Auto merge of #86817 - JohnTitor:rollup-rcysc95, r=JohnTitor

Rollup of 7 pull requests

Successful merges:

 - #84029 (add `track_path::path` fn for usage in `proc_macro`s)
 - #85001 (Merge `sys_common::bytestring` back into `os_str_bytes`)
 - #86308 (Docs: clarify that certain intrinsics are not unsafe)
 - #86796 (Add a regression test for issue-70703)
 - #86803 (Remove & from Command::args calls in documentation)
 - #86807 (Fix double import in wasm thread )
 - #86813 (Add a help message to `unused_doc_comments` lint)

Failed merges:

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

10 files changed, 210 insertions, 53 deletions

diff --git a/library/core/src/intrinsics.rs b/library/core/src/intrinsics.rs
index baa0952c8bb..b4311bbe5f4 100644
--- a/library/core/src/intrinsics.rs
+++ b/library/core/src/intrinsics.rs
@@ -712,6 +712,11 @@ extern "rust-intrinsic" {
 
     /// Aborts the execution of the process.
     ///
+    /// Note that, unlike most intrinsics, this is safe to call;
+    /// it does not require an `unsafe` block.
+    /// Therefore, implementations must not require the user to uphold
+    /// any safety invariants.
+    ///
     /// A more user-friendly and stable version of this operation is
     /// [`std::process::abort`](../../std/process/fn.abort.html).
     pub fn abort() -> !;
@@ -745,6 +750,11 @@ extern "rust-intrinsic" {
     ///
     /// Any use other than with `if` statements will probably not have an effect.
     ///
+    /// Note that, unlike most intrinsics, this is safe to call;
+    /// it does not require an `unsafe` block.
+    /// Therefore, implementations must not require the user to uphold
+    /// any safety invariants.
+    ///
     /// This intrinsic does not have a stable counterpart.
     #[rustc_const_unstable(feature = "const_likely", issue = "none")]
     pub fn likely(b: bool) -> bool;
@@ -754,6 +764,11 @@ extern "rust-intrinsic" {
     ///
     /// Any use other than with `if` statements will probably not have an effect.
     ///
+    /// Note that, unlike most intrinsics, this is safe to call;
+    /// it does not require an `unsafe` block.
+    /// Therefore, implementations must not require the user to uphold
+    /// any safety invariants.
+    ///
     /// This intrinsic does not have a stable counterpart.
     #[rustc_const_unstable(feature = "const_likely", issue = "none")]
     pub fn unlikely(b: bool) -> bool;
@@ -765,6 +780,11 @@ extern "rust-intrinsic" {
 
     /// The size of a type in bytes.
     ///
+    /// Note that, unlike most intrinsics, this is safe to call;
+    /// it does not require an `unsafe` block.
+    /// Therefore, implementations must not require the user to uphold
+    /// any safety invariants.
+    ///
     /// More specifically, this is the offset in bytes between successive
     /// items of the same type, including alignment padding.
     ///
@@ -774,6 +794,11 @@ extern "rust-intrinsic" {
 
     /// The minimum alignment of a type.
     ///
+    /// Note that, unlike most intrinsics, this is safe to call;
+    /// it does not require an `unsafe` block.
+    /// Therefore, implementations must not require the user to uphold
+    /// any safety invariants.
+    ///
     /// The stabilized version of this intrinsic is [`core::mem::align_of`].
     #[rustc_const_stable(feature = "const_min_align_of", since = "1.40.0")]
     pub fn min_align_of<T>() -> usize;
@@ -796,6 +821,11 @@ extern "rust-intrinsic" {
 
     /// Gets a static string slice containing the name of a type.
     ///
+    /// Note that, unlike most intrinsics, this is safe to call;
+    /// it does not require an `unsafe` block.
+    /// Therefore, implementations must not require the user to uphold
+    /// any safety invariants.
+    ///
     /// The stabilized version of this intrinsic is [`core::any::type_name`].
     #[rustc_const_unstable(feature = "const_type_name", issue = "63084")]
     pub fn type_name<T: ?Sized>() -> &'static str;
@@ -804,6 +834,11 @@ extern "rust-intrinsic" {
     /// function will return the same value for a type regardless of whichever
     /// crate it is invoked in.
     ///
+    /// Note that, unlike most intrinsics, this is safe to call;
+    /// it does not require an `unsafe` block.
+    /// Therefore, implementations must not require the user to uphold
+    /// any safety invariants.
+    ///
     /// The stabilized version of this intrinsic is [`core::any::TypeId::of`].
     #[rustc_const_unstable(feature = "const_type_id", issue = "77125")]
     pub fn type_id<T: ?Sized + 'static>() -> u64;
@@ -829,6 +864,11 @@ extern "rust-intrinsic" {
 
