Auto merge of #130907 - GuillaumeGomez:rollup-423r4i4, r=GuillaumeGomez

Rollup of 11 pull requests

Successful merges:

 - #130279 (Document subtleties of `ManuallyDrop`)
 - #130517 (Add the library workspace to the suggested rust-analyzer config)
 - #130820 (Fix diagnostics for coroutines with () as input.)
 - #130833 (Fix the misleading diagnostic for `let_underscore_drop` on type without `Drop` implementation)
 - #130845 (Utf8Chunks: add link to Utf8Chunk)
 - #130850 (Pass Module Analysis Manager to Standard Instrumentations)
 - #130861 (Use `mem::offset_of!` for `sockaddr_un.sun_path`)
 - #130862 (rustdoc: do not animate :target when user prefers reduced motion)
 - #130868 (Update FIXME comment in s390x_unknown_linux_*.rs)
 - #130879 (Pass correct HirId to late_bound_vars in diagnostic code)
 - #130880 (add missing FIXME(const-hack))

r? `@ghost`
`@rustbot` modify labels: rollup
This commit is contained in:
bors 2024-09-26 22:49:52 +00:00
commit 58420a065b
27 changed files with 281 additions and 99 deletions

View File

@ -882,7 +882,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
let ty = self.lowerer().lower_ty(hir_ty);
debug!(?ty, "return type (lowered)");
debug!(?expected, "expected type");
let bound_vars = self.tcx.late_bound_vars(hir_ty.hir_id.owner.into());
let bound_vars =
self.tcx.late_bound_vars(self.tcx.local_def_id_to_hir_id(fn_id));
let ty = Binder::bind_with_vars(ty, bound_vars);
let ty = self.normalize(hir_ty.span, ty);
let ty = self.tcx.instantiate_bound_regions_with_erased(ty);

View File

@ -531,7 +531,7 @@ lint_non_binding_let_multi_suggestion =
consider immediately dropping the value
lint_non_binding_let_on_drop_type =
non-binding let on a type that implements `Drop`
non-binding let on a type that has a destructor
lint_non_binding_let_on_sync_lock = non-binding let on a synchronization lock
.label = this lock is not assigned to a binding and is immediately dropped

View File

@ -51,7 +51,7 @@ declare_lint! {
/// intent.
pub LET_UNDERSCORE_DROP,
Allow,
"non-binding let on a type that implements `Drop`"
"non-binding let on a type that has a destructor"
}
declare_lint! {

View File

@ -732,12 +732,7 @@ extern "C" LLVMRustResult LLVMRustOptimize(
PTO.SLPVectorization = SLPVectorize;
PTO.MergeFunctions = MergeFunctions;
// FIXME: We may want to expose this as an option.
bool DebugPassManager = false;
PassInstrumentationCallbacks PIC;
StandardInstrumentations SI(TheModule->getContext(), DebugPassManager);
SI.registerCallbacks(PIC);
if (LlvmSelfProfiler) {
LLVMSelfProfileInitializeCallbacks(PIC, LlvmSelfProfiler,
@ -784,6 +779,12 @@ extern "C" LLVMRustResult LLVMRustOptimize(
CGSCCAnalysisManager CGAM;
ModuleAnalysisManager MAM;
// FIXME: We may want to expose this as an option.
bool DebugPassManager = false;
StandardInstrumentations SI(TheModule->getContext(), DebugPassManager);
SI.registerCallbacks(PIC, &MAM);
if (LLVMPluginsLen) {
auto PluginsStr = StringRef(LLVMPlugins, LLVMPluginsLen);
SmallVector<StringRef> Plugins;

View File

@ -6,9 +6,8 @@ pub(crate) fn target() -> Target {
base.endian = Endian::Big;
// z10 is the oldest CPU supported by LLVM
base.cpu = "z10".into();
// FIXME: The ABI implementation in cabi_s390x.rs is for now hard-coded to assume the no-vector
// ABI. Pass the -vector feature string to LLVM to respect this assumption. On LLVM < 16, we
// also strip v128 from the data_layout below to match the older LLVM's expectation.
// FIXME: The ABI implementation in abi/call/s390x.rs is for now hard-coded to assume the no-vector
// ABI. Pass the -vector feature string to LLVM to respect this assumption.
base.features = "-vector".into();
base.max_atomic_width = Some(128);
base.min_global_align = Some(16);

