bjoernager/rust
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Ambiguous Self lifetimes: don't elide.

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struct Concrete(u32);

  impl Concrete {
      fn m(self: &Box<Self>) -> &u32 {
          &self.0
      }
  }

resulted in a confusing error.

  impl Concrete {
      fn n(self: &Box<&Self>) -> &u32 {
          &self.0
      }
  }

resulted in no error or warning, despite apparent ambiguity over the elided
lifetime.

This commit changes two aspects of the behavior.

Previously, when examining the self type, we considered lifetimes only if they
were immediately adjacent to Self. We now consider lifetimes anywhere in the
self type.

Secondly, if more than one lifetime is discovered in the self type, we
disregard it as a possible lifetime elision candidate.

This is a compatibility break, and in fact has required some changes to tests
which assumed the earlier behavior.

Fixes https://github.com/rust-lang/rust/issues/117715
This commit is contained in:
Adrian Taylor 2023-11-15 19:46:42 +00:00
parent 1d0e4afd4c
commit 8d1958f0d2
9 changed files with 246 additions and 21 deletions
Download patch file Download diff file Expand all files Collapse all files

26
compiler/rustc_resolve/src/late.rs
View file

@ -2132,13 +2132,15 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
// Handle `self` specially.
if index == 0 && has_self {
let self_lifetime = self.find_lifetime_for_self(ty);
if let Set1::One(lifetime) = self_lifetime {
elision_lifetime = match self_lifetime {
// We found `self` elision.
elision_lifetime = Elision::Self_(lifetime);
} else {
Set1::One(lifetime) => Elision::Self_(lifetime),
// `self` itself had ambiguous lifetimes, e.g.
// &Box<&Self>
Set1::Many => Elision::None,
// We do not have `self` elision: disregard the `Elision::Param` that we may
// have found.
elision_lifetime = Elision::None;
Set1::Empty => Elision::None,
}
}
debug!("(resolving function / closure) recorded parameter");
@ -2162,6 +2164,7 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
r: &'r Resolver<'a, 'tcx>,
impl_self: Option<Res>,
lifetime: Set1<LifetimeRes>,
self_found: bool,
}
impl SelfVisitor<'_, '_, '_> {
@ -2185,9 +2188,11 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
impl<'a> Visitor<'a> for SelfVisitor<'_, '_, '_> {
fn visit_ty(&mut self, ty: &'a Ty) {
trace!("SelfVisitor considering ty={:?}", ty);
if let TyKind::Ref(lt, ref mt) = ty.kind
&& self.is_self_ty(&mt.ty)
{
if self.is_self_ty(ty) {
trace!("SelfVisitor found Self");
self.self_found = true;
}
if let TyKind::Ref(lt, _) = ty.kind {
let lt_id = if let Some(lt) = lt {
lt.id
} else {
@ -2228,10 +2233,11 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
Res::Def(DefKind::Struct | DefKind::Union | DefKind::Enum, _,) | Res::PrimTy(_)
)
});
let mut visitor = SelfVisitor { r: self.r, impl_self, lifetime: Set1::Empty };
let mut visitor =
SelfVisitor { r: self.r, impl_self, lifetime: Set1::Empty, self_found: false };
visitor.visit_ty(ty);
trace!("SelfVisitor found={:?}", visitor.lifetime);
visitor.lifetime
trace!("SelfVisitor found={:?}, self_found={:?}", visitor.lifetime, visitor.self_found);
if visitor.self_found { visitor.lifetime } else { Set1::Empty }
}
/// Searches the current set of local scopes for labels. Returns the `NodeId` of the resolved

6
tests/ui/self/elision/ref-assoc-async.rs
View file

@ -1,5 +1,4 @@
//@ edition:2018
//@ check-pass
#![allow(non_snake_case)]
@ -18,22 +17,27 @@ impl Trait for Struct {
impl Struct {
async fn ref_AssocType(self: &<Struct as Trait>::AssocType, f: &u32) -> &u32 {
f
//~^ ERROR lifetime may not live long enough
}
async fn box_ref_AssocType(self: Box<&<Struct as Trait>::AssocType>, f: &u32) -> &u32 {
f
//~^ ERROR lifetime may not live long enough
}
async fn pin_ref_AssocType(self: Pin<&<Struct as Trait>::AssocType>, f: &u32) -> &u32 {
f
//~^ ERROR lifetime may not live long enough
}
async fn box_box_ref_AssocType(self: Box<Box<&<Struct as Trait>::AssocType>>, f: &u32) -> &u32 {
f
//~^ ERROR lifetime may not live long enough
}
async fn box_pin_ref_AssocType(self: Box<Pin<&<Struct as Trait>::AssocType>>, f: &u32) -> &u32 {
f
//~^ ERROR lifetime may not live long enough
}
}

