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Auto merge of rust-lang#114272 - workingjubilee:rollup-ll9lwon, r=wor…
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…kingjubilee

Rollup of 4 pull requests

Successful merges:

 - rust-lang#95965 (Stabilize const-weak-new)
 - rust-lang#109075 (Use `LazyLock` to lazily resolve backtraces)
 - rust-lang#113741 (Don't install default projection bound for return-position `impl Trait` in trait methods with no body)
 - rust-lang#114268 (Fix empty_write since rust version attribute)

r? `@ghost`
`@rustbot` modify labels: rollup
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bors committed Jul 31, 2023
2 parents d9feb02 + 495e657 commit dfc9d3f
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Showing 11 changed files with 59 additions and 61 deletions.
8 changes: 1 addition & 7 deletions compiler/rustc_metadata/src/rmeta/encoder.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1144,13 +1144,7 @@ fn should_encode_type(tcx: TyCtxt<'_>, def_id: LocalDefId, def_kind: DefKind) ->
let assoc_item = tcx.associated_item(def_id);
match assoc_item.container {
ty::AssocItemContainer::ImplContainer => true,
// Always encode RPITITs, since we need to be able to project
// from an RPITIT associated item to an opaque when installing
// the default projection predicates in default trait methods
// with RPITITs.
ty::AssocItemContainer::TraitContainer => {
assoc_item.defaultness(tcx).has_value() || assoc_item.is_impl_trait_in_trait()
}
ty::AssocItemContainer::TraitContainer => assoc_item.defaultness(tcx).has_value(),
}
}
DefKind::TyParam => {
Expand Down
4 changes: 3 additions & 1 deletion compiler/rustc_ty_utils/src/ty.rs
Original file line number Diff line number Diff line change
Expand Up @@ -129,7 +129,9 @@ fn param_env(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ParamEnv<'_> {
// sure that this will succeed without errors anyway.

if tcx.def_kind(def_id) == DefKind::AssocFn
&& tcx.associated_item(def_id).container == ty::AssocItemContainer::TraitContainer
&& let assoc_item = tcx.associated_item(def_id)
&& assoc_item.container == ty::AssocItemContainer::TraitContainer
&& assoc_item.defaultness(tcx).has_value()
{
let sig = tcx.fn_sig(def_id).instantiate_identity();
// We accounted for the binder of the fn sig, so skip the binder.
Expand Down
2 changes: 1 addition & 1 deletion library/alloc/src/rc.rs
Original file line number Diff line number Diff line change
Expand Up @@ -2719,7 +2719,7 @@ impl<T> Weak<T> {
/// ```
#[inline]
#[stable(feature = "downgraded_weak", since = "1.10.0")]
#[rustc_const_unstable(feature = "const_weak_new", issue = "95091", reason = "recently added")]
#[rustc_const_stable(feature = "const_weak_new", since = "CURRENT_RUSTC_VERSION")]
#[must_use]
pub const fn new() -> Weak<T> {
Weak {
Expand Down
2 changes: 1 addition & 1 deletion library/alloc/src/sync.rs
Original file line number Diff line number Diff line change
Expand Up @@ -2503,7 +2503,7 @@ impl<T> Weak<T> {
/// ```
#[inline]
#[stable(feature = "downgraded_weak", since = "1.10.0")]
#[rustc_const_unstable(feature = "const_weak_new", issue = "95091", reason = "recently added")]
#[rustc_const_stable(feature = "const_weak_new", since = "CURRENT_RUSTC_VERSION")]
#[must_use]
pub const fn new() -> Weak<T> {
Weak {
Expand Down
58 changes: 13 additions & 45 deletions library/std/src/backtrace.rs
Original file line number Diff line number Diff line change
Expand Up @@ -89,12 +89,11 @@ mod tests;
// a backtrace or actually symbolizing it.