     /// Gets a reference to a static `Location` indicating where it was called.
     ///
+    /// Note that, unlike most intrinsics, this is safe to call;
+    /// it does not require an `unsafe` block.
+    /// Therefore, implementations must not require the user to uphold
+    /// any safety invariants.
+    ///
     /// Consider using [`core::panic::Location::caller`] instead.
     #[rustc_const_unstable(feature = "const_caller_location", issue = "76156")]
     pub fn caller_location() -> &'static crate::panic::Location<'static>;
@@ -837,6 +877,11 @@ extern "rust-intrinsic" {
     ///
     /// This exists solely for [`mem::forget_unsized`]; normal `forget` uses
     /// `ManuallyDrop` instead.
+    ///
+    /// Note that, unlike most intrinsics, this is safe to call;
+    /// it does not require an `unsafe` block.
+    /// Therefore, implementations must not require the user to uphold
+    /// any safety invariants.
     #[rustc_const_unstable(feature = "const_intrinsic_forget", issue = "none")]
     pub fn forget<T: ?Sized>(_: T);
 
@@ -1090,6 +1135,11 @@ extern "rust-intrinsic" {
     /// If the actual type neither requires drop glue nor implements
     /// `Copy`, then the return value of this function is unspecified.
     ///
+    /// Note that, unlike most intrinsics, this is safe to call;
+    /// it does not require an `unsafe` block.
+    /// Therefore, implementations must not require the user to uphold
+    /// any safety invariants.
+    ///
     /// The stabilized version of this intrinsic is [`mem::needs_drop`](crate::mem::needs_drop).
     #[rustc_const_stable(feature = "const_needs_drop", since = "1.40.0")]
     pub fn needs_drop<T>() -> bool;
@@ -1310,21 +1360,41 @@ extern "rust-intrinsic" {
 
     /// Returns the minimum of two `f32` values.
     ///
+    /// Note that, unlike most intrinsics, this is safe to call;
+    /// it does not require an `unsafe` block.
+    /// Therefore, implementations must not require the user to uphold
+    /// any safety invariants.
+    ///
     /// The stabilized version of this intrinsic is
     /// [`f32::min`]
     pub fn minnumf32(x: f32, y: f32) -> f32;
     /// Returns the minimum of two `f64` values.
     ///
+    /// Note that, unlike most intrinsics, this is safe to call;
+    /// it does not require an `unsafe` block.
+    /// Therefore, implementations must not require the user to uphold
+    /// any safety invariants.
+    ///
     /// The stabilized version of this intrinsic is
     /// [`f64::min`]
     pub fn minnumf64(x: f64, y: f64) -> f64;
     /// Returns the maximum of two `f32` values.
     ///
+    /// Note that, unlike most intrinsics, this is safe to call;
+    /// it does not require an `unsafe` block.
+    /// Therefore, implementations must not require the user to uphold
+    /// any safety invariants.
+    ///
     /// The stabilized version of this intrinsic is
     /// [`f32::max`]
     pub fn maxnumf32(x: f32, y: f32) -> f32;
     /// Returns the maximum of two `f64` values.
     ///
+    /// Note that, unlike most intrinsics, this is safe to call;
+    /// it does not require an `unsafe` block.
+    /// Therefore, implementations must not require the user to uphold
+    /// any safety invariants.
+    ///
     /// The stabilized version of this intrinsic is
     /// [`f64::max`]
     pub fn maxnumf64(x: f64, y: f64) -> f64;
@@ -1438,6 +1508,11 @@ extern "rust-intrinsic" {
 
     /// Returns the number of bits set in an integer type `T`
     ///
+    /// Note that, unlike most intrinsics, this is safe to call;
+    /// it does not require an `unsafe` block.
+    /// Therefore, implementations must not require the user to uphold
+    /// any safety invariants.
+    ///
     /// The stabilized versions of this intrinsic are available on the integer
     /// primitives via the `count_ones` method. For example,
     /// [`u32::count_ones`]
@@ -1446,6 +1521,11 @@ extern "rust-intrinsic" {
 
