Rollup of 10 pull requests

compiler/rustc_codegen_cranelift/patches/0029-stdlib-rawdylib-processprng.patch

@@ -12,7 +12,7 @@ diff --git a/library/std/src/sys/pal/windows/c.rs b/library/std/src/sys/pal/wind
 index ad8e01bfa9b..9ca8e4c16ce 100644
 --- a/library/std/src/sys/pal/windows/c.rs
 +++ b/library/std/src/sys/pal/windows/c.rs
-@@ -323,7 +323,7 @@ pub unsafe fn NtWriteFile(
+@@ -312,7 +312,7 @@ pub unsafe fn NtWriteFile(
 
  // Use raw-dylib to import ProcessPrng as we can't rely on there being an import library.
  cfg_if::cfg_if! {
@@ -26,8 +26,8 @@ index e427546222a..f2fe42a4d51 100644
 --- a/library/std/src/sys/pal/windows/rand.rs
 +++ b/library/std/src/sys/pal/windows/rand.rs
 @@ -2,7 +2,7 @@
- use core::mem;
- use core::ptr;
+
+ use crate::sys::c;
 
 -#[cfg(not(target_vendor = "win7"))]
 +#[cfg(any())]

compiler/rustc_hir/src/hir.rs

@@ -1038,6 +1038,7 @@ pub struct Block<'hir> {
     pub hir_id: HirId,
     /// Distinguishes between `unsafe { ... }` and `{ ... }`.
     pub rules: BlockCheckMode,
+    /// The span includes the curly braces `{` and `}` around the block.
     pub span: Span,
     /// If true, then there may exist `break 'a` values that aim to
     /// break out of this block early.

compiler/rustc_hir_analysis/src/collect/generics_of.rs

@@ -11,6 +11,7 @@ use rustc_session::lint;
 use rustc_span::symbol::{kw, Symbol};
 use rustc_span::Span;
 
+#[instrument(level = "debug", skip(tcx))]
 pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
     use rustc_hir::*;
 
@@ -66,7 +67,22 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
         // FIXME(#43408) always enable this once `lazy_normalization` is
         // stable enough and does not need a feature gate anymore.
         Node::AnonConst(_) => {
-            let parent_def_id = tcx.hir().get_parent_item(hir_id);
+            let parent_did = tcx.parent(def_id.to_def_id());
+
+            // We don't do this unconditionally because the `DefId` parent of an anon const
+            // might be an implicitly created closure during `async fn` desugaring. This would
+            // have the wrong generics.
+            //
+            // i.e. `async fn foo<'a>() { let a = [(); { 1 + 2 }]; bar().await() }`
+            // would implicitly have a closure in its body that would be the parent of
+            // the `{ 1 + 2 }` anon const. This closure's generics is simply a witness
+            // instead of `['a]`.
+            let parent_did = if let DefKind::AnonConst = tcx.def_kind(parent_did) {
+                parent_did
+            } else {
+                tcx.hir().get_parent_item(hir_id).to_def_id()
+            };
+            debug!(?parent_did);
 
             let mut in_param_ty = false;
             for (_parent, node) in tcx.hir().parent_iter(hir_id) {
@@ -121,7 +137,7 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
                     //
                     // This has some implications for how we get the predicates available to the anon const
                     // see `explicit_predicates_of` for more information on this
-                    let generics = tcx.generics_of(parent_def_id.to_def_id());
+                    let generics = tcx.generics_of(parent_did);
                     let param_def_idx = generics.param_def_id_to_index[&param_id.to_def_id()];
                     // In the above example this would be .params[..N#0]
                     let own_params = generics.params_to(param_def_idx as usize, tcx).to_owned();
@@ -147,7 +163,7 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
                     //
                     // Note that we do not supply the parent generics when using
                     // `min_const_generics`.
-                    Some(parent_def_id.to_def_id())
+                    Some(parent_did)
                 }
             } else {
                 let parent_node = tcx.parent_hir_node(hir_id);
@@ -159,7 +175,7 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
                     Node::Expr(Expr { kind: ExprKind::Repeat(_, constant), .. })
                         if constant.hir_id() == hir_id =>
                     {
-                        Some(parent_def_id.to_def_id())
+                        Some(parent_did)
                     }
                     // Exclude `GlobalAsm` here which cannot have generics.
                     Node::Expr(&Expr { kind: ExprKind::InlineAsm(asm), .. })
@@ -171,7 +187,7 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
                             _ => false,
                         }) =>
                     {
-                        Some(parent_def_id.to_def_id())
+                        Some(parent_did)
                     }
                     _ => None,
                 }

