Auto merge of rust-lang#126300 - workingjubilee:rollup-0v2ypgt, r=workingjubilee

Rollup of 8 pull requests

Successful merges:

 - rust-lang#123374 (DOC: Add FFI example for slice::from_raw_parts())
 - rust-lang#126210 (docs(core): make more const_ptr doctests assert instead of printing)
 - rust-lang#126228 (Provide correct parent for nested anon const)
 - rust-lang#126242 (Simplify provider api to improve llvm ir)
 - rust-lang#126249 (Simplify `[T; N]::try_map` signature)
 - rust-lang#126256 (Add {{target}} substitution to compiletest)
 - rust-lang#126263 (Make issue-122805.rs big endian compatible)
 - rust-lang#126286 (Make `storage-live.rs` robust against rustc internal changes.)

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors

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,
                 }

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/error.rs

@@ -404,9 +404,9 @@ fn request_by_type_tag<'a, I>(err: &'a (impl Error + ?Sized)) -> Option<I::Reifi
 where
     I: tags::Type<'a>,
 {
-    let mut tagged = TaggedOption::<'a, I>(None);
+    let mut tagged = Tagged { tag_id: TypeId::of::<I>(), value: TaggedOption::<'a, I>(None) };
     err.provide(tagged.as_request());
-    tagged.0
+    tagged.value.0
 }
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -507,16 +507,9 @@ where
 ///
 #[unstable(feature = "error_generic_member_access", issue = "99301")]
 #[cfg_attr(not(doc), repr(transparent))] // work around https://github.com/rust-lang/rust/issues/90435
-pub struct Request<'a>(dyn Erased<'a> + 'a);
+pub struct Request<'a>(Tagged<dyn Erased<'a> + 'a>);
 
 impl<'a> Request<'a> {
-    /// Create a new `&mut Request` from a `&mut dyn Erased` trait object.
-    fn new<'b>(erased: &'b mut (dyn Erased<'a> + 'a)) -> &'b mut Request<'a> {
-        // SAFETY: transmuting `&mut (dyn Erased<'a> + 'a)` to `&mut Request<'a>` is safe since
-        // `Request` is repr(transparent).
-        unsafe { &mut *(erased as *mut dyn Erased<'a> as *mut Request<'a>) }
-    }
-
     /// Provide a value or other type with only static lifetimes.
     ///
     /// # Examples
@@ -940,37 +933,38 @@ pub(crate) mod tags {
 #[repr(transparent)]
 pub(crate) struct TaggedOption<'a, I: tags::Type<'a>>(pub Option<I::Reified>);
 
-impl<'a, I: tags::Type<'a>> TaggedOption<'a, I> {
+impl<'a, I: tags::Type<'a>> Tagged<TaggedOption<'a, I>> {
     pub(crate) fn as_request(&mut self) -> &mut Request<'a> {
-        Request::new(self as &mut (dyn Erased<'a> + 'a))
+        let erased = self as &mut Tagged<dyn Erased<'a> + 'a>;
+        // SAFETY: transmuting `&mut Tagged<dyn Erased<'a> + 'a>` to `&mut Request<'a>` is safe since
+        // `Request` is repr(transparent).
+        unsafe { &mut *(erased as *mut Tagged<dyn Erased<'a>> as *mut Request<'a>) }
     }
 }
 
 /// Represents a type-erased but identifiable object.
 ///
 /// This trait is exclusively implemented by the `TaggedOption` type.
-unsafe trait Erased<'a>: 'a {
-    /// The `TypeId` of the erased type.
-    fn tag_id(&self) -> TypeId;
-}
+unsafe trait Erased<'a>: 'a {}
 
-unsafe impl<'a, I: tags::Type<'a>> Erased<'a> for TaggedOption<'a, I> {
-    fn tag_id(&self) -> TypeId {
-        TypeId::of::<I>()
-    }
+unsafe impl<'a, I: tags::Type<'a>> Erased<'a> for TaggedOption<'a, I> {}
+
+struct Tagged<E: ?Sized> {
+    tag_id: TypeId,
+    value: E,
 }
 
-impl<'a> dyn Erased<'a> + 'a {
+impl<'a> Tagged<dyn Erased<'a> + 'a> {
     /// Returns some reference to the dynamic value if it is tagged with `I`,
     /// or `None` otherwise.
     #[inline]
     fn downcast<I>(&self) -> Option<&TaggedOption<'a, I>>
     where
         I: tags::Type<'a>,
     {
-        if self.tag_id() == TypeId::of::<I>() {
+        if self.tag_id == TypeId::of::<I>() {
             // SAFETY: Just checked whether we're pointing to an I.
-            Some(unsafe { &*(self as *const Self).cast::<TaggedOption<'a, I>>() })
+            Some(&unsafe { &*(self as *const Self).cast::<Tagged<TaggedOption<'a, I>>>() }.value)
         } else {
             None
         }
@@ -983,9 +977,12 @@ impl<'a> dyn Erased<'a> + 'a {
     where
         I: tags::Type<'a>,
     {
-        if self.tag_id() == TypeId::of::<I>() {
-            // SAFETY: Just checked whether we're pointing to an I.
-            Some(unsafe { &mut *(self as *mut Self).cast::<TaggedOption<'a, I>>() })
+        if self.tag_id == TypeId::of::<I>() {
+            Some(
+                // SAFETY: Just checked whether we're pointing to an I.
+                &mut unsafe { &mut *(self as *mut Self).cast::<Tagged<TaggedOption<'a, I>>>() }
+                    .value,
+            )
         } else {
             None
         }

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]

src/tools/compiletest/src/header.rs

@@ -1281,6 +1281,7 @@ fn expand_variables(mut value: String, config: &Config) -> String {
     const BUILD_BASE: &str = "{{build-base}}";
     const SYSROOT_BASE: &str = "{{sysroot-base}}";
     const TARGET_LINKER: &str = "{{target-linker}}";
+    const TARGET: &str = "{{target}}";
 
     if value.contains(CWD) {
         let cwd = env::current_dir().unwrap();
@@ -1303,6 +1304,10 @@ fn expand_variables(mut value: String, config: &Config) -> String {
         value = value.replace(TARGET_LINKER, config.target_linker.as_deref().unwrap_or(""));
     }
 
+    if value.contains(TARGET) {
+        value = value.replace(TARGET, &config.target);
+    }
+
     value
 }