     /// Returns the number of leading unset bits (zeroes) in an integer type `T`.
     ///
+    /// Note that, unlike most intrinsics, this is safe to call;
+    /// it does not require an `unsafe` block.
+    /// Therefore, implementations must not require the user to uphold
+    /// any safety invariants.
+    ///
     /// The stabilized versions of this intrinsic are available on the integer
     /// primitives via the `leading_zeros` method. For example,
     /// [`u32::leading_zeros`]
@@ -1497,6 +1577,11 @@ extern "rust-intrinsic" {
 
     /// Returns the number of trailing unset bits (zeroes) in an integer type `T`.
     ///
+    /// Note that, unlike most intrinsics, this is safe to call;
+    /// it does not require an `unsafe` block.
+    /// Therefore, implementations must not require the user to uphold
+    /// any safety invariants.
+    ///
     /// The stabilized versions of this intrinsic are available on the integer
     /// primitives via the `trailing_zeros` method. For example,
     /// [`u32::trailing_zeros`]
@@ -1548,6 +1633,11 @@ extern "rust-intrinsic" {
 
     /// Reverses the bytes in an integer type `T`.
     ///
+    /// Note that, unlike most intrinsics, this is safe to call;
+    /// it does not require an `unsafe` block.
+    /// Therefore, implementations must not require the user to uphold
+    /// any safety invariants.
+    ///
     /// The stabilized versions of this intrinsic are available on the integer
     /// primitives via the `swap_bytes` method. For example,
     /// [`u32::swap_bytes`]
@@ -1556,6 +1646,11 @@ extern "rust-intrinsic" {
 
     /// Reverses the bits in an integer type `T`.
     ///
+    /// Note that, unlike most intrinsics, this is safe to call;
+    /// it does not require an `unsafe` block.
+    /// Therefore, implementations must not require the user to uphold
+    /// any safety invariants.
+    ///
     /// The stabilized versions of this intrinsic are available on the integer
     /// primitives via the `reverse_bits` method. For example,
     /// [`u32::reverse_bits`]
@@ -1564,6 +1659,11 @@ extern "rust-intrinsic" {
 
     /// Performs checked integer addition.
     ///
+    /// Note that, unlike most intrinsics, this is safe to call;
+    /// it does not require an `unsafe` block.
+    /// Therefore, implementations must not require the user to uphold
+    /// any safety invariants.
+    ///
     /// The stabilized versions of this intrinsic are available on the integer
     /// primitives via the `overflowing_add` method. For example,
     /// [`u32::overflowing_add`]
@@ -1572,6 +1672,11 @@ extern "rust-intrinsic" {
 
     /// Performs checked integer subtraction
     ///
+    /// Note that, unlike most intrinsics, this is safe to call;
+    /// it does not require an `unsafe` block.
+    /// Therefore, implementations must not require the user to uphold
+    /// any safety invariants.
+    ///
     /// The stabilized versions of this intrinsic are available on the integer
     /// primitives via the `overflowing_sub` method. For example,
     /// [`u32::overflowing_sub`]
@@ -1580,6 +1685,11 @@ extern "rust-intrinsic" {
 
     /// Performs checked integer multiplication
     ///
+    /// Note that, unlike most intrinsics, this is safe to call;
+    /// it does not require an `unsafe` block.
+    /// Therefore, implementations must not require the user to uphold
+    /// any safety invariants.
+    ///
     /// The stabilized versions of this intrinsic are available on the integer
     /// primitives via the `overflowing_mul` method. For example,
     /// [`u32::overflowing_mul`]
@@ -1649,6 +1759,11 @@ extern "rust-intrinsic" {
 
     /// Performs rotate left.
     ///
+    /// Note that, unlike most intrinsics, this is safe to call;
+    /// it does not require an `unsafe` block.
+    /// Therefore, implementations must not require the user to uphold
+    /// any safety invariants.
+    ///
     /// The stabilized versions of this intrinsic are available on the integer
     /// primitives via the `rotate_left` method. For example,
     /// [`u32::rotate_left`]
@@ -1657,6 +1772,11 @@ extern "rust-intrinsic" {
 
     /// Performs rotate right.
     ///
+    /// Note that, unlike most intrinsics, this is safe to call;
+    /// it does not require an `unsafe` block.
+    /// Therefore, implementations must not require the user to uphold
+    /// any safety invariants.
+    ///
     /// The stabilized versions of this intrinsic are available on the integer
     /// primitives via the `rotate_right` method. For example,
     /// [`u32::rotate_right`]
@@ -1665,6 +1785,11 @@ extern "rust-intrinsic" {
 
