Stabilize `Rc`, `Arc` and `Pin` as method receivers #56805

mikeyhew · 2018-12-14T06:05:24Z

Replaces #55880
Closes #55786
r? @nikomatsakis
cc @withoutboats @cramertj

This lets you write methods using self: Rc<Self>, self: Arc<Self>, self: Pin<&mut Self>, self: Pin<Box<Self>, and other combinations involving Pin and another stdlib receiver type, without needing the arbitrary_self_types. Other user-created receiver types can be used, but they still require the feature flag to use.

This is implemented by introducing a new trait, Receiver, which the method receiver's type must implement if the arbitrary_self_types feature is not enabled. To keep composed receiver types such as &Arc<Self> unstable, the receiver type is also required to implement Deref<Target=Self> when the feature flag is not enabled.

This lets you use self: Rc<Self> and self: Arc<Self> in stable Rust, which was not allowed previously. It was agreed that they would be stabilized in #55786. self: Pin<&Self> and other pinned receiver types do not require the arbitrary_self_types feature, but they cannot be used on stable because Pin still requires the pin feature.

nikomatsakis

Looks good to me. One nit, then r=me.

nikomatsakis · 2018-12-14T21:32:58Z

src/librustc_typeck/check/wfcheck.rs

+            return false
+        }
+
+        let deref_trait_def_id = match fcx.tcx.lang_items().deref_trait() {


It'd be nice to have some comments here, to document what we are requiring and why (basically what's in your PR comment).

This can reference the doc comment on the fn itself I guess.

mikeyhew · 2018-12-18T22:51:10Z

@nikomatsakis assuming this passes CI, it should be good to go

cramertj · 2018-12-18T23:33:19Z

@bors r=nikomatsakis

bors · 2018-12-18T23:33:20Z

📌 Commit 603175f78a3a2cad2f1c00ca3771ee16550f3022 has been approved by nikomatsakis

bors · 2018-12-20T01:39:28Z

☔ The latest upstream changes (presumably #54252) made this pull request unmergeable. Please resolve the merge conflicts.

This lets you write methods using `self: Rc<Self>`, `self: Arc<Self>`, `self: Pin<&mut Self>`, `self: Pin<Box<Self>`, and other combinations involving `Pin` and another stdlib receiver type, without needing the `arbitrary_self_types`. Other user-created receiver types can be used, but they still require the feature flag to use. This is implemented by introducing a new trait, `Receiver`, which the method receiver's type must implement if the `arbitrary_self_types` feature is not enabled. To keep composed receiver types such as `&Arc<Self>` unstable, the receiver type is also required to implement `Deref<Target=Self>` when the feature flag is not enabled. This lets you use `self: Rc<Self>` and `self: Arc<Self>` in stable Rust, which was not allowed previously. It was agreed that they would be stabilized in rust-lang#55786. `self: Pin<&Self>` and other pinned receiver types do not require the `arbitrary_self_types` feature, but they cannot be used on stable because `Pin` still requires the `pin` feature.

also updated some error messages removed the code manually checking for `receiver_ty: Deref<Target=self_ty>`, in favour of using autoderef but only doing one iteration. This will cause error messages to be more consistent. Before, a "mismatched method receiver" error would be emitted when `receiver_ty` was valid except for a lifetime parameter, but only when `feature(arbitrary_self_types)` was enabled, and without the feature flag the error would be "uncoercible receiver". Now it emits "mismatched method receiver" in both cases.

mikeyhew · 2018-12-20T06:41:46Z

This is good to go again.

cramertj · 2018-12-20T17:27:16Z

@bors r=nikomatsakis

bors · 2018-12-20T17:27:17Z

📌 Commit 286503a has been approved by nikomatsakis

bors · 2018-12-20T18:54:20Z

⌛ Testing commit 286503a with merge 37ab3e60c99c88ba24ef2d4572ad916490a44048...