View File

@ -6,9 +6,8 @@ pub(crate) fn target() -> Target {
base.endian = Endian::Big;
// z10 is the oldest CPU supported by LLVM
base.cpu = "z10".into();
// FIXME: The ABI implementation in cabi_s390x.rs is for now hard-coded to assume the no-vector
// ABI. Pass the -vector feature string to LLVM to respect this assumption. On LLVM < 16, we
// also strip v128 from the data_layout below to match the older LLVM's expectation.
// FIXME: The ABI implementation in abi/call/s390x.rs is for now hard-coded to assume the no-vector
// ABI. Pass the -vector feature string to LLVM to respect this assumption.
base.features = "-vector".into();
base.max_atomic_width = Some(128);
base.min_global_align = Some(16);

View File

@ -2635,21 +2635,39 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
// This shouldn't be common unless manually implementing one of the
// traits manually, but don't make it more confusing when it does
// happen.
Ok(
if Some(expected_trait_ref.def_id) != self.tcx.lang_items().coroutine_trait()
&& not_tupled
if Some(expected_trait_ref.def_id) != self.tcx.lang_items().coroutine_trait() && not_tupled
{
self.report_and_explain_type_error(
TypeTrace::trait_refs(
&obligation.cause,
true,
expected_trait_ref,
found_trait_ref,
),
return Ok(self.report_and_explain_type_error(
TypeTrace::trait_refs(&obligation.cause, true, expected_trait_ref, found_trait_ref),
ty::error::TypeError::Mismatch,
)
} else if found.len() == expected.len() {
self.report_closure_arg_mismatch(
));
}
if found.len() != expected.len() {
let (closure_span, closure_arg_span, found) = found_did
.and_then(|did| {
let node = self.tcx.hir().get_if_local(did)?;
let (found_span, closure_arg_span, found) = self.get_fn_like_arguments(node)?;
Some((Some(found_span), closure_arg_span, found))
})
.unwrap_or((found_span, None, found));
// If the coroutine take a single () as its argument,
// the trait argument would found the coroutine take 0 arguments,
// but get_fn_like_arguments would give 1 argument.
// This would result in "Expected to take 1 argument, but it takes 1 argument".
// Check again to avoid this.
if found.len() != expected.len() {
return Ok(self.report_arg_count_mismatch(
span,
closure_span,
expected,
found,
found_trait_ty.is_closure(),
closure_arg_span,
));
}
}
Ok(self.report_closure_arg_mismatch(
span,
found_span,
found_trait_ref,
@ -2657,27 +2675,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
obligation.cause.code(),
found_node,
obligation.param_env,
)
} else {
let (closure_span, closure_arg_span, found) = found_did
.and_then(|did| {
let node = self.tcx.hir().get_if_local(did)?;
let (found_span, closure_arg_span, found) =
self.get_fn_like_arguments(node)?;
Some((Some(found_span), closure_arg_span, found))
})
.unwrap_or((found_span, None, found));
self.report_arg_count_mismatch(
span,
closure_span,
expected,
found,
found_trait_ty.is_closure(),
closure_arg_span,
)
},
)
))
}
/// Given some node representing a fn-like thing in the HIR map,