     /// Returns (a + b) mod 2<sup>N</sup>, where N is the width of T in bits.
     ///
+    /// Note that, unlike most intrinsics, this is safe to call;
+    /// it does not require an `unsafe` block.
+    /// Therefore, implementations must not require the user to uphold
+    /// any safety invariants.
+    ///
     /// The stabilized versions of this intrinsic are available on the integer
     /// primitives via the `wrapping_add` method. For example,
     /// [`u32::wrapping_add`]
@@ -1672,6 +1797,11 @@ extern "rust-intrinsic" {
     pub fn wrapping_add<T: Copy>(a: T, b: T) -> T;
     /// Returns (a - b) mod 2<sup>N</sup>, where N is the width of T in bits.
     ///
+    /// Note that, unlike most intrinsics, this is safe to call;
+    /// it does not require an `unsafe` block.
+    /// Therefore, implementations must not require the user to uphold
+    /// any safety invariants.
+    ///
     /// The stabilized versions of this intrinsic are available on the integer
     /// primitives via the `wrapping_sub` method. For example,
     /// [`u32::wrapping_sub`]
@@ -1679,6 +1809,11 @@ extern "rust-intrinsic" {
     pub fn wrapping_sub<T: Copy>(a: T, b: T) -> T;
     /// Returns (a * b) mod 2<sup>N</sup>, where N is the width of T in bits.
     ///
+    /// Note that, unlike most intrinsics, this is safe to call;
+    /// it does not require an `unsafe` block.
+    /// Therefore, implementations must not require the user to uphold
+    /// any safety invariants.
+    ///
     /// The stabilized versions of this intrinsic are available on the integer
     /// primitives via the `wrapping_mul` method. For example,
     /// [`u32::wrapping_mul`]
@@ -1687,6 +1822,11 @@ extern "rust-intrinsic" {
 
     /// Computes `a + b`, saturating at numeric bounds.
     ///
+    /// Note that, unlike most intrinsics, this is safe to call;
+    /// it does not require an `unsafe` block.
+    /// Therefore, implementations must not require the user to uphold
+    /// any safety invariants.
+    ///
     /// The stabilized versions of this intrinsic are available on the integer
     /// primitives via the `saturating_add` method. For example,
     /// [`u32::saturating_add`]
@@ -1694,6 +1834,11 @@ extern "rust-intrinsic" {
     pub fn saturating_add<T: Copy>(a: T, b: T) -> T;
     /// Computes `a - b`, saturating at numeric bounds.
     ///
+    /// Note that, unlike most intrinsics, this is safe to call;
+    /// it does not require an `unsafe` block.
+    /// Therefore, implementations must not require the user to uphold
+    /// any safety invariants.
+    ///
     /// The stabilized versions of this intrinsic are available on the integer
     /// primitives via the `saturating_sub` method. For example,
     /// [`u32::saturating_sub`]
@@ -1703,6 +1848,11 @@ extern "rust-intrinsic" {
     /// Returns the value of the discriminant for the variant in 'v';
     /// if `T` has no discriminant, returns `0`.
     ///
+    /// Note that, unlike most intrinsics, this is safe to call;
+    /// it does not require an `unsafe` block.
+    /// Therefore, implementations must not require the user to uphold
+    /// any safety invariants.
+    ///
     /// The stabilized version of this intrinsic is [`core::mem::discriminant`].
     #[rustc_const_unstable(feature = "const_discriminant", issue = "69821")]
     pub fn discriminant_value<T>(v: &T) -> <T as DiscriminantKind>::Discriminant;
@@ -1710,6 +1860,11 @@ extern "rust-intrinsic" {
     /// Returns the number of variants of the type `T` cast to a `usize`;
     /// if `T` has no variants, returns `0`. Uninhabited variants will be counted.
     ///
+    /// Note that, unlike most intrinsics, this is safe to call;
+    /// it does not require an `unsafe` block.
+    /// Therefore, implementations must not require the user to uphold
+    /// any safety invariants.
+    ///
     /// The to-be-stabilized version of this intrinsic is [`mem::variant_count`].
     #[rustc_const_unstable(feature = "variant_count", issue = "73662")]
     pub fn variant_count<T>() -> usize;
@@ -1732,10 +1887,20 @@ extern "rust-intrinsic" {
     pub fn ptr_offset_from<T>(ptr: *const T, base: *const T) -> isize;
 