bors · 2018-12-20T19:02:16Z

💔 Test failed - status-travis

rust-highfive · 2018-12-20T19:02:17Z

The job x86_64-gnu-distcheck of your PR failed on Travis (raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

[00:03:47]    Compiling cargo v0.32.0
[00:03:54] error[E0308]: mismatched types
[00:03:54]  --> /cargo/registry/src/github.mirror.nvdadr.com-1ecc6299db9ec823/cargo-0.32.0/src/cargo/util/sha256.rs:9:34
[00:03:54]   |
[00:03:54] 9 |         let hasher = Hasher::new(Algorithm::SHA256);
[00:03:54]   |                                  |
[00:03:54]   |                                  |
[00:03:54]   |                                  expected reference, found enum `util::sha256::crypto_hash::Algorithm`
[00:03:54]   |                                  help: consider borrowing here: `&Algorithm::SHA256`
[00:03:54]   |
[00:03:54]   = note: expected type `&util::sha256::crypto_hash::Algorithm`
[00:03:54]              found type `util::sha256::crypto_hash::Algorithm`
[00:03:54] error: aborting due to previous error
[00:03:54] 
[00:03:54] For more information about this error, try `rustc --explain E0308`.
[00:03:54] For more information about this error, try `rustc --explain E0308`.
[00:03:54] error: failed to compile `cargo-vendor v0.1.22`, intermediate artifacts can be found at `/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-bootstrap-tools`
[00:03:54] Caused by:
[00:03:54]   Could not compile `cargo`.
[00:03:54] 
[00:03:54] To learn more, run the command again with --verbose.
[00:03:54] To learn more, run the command again with --verbose.
[00:03:54] 
[00:03:54] 
[00:03:54] command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo" "install" "-j" "4" "--locked" "--color" "always" "--force" "--debug" "--vers" "0.1.22" "cargo-vendor"
[00:03:54] 
[00:03:54] 
[00:03:54] failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test distcheck
[00:03:54] Build completed unsuccessfully in 0:01:35
---
travis_time:end:14329584:start=1545332461225148456,finish=1545332461233051499,duration=7903043
travis_fold:end:after_failure.3
travis_fold:start:after_failure.4
travis_time:start:24badd88
$ ln -s . checkout && for CORE in obj/cores/core.*; do EXE=$(echo $CORE | sed 's|obj/cores/core\.[0-9]*\.!checkout!\(.*\)|\1|;y|!|/|'); if [ -f "$EXE" ]; then printf travis_fold":start:crashlog\n\033[31;1m%s\033[0m\n" "$CORE"; gdb --batch -q -c "$CORE" "$EXE" -iex 'set auto-load off' -iex 'dir src/' -iex 'set sysroot .' -ex bt -ex q; echo travis_fold":"end:crashlog; fi; done || true
travis_fold:end:after_failure.4
travis_fold:start:after_failure.5
travis_time:start:0662e327
travis_time:start:0662e327
$ cat ./obj/build/x86_64-unknown-linux-gnu/native/asan/build/lib/asan/clang_rt.asan-dynamic-i386.vers || true
cat: ./obj/build/x86_64-unknown-linux-gnu/native/asan/build/lib/asan/clang_rt.asan-dynamic-i386.vers: No such file or directory
travis_fold:end:after_failure.5
travis_fold:start:after_failure.6
travis_time:start:0462256e
$ dmesg | grep -i kill

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

alexcrichton · 2018-12-20T19:30:04Z

@bors: retry

0.3.2 contains a breaking change malept/crypto-hash#6

bors · 2018-12-21T06:24:18Z

⌛ Testing commit 286503a with merge 64cb29976a51585c30bdf20a71c255c66b9bcbed...

bors · 2018-12-21T09:25:29Z

💔 Test failed - status-travis

rust-highfive · 2018-12-21T09:25:31Z

The job dist-x86_64-linux of your PR failed on Travis (raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

[02:58:21] [ 46%] Building CXX object lib/IR/CMakeFiles/LLVMCore.dir/Instruction.cpp.o
[02:58:32] [ 46%] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/DeadMachineInstructionElim.cpp.o
[02:58:42] [ 46%] Building CXX object lib/CodeGen/AsmPrinter/CMakeFiles/LLVMAsmPrinter.dir/DebugLocStream.cpp.o

Broadcast message from root@travis-job-3fdf3aa9-85be-4ce0-8bb9-67e639ddc737
 (unknown) at 9:25 ...
The system is going down for power off NOW!

