Auto merge of rust-lang#102632 - matthiaskrgr:rollup-h8s3zmo, r=matthiaskrgr

Rollup of 7 pull requests

Successful merges:

 - rust-lang#98218 (Document the conditional existence of `alloc::sync` and `alloc::task`.)
 - rust-lang#99216 (docs: be less harsh in wording for Vec::from_raw_parts)
 - rust-lang#99460 (docs: Improve AsRef / AsMut docs on blanket impls)
 - rust-lang#100470 (Tweak `FpCategory` example order.)
 - rust-lang#101040 (Fix `#[derive(Default)]` on a generic `#[default]` enum adding unnecessary `Default` bounds)
 - rust-lang#101308 (introduce `{char, u8}::is_ascii_octdigit`)
 - rust-lang#102486 (Add diagnostic struct for const eval error in `rustc_middle`)

Failed merges:

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

Author: bors

compiler/rustc_builtin_macros/src/deriving/bounds.rs

@@ -16,6 +16,7 @@ pub fn expand_deriving_copy(
     let trait_def = TraitDef {
         span,
         path: path_std!(marker::Copy),
+        skip_path_as_bound: false,
         additional_bounds: Vec::new(),
         generics: Bounds::empty(),
         supports_unions: true,

compiler/rustc_builtin_macros/src/deriving/clone.rs

@@ -72,6 +72,7 @@ pub fn expand_deriving_clone(
     let trait_def = TraitDef {
         span,
         path: path_std!(clone::Clone),
+        skip_path_as_bound: false,
         additional_bounds: bounds,
         generics: Bounds::empty(),
         supports_unions: true,

compiler/rustc_builtin_macros/src/deriving/cmp/eq.rs

@@ -25,6 +25,7 @@ pub fn expand_deriving_eq(
     let trait_def = TraitDef {
         span,
         path: path_std!(cmp::Eq),
+        skip_path_as_bound: false,
         additional_bounds: Vec::new(),
         generics: Bounds::empty(),
         supports_unions: true,

compiler/rustc_builtin_macros/src/deriving/cmp/ord.rs

@@ -19,6 +19,7 @@ pub fn expand_deriving_ord(
     let trait_def = TraitDef {
         span,
         path: path_std!(cmp::Ord),
+        skip_path_as_bound: false,
         additional_bounds: Vec::new(),
         generics: Bounds::empty(),
         supports_unions: false,

compiler/rustc_builtin_macros/src/deriving/cmp/partial_eq.rs

@@ -83,6 +83,7 @@ pub fn expand_deriving_partial_eq(
     let trait_def = TraitDef {
         span,
         path: path_std!(cmp::PartialEq),
+        skip_path_as_bound: false,
         additional_bounds: Vec::new(),
         generics: Bounds::empty(),
         supports_unions: false,

compiler/rustc_builtin_macros/src/deriving/cmp/partial_ord.rs

@@ -37,6 +37,7 @@ pub fn expand_deriving_partial_ord(
     let trait_def = TraitDef {
         span,
         path: path_std!(cmp::PartialOrd),
+        skip_path_as_bound: false,
         additional_bounds: vec![],
         generics: Bounds::empty(),
         supports_unions: false,

compiler/rustc_builtin_macros/src/deriving/debug.rs

@@ -20,6 +20,7 @@ pub fn expand_deriving_debug(
     let trait_def = TraitDef {
         span,
         path: path_std!(fmt::Debug),
+        skip_path_as_bound: false,
         additional_bounds: Vec::new(),
         generics: Bounds::empty(),
         supports_unions: false,

compiler/rustc_builtin_macros/src/deriving/decodable.rs

@@ -23,6 +23,7 @@ pub fn expand_deriving_rustc_decodable(
     let trait_def = TraitDef {
         span,
         path: Path::new_(vec![krate, sym::Decodable], vec![], PathKind::Global),
+        skip_path_as_bound: false,
         additional_bounds: Vec::new(),
         generics: Bounds::empty(),
         supports_unions: false,