View File

@ -1,22 +1,21 @@
use crate::ops::{Deref, DerefMut, DerefPure};
use crate::ptr;
/// A wrapper to inhibit the compiler from automatically calling `T`s destructor.
/// This wrapper is 0-cost.
/// A wrapper to inhibit the compiler from automatically calling `T`s
/// destructor. This wrapper is 0-cost.
///
/// `ManuallyDrop<T>` is guaranteed to have the same layout and bit validity as
/// `T`, and is subject to the same layout optimizations as `T`. As a consequence,
/// it has *no effect* on the assumptions that the compiler makes about its
/// contents. For example, initializing a `ManuallyDrop<&mut T>` with [`mem::zeroed`]
/// is undefined behavior. If you need to handle uninitialized data, use
/// [`MaybeUninit<T>`] instead.
/// `T`, and is subject to the same layout optimizations as `T`. As a
/// consequence, it has *no effect* on the assumptions that the compiler makes
/// about its contents. For example, initializing a `ManuallyDrop<&mut T>` with
/// [`mem::zeroed`] is undefined behavior. If you need to handle uninitialized
/// data, use [`MaybeUninit<T>`] instead.
///
/// Note that accessing the value inside a `ManuallyDrop<T>` is safe.
/// This means that a `ManuallyDrop<T>` whose content has been dropped must not
/// be exposed through a public safe API.
/// Correspondingly, `ManuallyDrop::drop` is unsafe.
/// Note that accessing the value inside a `ManuallyDrop<T>` is safe. This means
/// that a `ManuallyDrop<T>` whose content has been dropped must not be exposed
/// through a public safe API. Correspondingly, `ManuallyDrop::drop` is unsafe.
///
/// # `ManuallyDrop` and drop order.
/// # `ManuallyDrop` and drop order
///
/// Rust has a well-defined [drop order] of values. To make sure that fields or
/// locals are dropped in a specific order, reorder the declarations such that
@ -40,9 +39,116 @@ use crate::ptr;
/// }
/// ```
///
/// # Interaction with `Box`
///
/// Currently, if you have a `ManuallyDrop<T>`, where the type `T` is a `Box` or
/// contains a `Box` inside, then dropping the `T` followed by moving the
/// `ManuallyDrop<T>` is [considered to be undefined
/// behavior](https://github.com/rust-lang/unsafe-code-guidelines/issues/245).
/// That is, the following code causes undefined behavior:
///
/// ```no_run
/// use std::mem::ManuallyDrop;
///
/// let mut x = ManuallyDrop::new(Box::new(42));
/// unsafe {
/// ManuallyDrop::drop(&mut x);
/// }
/// let y = x; // Undefined behavior!
/// ```
///
/// This is [likely to change in the
/// future](https://rust-lang.github.io/rfcs/3336-maybe-dangling.html). In the
/// meantime, consider using [`MaybeUninit`] instead.
///
/// # Safety hazards when storing `ManuallyDrop` in a struct or an enum.
///
/// Special care is needed when all of the conditions below are met:
/// * A struct or enum contains a `ManuallyDrop`.
/// * The `ManuallyDrop` is not inside a `union`.
/// * The struct or enum is part of public API, or is stored in a struct or an
/// enum that is part of public API.
/// * There is code that drops the contents of the `ManuallyDrop` field, and
/// this code is outside the struct or enum's `Drop` implementation.
///
/// In particular, the following hazards may occur:
///
/// #### Storing generic types
///
/// If the `ManuallyDrop` contains a client-supplied generic type, the client
/// might provide a `Box` as that type. This would cause undefined behavior when
/// the struct or enum is later moved, as mentioned in the previous section. For
/// example, the following code causes undefined behavior:
///
/// ```no_run
/// use std::mem::ManuallyDrop;
///
/// pub struct BadOption<T> {
/// // Invariant: Has been dropped iff `is_some` is false.
/// value: ManuallyDrop<T>,
/// is_some: bool,
/// }
/// impl<T> BadOption<T> {
/// pub fn new(value: T) -> Self {
/// Self { value: ManuallyDrop::new(value), is_some: true }
/// }
/// pub fn change_to_none(&mut self) {
/// if self.is_some {
/// self.is_some = false;
/// unsafe {
/// // SAFETY: `value` hasn't been dropped yet, as per the invariant
/// // (This is actually unsound!)
/// ManuallyDrop::drop(&mut self.value);
/// }
/// }
/// }
/// }
///
/// // In another crate:
///
/// let mut option = BadOption::new(Box::new(42));
/// option.change_to_none();
/// let option2 = option; // Undefined behavior!
/// ```
///
/// #### Deriving traits
///
/// Deriving `Debug`, `Clone`, `PartialEq`, `PartialOrd`, `Ord`, or `Hash` on
/// the struct or enum could be unsound, since the derived implementations of
/// these traits would access the `ManuallyDrop` field. For example, the
/// following code causes undefined behavior:
///
/// ```no_run
/// use std::mem::ManuallyDrop;
///
/// // This derive is unsound in combination with the `ManuallyDrop::drop` call.
/// #[derive(Debug)]
/// pub struct Foo {
/// value: ManuallyDrop<String>,
/// }
/// impl Foo {
/// pub fn new() -> Self {
/// let mut temp = Self {
/// value: ManuallyDrop::new(String::from("Unsafe rust is hard."))
/// };
/// unsafe {
/// // SAFETY: `value` hasn't been dropped yet.
/// ManuallyDrop::drop(&mut temp.value);
/// }
/// temp
/// }
/// }
///
/// // In another crate:
///
/// let foo = Foo::new();
/// println!("{:?}", foo); // Undefined behavior!
/// ```
///
/// [drop order]: https://doc.rust-lang.org/reference/destructors.html
/// [`mem::zeroed`]: crate::mem::zeroed
/// [`MaybeUninit<T>`]: crate::mem::MaybeUninit
/// [`MaybeUninit`]: crate::mem::MaybeUninit
#[stable(feature = "manually_drop", since = "1.20.0")]
#[lang = "manually_drop"]
#[derive(Copy, Clone, Debug, Default, PartialEq, Eq, PartialOrd, Ord, Hash)]

