/struct.AtomicUsize.html#method.into_inner) - [`io::Cursor::new`] (https://doc.rust-lang.org/stable/std/io/struct.Cursor.html#method.new) - [`io::Cursor::get_ref`] (https://doc.rust-lang.org/stable/std/io/struct.Cursor.html#method.get_ref) - [`io::Cursor::position`] (https://doc.rust-lang.org/stable/std/io/struct.Cursor.html#method.position) - [`io::empty`] (https://doc.rust-lang.org/stable/std/io/fn.empty.html) - [`io::repeat`] (https://doc.rust-lang.org/stable/std/io/fn.repeat.html) - [`io::sink`] (https://doc.rust-lang.org/stable/std/io/fn.sink.html) - [`panic::Location::caller`] (https://doc.rust-lang.org/stable/std/panic/struct.Location.html#method.caller) - [`panic::Location::file`] (https://doc.rust-lang.org/stable/std/panic/struct.Location.html#method.file) - [`panic::Location::line`] (https://doc.rust-lang.org/stable/std/panic/struct.Location.html#method.line) - [`panic::Location::column`] (https://doc.rust-lang.org/stable/std/panic/struct.Location.html#method.column) Cargo ----- - [Prevent dashes in `lib.name`, always normalizing to `_`.] (rust-lang/cargo#12783) - [Stabilize MSRV-aware version requirement selection in `cargo add`.] (rust-lang/cargo#13608) - [Switch to using `gitoxide` by default for listing files.] (rust-lang/cargo#13696) Rustdoc ----- - [Always display stability version even if it's the same as the containing item.] (rust-lang/rust#118441) - [Show a single search result for items with multiple paths.] (rust-lang/rust#119912) - [Support typing `/` in docs to begin a search.] (rust-lang/rust#123355) Misc ---- Compatibility Notes ------------------- - [Update the minimum external LLVM to 17.] (rust-lang/rust#122649) - [`RustcEncodable` and `RustcDecodable` are soft-destabilized, to be removed from the prelude in next edition.] (rust-lang/rust#116016) - [The `wasm_c_abi` future-incompatibility lint will warn about use of the non-spec-compliant C ABI.] (rust-lang/rust#117918) Use `wasm-bindgen v0.2.88` to generate forward-compatible bindings. - [Check return types of function types for well-formedness] (rust-lang/rust#115538) Version 1.78.0 (2024-05-02) =========================== Language -------- - [Stabilize `#[cfg(target_abi = ...)]`] (rust-lang/rust#119590) - [Stabilize the `#[diagnostic]` namespace and `#[diagnostic::on_unimplemented]` attribute] (rust-lang/rust#119888) - [Make async-fn-in-trait implementable with concrete signatures] (rust-lang/rust#120103) - [Make matching on NaN a hard error, and remove the rest of `illegal_floating_point_literal_pattern`] (rust-lang/rust#116284) - [static mut: allow mutable reference to arbitrary types, not just slices and arrays] (rust-lang/rust#117614) - [Extend `invalid_reference_casting` to include references casting to bigger memory layout] (rust-lang/rust#118983) - [Add `non_contiguous_range_endpoints` lint for singleton gaps after exclusive ranges] (rust-lang/rust#118879) - [Add `wasm_c_abi` lint for use of older wasm-bindgen versions] (rust-lang/rust#117918) This lint currently only works when using Cargo. - [Update `indirect_structural_match` and `pointer_structural_match` lints to match RFC] (rust-lang/rust#120423) - [Make non-`PartialEq`-typed consts as patterns a hard error] (rust-lang/rust#120805) - [Split `refining_impl_trait` lint into `_reachable`, `_internal` variants] (rust-lang/rust#121720) - [Remove unnecessary type inference when using associated types inside of higher ranked `where`-bounds] (rust-lang/rust#119849) - [Weaken eager detection of cyclic types during type inference] (rust-lang/rust#119989) - [`trait Trait: Auto {}`: allow upcasting from `dyn Trait` to `dyn Auto`] (rust-lang/rust#119338) Compiler -------- - [Made `INVALID_DOC_ATTRIBUTES` lint deny by default] (rust-lang/rust#111505) - [Increase accuracy of redundant `use` checking] (rust-lang/rust#117772) - [Suggest moving definition if non-found macro_rules! is defined later] (rust-lang/rust#121130) - [Lower transmutes from int to pointer type as gep on null] (rust-lang/rust#121282) Target changes: - [Windows tier 1 targets now require at least Windows 10] (rust-lang/rust#115141) - [Enable CMPXCHG16B, SSE3, SAHF/LAHF and 128-bit Atomics in tier 1 Windows] (rust-lang/rust#120820) - [Add `wasm32-wasip1` tier 2 (without host tools) target] (rust-lang/rust#120468) - [Add `wasm32-wasip2` tier 3 target] (rust-lang/rust#119616) - [Rename `wasm32-wasi-preview1-threads` to `wasm32-wasip1-threads`] (rust-lang/rust#122170) - [Add `arm64ec-pc-windows-msvc` tier 3 target] (rust-lang/rust#119199) - [Add `armv8r-none-eabihf` tier 3 target for the Cortex-R52] (rust-lang/rust#110482) - [Add `loongarch64-unknown-linux-musl` tier 3 target] (rust-lang/rust#121832) Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support. Libraries --------- - [Bump Unicode to version 15.1.0, regenerate tables] (rust-lang/rust#120777) - [Make align_offset, align_to well-behaved in all cases] (rust-lang/rust#121201) - [PartialEq, PartialOrd: document expectations for transitive chains] (rust-lang/rust#115386) - [Optimize away poison guards when std is built with panic=abort] (rust-lang/rust#100603) - [Replace pthread `RwLock` with custom implementation] (rust-lang/rust#110211) - [Implement unwind safety for Condvar on all platforms] (rust-lang/rust#121768) - [Add ASCII fast-path for `char::is_grapheme_extended`] (rust-lang/rust#121138) Stabilized APIs --------------- - [`impl Read for &Stdin`] (https://doc.rust-lang.org/stable/std/io/struct.Stdin.html#impl-Read-for-%26Stdin) - [Accept non `'static` lifetimes for several `std::error::Error` related implementations] (rust-lang/rust#113833) - [Make `impl<Fd: AsFd>` impl take `?Sized`] (rust-lang/rust#114655) - [`impl From<TryReserveError> for io::Error`] (https://doc.rust-lang.org/stable/std/io/struct.Error.html#impl-From%3CTryReserveError%3E-for-Error) These APIs are now stable in const contexts: - [`Barrier::new()`] (https://doc.rust-lang.org/stable/std/sync/struct.Barrier.html#method.new) Cargo ----- - [Stabilize lockfile v4](rust-lang/cargo#12852) - [Respect `rust-version` when generating lockfile] (rust-lang/cargo#12861) - [Control `--charset` via auto-detecting config value] (rust-lang/cargo#13337) - [Support `target.<triple>.rustdocflags` officially] (rust-lang/cargo#13197) - [Stabilize global cache data tracking] (rust-lang/cargo#13492) Misc ---- - [rustdoc: add `--test-builder-wrapper` arg to support wrappers such as RUSTC_WRAPPER when building doctests] (rust-lang/rust#114651) Compatibility Notes ------------------- - [Many unsafe precondition checks now run for user code with debug assertions enabled] (rust-lang/rust#120594) This change helps users catch undefined behavior in their code, though the details of how much is checked are generally not stable. - [riscv only supports split_debuginfo=off for now] (rust-lang/rust#120518) - [Consistently check bounds on hidden types of `impl Trait`] (rust-lang/rust#121679) - [Change equality of higher ranked types to not rely on subtyping] (rust-lang/rust#118247) - [When called, additionally check bounds on normalized function return type] (rust-lang/rust#118882) - [Expand coverage for `arithmetic_overflow` lint] (rust-lang/rust#119432) Internal Changes ---------------- These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools. - [Update to LLVM 18](rust-lang/rust#120055) - [Build `rustc` with 1CGU on `x86_64-pc-windows-msvc`] (rust-lang/rust#112267) - [Build `rustc` with 1CGU on `x86_64-apple-darwin`] (rust-lang/rust#112268) - [Introduce `run-make` V2 infrastructure, a `run_make_support` library and port over 2 tests as example] (rust-lang/rust#113026) - [Windows: Implement condvar, mutex and rwlock using futex] (rust-lang/rust#121956) Version 1.77.0 (2024-03-21) ========================== - [Reveal opaque types within the defining body for exhaustiveness checking.] (rust-lang/rust#116821) - [Stabilize C-string literals.] (rust-lang/rust#117472) - [Stabilize THIR unsafeck.] (rust-lang/rust#117673) - [Add lint `static_mut_refs` to warn on references to mutable statics.] (rust-lang/rust#117556) - [Support async recursive calls (as long as they have indirection).] (rust-lang/rust#117703) - [Undeprecate lint `unstable_features` and make use of it in the compiler.] (rust-lang/rust#118639) - [Make inductive cycles in coherence ambiguous always.] (rust-lang/rust#118649) - [Get rid of type-driven traversal in const-eval interning] (rust-lang/rust#119044), only as a [future compatiblity lint] (rust-lang/rust#122204) for now. - [Deny braced macro invocations in let-else.] (rust-lang/rust#119062) Compiler -------- - [Include lint `soft_unstable` in future breakage reports.] (rust-lang/rust#116274) - [Make `i128` and `u128` 16-byte aligned on x86-based targets.] (rust-lang/rust#116672) - [Use `--verbose` in diagnostic output.] (rust-lang/rust#119129) - [Improve spacing between printed tokens.] (rust-lang/rust#120227) - [Merge the `unused_tuple_struct_fields` lint into `dead_code`.] (rust-lang/rust#118297) - [Error on incorrect implied bounds in well-formedness check] (rust-lang/rust#118553), with