Auto merge of rust-lang#136534 - jhpratt:rollup-dnz57dq, r=jhpratt

Rollup of 6 pull requests

Successful merges:

 - rust-lang#136398 (add UnsafeCell direct access APIs)
 - rust-lang#136465 (Some `rustc_middle` cleanups)
 - rust-lang#136479 (std::fs: further simplify dirent64 handling)
 - rust-lang#136504 (Fix last compare-mode false negatives in tests)
 - rust-lang#136511 (Add `cast_signed` and `cast_unsigned` methods for `NonZero` types)
 - rust-lang#136518 (Add note about `FnPtr` trait being exposed as public bound)

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

Author: bors

core/src/cell.rs

@@ -2118,6 +2118,35 @@ impl<T> UnsafeCell<T> {
     pub const fn into_inner(self) -> T {
         self.value
     }
+
+    /// Replace the value in this `UnsafeCell` and return the old value.
+    ///
+    /// # Safety
+    ///
+    /// The caller must take care to avoid aliasing and data races.
+    ///
+    /// - It is Undefined Behavior to allow calls to race with
+    ///   any other access to the wrapped value.
+    /// - It is Undefined Behavior to call this while any other
+    ///   reference(s) to the wrapped value are alive.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(unsafe_cell_access)]
+    /// use std::cell::UnsafeCell;
+    ///
+    /// let uc = UnsafeCell::new(5);
+    ///
+    /// let old = unsafe { uc.replace(10) };
+    /// assert_eq!(old, 5);
+    /// ```
+    #[inline]
+    #[unstable(feature = "unsafe_cell_access", issue = "136327")]
+    pub const unsafe fn replace(&self, value: T) -> T {
+        // SAFETY: pointer comes from `&self` so naturally satisfies invariants.
+        unsafe { ptr::replace(self.get(), value) }
+    }
 }
 
 impl<T: ?Sized> UnsafeCell<T> {
@@ -2230,6 +2259,61 @@ impl<T: ?Sized> UnsafeCell<T> {
         // no guarantee for user code that this will work in future versions of the compiler!
         this as *const T as *mut T
     }
+
+    /// Get a shared reference to the value within the `UnsafeCell`.
+    ///
+    /// # Safety
+    ///
+    /// - It is Undefined Behavior to call this while any mutable
+    ///   reference to the wrapped value is alive.
+    /// - Mutating the wrapped value while the returned
+    ///   reference is alive is Undefined Behavior.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(unsafe_cell_access)]
+    /// use std::cell::UnsafeCell;
+    ///
+    /// let uc = UnsafeCell::new(5);
+    ///
+    /// let val = unsafe { uc.as_ref_unchecked() };
+    /// assert_eq!(val, &5);
+    /// ```
+    #[inline]
+    #[unstable(feature = "unsafe_cell_access", issue = "136327")]
+    pub const unsafe fn as_ref_unchecked(&self) -> &T {
+        // SAFETY: pointer comes from `&self` so naturally satisfies ptr-to-ref invariants.
+        unsafe { self.get().as_ref_unchecked() }
+    }
+
+    /// Get an exclusive reference to the value within the `UnsafeCell`.
+    ///
+    /// # Safety
+    ///
+    /// - It is Undefined Behavior to call this while any other
+    ///   reference(s) to the wrapped value are alive.
+    /// - Mutating the wrapped value through other means while the
+    ///   returned reference is alive is Undefined Behavior.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(unsafe_cell_access)]
+    /// use std::cell::UnsafeCell;
+    ///
+    /// let uc = UnsafeCell::new(5);
+    ///
+    /// unsafe { *uc.as_mut_unchecked() += 1; }
+    /// assert_eq!(uc.into_inner(), 6);
+    /// ```
+    #[inline]
+    #[unstable(feature = "unsafe_cell_access", issue = "136327")]
+    #[allow(clippy::mut_from_ref)]
+    pub const unsafe fn as_mut_unchecked(&self) -> &mut T {
+        // SAFETY: pointer comes from `&self` so naturally satisfies ptr-to-ref invariants.
+        unsafe { self.get().as_mut_unchecked() }
+    }
 }
 
 #[stable(feature = "unsafe_cell_default", since = "1.10.0")]

core/src/marker.rs

@@ -1077,6 +1077,9 @@ marker_impls! {
 }
 
 /// A common trait implemented by all function pointers.
+//
+// Note that while the trait is internal and unstable it is nevertheless
+// exposed as a public bound of the stable `core::ptr::fn_addr_eq` function.
 #[unstable(
     feature = "fn_ptr_trait",
     issue = "none",

core/src/num/nonzero.rs

@@ -474,6 +474,7 @@ macro_rules! nonzero_integer {
         #[$stability:meta]
         Self = $Ty:ident,
         Primitive = $signedness:ident $Int:ident,
+        SignedPrimitive = $Sint:ty,
         UnsignedPrimitive = $Uint:ty,
 