View File

@ -155,7 +155,7 @@ impl Alignment {
!(unsafe { self.as_usize().unchecked_sub(1) })
}
// Remove me once `Ord::max` is usable in const
// FIXME(const-hack) Remove me once `Ord::max` is usable in const
pub(crate) const fn max(a: Self, b: Self) -> Self {
if a.as_usize() > b.as_usize() { a } else { b }
}

View File

@ -8,6 +8,8 @@ impl [u8] {
/// Creates an iterator over the contiguous valid UTF-8 ranges of this
/// slice, and the non-UTF-8 fragments in between.
///
/// See the [`Utf8Chunk`] type for documenation of the items yielded by this iterator.
///
/// # Examples
///
/// This function formats arbitrary but mostly-UTF-8 bytes into Rust source
@ -148,6 +150,8 @@ impl fmt::Debug for Debug<'_> {
/// If you want a simple conversion from UTF-8 byte slices to string slices,
/// [`from_utf8`] is easier to use.
///
/// See the [`Utf8Chunk`] type for documenation of the items yielded by this iterator.
///
/// [byteslice]: slice
/// [`from_utf8`]: super::from_utf8
///

View File

@ -15,15 +15,12 @@ mod libc {
pub type socklen_t = u32;
pub struct sockaddr;
#[derive(Clone)]
pub struct sockaddr_un;
pub struct sockaddr_un {
pub sun_path: [u8; 1],
}
}
fn sun_path_offset(addr: &libc::sockaddr_un) -> usize {
// Work with an actual instance of the type since using a null pointer is UB
let base = (addr as *const libc::sockaddr_un).addr();
let path = core::ptr::addr_of!(addr.sun_path).addr();
path - base
}
const SUN_PATH_OFFSET: usize = mem::offset_of!(libc::sockaddr_un, sun_path);
pub(super) fn sockaddr_un(path: &Path) -> io::Result<(libc::sockaddr_un, libc::socklen_t)> {
// SAFETY: All zeros is a valid representation for `sockaddr_un`.
@ -53,7 +50,7 @@ pub(super) fn sockaddr_un(path: &Path) -> io::Result<(libc::sockaddr_un, libc::s
ptr::copy_nonoverlapping(bytes.as_ptr(), addr.sun_path.as_mut_ptr().cast(), bytes.len())
};
let mut len = sun_path_offset(&addr) + bytes.len();
let mut len = SUN_PATH_OFFSET + bytes.len();
match bytes.get(0) {
Some(&0) | None => {}
Some(_) => len += 1,
@ -114,13 +111,13 @@ impl SocketAddr {
let sun_path: &[u8] =
unsafe { mem::transmute::<&[libc::c_char], &[u8]>(&addr.sun_path) };
len = core::slice::memchr::memchr(0, sun_path)
.map_or(len, |new_len| (new_len + sun_path_offset(&addr)) as libc::socklen_t);
.map_or(len, |new_len| (new_len + SUN_PATH_OFFSET) as libc::socklen_t);
}
if len == 0 {
// When there is a datagram from unnamed unix socket
// linux returns zero bytes of address
len = sun_path_offset(&addr) as libc::socklen_t; // i.e., zero-length address
len = SUN_PATH_OFFSET as libc::socklen_t; // i.e., zero-length address
} else if addr.sun_family != libc::AF_UNIX as libc::sa_family_t {
return Err(io::const_io_error!(
io::ErrorKind::InvalidInput,
@ -238,7 +235,7 @@ impl SocketAddr {
}
fn address(&self) -> AddressKind<'_> {
let len = self.len as usize - sun_path_offset(&self.addr);
let len = self.len as usize - SUN_PATH_OFFSET;
let path = unsafe { mem::transmute::<&[libc::c_char], &[u8]>(&self.addr.sun_path) };
// macOS seems to return a len of 16 and a zeroed sun_path for unnamed addresses
@ -287,7 +284,7 @@ impl linux_ext::addr::SocketAddrExt for SocketAddr {
addr.sun_path.as_mut_ptr().add(1) as *mut u8,
name.len(),
);
let len = (sun_path_offset(&addr) + 1 + name.len()) as libc::socklen_t;
let len = (SUN_PATH_OFFSET + 1 + name.len()) as libc::socklen_t;
SocketAddr::from_parts(addr, len)
}
}