use crate::backtrace_rs::{self, BytesOrWideString};
use crate::cell::UnsafeCell;
use crate::env;
use crate::ffi::c_void;
use crate::fmt;
use crate::sync::atomic::{AtomicUsize, Ordering::Relaxed};
use crate::sync::Once;
use crate::sync::LazyLock;
use crate::sys_common::backtrace::{lock, output_filename};
use crate::vec::Vec;

Expand Down Expand Up @@ -133,12 +132,11 @@ pub enum BacktraceStatus {
enum Inner {
Unsupported,
Disabled,
Captured(LazilyResolvedCapture),
Captured(LazyLock<Capture, LazyResolve>),
}

struct Capture {
actual_start: usize,
resolved: bool,
frames: Vec<BacktraceFrame>,
}

Expand Down Expand Up @@ -179,7 +177,7 @@ impl fmt::Debug for Backtrace {
let capture = match &self.inner {
Inner::Unsupported => return fmt.write_str("<unsupported>"),
Inner::Disabled => return fmt.write_str("<disabled>"),
Inner::Captured(c) => c.force(),
Inner::Captured(c) => &**c,
};

let frames = &capture.frames[capture.actual_start..];
Expand Down Expand Up @@ -347,11 +345,10 @@ impl Backtrace {
let inner = if frames.is_empty() {
Inner::Unsupported
} else {
Inner::Captured(LazilyResolvedCapture::new(Capture {
Inner::Captured(LazyLock::new(lazy_resolve(Capture {
actual_start: actual_start.unwrap_or(0),
frames,
resolved: false,
}))
})))
};

Backtrace { inner }
Expand All @@ -376,7 +373,7 @@ impl<'a> Backtrace {
#[must_use]
#[unstable(feature = "backtrace_frames", issue = "79676")]
pub fn frames(&'a self) -> &'a [BacktraceFrame] {
if let Inner::Captured(c) = &self.inner { &c.force().frames } else { &[] }
if let Inner::Captured(c) = &self.inner { &c.frames } else { &[] }
}
}

Expand All @@ -386,7 +383,7 @@ impl fmt::Display for Backtrace {
let capture = match &self.inner {
Inner::Unsupported => return fmt.write_str("unsupported backtrace"),
Inner::Disabled => return fmt.write_str("disabled backtrace"),
Inner::Captured(c) => c.force(),
Inner::Captured(c) => &**c,
};

let full = fmt.alternate();
Expand Down Expand Up @@ -430,46 +427,15 @@ impl fmt::Display for Backtrace {
}
}

struct LazilyResolvedCapture {
sync: Once,
capture: UnsafeCell<Capture>,
}

impl LazilyResolvedCapture {
fn new(capture: Capture) -> Self {
LazilyResolvedCapture { sync: Once::new(), capture: UnsafeCell::new(capture) }
}

fn force(&self) -> &Capture {
self.sync.call_once(|| {
// SAFETY: This exclusive reference can't overlap with any others
// `Once` guarantees callers will block until this closure returns
// `Once` also guarantees only a single caller will enter this closure
unsafe { &mut *self.capture.get() }.resolve();
});

// SAFETY: This shared reference can't overlap with the exclusive reference above
unsafe { &*self.capture.get() }
}
}

// SAFETY: Access to the inner value is synchronized using a thread-safe `Once`
// So long as `Capture` is `Sync`, `LazilyResolvedCapture` is too
unsafe impl Sync for LazilyResolvedCapture where Capture: Sync {}

impl Capture {
fn resolve(&mut self) {
// If we're already resolved, nothing to do!
if self.resolved {
return;
}
self.resolved = true;
type LazyResolve = impl (FnOnce() -> Capture) + Send + Sync;

fn lazy_resolve(mut capture: Capture) -> LazyResolve {
move || {
// Use the global backtrace lock to synchronize this as it's a
// requirement of the `backtrace` crate, and then actually resolve
// everything.
let _lock = lock();
for frame in self.frames.iter_mut() {
for frame in capture.frames.iter_mut() {
let symbols = &mut frame.symbols;
let frame = match &frame.frame {
RawFrame::Actual(frame) => frame,
Expand All @@ -490,6 +456,8 @@ impl Capture {
});
}
}