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

cramertj · 2018-12-21T17:02:44Z

@bors retry

[02:58:21] [ 46%] Building CXX object lib/IR/CMakeFiles/LLVMCore.dir/Instruction.cpp.o
[02:58:32] [ 46%] Building CXX object lib/CodeGen/CMakeFiles/LLVMCodeGen.dir/DeadMachineInstructionElim.cpp.o
[02:58:42] [ 46%] Building CXX object lib/CodeGen/AsmPrinter/CMakeFiles/LLVMAsmPrinter.dir/DebugLocStream.cpp.o

Broadcast message from root@travis-job-3fdf3aa9-85be-4ce0-8bb9-67e639ddc737
 (unknown) at 9:25 ...
The system is going down for power off NOW!

:(

bors · 2018-12-22T01:42:32Z

⌛ Testing commit 286503a with merge abaa934...

@nikomatsakis

…akis Stabilize `Rc`, `Arc` and `Pin` as method receivers Replaces #55880 Closes #55786 r? @nikomatsakis cc @withoutboats @cramertj This lets you write methods using `self: Rc<Self>`, `self: Arc<Self>`, `self: Pin<&mut Self>`, `self: Pin<Box<Self>`, and other combinations involving `Pin` and another stdlib receiver type, without needing the `arbitrary_self_types`. Other user-created receiver types can be used, but they still require the feature flag to use. This is implemented by introducing a new trait, `Receiver`, which the method receiver's type must implement if the `arbitrary_self_types` feature is not enabled. To keep composed receiver types such as `&Arc<Self>` unstable, the receiver type is also required to implement `Deref<Target=Self>` when the feature flag is not enabled. This lets you use `self: Rc<Self>` and `self: Arc<Self>` in stable Rust, which was not allowed previously. It was agreed that they would be stabilized in #55786. `self: Pin<&Self>` and other pinned receiver types do not require the `arbitrary_self_types` feature, but they cannot be used on stable because `Pin` still requires the `pin` feature.

bors · 2018-12-22T04:21:18Z

☀️ Test successful - status-appveyor, status-travis
Approved by: nikomatsakis
Pushing abaa934 to master...