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

@@ -4587,6 +4587,47 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
             _ => "/* value */".to_string(),
         })
     }
+
+    fn suggest_add_result_as_return_type(
+        &self,
+        obligation: &PredicateObligation<'tcx>,
+        err: &mut Diag<'_>,
+        trait_ref: ty::PolyTraitRef<'tcx>,
+    ) {
+        if ObligationCauseCode::QuestionMark != *obligation.cause.code().peel_derives() {
+            return;
+        }
+
+        let node = self.tcx.hir_node_by_def_id(obligation.cause.body_id);
+        if let hir::Node::Item(item) = node
+            && let hir::ItemKind::Fn(sig, _, body_id) = item.kind
+            && let hir::FnRetTy::DefaultReturn(ret_span) = sig.decl.output
+            && self.tcx.is_diagnostic_item(sym::FromResidual, trait_ref.def_id())
+            && let ty::Tuple(l) = trait_ref.skip_binder().args.type_at(0).kind()
+            && l.len() == 0
+            && let ty::Adt(def, _) = trait_ref.skip_binder().args.type_at(1).kind()
+            && self.tcx.is_diagnostic_item(sym::Result, def.did())
+        {
+            let body = self.tcx.hir().body(body_id);
+            let mut sugg_spans =
+                vec![(ret_span, " -> Result<(), Box<dyn std::error::Error>>".to_string())];
+
+            if let hir::ExprKind::Block(b, _) = body.value.kind
+                && b.expr.is_none()
+            {
+                sugg_spans.push((
+                    // The span will point to the closing curly brace `}` of the block.
+                    b.span.shrink_to_hi().with_lo(b.span.hi() - BytePos(1)),
+                    "\n    Ok(())\n}".to_string(),
+                ));
+            }
+            err.multipart_suggestion_verbose(
+                format!("consider adding return type"),
+                sugg_spans,
+                Applicability::MaybeIncorrect,
+            );
+        }
+    }
 }
 
 /// Add a hint to add a missing borrow or remove an unnecessary one.

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

@@ -611,6 +611,10 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                             &mut err,
                             trait_predicate,
                         );
+                        self.suggest_add_result_as_return_type(&obligation,
+                            &mut err,
+                            trait_ref);
+
                         if self.suggest_add_reference_to_arg(
                             &obligation,
                             &mut err,

library/core/src/array/mod.rs

@@ -533,11 +533,9 @@ impl<T, const N: usize> [T; N] {
     /// assert_eq!(c, Some(a));
     /// ```
     #[unstable(feature = "array_try_map", issue = "79711")]
-    pub fn try_map<F, R>(self, f: F) -> ChangeOutputType<R, [R::Output; N]>
+    pub fn try_map<R>(self, f: impl FnMut(T) -> R) -> ChangeOutputType<R, [R::Output; N]>
     where
-        F: FnMut(T) -> R,
-        R: Try,
-        R::Residual: Residual<[R::Output; N]>,
+        R: Try<Residual: Residual<[R::Output; N]>>,
     {
         drain_array_with(self, |iter| try_from_trusted_iterator(iter.map(f)))
     }

library/core/src/ops/try_trait.rs

@@ -363,7 +363,9 @@ pub trait Residual<O> {
 }
 
 #[unstable(feature = "pub_crate_should_not_need_unstable_attr", issue = "none")]
-pub(crate) type ChangeOutputType<T, V> = <<T as Try>::Residual as Residual<V>>::TryType;
+#[allow(type_alias_bounds)]
+pub(crate) type ChangeOutputType<T: Try<Residual: Residual<V>>, V> =
+    <T::Residual as Residual<V>>::TryType;
 
