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Rollup merge of rust-lang#61207 - taiki-e:arbitrary_self_types-lifeti…
…me-elision-2, r=Centril Allow lifetime elision in `Pin<&(mut) Self>` This PR changes `self: &(mut) S` elision rules to instead visit the type of `self` and look for `&(mut) S` (where `is_self_ty(S)`) within it Replaces rust-lang#60944 Closes rust-lang#52675 r? @eddyb cc @cramertj @Centril @withoutboats @scottmcm
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// check-pass | ||
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use std::pin::Pin; | ||
use std::task::{Context, Poll}; | ||
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struct Foo; | ||
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impl Foo { | ||
fn pin_ref(self: Pin<&Self>) -> Pin<&Self> { self } | ||
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fn pin_mut(self: Pin<&mut Self>) -> Pin<&mut Self> { self } | ||
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fn pin_pin_pin_ref(self: Pin<Pin<Pin<&Self>>>) -> Pin<Pin<Pin<&Self>>> { self } | ||
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fn pin_ref_impl_trait(self: Pin<&Self>) -> impl Clone + '_ { self } | ||
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fn b(self: Pin<&Foo>, f: &Foo) -> Pin<&Foo> { self } | ||
} | ||
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type Alias<T> = Pin<T>; | ||
impl Foo { | ||
fn bar<'a>(self: Alias<&Self>, arg: &'a ()) -> Alias<&Self> { self } | ||
} | ||
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struct Bar<T: Unpin, U: Unpin> { | ||
field1: T, | ||
field2: U, | ||
} | ||
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impl<T: Unpin, U: Unpin> Bar<T, U> { | ||
fn fields(self: Pin<&mut Self>) -> (Pin<&mut T>, Pin<&mut U>) { | ||
let this = self.get_mut(); | ||
(Pin::new(&mut this.field1), Pin::new(&mut this.field2)) | ||
} | ||
} | ||
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trait AsyncBufRead { | ||
fn poll_fill_buf(self: Pin<&mut Self>, cx: &mut Context<'_>) | ||
-> Poll<std::io::Result<&[u8]>>; | ||
} | ||
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struct Baz(Vec<u8>); | ||
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impl AsyncBufRead for Baz { | ||
fn poll_fill_buf(self: Pin<&mut Self>, cx: &mut Context<'_>) | ||
-> Poll<std::io::Result<&[u8]>> | ||
{ | ||
Poll::Ready(Ok(&self.get_mut().0)) | ||
} | ||
} | ||
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fn main() { | ||
let mut foo = Foo; | ||
{ Pin::new(&foo).pin_ref() }; | ||
{ Pin::new(&mut foo).pin_mut() }; | ||
{ Pin::new(Pin::new(Pin::new(&foo))).pin_pin_pin_ref() }; | ||
{ Pin::new(&foo).pin_ref_impl_trait() }; | ||
let mut bar = Bar { field1: 0u8, field2: 1u8 }; | ||
{ Pin::new(&mut bar).fields() }; | ||
} |
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13
src/test/ui/self/arbitrary_self_types_pin_lifetime_impl_trait.rs
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// compile-fail | ||
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use std::pin::Pin; | ||
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struct Foo; | ||
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impl Foo { | ||
fn f(self: Pin<&Self>) -> impl Clone { self } //~ ERROR cannot infer an appropriate lifetime | ||
} | ||
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fn main() { | ||
{ Pin::new(&Foo).f() }; | ||
} |
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20
src/test/ui/self/arbitrary_self_types_pin_lifetime_impl_trait.stderr
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error: cannot infer an appropriate lifetime | ||
--> $DIR/arbitrary_self_types_pin_lifetime_impl_trait.rs:8:44 | ||
| | ||
LL | fn f(self: Pin<&Self>) -> impl Clone { self } | ||
| ---------- ^^^^ ...but this borrow... | ||
| | | ||
| this return type evaluates to the `'static` lifetime... | ||
| | ||
note: ...can't outlive the anonymous lifetime #1 defined on the method body at 8:5 | ||
--> $DIR/arbitrary_self_types_pin_lifetime_impl_trait.rs:8:5 | ||
| | ||
LL | fn f(self: Pin<&Self>) -> impl Clone { self } | ||
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | ||
help: you can add a constraint to the return type to make it last less than `'static` and match the anonymous lifetime #1 defined on the method body at 8:5 | ||
| | ||
LL | fn f(self: Pin<&Self>) -> impl Clone + '_ { self } | ||
| ^^^^^^^^^^^^^^^ | ||
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error: aborting due to previous error | ||
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src/test/ui/self/arbitrary_self_types_pin_lifetime_mismatch.rs
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// compile-fail | ||
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use std::pin::Pin; | ||
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struct Foo; | ||
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impl Foo { | ||
fn a(self: Pin<&Foo>, f: &Foo) -> &Foo { f } //~ ERROR E0623 | ||
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fn c(self: Pin<&Self>, f: &Foo, g: &Foo) -> (Pin<&Foo>, &Foo) { (self, f) } //~ ERROR E0623 | ||
} | ||
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type Alias<T> = Pin<T>; | ||
impl Foo { | ||
fn bar<'a>(self: Alias<&Self>, arg: &'a ()) -> &() { arg } //~ ERROR E0623 | ||
} | ||
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fn main() {} |
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src/test/ui/self/arbitrary_self_types_pin_lifetime_mismatch.stderr
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error[E0623]: lifetime mismatch | ||
--> $DIR/arbitrary_self_types_pin_lifetime_mismatch.rs:8:46 | ||
| | ||
LL | fn a(self: Pin<&Foo>, f: &Foo) -> &Foo { f } | ||
| ---- ---- ^ ...but data from `f` is returned here | ||
| | | ||
| this parameter and the return type are declared with different lifetimes... | ||
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error[E0623]: lifetime mismatch | ||
--> $DIR/arbitrary_self_types_pin_lifetime_mismatch.rs:10:76 | ||
| | ||