View File

@ -46,6 +46,7 @@ static SETTINGS_HASHES: &[&str] = &[
"47d227f424bf889b0d899b9cc992d5695e1b78c406e183cd78eafefbe5488923",
"b526bd58d0262dd4dda2bff5bc5515b705fb668a46235ace3e057f807963a11a",
"828666b021d837a33e78d870b56d34c88a5e2c85de58b693607ec574f0c27000",
"811fb3b063c739d261fd8590dd30242e117908f5a095d594fa04585daa18ec4d",
];
static RUST_ANALYZER_SETTINGS: &str = include_str!("../../../../etc/rust_analyzer_settings.json");

View File

@ -10,6 +10,7 @@
],
"rust-analyzer.linkedProjects": [
"Cargo.toml",
"library/Cargo.toml",
"src/tools/x/Cargo.toml",
"src/bootstrap/Cargo.toml",
"src/tools/rust-analyzer/Cargo.toml",

View File

@ -1687,7 +1687,6 @@ instead, we check that it's not a "finger" cursor.
padding-right: 3px;
background-color: var(--target-background-color);
border-right: 3px solid var(--target-border-color);
animation: 0.65s cubic-bezier(0, 0, 0.1, 1.0) 0.1s targetfadein;
}
.code-header a.tooltip {
@ -1712,12 +1711,18 @@ a.tooltip:hover::after {
content: "\00a0";
}
/* This animation is layered onto the mistake-proofing delay for dismissing
@media not (prefers-reduced-motion) {
:target {
animation: 0.65s cubic-bezier(0, 0, 0.1, 1.0) 0.1s targetfadein;
}
/* This animation is layered onto the mistake-proofing delay for dismissing
a hovered tooltip, to ensure it feels responsive even with the delay.
*/
.fade-out {
.fade-out {
opacity: 0;
transition: opacity 0.45s cubic-bezier(0, 0, 0.1, 1.0);
}
}
.popover.tooltip .content {

View File

@ -1,8 +0,0 @@
//@ known-bug: rust-lang/rust#125655
fn main() {
static foo: dyn Fn() -> u32 = || -> u32 {
...
0
};
}

View File

@ -0,0 +1,15 @@
// We used to bind the closure return type `&'a ()` with the late-bound vars of
// the owner (here `main` & `env` resp.) instead of the ones of the enclosing
// function-like / closure inside diagnostic code which was incorrect.
#![feature(closure_lifetime_binder)]
// issue: rust-lang/rust#130391
fn main() {
let _ = for<'a> |x: &'a u8| -> &'a () { x }; //~ ERROR mismatched types
}
// issue: rust-lang/rust#130663
fn env<'r>() {
let _ = for<'a> |x: &'a u8| -> &'a () { x }; //~ ERROR mismatched types
}

View File

@ -0,0 +1,25 @@
error[E0308]: mismatched types
--> $DIR/closure-return-type-mismatch.rs:9:45
|
LL | let _ = for<'a> |x: &'a u8| -> &'a () { x };
| ------ ^ expected `&()`, found `&u8`
| |
| expected `&'a ()` because of return type
|
= note: expected reference `&'a ()`
found reference `&'a u8`
error[E0308]: mismatched types
--> $DIR/closure-return-type-mismatch.rs:14:45
|
LL | let _ = for<'a> |x: &'a u8| -> &'a () { x };
| ------ ^ expected `&()`, found `&u8`
| |
| expected `&'a ()` because of return type
|
= note: expected reference `&'a ()`
found reference `&'a u8`
error: aborting due to 2 previous errors
For more information about this error, try `rustc --explain E0308`.