     /// See documentation of `<*const T>::guaranteed_eq` for details.
+    ///
+    /// Note that, unlike most intrinsics, this is safe to call;
+    /// it does not require an `unsafe` block.
+    /// Therefore, implementations must not require the user to uphold
+    /// any safety invariants.
     #[rustc_const_unstable(feature = "const_raw_ptr_comparison", issue = "53020")]
     pub fn ptr_guaranteed_eq<T>(ptr: *const T, other: *const T) -> bool;
 
     /// See documentation of `<*const T>::guaranteed_ne` for details.
+    ///
+    /// Note that, unlike most intrinsics, this is safe to call;
+    /// it does not require an `unsafe` block.
+    /// Therefore, implementations must not require the user to uphold
+    /// any safety invariants.
     #[rustc_const_unstable(feature = "const_raw_ptr_comparison", issue = "53020")]
     pub fn ptr_guaranteed_ne<T>(ptr: *const T, other: *const T) -> bool;
 
diff --git a/library/proc_macro/src/bridge/mod.rs b/library/proc_macro/src/bridge/mod.rs
index a2953b68564..b968d44fe48 100644
--- a/library/proc_macro/src/bridge/mod.rs
+++ b/library/proc_macro/src/bridge/mod.rs
@@ -55,6 +55,7 @@ macro_rules! with_api {
             FreeFunctions {
                 fn drop($self: $S::FreeFunctions);
                 fn track_env_var(var: &str, value: Option<&str>);
+                fn track_path(path: &str);
             },
             TokenStream {
                 fn drop($self: $S::TokenStream);
diff --git a/library/proc_macro/src/lib.rs b/library/proc_macro/src/lib.rs
index 9b155db6d7b..53fd58a29d8 100644
--- a/library/proc_macro/src/lib.rs
+++ b/library/proc_macro/src/lib.rs
@@ -1234,3 +1234,17 @@ pub mod tracked_env {
         value
     }
 }
+
+/// Tracked access to additional files.
+#[unstable(feature = "track_path", issue = "73921")]
+pub mod tracked_path {
+
+    /// Track a file explicitly.
+    ///
+    /// Commonly used for tracking asset preprocessing.
+    #[unstable(feature = "track_path", issue = "73921")]
+    pub fn path<P: AsRef<str>>(path: P) {
+        let path: &str = path.as_ref();
+        crate::bridge::client::FreeFunctions::track_path(path);
+    }
+}
diff --git a/library/std/src/process.rs b/library/std/src/process.rs
index e6f8b9cfcc7..b46d3dfc1e7 100644
--- a/library/std/src/process.rs
+++ b/library/std/src/process.rs
@@ -452,7 +452,7 @@ impl fmt::Debug for ChildStderr {
 ///
 /// let output = if cfg!(target_os = "windows") {
 ///     Command::new("cmd")
-///             .args(&["/C", "echo hello"])
+///             .args(["/C", "echo hello"])
 ///             .output()
 ///             .expect("failed to execute process")
 /// } else {
@@ -609,7 +609,7 @@ impl Command {
     /// use std::process::Command;
     ///
     /// Command::new("ls")
-    ///         .args(&["-l", "-a"])
+    ///         .args(["-l", "-a"])
     ///         .spawn()
     ///         .expect("ls command failed to start");
     /// ```
diff --git a/library/std/src/sys/wasm/atomics/thread.rs b/library/std/src/sys/wasm/atomics/thread.rs
index 09714835104..a66ab083757 100644
--- a/library/std/src/sys/wasm/atomics/thread.rs
+++ b/library/std/src/sys/wasm/atomics/thread.rs
@@ -1,4 +1,3 @@
-use super::unsupported;
 use crate::ffi::CStr;
 use crate::io;
 use crate::num::NonZeroUsize;
diff --git a/library/std/src/sys_common/bytestring.rs b/library/std/src/sys_common/bytestring.rs
deleted file mode 100644
index 97fba60c271..00000000000
--- a/library/std/src/sys_common/bytestring.rs
+++ /dev/null
@@ -1,26 +0,0 @@
-#![allow(dead_code)]
-
-#[cfg(test)]
-mod tests;
-
-use crate::fmt::{Formatter, Result, Write};
-use core::str::lossy::{Utf8Lossy, Utf8LossyChunk};
-
-pub fn debug_fmt_bytestring(slice: &[u8], f: &mut Formatter<'_>) -> Result {
-    // Writes out a valid unicode string with the correct escape sequences
-    fn write_str_escaped(f: &mut Formatter<'_>, s: &str) -> Result {
-        for c in s.chars().flat_map(|c| c.escape_debug()) {
-            f.write_char(c)?
-        }
-        Ok(())
-    }
-
-    f.write_str("\"")?;
-    for Utf8LossyChunk { valid, broken } in Utf8Lossy::from_bytes(slice).chunks() {
-        write_str_escaped(f, valid)?;
-        for b in broken {
-            write!(f, "\\x{:02X}", b)?;
-        }
-    }
-    f.write_str("\"")
-}
diff --git a/library/std/src/sys_common/bytestring/tests.rs b/library/std/src/sys_common/bytestring/tests.rs
deleted file mode 100644
index 1685f087d18..00000000000
--- a/library/std/src/sys_common/bytestring/tests.rs
+++ /dev/null
@@ -1,19 +0,0 @@
-use super::*;
-use crate::fmt::{Debug, Formatter, Result};
-
-#[test]
-fn smoke() {
-    struct Helper<'a>(&'a [u8]);
-
-    impl Debug for Helper<'_> {
-        fn fmt(&self, f: &mut Formatter<'_>) -> Result {
-            debug_fmt_bytestring(self.0, f)
-        }
-    }
-
-    let input = b"\xF0hello,\tworld";
-    let expected = r#""\xF0hello,\tworld""#;
-    let output = format!("{:?}", Helper(input));
-
-    assert!(output == expected);
-}
diff --git a/library/std/src/sys_common/mod.rs b/library/std/src/sys_common/mod.rs
index 1a9caa22c92..db83bad60d8 100644
--- a/library/std/src/sys_common/mod.rs
+++ b/library/std/src/sys_common/mod.rs
@@ -21,7 +21,6 @@
 mod tests;
 
