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Rollup merge of rust-lang#116952 - compiler-errors:lifetime_capture_r…
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…ules_2024, r=TaKO8Ki

Implement 2024-edition lifetime capture rules RFC

Implements rust-lang/rfcs#3498.
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compiler-errors authored Dec 5, 2023
2 parents ec94480 + 52143ff commit 4af8013
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Showing 10 changed files with 94 additions and 8 deletions.
6 changes: 4 additions & 2 deletions compiler/rustc_ast_lowering/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1571,8 +1571,10 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
Vec::new()
}
hir::OpaqueTyOrigin::FnReturn(..) => {
if let FnDeclKind::Impl | FnDeclKind::Trait =
fn_kind.expect("expected RPITs to be lowered with a FnKind")
if matches!(
fn_kind.expect("expected RPITs to be lowered with a FnKind"),
FnDeclKind::Impl | FnDeclKind::Trait
) || self.tcx.features().lifetime_capture_rules_2024
{
// return-position impl trait in trait was decided to capture all
// in-scope lifetimes, which we collect for all opaques during resolution.
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2 changes: 2 additions & 0 deletions compiler/rustc_feature/src/unstable.rs
Original file line number Diff line number Diff line change
Expand Up @@ -195,6 +195,8 @@ declare_features! (
(internal, intrinsics, "1.0.0", None, None),
/// Allows using `#[lang = ".."]` attribute for linking items to special compiler logic.
(internal, lang_items, "1.0.0", None, None),
/// Changes `impl Trait` to capture all lifetimes in scope.
(unstable, lifetime_capture_rules_2024, "CURRENT_RUSTC_VERSION", None, None),
/// Allows `#[link(..., cfg(..))]`; perma-unstable per #37406
(unstable, link_cfg, "1.14.0", None, None),
/// Allows the `multiple_supertrait_upcastable` lint.
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1 change: 1 addition & 0 deletions compiler/rustc_span/src/symbol.rs
Original file line number Diff line number Diff line change
Expand Up @@ -929,6 +929,7 @@ symbols! {
lib,
libc,
lifetime,
lifetime_capture_rules_2024,
lifetimes,
likely,
line,
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Original file line number Diff line number Diff line change
@@ -0,0 +1,6 @@
fn foo(x: &Vec<i32>) -> impl Sized {
x
//~^ ERROR hidden type for `impl Sized` captures lifetime that does not appear in bounds
}

fn main() {}
Original file line number Diff line number Diff line change
@@ -0,0 +1,18 @@
error[E0700]: hidden type for `impl Sized` captures lifetime that does not appear in bounds
--> $DIR/feature-gate-lifetime-capture-rules-2024.rs:2:5
|
LL | fn foo(x: &Vec<i32>) -> impl Sized {
| --------- ---------- opaque type defined here
| |
| hidden type `&Vec<i32>` captures the anonymous lifetime defined here
LL | x
| ^
|
help: to declare that `impl Sized` captures `'_`, you can add an explicit `'_` lifetime bound
|
LL | fn foo(x: &Vec<i32>) -> impl Sized + '_ {
| ++++

error: aborting due to previous error

For more information about this error, try `rustc --explain E0700`.
14 changes: 14 additions & 0 deletions tests/ui/impl-trait/implicit-capture-late.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,14 @@
// known-bug: #117647

#![feature(lifetime_capture_rules_2024)]
#![feature(rustc_attrs)]
#![allow(internal_features)]
#![rustc_variance_of_opaques]

use std::ops::Deref;

fn foo(x: Vec<i32>) -> Box<dyn for<'a> Deref<Target = impl ?Sized>> {
Box::new(x)
}

fn main() {}
9 changes: 9 additions & 0 deletions tests/ui/impl-trait/implicit-capture-late.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,9 @@
error[E0657]: `impl Trait` can only capture lifetimes bound at the fn or impl level
--> $DIR/implicit-capture-late.rs:10:36
|
LL | fn foo(x: Vec<i32>) -> Box<dyn for<'a> Deref<Target = impl ?Sized>> {
| ^^

error: aborting due to previous error

For more information about this error, try `rustc --explain E0657`.
26 changes: 26 additions & 0 deletions tests/ui/impl-trait/variance.new.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,26 @@
error: [*, o]
--> $DIR/variance.rs:12:36
|
LL | fn not_captured_early<'a: 'a>() -> impl Sized {}
| ^^^^^^^^^^

error: [*, o]
--> $DIR/variance.rs:16:32
|
LL | fn captured_early<'a: 'a>() -> impl Sized + Captures<'a> {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^

error: [o]
--> $DIR/variance.rs:18:40
|
LL | fn not_captured_late<'a>(_: &'a ()) -> impl Sized {}
| ^^^^^^^^^^

error: [o]
--> $DIR/variance.rs:22:36
|
LL | fn captured_late<'a>(_: &'a ()) -> impl Sized + Captures<'a> {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to 4 previous errors

Original file line number Diff line number Diff line change
@@ -1,23 +1,23 @@
error: [*]
--> $DIR/variance.rs:8:36
--> $DIR/variance.rs:12:36
|
LL | fn not_captured_early<'a: 'a>() -> impl Sized {}
| ^^^^^^^^^^

error: [*, o]
--> $DIR/variance.rs:10:32
--> $DIR/variance.rs:16:32
|
LL | fn captured_early<'a: 'a>() -> impl Sized + Captures<'a> {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^

error: []
--> $DIR/variance.rs:12:40
--> $DIR/variance.rs:18:40
|
LL | fn not_captured_late<'a>(_: &'a ()) -> impl Sized {}
| ^^^^^^^^^^

error: [o]
--> $DIR/variance.rs:14:36
--> $DIR/variance.rs:22:36
|
LL | fn captured_late<'a>(_: &'a ()) -> impl Sized + Captures<'a> {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^
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12 changes: 10 additions & 2 deletions tests/ui/impl-trait/variance.rs
Original file line number Diff line number Diff line change
@@ -1,15 +1,23 @@
// revisions: old new

#![cfg_attr(new, feature(lifetime_capture_rules_2024))]

#![feature(rustc_attrs)]
#![allow(internal_features)]
#![rustc_variance_of_opaques]

trait Captures<'a> {}
impl<T> Captures<'_> for T {}

fn not_captured_early<'a: 'a>() -> impl Sized {} //~ [*]
fn not_captured_early<'a: 'a>() -> impl Sized {}
//[old]~^ [*]
//[new]~^^ [*, o]

fn captured_early<'a: 'a>() -> impl Sized + Captures<'a> {} //~ [*, o]

fn not_captured_late<'a>(_: &'a ()) -> impl Sized {} //~ []
fn not_captured_late<'a>(_: &'a ()) -> impl Sized {}
//[old]~^ []
//[new]~^^ [o]

fn captured_late<'a>(_: &'a ()) -> impl Sized + Captures<'a> {} //~ [o]

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