View File

@ -15,3 +15,7 @@ fn main() {
b
};
}
// issue: rust-lang/rust#130858 rust-lang/rust#125655
static FOO: fn() -> bool = || -> bool { 1 };
//~^ ERROR mismatched types

View File

@ -1,3 +1,11 @@
error[E0308]: mismatched types
--> $DIR/closure-return-type-mismatch.rs:20:41
|
LL | static FOO: fn() -> bool = || -> bool { 1 };
| ---- ^ expected `bool`, found integer
| |
| expected `bool` because of return type
error[E0308]: mismatched types
--> $DIR/closure-return-type-mismatch.rs:7:9
|
@ -19,6 +27,6 @@ LL | if false {
LL | return "hello"
| ^^^^^^^ expected `bool`, found `&str`
error: aborting due to 2 previous errors
error: aborting due to 3 previous errors
For more information about this error, try `rustc --explain E0308`.

View File

@ -0,0 +1,11 @@
#![feature(coroutines, coroutine_trait, stmt_expr_attributes)]
use std::ops::Coroutine;
fn foo() -> impl Coroutine<u8> {
//~^ ERROR type mismatch in coroutine arguments
#[coroutine]
|_: ()| {}
}
fn main() { }

View File

@ -0,0 +1,15 @@
error[E0631]: type mismatch in coroutine arguments
--> $DIR/arg-count-mismatch-on-unit-input.rs:5:13
|
LL | fn foo() -> impl Coroutine<u8> {
| ^^^^^^^^^^^^^^^^^^ expected due to this
...
LL | |_: ()| {}
| ------- found signature defined here
|
= note: expected coroutine signature `fn(u8) -> _`
found coroutine signature `fn(()) -> _`
error: aborting due to 1 previous error
For more information about this error, try `rustc --explain E0631`.

View File

@ -2,7 +2,7 @@
#![deny(let_underscore_drop)]
fn main() {
let _ = foo(); //~ ERROR non-binding let on a type that implements `Drop`
let _ = foo(); //~ ERROR non-binding let on a type that has a destructor
}
async fn from_config(_: Config) {}

View File

@ -1,4 +1,4 @@
error: non-binding let on a type that implements `Drop`
error: non-binding let on a type that has a destructor
--> $DIR/issue-119696-err-on-fn.rs:5:5
|
LL | let _ = foo();

View File

@ -12,9 +12,9 @@ pub fn ice_cold(beverage: Tait) {
// Must destructure at least one field of `Foo`
let Foo { field } = beverage;
// boom
_ = field; //~ ERROR non-binding let on a type that implements `Drop`
_ = field; //~ ERROR non-binding let on a type that has a destructor
let _ = field; //~ ERROR non-binding let on a type that implements `Drop`
let _ = field; //~ ERROR non-binding let on a type that has a destructor
}

View File

@ -1,4 +1,4 @@
error: non-binding let on a type that implements `Drop`
error: non-binding let on a type that has a destructor
--> $DIR/issue-119697-extra-let.rs:15:5
|
LL | _ = field;
@ -18,7 +18,7 @@ help: consider immediately dropping the value
LL | drop(field);
| ~~~~~ +
error: non-binding let on a type that implements `Drop`
error: non-binding let on a type that has a destructor
--> $DIR/issue-119697-extra-let.rs:17:5
|
LL | let _ = field;

View File

@ -10,7 +10,7 @@ impl Drop for NontrivialDrop {
}
fn main() {
let _ = NontrivialDrop; //~WARNING non-binding let on a type that implements `Drop`
let _ = NontrivialDrop; //~WARNING non-binding let on a type that has a destructor
let (_, _) = (NontrivialDrop, NontrivialDrop); // This should be ignored.
}

View File

@ -1,4 +1,4 @@
warning: non-binding let on a type that implements `Drop`
warning: non-binding let on a type that has a destructor
--> $DIR/let_underscore_drop.rs:13:5
|
LL | let _ = NontrivialDrop;