a temporary exception for Bevy. - [Fix coverage instrumentation/reports for non-ASCII source code.] (rust-lang/rust#119033) - [Fix `fn`/`const` items implied bounds and well-formedness check.] (rust-lang/rust#120019) - [Promote `riscv32{im|imafc}-unknown-none-elf` targets to tier 2.] (rust-lang/rust#118704) - Add several new tier 3 targets: - [`aarch64-unknown-illumos`] (rust-lang/rust#112936) - [`hexagon-unknown-none-elf`] (rust-lang/rust#117601) - [`riscv32imafc-esp-espidf`] (rust-lang/rust#119738) - [`riscv32im-risc0-zkvm-elf`] (rust-lang/rust#117958) Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support. Libraries --------- - [Implement `From<&[T; N]>` for `Cow<[T]>`.] (rust-lang/rust#113489) - [Remove special-case handling of `vec.split_off (0)`.](rust-lang/rust#119917) Stabilized APIs --------------- - [`array::each_ref`] (https://doc.rust-lang.org/stable/std/primitive.array.html#method.each_ref) - [`array::each_mut`] (https://doc.rust-lang.org/stable/std/primitive.array.html#method.each_mut) - [`core::net`] (https://doc.rust-lang.org/stable/core/net/index.html) - [`f32::round_ties_even`] (https://doc.rust-lang.org/stable/std/primitive.f32.html#method.round_ties_even) - [`f64::round_ties_even`] (https://doc.rust-lang.org/stable/std/primitive.f64.html#method.round_ties_even) - [`mem::offset_of!`] (https://doc.rust-lang.org/stable/std/mem/macro.offset_of.html) - [`slice::first_chunk`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.first_chunk) - [`slice::first_chunk_mut`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.first_chunk_mut) - [`slice::split_first_chunk`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_first_chunk) - [`slice::split_first_chunk_mut`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_first_chunk_mut) - [`slice::last_chunk`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.last_chunk) - [`slice::last_chunk_mut`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.last_chunk_mut) - [`slice::split_last_chunk`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_last_chunk) - [`slice::split_last_chunk_mut`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_last_chunk_mut) - [`slice::chunk_by`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.chunk_by) - [`slice::chunk_by_mut`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.chunk_by_mut) - [`Bound::map`] (https://doc.rust-lang.org/stable/std/ops/enum.Bound.html#method.map) - [`File::create_new`] (https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.create_new) - [`Mutex::clear_poison`] (https://doc.rust-lang.org/stable/std/sync/struct.Mutex.html#method.clear_poison) - [`RwLock::clear_poison`] (https://doc.rust-lang.org/stable/std/sync/struct.RwLock.html#method.clear_poison) Cargo ----- - [Extend the build directive syntax with `cargo::`.] (rust-lang/cargo#12201) - [Stabilize metadata `id` format as `PackageIDSpec`.] (rust-lang/cargo#12914) - [Pull out as `cargo-util-schemas` as a crate.] (rust-lang/cargo#13178) - [Strip all debuginfo when debuginfo is not requested.] (rust-lang/cargo#13257) - [Inherit jobserver from env for all kinds of runners.] (rust-lang/cargo#12776) - [Deprecate rustc plugin support in cargo.] (rust-lang/cargo#13248) Rustdoc ----- - [Allows links in markdown headings.] (rust-lang/rust#117662) - [Search for tuples and unit by type with `()`.] (rust-lang/rust#118194) - [Clean up the source sidebar's hide button.] (rust-lang/rust#119066) - [Prevent JS injection from `localStorage`.] (rust-lang/rust#120250) Misc ---- - [Recommend version-sorting for all sorting in style guide.] (rust-lang/rust#115046) Internal Changes ---------------- These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools. - [Add more weirdness to `weird-exprs.rs`.] (rust-lang/rust#119028)
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As mentioned in #96979 (comment)
Specifically, when an override doesn't just forward to an inner type, document the behavior and that it's preferred over simply assigning a clone of source. Also, change instances where the second parameter is "other" to "source".
I reused some of the wording over and over for similar impls, but I'm not sure that the wording is actually good. Would appreciate feedback about that.
Also, now some of these seem to provide pretty specific guarantees about behavior (e.g. will reuse the exact same allocation iff the len is the same), but I was basing it off of the docs for
Box::clone_from- I'm not sure if providing those strong guarantees is actually good or not.