compiler/rustc_builtin_macros/src/deriving/default.rs

@@ -24,6 +24,7 @@ pub fn expand_deriving_default(
     let trait_def = TraitDef {
         span,
         path: Path::new(vec![kw::Default, sym::Default]),
+        skip_path_as_bound: has_a_default_variant(item),
         additional_bounds: Vec::new(),
         generics: Bounds::empty(),
         supports_unions: false,
@@ -262,3 +263,22 @@ impl<'a, 'b> rustc_ast::visit::Visitor<'a> for DetectNonVariantDefaultAttr<'a, '
         }
     }
 }
+
+fn has_a_default_variant(item: &Annotatable) -> bool {
+    struct HasDefaultAttrOnVariant {
+        found: bool,
+    }
+
+    impl<'ast> rustc_ast::visit::Visitor<'ast> for HasDefaultAttrOnVariant {
+        fn visit_variant(&mut self, v: &'ast rustc_ast::Variant) {
+            if v.attrs.iter().any(|attr| attr.has_name(kw::Default)) {
+                self.found = true;
+            }
+            // no need to subrecurse.
+        }
+    }
+
+    let mut visitor = HasDefaultAttrOnVariant { found: false };
+    item.visit_with(&mut visitor);
+    visitor.found
+}

compiler/rustc_builtin_macros/src/deriving/encodable.rs

@@ -107,6 +107,7 @@ pub fn expand_deriving_rustc_encodable(
     let trait_def = TraitDef {
         span,
         path: Path::new_(vec![krate, sym::Encodable], vec![], PathKind::Global),
+        skip_path_as_bound: false,
         additional_bounds: Vec::new(),
         generics: Bounds::empty(),
         supports_unions: false,

compiler/rustc_builtin_macros/src/deriving/generic/mod.rs

@@ -174,6 +174,7 @@ use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::Span;
 use std::cell::RefCell;
 use std::iter;
+use std::ops::Not;
 use std::vec;
 use thin_vec::thin_vec;
 use ty::{Bounds, Path, Ref, Self_, Ty};
@@ -187,6 +188,9 @@ pub struct TraitDef<'a> {
     /// Path of the trait, including any type parameters
     pub path: Path,
 
+    /// Whether to skip adding the current trait as a bound to the type parameters of the type.
+    pub skip_path_as_bound: bool,
+
     /// Additional bounds required of any type parameters of the type,
     /// other than the current trait
     pub additional_bounds: Vec<Ty>,
@@ -596,7 +600,7 @@ impl<'a> TraitDef<'a> {
                         cx.trait_bound(p.to_path(cx, self.span, type_ident, generics))
                     }).chain(
                         // require the current trait
-                        iter::once(cx.trait_bound(trait_path.clone()))
+                        self.skip_path_as_bound.not().then(|| cx.trait_bound(trait_path.clone()))
                     ).chain(
                         // also add in any bounds from the declaration
                         param.bounds.iter().cloned()

compiler/rustc_builtin_macros/src/deriving/hash.rs

@@ -22,6 +22,7 @@ pub fn expand_deriving_hash(
     let hash_trait_def = TraitDef {
         span,
         path,
+        skip_path_as_bound: false,
         additional_bounds: Vec::new(),
         generics: Bounds::empty(),
         supports_unions: false,

compiler/rustc_error_messages/locales/en-US/middle.ftl

@@ -15,3 +15,6 @@ middle_previous_use_here =
 middle_limit_invalid =
     `limit` must be a non-negative integer
     .label = {$error_str}
+
+middle_const_eval_non_int =
+    constant evaluation of enum discriminant resulted in non-integer

compiler/rustc_middle/src/error.rs

@@ -48,3 +48,10 @@ pub struct LimitInvalid<'a> {
     pub value_span: Span,
     pub error_str: &'a str,
 }
+
+#[derive(Diagnostic)]
+#[diag(middle::const_eval_non_int)]
+pub struct ConstEvalNonIntError {
+    #[primary_span]
+    pub span: Span,
+}

compiler/rustc_middle/src/ty/adt.rs

@@ -458,11 +458,9 @@ impl<'tcx> AdtDef<'tcx> {
                     Some(Discr { val: b, ty })
                 } else {
                     info!("invalid enum discriminant: {:#?}", val);
-                    crate::mir::interpret::struct_error(
-                        tcx.at(tcx.def_span(expr_did)),
-                        "constant evaluation of enum discriminant resulted in non-integer",
-                    )
-                    .emit();
+                    tcx.sess.emit_err(crate::error::ConstEvalNonIntError {
+                        span: tcx.def_span(expr_did),
+                    });
                     None
                 }
             }

library/alloc/src/sync.rs

@@ -3,6 +3,10 @@
 //! Thread-safe reference-counting pointers.
 //!
 //! See the [`Arc<T>`][Arc] documentation for more details.
+//!
+//! **Note**: This module is only available on platforms that support atomic
+//! loads and stores of pointers. This may be detected at compile time using
+//! `#[cfg(target_has_atomic = "ptr")]`.
 