 /// An adapter for implementing non-try methods via the `Try` implementation.
 ///

library/core/src/ptr/const_ptr.rs

@@ -330,7 +330,7 @@ impl<T: ?Sized> *const T {
     ///
     /// unsafe {
     ///     if let Some(val_back) = ptr.as_ref() {
-    ///         println!("We got back the value: {val_back}!");
+    ///         assert_eq!(val_back, &10);
     ///     }
     /// }
     /// ```
@@ -346,7 +346,7 @@ impl<T: ?Sized> *const T {
     ///
     /// unsafe {
     ///     let val_back = &*ptr;
-    ///     println!("We got back the value: {val_back}!");
+    ///     assert_eq!(val_back, &10);
     /// }
     /// ```
     #[stable(feature = "ptr_as_ref", since = "1.9.0")]
@@ -393,7 +393,7 @@ impl<T: ?Sized> *const T {
     /// let ptr: *const u8 = &10u8 as *const u8;
     ///
     /// unsafe {
-    ///     println!("We got back the value: {}!", ptr.as_ref_unchecked());
+    ///     assert_eq!(ptr.as_ref_unchecked(), &10);
     /// }
     /// ```
     // FIXME: mention it in the docs for `as_ref` and `as_uninit_ref` once stabilized.
@@ -439,7 +439,7 @@ impl<T: ?Sized> *const T {
     ///
     /// unsafe {
     ///     if let Some(val_back) = ptr.as_uninit_ref() {
-    ///         println!("We got back the value: {}!", val_back.assume_init());
+    ///         assert_eq!(val_back.assume_init(), 10);
     ///     }
     /// }
     /// ```
@@ -501,8 +501,8 @@ impl<T: ?Sized> *const T {
     /// let ptr: *const u8 = s.as_ptr();
     ///
     /// unsafe {
-    ///     println!("{}", *ptr.offset(1) as char);
-    ///     println!("{}", *ptr.offset(2) as char);
+    ///     assert_eq!(*ptr.offset(1) as char, '2');
+    ///     assert_eq!(*ptr.offset(2) as char, '3');
     /// }
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
@@ -573,19 +573,21 @@ impl<T: ?Sized> *const T {
     /// # Examples
     ///
     /// ```
+    /// # use std::fmt::Write;
     /// // Iterate using a raw pointer in increments of two elements
     /// let data = [1u8, 2, 3, 4, 5];
     /// let mut ptr: *const u8 = data.as_ptr();
     /// let step = 2;
     /// let end_rounded_up = ptr.wrapping_offset(6);
     ///
-    /// // This loop prints "1, 3, 5, "
+    /// let mut out = String::new();
     /// while ptr != end_rounded_up {
     ///     unsafe {
-    ///         print!("{}, ", *ptr);
+    ///         write!(&mut out, "{}, ", *ptr).unwrap();
     ///     }
     ///     ptr = ptr.wrapping_offset(step);
     /// }
+    /// assert_eq!(out.as_str(), "1, 3, 5, ");
     /// ```
     #[stable(feature = "ptr_wrapping_offset", since = "1.16.0")]
     #[must_use = "returns a new pointer rather than modifying its argument"]
@@ -988,8 +990,8 @@ impl<T: ?Sized> *const T {
     /// let ptr: *const u8 = s.as_ptr();
     ///
     /// unsafe {
-    ///     println!("{}", *ptr.add(1) as char);
-    ///     println!("{}", *ptr.add(2) as char);
+    ///     assert_eq!(*ptr.add(1), b'2');
+    ///     assert_eq!(*ptr.add(2), b'3');
     /// }
     /// ```
     #[stable(feature = "pointer_methods", since = "1.26.0")]
@@ -1073,8 +1075,8 @@ impl<T: ?Sized> *const T {
     ///
     /// unsafe {
     ///     let end: *const u8 = s.as_ptr().add(3);
-    ///     println!("{}", *end.sub(1) as char);
-    ///     println!("{}", *end.sub(2) as char);
+    ///     assert_eq!(*end.sub(1), b'3');
+    ///     assert_eq!(*end.sub(2), b'2');
     /// }
     /// ```
     #[stable(feature = "pointer_methods", since = "1.26.0")]
@@ -1155,19 +1157,21 @@ impl<T: ?Sized> *const T {
     /// # Examples
     ///
     /// ```
+    /// # use std::fmt::Write;
     /// // Iterate using a raw pointer in increments of two elements
     /// let data = [1u8, 2, 3, 4, 5];
     /// let mut ptr: *const u8 = data.as_ptr();
     /// let step = 2;
     /// let end_rounded_up = ptr.wrapping_add(6);
     ///
-    /// // This loop prints "1, 3, 5, "
+    /// let mut out = String::new();
     /// while ptr != end_rounded_up {
     ///     unsafe {
-    ///         print!("{}, ", *ptr);
+    ///         write!(&mut out, "{}, ", *ptr).unwrap();
     ///     }
     ///     ptr = ptr.wrapping_add(step);
     /// }
+    /// assert_eq!(out, "1, 3, 5, ");
     /// ```
     #[stable(feature = "pointer_methods", since = "1.26.0")]
     #[must_use = "returns a new pointer rather than modifying its argument"]
@@ -1234,19 +1238,21 @@ impl<T: ?Sized> *const T {
     /// # Examples
     ///
     /// ```
+    /// # use std::fmt::Write;
     /// // Iterate using a raw pointer in increments of two elements (backwards)
     /// let data = [1u8, 2, 3, 4, 5];
     /// let mut ptr: *const u8 = data.as_ptr();
     /// let start_rounded_down = ptr.wrapping_sub(2);
     /// ptr = ptr.wrapping_add(4);
     /// let step = 2;
-    /// // This loop prints "5, 3, 1, "
+    /// let mut out = String::new();
     /// while ptr != start_rounded_down {
     ///     unsafe {
-    ///         print!("{}, ", *ptr);
+    ///         write!(&mut out, "{}, ", *ptr).unwrap();
     ///     }
     ///     ptr = ptr.wrapping_sub(step);
     /// }
+    /// assert_eq!(out, "5, 3, 1, ");
     /// ```
     #[stable(feature = "pointer_methods", since = "1.26.0")]
     #[must_use = "returns a new pointer rather than modifying its argument"]

