Allow lifetime elision in Pin<&(mut) Self>
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09e3989758
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7 changed files with 165 additions and 1 deletions
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@ -2174,7 +2174,34 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
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false
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};
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if let hir::TyKind::Rptr(lifetime_ref, ref mt) = inputs[0].node {
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let mut self_arg = &inputs[0].node;
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// Apply `self: &(mut) Self` elision rules even if nested in `Pin`.
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loop {
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if let hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) = *self_arg {
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if let Res::Def(DefKind::Struct, def_id) = path.res {
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if self.tcx.lang_items().pin_type() == Some(def_id) {
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if let Some(args) = path
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.segments
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.last()
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.and_then(|segment| segment.args.as_ref())
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{
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if args.args.len() == 1 {
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if let GenericArg::Type(ty) = &args.args[0] {
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self_arg = &ty.node;
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// Keep dereferencing `self_arg` until we get to non-`Pin`
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// types.
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continue;
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}
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}
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}
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}
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}
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}
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break;
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}
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if let hir::TyKind::Rptr(lifetime_ref, ref mt) = *self_arg {
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if let hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) = mt.ty.node {
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if is_self_ty(path.res) {
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if let Some(&lifetime) = self.map.defs.get(&lifetime_ref.hir_id) {
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60
src/test/ui/self/arbitrary_self_types_pin_lifetime.rs
Normal file
60
src/test/ui/self/arbitrary_self_types_pin_lifetime.rs
Normal file
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@ -0,0 +1,60 @@
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// compile-pass
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use std::pin::Pin;
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use std::task::{Context, Poll};
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struct Foo;
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impl Foo {
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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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}
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type Alias<T> = Pin<T>;
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impl Foo {
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fn bar<'a>(self: Alias<&Self>, arg: &'a ()) -> &() { arg }
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}
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struct Bar<T: Unpin, U: Unpin> {
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field1: T,
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field2: U,
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}
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impl<T: Unpin, U: Unpin> Bar<T, U> {
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fn fields(self: Pin<&mut Self>) -> (Pin<&mut T>, Pin<&mut U>) {
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let this = self.get_mut();
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(Pin::new(&mut this.field1), Pin::new(&mut this.field2))
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}
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}
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trait AsyncBufRead {
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fn poll_fill_buf(self: Pin<&mut Self>, cx: &mut Context<'_>)
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-> Poll<std::io::Result<&[u8]>>;
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}
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struct Baz(Vec<u8>);
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impl AsyncBufRead for Baz {
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fn poll_fill_buf(self: Pin<&mut Self>, cx: &mut Context<'_>)
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-> Poll<std::io::Result<&[u8]>>
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{
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Poll::Ready(Ok(&self.get_mut().0))
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}
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}
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fn main() {
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let mut foo = Foo;
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{ Pin::new(&foo).pin_ref() };
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{ Pin::new(&mut foo).pin_mut() };
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{ Pin::new(Pin::new(Pin::new(&foo))).pin_pin_pin_ref() };
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{ Pin::new(&foo).pin_ref_impl_trait() };
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let mut bar = Bar { field1: 0u8, field2: 1u8 };
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{ Pin::new(&mut bar).fields() };
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}
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@ -0,0 +1,13 @@
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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 {
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fn f(self: Pin<&Self>) -> impl Clone { self } //~ ERROR cannot infer an appropriate lifetime
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}
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fn main() {
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{ Pin::new(&Foo).f() };
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}
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@ -0,0 +1,20 @@
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error: cannot infer an appropriate lifetime
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--> $DIR/arbitrary_self_types_pin_lifetime_impl_trait.rs:8:44
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LL | fn f(self: Pin<&Self>) -> impl Clone { self }
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| ---------- ^^^^ ...but this borrow...
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| |
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| this return type evaluates to the `'static` lifetime...
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note: ...can't outlive the anonymous lifetime #1 defined on the method body at 8:5
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--> $DIR/arbitrary_self_types_pin_lifetime_impl_trait.rs:8:5
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LL | fn f(self: Pin<&Self>) -> impl Clone { self }
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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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
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LL | fn f(self: Pin<&Self>) -> impl Clone + '_ { self }
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| ^^^^^^^^^^^^^^^
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error: aborting due to previous error
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@ -0,0 +1,13 @@
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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 {
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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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}
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fn main() {}
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@ -0,0 +1,18 @@
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error[E0623]: lifetime mismatch
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--> $DIR/arbitrary_self_types_pin_lifetime_mismatch.rs:8:46
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LL | fn a(self: Pin<&Foo>, f: &Foo) -> &Foo { f }
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| ---- ---- ^ ...but data from `f` is returned here
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| |
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| this parameter and the return type are declared with different lifetimes...
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error[E0623]: lifetime mismatch
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--> $DIR/arbitrary_self_types_pin_lifetime_mismatch.rs:10:76
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LL | fn c(self: Pin<&Self>, f: &Foo, g: &Foo) -> (Pin<&Foo>, &Foo) { (self, f) }
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| ---- ----------------- ^ ...but data from `f` is returned here
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| |
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| this parameter and the return type are declared with different lifetimes...
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error: aborting due to 2 previous errors
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13
src/test/ui/self/self_lifetime.rs
Normal file
13
src/test/ui/self/self_lifetime.rs
Normal file
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@ -0,0 +1,13 @@
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// compile-pass
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struct Foo<'a>(&'a ());
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impl<'a> Foo<'a> {
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fn foo<'b>(self: &'b Foo<'a>) -> &() { self.0 }
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}
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type Alias = Foo<'static>;
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impl Alias {
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fn bar<'a>(self: &Alias, arg: &'a ()) -> &() { arg }
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}
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fn main() {}
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