 use core::any::Any;
 use core::borrow;
@@ -82,6 +86,11 @@ macro_rules! acquire {
 /// [`Mutex`][mutex], [`RwLock`][rwlock], or one of the [`Atomic`][atomic]
 /// types.
 ///
+/// **Note**: This type is only available on platforms that support atomic
+/// loads and stores of pointers, which includes all platforms that support
+/// the `std` crate but not all those which only support [`alloc`](crate).
+/// This may be detected at compile time using `#[cfg(target_has_atomic = "ptr")]`.
+///
 /// ## Thread Safety
 ///
 /// Unlike [`Rc<T>`], `Arc<T>` uses atomic operations for its reference

library/alloc/src/task.rs

@@ -1,5 +1,11 @@
 #![stable(feature = "wake_trait", since = "1.51.0")]
+
 //! Types and Traits for working with asynchronous tasks.
+//!
+//! **Note**: This module is only available on platforms that support atomic
+//! loads and stores of pointers. This may be detected at compile time using
+//! `#[cfg(target_has_atomic = "ptr")]`.
+
 use core::mem::ManuallyDrop;
 use core::task::{RawWaker, RawWakerVTable, Waker};
 

library/alloc/src/vec/mod.rs

@@ -483,15 +483,13 @@ impl<T> Vec<T> {
         Self::with_capacity_in(capacity, Global)
     }
 
-    /// Creates a `Vec<T>` directly from the raw components of another vector.
+    /// Creates a `Vec<T>` directly from a pointer, a capacity, and a length.
     ///
     /// # Safety
     ///
     /// This is highly unsafe, due to the number of invariants that aren't
     /// checked:
     ///
-    /// * `ptr` needs to have been previously allocated via [`String`]/`Vec<T>`
-    ///   (at least, it's highly likely to be incorrect if it wasn't).
     /// * `T` needs to have the same alignment as what `ptr` was allocated with.
     ///   (`T` having a less strict alignment is not sufficient, the alignment really
     ///   needs to be equal to satisfy the [`dealloc`] requirement that memory must be
@@ -500,6 +498,14 @@ impl<T> Vec<T> {
     ///   to be the same size as the pointer was allocated with. (Because similar to
     ///   alignment, [`dealloc`] must be called with the same layout `size`.)
     /// * `length` needs to be less than or equal to `capacity`.
+    /// * The first `length` values must be properly initialized values of type `T`.
+    /// * `capacity` needs to be the capacity that the pointer was allocated with.
+    /// * The allocated size in bytes must be no larger than `isize::MAX`.
+    ///   See the safety documentation of [`pointer::offset`].
+    ///
+    /// These requirements are always upheld by any `ptr` that has been allocated
+    /// via `Vec<T>`. Other allocation sources are allowed if the invariants are
+    /// upheld.
     ///
     /// Violating these may cause problems like corrupting the allocator's
     /// internal data structures. For example it is normally **not** safe
@@ -551,6 +557,32 @@ impl<T> Vec<T> {
     ///     assert_eq!(rebuilt, [4, 5, 6]);
     /// }
     /// ```
+    ///
+    /// Using memory that was allocated elsewhere:
+    ///
+    /// ```rust
+    /// #![feature(allocator_api)]
+    ///
+    /// use std::alloc::{AllocError, Allocator, Global, Layout};
+    ///
+    /// fn main() {
+    ///     let layout = Layout::array::<u32>(16).expect("overflow cannot happen");
+    ///
+    ///     let vec = unsafe {
+    ///         let mem = match Global.allocate(layout) {
+    ///             Ok(mem) => mem.cast::<u32>().as_ptr(),
+    ///             Err(AllocError) => return,
+    ///         };
+    ///
+    ///         mem.write(1_000_000);
+    ///
+    ///         Vec::from_raw_parts_in(mem, 1, 16, Global)
+    ///     };
+    ///
+    ///     assert_eq!(vec, &[1_000_000]);
+    ///     assert_eq!(vec.capacity(), 16);
+    /// }
+    /// ```
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub unsafe fn from_raw_parts(ptr: *mut T, length: usize, capacity: usize) -> Self {
@@ -641,21 +673,30 @@ impl<T, A: Allocator> Vec<T, A> {
         Vec { buf: RawVec::with_capacity_in(capacity, alloc), len: 0 }
     }
 