 pub mod backtrace;
-pub mod bytestring;
 pub mod condvar;
 pub mod fs;
 pub mod io;
diff --git a/library/std/src/sys_common/os_str_bytes.rs b/library/std/src/sys_common/os_str_bytes.rs
index 470f401a6d2..569600470db 100644
--- a/library/std/src/sys_common/os_str_bytes.rs
+++ b/library/std/src/sys_common/os_str_bytes.rs
@@ -2,16 +2,18 @@
 //! systems: just a `Vec<u8>`/`[u8]`.
 
 use crate::borrow::Cow;
-
 use crate::fmt;
+use crate::fmt::Write;
 use crate::mem;
 use crate::rc::Rc;
 use crate::str;
 use crate::sync::Arc;
-use crate::sys_common::bytestring::debug_fmt_bytestring;
 use crate::sys_common::{AsInner, IntoInner};
 
-use core::str::lossy::Utf8Lossy;
+use core::str::lossy::{Utf8Lossy, Utf8LossyChunk};
+
+#[cfg(test)]
+mod tests;
 
 #[derive(Hash)]
 #[repr(transparent)]
@@ -26,7 +28,19 @@ pub struct Slice {
 
 impl fmt::Debug for Slice {
     fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
-        debug_fmt_bytestring(&self.inner, formatter)
+        // Writes out a valid unicode string with the correct escape sequences
+
+        formatter.write_str("\"")?;
+        for Utf8LossyChunk { valid, broken } in Utf8Lossy::from_bytes(&self.inner).chunks() {
+            for c in valid.chars().flat_map(|c| c.escape_debug()) {
+                formatter.write_char(c)?
+            }
+
+            for b in broken {
+                write!(formatter, "\\x{:02X}", b)?;
+            }
+        }
+        formatter.write_str("\"")
     }
 }
 
diff --git a/library/std/src/sys_common/os_str_bytes/tests.rs b/library/std/src/sys_common/os_str_bytes/tests.rs
new file mode 100644
index 00000000000..37967378155
--- /dev/null
+++ b/library/std/src/sys_common/os_str_bytes/tests.rs
@@ -0,0 +1,10 @@
+use super::*;
+
+#[test]
+fn slice_debug_output() {
+    let input = Slice::from_u8_slice(b"\xF0hello,\tworld");
+    let expected = r#""\xF0hello,\tworld""#;
+    let output = format!("{:?}", input);
+
+    assert_eq!(output, expected);
+}