77
tests/ui/self/elision/ref-assoc-async.stderr Normal file
View file

@ -0,0 +1,77 @@
error: lifetime may not live long enough
--> $DIR/ref-assoc-async.rs:19:9
|
LL | async fn ref_AssocType(self: &<Struct as Trait>::AssocType, f: &u32) -> &u32 {
| - - let's call the lifetime of this reference `'1`
| |
| let's call the lifetime of this reference `'2`
LL | f
| ^ method was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
|
help: consider introducing a named lifetime parameter and update trait if needed
|
LL | async fn ref_AssocType<'a>(self: &'a <Struct as Trait>::AssocType, f: &'a u32) -> &u32 {
| ++++ ++ ++
error: lifetime may not live long enough
--> $DIR/ref-assoc-async.rs:24:9
|
LL | async fn box_ref_AssocType(self: Box<&<Struct as Trait>::AssocType>, f: &u32) -> &u32 {
| - - let's call the lifetime of this reference `'1`
| |
| let's call the lifetime of this reference `'2`
LL | f
| ^ method was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
|
help: consider introducing a named lifetime parameter and update trait if needed
|
LL | async fn box_ref_AssocType<'a>(self: Box<&'a <Struct as Trait>::AssocType>, f: &'a u32) -> &u32 {
| ++++ ++ ++
error: lifetime may not live long enough
--> $DIR/ref-assoc-async.rs:29:9
|
LL | async fn pin_ref_AssocType(self: Pin<&<Struct as Trait>::AssocType>, f: &u32) -> &u32 {
| - - let's call the lifetime of this reference `'1`
| |
| let's call the lifetime of this reference `'2`
LL | f
| ^ method was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
|
help: consider introducing a named lifetime parameter and update trait if needed
|
LL | async fn pin_ref_AssocType<'a>(self: Pin<&'a <Struct as Trait>::AssocType>, f: &'a u32) -> &u32 {
| ++++ ++ ++
error: lifetime may not live long enough
--> $DIR/ref-assoc-async.rs:34:9
|
LL | async fn box_box_ref_AssocType(self: Box<Box<&<Struct as Trait>::AssocType>>, f: &u32) -> &u32 {
| - - let's call the lifetime of this reference `'1`
| |
| let's call the lifetime of this reference `'2`
LL | f
| ^ method was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
|
help: consider introducing a named lifetime parameter and update trait if needed
|
LL | async fn box_box_ref_AssocType<'a>(self: Box<Box<&'a <Struct as Trait>::AssocType>>, f: &'a u32) -> &u32 {
| ++++ ++ ++
error: lifetime may not live long enough
--> $DIR/ref-assoc-async.rs:39:9
|
LL | async fn box_pin_ref_AssocType(self: Box<Pin<&<Struct as Trait>::AssocType>>, f: &u32) -> &u32 {
| - - let's call the lifetime of this reference `'1`
| |
| let's call the lifetime of this reference `'2`
LL | f
| ^ method was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
|
help: consider introducing a named lifetime parameter and update trait if needed
|
LL | async fn box_pin_ref_AssocType<'a>(self: Box<Pin<&'a <Struct as Trait>::AssocType>>, f: &'a u32) -> &u32 {
| ++++ ++ ++
error: aborting due to 5 previous errors

7
tests/ui/self/elision/ref-assoc.rs
View file

@ -1,5 +1,3 @@
//@ check-pass
#![allow(non_snake_case)]
use std::pin::Pin;
@ -17,22 +15,27 @@ impl Trait for Struct {
impl Struct {
fn ref_AssocType(self: &<Struct as Trait>::AssocType, f: &u32) -> &u32 {
f
//~^ ERROR lifetime may not live long enough
}
fn box_ref_AssocType(self: Box<&<Struct as Trait>::AssocType>, f: &u32) -> &u32 {
f
//~^ ERROR lifetime may not live long enough
}
fn pin_ref_AssocType(self: Pin<&<Struct as Trait>::AssocType>, f: &u32) -> &u32 {
f
//~^ ERROR lifetime may not live long enough
}
fn box_box_ref_AssocType(self: Box<Box<&<Struct as Trait>::AssocType>>, f: &u32) -> &u32 {
f
//~^ ERROR lifetime may not live long enough
}
fn box_pin_ref_AssocType(self: Box<Pin<&<Struct as Trait>::AssocType>>, f: &u32) -> &u32 {
f
//~^ ERROR lifetime may not live long enough
}
}

