Update subtree/library to 2025-10-10

core/src/iter/sources/repeat.rs

@@ -8,13 +8,17 @@ use crate::num::NonZero;
 /// Infinite iterators like `repeat()` are often used with adapters like
 /// [`Iterator::take()`], in order to make them finite.
 ///
+/// If you know the number of repetitions in advance, consider using [`repeat_n()`]
+/// instead, as it is more efficient and conveys the intent more clearly.
+///
 /// Use [`str::repeat()`] instead of this function if you just want to repeat
 /// a char/string `n` times.
 ///
 /// If the element type of the iterator you need does not implement `Clone`,
 /// or if you do not want to keep the repeated element in memory, you can
 /// instead use the [`repeat_with()`] function.
 ///
+/// [`repeat_n()`]: crate::iter::repeat_n
 /// [`repeat_with()`]: crate::iter::repeat_with
 /// [`str::repeat()`]: ../../std/primitive.str.html#method.repeat
 ///

core/src/num/f128.rs

@@ -18,6 +18,7 @@ use crate::{intrinsics, mem};
 
 /// Basic mathematical constants.
 #[unstable(feature = "f128", issue = "116909")]
+#[rustc_diagnostic_item = "f128_consts_mod"]
 pub mod consts {
     // FIXME: replace with mathematical constants from cmath.
 

core/src/num/f16.rs

@@ -20,6 +20,7 @@ use crate::{intrinsics, mem};
 
 /// Basic mathematical constants.
 #[unstable(feature = "f16", issue = "116909")]
+#[rustc_diagnostic_item = "f16_consts_mod"]
 pub mod consts {
     // FIXME: replace with mathematical constants from cmath.
 

core/src/num/f32.rs

@@ -277,6 +277,7 @@ pub const NEG_INFINITY: f32 = f32::NEG_INFINITY;
 
 /// Basic mathematical constants.
 #[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_diagnostic_item = "f32_consts_mod"]
 pub mod consts {
     // FIXME: replace with mathematical constants from cmath.
 

core/src/num/f64.rs

@@ -277,6 +277,7 @@ pub const NEG_INFINITY: f64 = f64::NEG_INFINITY;
 
 /// Basic mathematical constants.
 #[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_diagnostic_item = "f64_consts_mod"]
 pub mod consts {
     // FIXME: replace with mathematical constants from cmath.
 

core/src/panicking.rs

@@ -36,7 +36,8 @@ use crate::panic::{Location, PanicInfo};
 compile_error!(
     "panic_immediate_abort is now a real panic strategy! \
     Enable it with `panic = \"immediate-abort\"` in Cargo.toml, \
-    or with the compiler flags `-Zunstable-options -Cpanic=immediate-abort`"
+    or with the compiler flags `-Zunstable-options -Cpanic=immediate-abort`. \
+    In both cases, you still need to build core, e.g. with `-Zbuild-std`"
 );
 
 // First we define the two main entry points that all panics go through.

core/src/slice/specialize.rs

@@ -15,9 +15,54 @@ impl<T: Clone> SpecFill<T> for [T] {
 }
 
 impl<T: Copy> SpecFill<T> for [T] {
-    fn spec_fill(&mut self, value: T) {
+    default fn spec_fill(&mut self, value: T) {
         for item in self.iter_mut() {
             *item = value;
         }
     }
 }
+
+impl SpecFill<u8> for [u8] {
+    fn spec_fill(&mut self, value: u8) {
+        // SAFETY: The pointer is derived from a reference, so it's writable.
+        unsafe {
+            crate::intrinsics::write_bytes(self.as_mut_ptr(), value, self.len());
+        }
+    }
+}
+
+impl SpecFill<i8> for [i8] {
+    fn spec_fill(&mut self, value: i8) {
+        // SAFETY: The pointer is derived from a reference, so it's writable.
+        unsafe {
+            crate::intrinsics::write_bytes(self.as_mut_ptr(), value.cast_unsigned(), self.len());
+        }
+    }
+}
+
+macro spec_fill_int {
+    ($($type:ty)*) => {$(
+        impl SpecFill<$type> for [$type] {
+            #[inline]
+            fn spec_fill(&mut self, value: $type) {
+                // We always take this fastpath in Miri for long slices as the manual `for`
+                // loop can be prohibitively slow.
+                if (cfg!(miri) && self.len() > 32) || crate::intrinsics::is_val_statically_known(value) {
+                    let bytes = value.to_ne_bytes();
+                    if value == <$type>::from_ne_bytes([bytes[0]; size_of::<$type>()]) {
+                        // SAFETY: The pointer is derived from a reference, so it's writable.
+                        unsafe {
+                            crate::intrinsics::write_bytes(self.as_mut_ptr(), bytes[0], self.len());
+                        }
+                        return;
+                    }
+                }
+                for item in self.iter_mut() {
+                    *item = value;
+                }
+            }
+        }
+    )*}
+}
+
+spec_fill_int! { u16 i16 u32 i32 u64 i64 u128 i128 usize isize }

std/src/lib.rs

@@ -63,10 +63,10 @@
 //!    type, but not the all-important methods.
 //!
 //! So for example there is a [page for the primitive type
-//! `i32`](primitive::i32) that lists all the methods that can be called on
-//! 32-bit integers (very useful), and there is a [page for the module
-//! `std::i32`] that documents the constant values [`MIN`] and [`MAX`] (rarely
-//! useful).
+//! `char`](primitive::char) that lists all the methods that can be called on
+//! characters (very useful), and there is a [page for the module
+//! `std::char`] that documents iterator and error types created by these methods
+//! (rarely useful).
 //!
 //! Note the documentation for the primitives [`str`] and [`[T]`][prim@slice] (also
 //! called 'slice'). Many method calls on [`String`] and [`Vec<T>`] are actually