LL | fn c(self: Pin<&Self>, f: &Foo, g: &Foo) -> (Pin<&Foo>, &Foo) { (self, f) } | ||
| ---- ----------------- ^ ...but data from `f` is returned here | ||
| | | ||
| this parameter and the return type are declared with different lifetimes... | ||
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error[E0623]: lifetime mismatch | ||
--> $DIR/arbitrary_self_types_pin_lifetime_mismatch.rs:15:58 | ||
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LL | fn bar<'a>(self: Alias<&Self>, arg: &'a ()) -> &() { arg } | ||
| ------ --- ^^^ ...but data from `arg` is returned here | ||
| | | ||
| this parameter and the return type are declared with different lifetimes... | ||
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error: aborting due to 3 previous errors | ||
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Test cases intended to to document behavior and try to exhaustively | ||
explore the combinations. | ||
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## Confidence | ||
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These tests are not yet considered 100% normative, in that some | ||
aspects of the current behavior are not desirable. This is expressed | ||
in the "confidence" field in the following table. Values: | ||
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| Confidence | Interpretation | | ||
| --- | --- | | ||
| 100% | this will remain recommended behavior | | ||
| 75% | unclear whether we will continue to accept this | | ||
| 50% | this will likely be deprecated but remain valid | | ||
| 25% | this could change in the future | | ||
| 0% | this is definitely bogus and will likely change in the future in *some* way | | ||
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## Tests | ||
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| Test file | `Self` type | Pattern | Current elision behavior | Confidence | | ||
| --- | --- | --- | --- | --- | | ||
| `self.rs` | `Struct` | `Self` | ignore `self` parameter | 100% | | ||
| `struct.rs` | `Struct` | `Struct` | ignore `self` parameter | 100% | | ||
| `alias.rs` | `Struct` | `Alias` | ignore `self` parameter | 100% | | ||
| `ref-self.rs` | `Struct` | `&Self` | take lifetime from `&Self` | 100% | | ||
| `ref-mut-self.rs` | `Struct` | `&mut Self` | take lifetime from `&mut Self` | 100% | | ||
| `ref-struct.rs` | `Struct` | `&Struct` | take lifetime from `&Self` | 50% | | ||
| `ref-mut-struct.rs` | `Struct` | `&mut Struct` | take lifetime from `&mut Self` | 50% | | ||
| `ref-alias.rs` | `Struct` | `&Alias` | ignore `Alias` | 0% | | ||
| `ref-mut-alias.rs` | `Struct` | `&mut Alias` | ignore `Alias` | 0% | | ||
| `lt-self.rs` | `Struct<'a>` | `Self` | ignore `Self` (and hence `'a`) | 25% | | ||
| `lt-struct.rs` | `Struct<'a>` | `Self` | ignore `Self` (and hence `'a`) | 0% | | ||
| `lt-alias.rs` | `Alias<'a>` | `Self` | ignore `Self` (and hence `'a`) | 0% | | ||
| `lt-ref-self.rs` | `Struct<'a>` | `&Self` | take lifetime from `&Self` | 75% | | ||
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In each case, we test the following patterns: | ||
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- `self: XXX` | ||
- `self: Box<XXX>` | ||
- `self: Pin<XXX>` | ||
- `self: Box<Box<XXX>>` | ||
- `self: Box<Pin<XXX>>` | ||
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In the non-reference cases, `Pin` causes errors so we substitute `Rc`. |
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// check-pass | ||
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#![feature(arbitrary_self_types)] | ||
#![allow(non_snake_case)] | ||
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use std::rc::Rc; | ||
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struct Struct { } | ||
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type Alias = Struct; | ||
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impl Struct { | ||
// Test using an alias for `Struct`: | ||
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fn alias(self: Alias, f: &u32) -> &u32 { | ||
f | ||
} | ||
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fn box_Alias(self: Box<Alias>, f: &u32) -> &u32 { | ||
f | ||
} | ||
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fn rc_Alias(self: Rc<Alias>, f: &u32) -> &u32 { | ||
f | ||
} | ||
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fn box_box_Alias(self: Box<Box<Alias>>, f: &u32) -> &u32 { | ||
f | ||
} | ||
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fn box_rc_Alias(self: Box<Rc<Alias>>, f: &u32) -> &u32 { | ||
f | ||
} | ||
} | ||
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fn main() { } |
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// check-pass | ||
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#![feature(arbitrary_self_types)] | ||
#![allow(non_snake_case)] | ||
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use std::rc::Rc; | ||
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trait Trait { | ||
type AssocType; | ||
} | ||
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struct Struct { } | ||
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impl Trait for Struct { | ||
type AssocType = Self; | ||
} | ||
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impl Struct { | ||
fn assoc(self: <Struct as Trait>::AssocType, f: &u32) -> &u32 { | ||
f | ||
} | ||
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fn box_AssocType(self: Box<<Struct as Trait>::AssocType>, f: &u32) -> &u32 { | ||
f | ||
} | ||
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fn rc_AssocType(self: Rc<<Struct as Trait>::AssocType>, f: &u32) -> &u32 { | ||
f | ||
} | ||
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fn box_box_AssocType(self: Box<Box<<Struct as Trait>::AssocType>>, f: &u32) -> &u32 { | ||
f | ||
} | ||
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fn box_rc_AssocType(self: Box<Rc<<Struct as Trait>::AssocType>>, f: &u32) -> &u32 { | ||
f | ||
} | ||
} | ||
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fn main() { } |
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