77
tests/ui/self/elision/ref-assoc.stderr Normal file
View file

@ -0,0 +1,77 @@
error: lifetime may not live long enough
--> $DIR/ref-assoc.rs:17:9
|
LL | fn ref_AssocType(self: &<Struct as Trait>::AssocType, f: &u32) -> &u32 {
| - - let's call the lifetime of this reference `'1`
| |
| let's call the lifetime of this reference `'2`
LL | f
| ^ method was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
|
help: consider introducing a named lifetime parameter and update trait if needed
|
LL | fn ref_AssocType<'a>(self: &<Struct as Trait>::AssocType, f: &'a u32) -> &'a u32 {
| ++++ ++ ++
error: lifetime may not live long enough
--> $DIR/ref-assoc.rs:22:9
|
LL | fn box_ref_AssocType(self: Box<&<Struct as Trait>::AssocType>, f: &u32) -> &u32 {
| - - let's call the lifetime of this reference `'1`
| |
| let's call the lifetime of this reference `'2`
LL | f
| ^ method was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
|
help: consider introducing a named lifetime parameter and update trait if needed
|
LL | fn box_ref_AssocType<'a>(self: Box<&<Struct as Trait>::AssocType>, f: &'a u32) -> &'a u32 {
| ++++ ++ ++
error: lifetime may not live long enough
--> $DIR/ref-assoc.rs:27:9
|
LL | fn pin_ref_AssocType(self: Pin<&<Struct as Trait>::AssocType>, f: &u32) -> &u32 {
| - - let's call the lifetime of this reference `'1`
| |
| let's call the lifetime of this reference `'2`
LL | f
| ^ method was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
|
help: consider introducing a named lifetime parameter and update trait if needed
|
LL | fn pin_ref_AssocType<'a>(self: Pin<&<Struct as Trait>::AssocType>, f: &'a u32) -> &'a u32 {
| ++++ ++ ++
error: lifetime may not live long enough
--> $DIR/ref-assoc.rs:32:9
|
LL | fn box_box_ref_AssocType(self: Box<Box<&<Struct as Trait>::AssocType>>, f: &u32) -> &u32 {
| - - let's call the lifetime of this reference `'1`
| |
| let's call the lifetime of this reference `'2`
LL | f
| ^ method was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
|
help: consider introducing a named lifetime parameter and update trait if needed
|
LL | fn box_box_ref_AssocType<'a>(self: Box<Box<&<Struct as Trait>::AssocType>>, f: &'a u32) -> &'a u32 {
| ++++ ++ ++
error: lifetime may not live long enough
--> $DIR/ref-assoc.rs:37:9
|
LL | fn box_pin_ref_AssocType(self: Box<Pin<&<Struct as Trait>::AssocType>>, f: &u32) -> &u32 {
| - - let's call the lifetime of this reference `'1`
| |
| let's call the lifetime of this reference `'2`
LL | f
| ^ method was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
|
help: consider introducing a named lifetime parameter and update trait if needed
|
LL | fn box_pin_ref_AssocType<'a>(self: Box<Pin<&<Struct as Trait>::AssocType>>, f: &'a u32) -> &'a u32 {
| ++++ ++ ++
error: aborting due to 5 previous errors

29
tests/ui/self/elision/ref-self-multi.rs Normal file
View file

@ -0,0 +1,29 @@
//@ run-pass
#![feature(arbitrary_self_types)]
#![allow(non_snake_case)]
#![allow(unused)]
use std::marker::PhantomData;
use std::ops::Deref;
struct Struct { }
struct Wrap<T, P>(T, PhantomData<P>);
impl<T, P> Deref for Wrap<T, P> {
type Target = T;
fn deref(&self) -> &T { &self.0 }
}
impl Struct {
fn ref_box_ref_Self(self: &Box<&Self>, f: &u32) -> &u32 {
f
}
fn ref_wrap_ref_Self(self: &Wrap<&Self, u32>, f: &u32) -> &u32 {
f
}
}
fn main() { }

7
tests/ui/self/elision/ref-self.fixed
View file

@ -1,4 +1,6 @@
//@ run-rustfix
//@ edition:2018
#![feature(arbitrary_self_types)]
#![allow(non_snake_case, dead_code)]
@ -56,6 +58,11 @@ impl Struct {
f
//~^ ERROR lifetime may not live long enough
}
fn ref_box_Self<'a>(self: &Box<Self>, f: &'a u32) -> &'a u32 {
f
//~^ ERROR lifetime may not live long enough
}
}
fn main() {}