library/core/src/slice/raw.rs

@@ -82,6 +82,39 @@ use crate::ub_checks;
 /// }
 /// ```
 ///
+/// ### FFI: Handling null pointers
+///
+/// In languages such as C++, pointers to empty collections are not guaranteed to be non-null.
+/// When accepting such pointers, they have to be checked for null-ness to avoid undefined
+/// behavior.
+///
+/// ```
+/// use std::slice;
+///
+/// /// Sum the elements of an FFI slice.
+/// ///
+/// /// # Safety
+/// ///
+/// /// If ptr is not NULL, it must be correctly aligned and
+/// /// point to `len` initialized items of type `f32`.
+/// unsafe extern "C" fn sum_slice(ptr: *const f32, len: usize) -> f32 {
+///     let data = if ptr.is_null() {
+///         // `len` is assumed to be 0.
+///         &[]
+///     } else {
+///         // SAFETY: see function docstring.
+///         unsafe { slice::from_raw_parts(ptr, len) }
+///     };
+///     data.into_iter().sum()
+/// }
+///
+/// // This could be the result of C++'s std::vector::data():
+/// let ptr = std::ptr::null();
+/// // And this could be std::vector::size():
+/// let len = 0;
+/// assert_eq!(unsafe { sum_slice(ptr, len) }, 0.0);
+/// ```
+///
 /// [valid]: ptr#safety
 /// [`NonNull::dangling()`]: ptr::NonNull::dangling
 #[inline]

library/std/src/env.rs

@@ -323,8 +323,10 @@ impl Error for VarError {
 /// This function is also always safe to call on Windows, in single-threaded
 /// and multi-threaded programs.
 ///
-/// In multi-threaded programs on other operating systems, we strongly suggest
-/// not using `set_var` or `remove_var` at all. The exact requirement is: you
+/// In multi-threaded programs on other operating systems, the only safe option is
+/// to not use `set_var` or `remove_var` at all.
+///
+/// The exact requirement is: you
 /// must ensure that there are no other threads concurrently writing or
 /// *reading*(!) the environment through functions or global variables other
 /// than the ones in this module. The problem is that these operating systems
@@ -390,8 +392,10 @@ unsafe fn _set_var(key: &OsStr, value: &OsStr) {
 /// This function is also always safe to call on Windows, in single-threaded
 /// and multi-threaded programs.
 ///
-/// In multi-threaded programs on other operating systems, we strongly suggest
-/// not using `set_var` or `remove_var` at all. The exact requirement is: you
+/// In multi-threaded programs on other operating systems, the only safe option is
+/// to not use `set_var` or `remove_var` at all.
+///
+/// The exact requirement is: you
 /// must ensure that there are no other threads concurrently writing or
 /// *reading*(!) the environment through functions or global variables other
 /// than the ones in this module. The problem is that these operating systems

library/std/src/sys/pal/windows/rand.rs

@@ -1,6 +1,6 @@
+use core::{mem, ptr};
+
 use crate::sys::c;
-use core::mem;
-use core::ptr;
 
 #[cfg(not(target_vendor = "win7"))]
 #[inline]