Pkgsrc changes: * Bump required rust version to build to 1.32.0. * Adapt patches to changed file locations. * Since we now patch some more vendor/ modules, doctor the corresponding .cargo-checksum.json files accordingly Upstream changes: Version 1.33.0 (2019-02-28) ========================== Language -------- - [You can now use the `cfg(target_vendor)` attribute.][57465] E.g. `#[cfg(target_vendor="apple")] fn main() { println!("Hello Apple!"); }` - [Integer patterns such as in a match expression can now be exhaustive.][56362] E.g. You can have match statement on a `u8` that covers `0..=255` and you would no longer be required to have a `_ => unreachable!()` case. - [You can now have multiple patterns in `if let` and `while let` expressions.][57532] You can do this with the same syntax as a `match` expression. E.g. ```rust enum Creature { Crab(String), Lobster(String), Person(String), } fn main() { let state = Creature::Crab("Ferris"); if let Creature::Crab(name) | Creature::Person(name) = state { println!("This creature's name is: {}", name); } } ``` - [You can now have irrefutable `if let` and `while let` patterns.][57535] Using this feature will by default produce a warning as this behaviour can be unintuitive. E.g. `if let _ = 5 {}` - [You can now use `let` bindings, assignments, expression statements, and irrefutable pattern destructuring in const functions.][57175] - [You can now call unsafe const functions.][57067] E.g. ```rust const unsafe fn foo() -> i32 { 5 } const fn bar() -> i32 { unsafe { foo() } } ``` - [You can now specify multiple attributes in a `cfg_attr` attribute.][57332] E.g. `#[cfg_attr(all(), must_use, optimize)]` - [You can now specify a specific alignment with the `#[repr(packed)]` attribute.][57049] E.g. `#[repr(packed(2))] struct Foo(i16, i32);` is a struct with an alignment of 2 bytes and a size of 6 bytes. - [You can now import an item from a module as an `_`.][56303] This allows you to import a trait's impls, and not have the name in the namespace. E.g. ```rust use std::io::Read as _; // Allowed as there is only one `Read` in the module. pub trait Read {} ``` - [You may now use `Rc`, `Arc`, and `Pin` as method receivers][56805]. Compiler -------- - [You can now set a linker flavor for `rustc` with the `-Clinker-flavor` command line argument.][56351] - [The mininum required LLVM version has been bumped to 6.0.][56642] - [Added support for the PowerPC64 architecture on FreeBSD.][57615] - [The `x86_64-fortanix-unknown-sgx` target support has been upgraded to tier 2 support.][57130] Visit the [platform support][platform-support] page for information on Rust's platform support. - [Added support for the `thumbv7neon-linux-androideabi` and `thumbv7neon-unknown-linux-gnueabihf` targets.][56947] - [Added support for the `x86_64-unknown-uefi` target.][56769] Libraries --------- - [The methods `overflowing_{add, sub, mul, shl, shr}` are now `const` functions for all numeric types.][57566] - [The methods `rotate_left`, `rotate_right`, and `wrapping_{add, sub, mul, shl, shr}` are now `const` functions for all numeric types.][57105] - [The methods `is_positive` and `is_negative` are now `const` functions for all signed numeric types.][57105] - [The `get` method for all `NonZero` types is now `const`.][57167] - [The methods `count_ones`, `count_zeros`, `leading_zeros`, `trailing_zeros`, `swap_bytes`, `from_be`, `from_le`, `to_be`, `to_le` are now `const` for all numeric types.][57234] - [`Ipv4Addr::new` is now a `const` function][57234] Stabilized APIs --------------- - [`unix::FileExt::read_exact_at`] - [`unix::FileExt::write_all_at`] - [`Option::transpose`] - [`Result::transpose`] - [`convert::identity`] - [`pin::Pin`] - [`marker::Unpin`] - [`marker::PhantomPinned`] - [`Vec::resize_with`] - [`VecDeque::resize_with`] - [`Duration::as_millis`] - [`Duration::as_micros`] - [`Duration::as_nanos`] Cargo ----- - [Cargo should now rebuild a crate if a file was modified during the initial build.][cargo/6484] Compatibility Notes ------------------- - The methods `str::{trim_left, trim_right, trim_left_matches, trim_right_matches}` are now deprecated in the standard library, and their usage will now produce a warning. Please use the `str::{trim_start, trim_end, trim_start_matches, trim_end_matches}` methods instead. - The `Error::cause` method has been deprecated in favor of `Error::source` which supports downcasting. [55982]: rust-lang/rust#55982 [56303]: rust-lang/rust#56303 [56351]: rust-lang/rust#56351 [56362]: rust-lang/rust#56362 [56642]: rust-lang/rust#56642 [56769]: rust-lang/rust#56769 [56805]: rust-lang/rust#56805 [56947]: rust-lang/rust#56947 [57049]: rust-lang/rust#57049 [57067]: rust-lang/rust#57067 [57105]: rust-lang/rust#57105 [57130]: rust-lang/rust#57130 [57167]: rust-lang/rust#57167 [57175]: rust-lang/rust#57175 [57234]: rust-lang/rust#57234 [57332]: rust-lang/rust#57332 [57465]: rust-lang/rust#57465 [57532]: rust-lang/rust#57532 [57535]: rust-lang/rust#57535 [57566]: rust-lang/rust#57566 [57615]: rust-lang/rust#57615 [cargo/6484]: rust-lang/cargo#6484 [`unix::FileExt::read_exact_at`]: https://doc.rust-lang.org/std/os/unix/fs/trait.FileExt.html#method.read_exact_at [`unix::FileExt::write_all_at`]: https://doc.rust-lang.org/std/os/unix/fs/trait.FileExt.html#method.write_all_at [`Option::transpose`]: https://doc.rust-lang.org/std/option/enum.Option.html#method.transpose [`Result::transpose`]: https://doc.rust-lang.org/std/result/enum.Result.html#method.transpose [`convert::identity`]: https://doc.rust-lang.org/std/convert/fn.identity.html [`pin::Pin`]: https://doc.rust-lang.org/std/pin/struct.Pin.html [`marker::Unpin`]: https://doc.rust-lang.org/stable/std/marker/trait.Unpin.html [`marker::PhantomPinned`]: https://doc.rust-lang.org/nightly/std/marker/struct.PhantomPinned.html [`Vec::resize_with`]: https://doc.rust-lang.org/std/vec/struct.Vec.html#method.resize_with [`VecDeque::resize_with`]: https://doc.rust-lang.org/std/collections/struct.VecDeque.html#method.resize_with [`Duration::as_millis`]: https://doc.rust-lang.org/std/time/struct.Duration.html#method.as_millis [`Duration::as_micros`]: https://doc.rust-lang.org/std/time/struct.Duration.html#method.as_micros [`Duration::as_nanos`]: https://doc.rust-lang.org/std/time/struct.Duration.html#method.as_nanos [platform-support]: https://forge.rust-lang.org/platform-support.html