capture
}
}

Expand Down
6 changes: 2 additions & 4 deletions library/std/src/backtrace/tests.rs
Original file line number Diff line number Diff line change
Expand Up @@ -43,9 +43,8 @@ fn generate_fake_frames() -> Vec<BacktraceFrame> {
#[test]
fn test_debug() {
let backtrace = Backtrace {
inner: Inner::Captured(LazilyResolvedCapture::new(Capture {
inner: Inner::Captured(LazyLock::preinit(Capture {
actual_start: 1,
resolved: true,
frames: generate_fake_frames(),
})),
};
Expand All @@ -66,9 +65,8 @@ fn test_debug() {
#[test]
fn test_frames() {
let backtrace = Backtrace {
inner: Inner::Captured(LazilyResolvedCapture::new(Capture {
inner: Inner::Captured(LazyLock::preinit(Capture {
actual_start: 1,
resolved: true,
frames: generate_fake_frames(),
})),
};
Expand Down
4 changes: 2 additions & 2 deletions library/std/src/io/util.rs
Original file line number Diff line number Diff line change
Expand Up @@ -100,7 +100,7 @@ impl SizeHint for Empty {
}
}

#[stable(feature = "empty_write", since = "1.64.0")]
#[stable(feature = "empty_write", since = "CURRENT_RUSTC_VERSION")]
impl Write for Empty {
#[inline]
fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
Expand All @@ -124,7 +124,7 @@ impl Write for Empty {
}
}

#[stable(feature = "empty_write", since = "1.64.0")]
#[stable(feature = "empty_write", since = "CURRENT_RUSTC_VERSION")]
impl Write for &Empty {
#[inline]
fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
Expand Down
1 change: 1 addition & 0 deletions library/std/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -272,6 +272,7 @@
#![feature(staged_api)]
#![feature(thread_local)]
#![feature(try_blocks)]
#![feature(type_alias_impl_trait)]
#![feature(utf8_chunks)]
// tidy-alphabetical-end
//
Expand Down
9 changes: 9 additions & 0 deletions library/std/src/sync/lazy_lock.rs
Original file line number Diff line number Diff line change
Expand Up @@ -89,6 +89,15 @@ impl<T, F: FnOnce() -> T> LazyLock<T, F> {
LazyLock { once: Once::new(), data: UnsafeCell::new(Data { f: ManuallyDrop::new(f) }) }
}

/// Creates a new lazy value that is already initialized.
#[inline]
#[cfg(test)]
pub(crate) fn preinit(value: T) -> LazyLock<T, F> {
let once = Once::new();
once.call_once(|| {});
LazyLock { once, data: UnsafeCell::new(Data { value: ManuallyDrop::new(value) }) }
}

/// Consumes this `LazyLock` returning the stored value.
///
/// Returns `Ok(value)` if `Lazy` is initialized and `Err(f)` otherwise.
Expand Down
10 changes: 10 additions & 0 deletions tests/ui/impl-trait/in-trait/check-wf-on-non-defaulted-rpitit.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,10 @@
#![feature(return_position_impl_trait_in_trait)]

struct Wrapper<G: Send>(G);

trait Foo {
fn bar() -> Wrapper<impl Sized>;
//~^ ERROR `impl Sized` cannot be sent between threads safely
}

fn main() {}
Original file line number Diff line number Diff line change
@@ -0,0 +1,16 @@
error[E0277]: `impl Sized` cannot be sent between threads safely
--> $DIR/check-wf-on-non-defaulted-rpitit.rs:6:17
|
LL | fn bar() -> Wrapper<impl Sized>;
| ^^^^^^^^^^^^^^^^^^^ `impl Sized` cannot be sent between threads safely
|
= help: the trait `Send` is not implemented for `impl Sized`
note: required by a bound in `Wrapper`
--> $DIR/check-wf-on-non-defaulted-rpitit.rs:3:19
|
LL | struct Wrapper<G: Send>(G);
| ^^^^ required by this bound in `Wrapper`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0277`.

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