Rollup of 11 pull requests

compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs

@@ -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);

compiler/rustc_lint/messages.ftl

@@ -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

compiler/rustc_lint/src/let_underscore.rs

@@ -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! {

compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp

@@ -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;

compiler/rustc_target/src/spec/targets/s390x_unknown_linux_gnu.rs

@@ -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);

compiler/rustc_target/src/spec/targets/s390x_unknown_linux_musl.rs

@@ -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);

compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs

@@ -2635,49 +2635,47 @@ 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
-            {
-                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(
-                    span,
-                    found_span,
-                    found_trait_ref,
-                    expected_trait_ref,
-                    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(
+        if Some(expected_trait_ref.def_id) != self.tcx.lang_items().coroutine_trait() && not_tupled
+        {
+            return Ok(self.report_and_explain_type_error(
+                TypeTrace::trait_refs(&obligation.cause, true, expected_trait_ref, found_trait_ref),
+                ty::error::TypeError::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,
+            expected_trait_ref,
+            obligation.cause.code(),
+            found_node,
+            obligation.param_env,
+        ))
     }
 
     /// Given some node representing a fn-like thing in the HIR map,

library/core/src/mem/manually_drop.rs

@@ -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)]

library/core/src/ptr/alignment.rs

@@ -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 }
     }

library/core/src/str/lossy.rs

@@ -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
 ///