-    /// Creates a `Vec<T, A>` directly from the raw components of another vector.
+    /// Creates a `Vec<T, A>` directly from a pointer, a capacity, a length,
+    /// and an allocator.
     ///
     /// # Safety
     ///
     /// This is highly unsafe, due to the number of invariants that aren't
     /// checked:
     ///
-    /// * `ptr` needs to have been previously allocated via [`String`]/`Vec<T>`
-    ///   (at least, it's highly likely to be incorrect if it wasn't).
-    /// * `T` needs to have the same size and alignment as what `ptr` was allocated with.
+    /// * `T` needs to have the same alignment as what `ptr` was allocated with.
     ///   (`T` having a less strict alignment is not sufficient, the alignment really
     ///   needs to be equal to satisfy the [`dealloc`] requirement that memory must be
     ///   allocated and deallocated with the same layout.)
+    /// * The size of `T` times the `capacity` (ie. the allocated size in bytes) needs
+    ///   to be the same size as the pointer was allocated with. (Because similar to
+    ///   alignment, [`dealloc`] must be called with the same layout `size`.)
     /// * `length` needs to be less than or equal to `capacity`.
-    /// * `capacity` needs to be the capacity that the pointer was allocated with.
+    /// * The first `length` values must be properly initialized values of type `T`.
+    /// * `capacity` needs to [*fit*] the layout size that the pointer was allocated with.
+    /// * The allocated size in bytes must be no larger than `isize::MAX`.
+    ///   See the safety documentation of [`pointer::offset`].
+    ///
+    /// These requirements are always upheld by any `ptr` that has been allocated
+    /// via `Vec<T, A>`. Other allocation sources are allowed if the invariants are
+    /// upheld.
     ///
     /// Violating these may cause problems like corrupting the allocator's
     /// internal data structures. For example it is **not** safe
@@ -673,6 +714,7 @@ impl<T, A: Allocator> Vec<T, A> {
     ///
     /// [`String`]: crate::string::String
     /// [`dealloc`]: crate::alloc::GlobalAlloc::dealloc
+    /// [*fit*]: crate::alloc::Allocator#memory-fitting
     ///
     /// # Examples
     ///
@@ -711,6 +753,29 @@ impl<T, A: Allocator> Vec<T, A> {
     ///     assert_eq!(rebuilt, [4, 5, 6]);
     /// }
     /// ```
+    ///
+    /// Using memory that was allocated elsewhere:
+    ///
+    /// ```rust
+    /// use std::alloc::{alloc, Layout};
+    ///
+    /// fn main() {
+    ///     let layout = Layout::array::<u32>(16).expect("overflow cannot happen");
+    ///     let vec = unsafe {
+    ///         let mem = alloc(layout).cast::<u32>();
+    ///         if mem.is_null() {
+    ///             return;
+    ///         }
+    ///
+    ///         mem.write(1_000_000);
+    ///
+    ///         Vec::from_raw_parts(mem, 1, 16)
+    ///     };
+    ///
+    ///     assert_eq!(vec, &[1_000_000]);
+    ///     assert_eq!(vec.capacity(), 16);
+    /// }
+    /// ```
     #[inline]
     #[unstable(feature = "allocator_api", issue = "32838")]
     pub unsafe fn from_raw_parts_in(ptr: *mut T, length: usize, capacity: usize, alloc: A) -> Self {

library/core/src/char/methods.rs

@@ -1444,6 +1444,38 @@ impl char {
         matches!(*self, '0'..='9')
     }
 
+    /// Checks if the value is an ASCII octal digit:
+    /// U+0030 '0' ..= U+0037 '7'.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(is_ascii_octdigit)]
+    ///
+    /// let uppercase_a = 'A';
+    /// let a = 'a';
+    /// let zero = '0';
+    /// let seven = '7';
+    /// let nine = '9';
+    /// let percent = '%';
+    /// let lf = '\n';
+    ///
+    /// assert!(!uppercase_a.is_ascii_octdigit());
+    /// assert!(!a.is_ascii_octdigit());
+    /// assert!(zero.is_ascii_octdigit());
+    /// assert!(seven.is_ascii_octdigit());
+    /// assert!(!nine.is_ascii_octdigit());
+    /// assert!(!percent.is_ascii_octdigit());
+    /// assert!(!lf.is_ascii_octdigit());
+    /// ```
+    #[must_use]
+    #[unstable(feature = "is_ascii_octdigit", issue = "101288")]
+    #[rustc_const_unstable(feature = "is_ascii_octdigit", issue = "101288")]
+    #[inline]
+    pub const fn is_ascii_octdigit(&self) -> bool {
+        matches!(*self, '0'..='7')
+    }
+
     /// Checks if the value is an ASCII hexadecimal digit:
     ///
     /// - U+0030 '0' ..= U+0039 '9', or