rust-highfive assigned nikomatsakis Dec 14, 2018

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mikeyhew mentioned this pull request Dec 14, 2018

stabilize Rc, Arc and Pin as method receivers #55880

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mikeyhew force-pushed the stabilize-pin-as-receiver branch from 99367f7 to 70cbc55 Compare December 14, 2018 06:29

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mikeyhew added 3 commits December 20, 2018 01:14

add a doc comment on receiver_is_valid

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mikeyhew force-pushed the stabilize-pin-as-receiver branch from 603175f to 286503a Compare December 20, 2018 06:21

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bors merged commit 286503a into rust-lang:master Dec 22, 2018

This was referenced Dec 22, 2018

Pin stabilization #56939

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Rollup of 41 pull requests #57058

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mikeyhew mentioned this pull request Dec 24, 2018

Tracking issue for RFC 3519: arbitrary_self_types #44874

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9 tasks

ehuss mentioned this pull request Dec 31, 2018

Document Rc/Arc method receivers. rust-lang/reference#494

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taiki-e mentioned this pull request Feb 22, 2019

Remove #![feature(arbitrary_self_types)] withoutboats/romio#68

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Centril added this to the 1.33 milestone Apr 26, 2019

mikeyhew mentioned this pull request Sep 11, 2019

ManuallyDrop should be an object-safe receiver type #64351

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Centril mentioned this pull request Sep 14, 2019

Stabilize nested self receivers in 1.41.0 #64325

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nagisa mentioned this pull request Oct 7, 2019

Trait bound is ignored #65149

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mhammond mentioned this pull request Mar 16, 2021

Allow [Threadsafe] interfaces access to Arc<Self> mozilla/uniffi-rs#417

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cuviper mentioned this pull request Oct 18, 2021

Inference failure sometimes results in things being considered functions. #89995

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psychon mentioned this pull request Jan 30, 2022

Async/await pattern psychon/x11rb#318

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Stabilize `Rc`, `Arc` and `Pin` as method receivers #56805

Stabilize `Rc`, `Arc` and `Pin` as method receivers #56805

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Stabilize Rc, Arc and Pin as method receivers #56805

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Stabilize `Rc`, `Arc` and `Pin` as method receivers #56805

Stabilize `Rc`, `Arc` and `Pin` as method receivers #56805