7
tests/ui/self/elision/ref-self.rs
View file

@ -1,4 +1,6 @@
//@ run-rustfix
//@ edition:2018
#![feature(arbitrary_self_types)]
#![allow(non_snake_case, dead_code)]
@ -56,6 +58,11 @@ impl Struct {
f
//~^ ERROR lifetime may not live long enough
}
fn ref_box_Self(self: &Box<Self>, f: &u32) -> &u32 {
f
//~^ ERROR lifetime may not live long enough
}
}
fn main() {}

31
tests/ui/self/elision/ref-self.stderr
View file

@ -1,5 +1,5 @@
error: lifetime may not live long enough
--> $DIR/ref-self.rs:24:9
--> $DIR/ref-self.rs:26:9
|
LL | fn ref_self(&self, f: &u32) -> &u32 {
| - - let's call the lifetime of this reference `'1`
@ -14,7 +14,7 @@ LL | fn ref_self<'a>(&self, f: &'a u32) -> &'a u32 {
| ++++ ++ ++
error: lifetime may not live long enough
--> $DIR/ref-self.rs:31:9
--> $DIR/ref-self.rs:33:9
|
LL | fn ref_Self(self: &Self, f: &u32) -> &u32 {
| - - let's call the lifetime of this reference `'1`
@ -29,7 +29,7 @@ LL | fn ref_Self<'a>(self: &Self, f: &'a u32) -> &'a u32 {
| ++++ ++ ++
error: lifetime may not live long enough
--> $DIR/ref-self.rs:36:9
--> $DIR/ref-self.rs:38:9
|
LL | fn box_ref_Self(self: Box<&Self>, f: &u32) -> &u32 {
| - - let's call the lifetime of this reference `'1`
@ -44,7 +44,7 @@ LL | fn box_ref_Self<'a>(self: Box<&Self>, f: &'a u32) -> &'a u32 {
| ++++ ++ ++
error: lifetime may not live long enough
--> $DIR/ref-self.rs:41:9
--> $DIR/ref-self.rs:43:9
|
LL | fn pin_ref_Self(self: Pin<&Self>, f: &u32) -> &u32 {
| - - let's call the lifetime of this reference `'1`
@ -59,7 +59,7 @@ LL | fn pin_ref_Self<'a>(self: Pin<&Self>, f: &'a u32) -> &'a u32 {
| ++++ ++ ++
error: lifetime may not live long enough
--> $DIR/ref-self.rs:46:9
--> $DIR/ref-self.rs:48:9
|
LL | fn box_box_ref_Self(self: Box<Box<&Self>>, f: &u32) -> &u32 {
| - - let's call the lifetime of this reference `'1`
@ -74,7 +74,7 @@ LL | fn box_box_ref_Self<'a>(self: Box<Box<&Self>>, f: &'a u32) -> &'a u32 {
| ++++ ++ ++
error: lifetime may not live long enough
--> $DIR/ref-self.rs:51:9
--> $DIR/ref-self.rs:53:9
|
LL | fn box_pin_ref_Self(self: Box<Pin<&Self>>, f: &u32) -> &u32 {
| - - let's call the lifetime of this reference `'1`
@ -89,7 +89,7 @@ LL | fn box_pin_ref_Self<'a>(self: Box<Pin<&Self>>, f: &'a u32) -> &'a u32 {
| ++++ ++ ++
error: lifetime may not live long enough
--> $DIR/ref-self.rs:56:9
--> $DIR/ref-self.rs:58:9
|
LL | fn wrap_ref_Self_Self(self: Wrap<&Self, Self>, f: &u8) -> &u8 {
| - - let's call the lifetime of this reference `'1`
@ -103,5 +103,20 @@ help: consider introducing a named lifetime parameter and update trait if needed
LL | fn wrap_ref_Self_Self<'a>(self: Wrap<&Self, Self>, f: &'a u8) -> &'a u8 {
| ++++ ++ ++
error: aborting due to 7 previous errors
error: lifetime may not live long enough
--> $DIR/ref-self.rs:63:9
|
LL | fn ref_box_Self(self: &Box<Self>, f: &u32) -> &u32 {
| - - let's call the lifetime of this reference `'1`
| |
| let's call the lifetime of this reference `'2`
LL | f
| ^ method was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
|
help: consider introducing a named lifetime parameter and update trait if needed
|
LL | fn ref_box_Self<'a>(self: &Box<Self>, f: &'a u32) -> &'a u32 {
| ++++ ++ ++
error: aborting due to 8 previous errors