         // Used in doc comments.
@@ -905,6 +906,7 @@ macro_rules! nonzero_integer {
 
             nonzero_integer_signedness_dependent_methods! {
                 Primitive = $signedness $Int,
+                SignedPrimitive = $Sint,
                 UnsignedPrimitive = $Uint,
             }
 
@@ -1128,6 +1130,7 @@ macro_rules! nonzero_integer {
     (
         Self = $Ty:ident,
         Primitive = unsigned $Int:ident,
+        SignedPrimitive = $Sint:ident,
         rot = $rot:literal,
         rot_op = $rot_op:literal,
         rot_result = $rot_result:literal,
@@ -1140,6 +1143,7 @@ macro_rules! nonzero_integer {
             #[stable(feature = "nonzero", since = "1.28.0")]
             Self = $Ty,
             Primitive = unsigned $Int,
+            SignedPrimitive = $Sint,
             UnsignedPrimitive = $Int,
             rot = $rot,
             rot_op = $rot_op,
@@ -1154,7 +1158,7 @@ macro_rules! nonzero_integer {
     (
         Self = $Ty:ident,
         Primitive = signed $Int:ident,
-        UnsignedPrimitive = $UInt:ident,
+        UnsignedPrimitive = $Uint:ident,
         rot = $rot:literal,
         rot_op = $rot_op:literal,
         rot_result = $rot_result:literal,
@@ -1166,7 +1170,8 @@ macro_rules! nonzero_integer {
             #[stable(feature = "signed_nonzero", since = "1.34.0")]
             Self = $Ty,
             Primitive = signed $Int,
-            UnsignedPrimitive = $UInt,
+            SignedPrimitive = $Int,
+            UnsignedPrimitive = $Uint,
             rot = $rot,
             rot_op = $rot_op,
             rot_result = $rot_result,
@@ -1286,6 +1291,7 @@ macro_rules! nonzero_integer_signedness_dependent_methods {
     // Associated items for unsigned nonzero types only.
     (
         Primitive = unsigned $Int:ident,
+        SignedPrimitive = $Sint:ty,
         UnsignedPrimitive = $Uint:ty,
     ) => {
         /// The smallest value that can be represented by this non-zero
@@ -1620,11 +1626,35 @@ macro_rules! nonzero_integer_signedness_dependent_methods {
             // results will be sqrt(1), which is 1, so a result can't be zero.
             unsafe { Self::new_unchecked(result) }
         }
+
+        /// Returns the bit pattern of `self` reinterpreted as a signed integer of the same size.
+        ///
+        /// # Examples
+        ///
+        /// Basic usage:
+        ///
+        /// ```
+        /// #![feature(integer_sign_cast)]
+        /// # use std::num::NonZero;
+        ///
+        #[doc = concat!("let n = NonZero::<", stringify!($Int), ">::MAX;")]
+        ///
+        #[doc = concat!("assert_eq!(n.cast_signed(), NonZero::new(-1", stringify!($Sint), ").unwrap());")]
+        /// ```
+        #[unstable(feature = "integer_sign_cast", issue = "125882")]
+        #[must_use = "this returns the result of the operation, \
+                      without modifying the original"]
+        #[inline(always)]
+        pub const fn cast_signed(self) -> NonZero<$Sint> {
+            // SAFETY: `self.get()` can't be zero
+            unsafe { NonZero::new_unchecked(self.get().cast_signed()) }
+        }
     };
 
     // Associated items for signed nonzero types only.
     (
         Primitive = signed $Int:ident,
+        SignedPrimitive = $Sint:ty,
         UnsignedPrimitive = $Uint:ty,
     ) => {
         /// The smallest value that can be represented by this non-zero
@@ -2035,12 +2065,37 @@ macro_rules! nonzero_integer_signedness_dependent_methods {
             // SAFETY: negation of nonzero cannot yield zero values.
             unsafe { Self::new_unchecked(result) }
         }
+
+        /// Returns the bit pattern of `self` reinterpreted as an unsigned integer of the same size.
+        ///
+        /// # Examples
+        ///
+        /// Basic usage:
+        ///
+        /// ```
+        /// #![feature(integer_sign_cast)]
+        /// # use std::num::NonZero;
+        ///
+        #[doc = concat!("let n = NonZero::new(-1", stringify!($Int), ").unwrap();")]
+        ///
+        #[doc = concat!("assert_eq!(n.cast_unsigned(), NonZero::<", stringify!($Uint), ">::MAX);")]
+        /// ```
+        #[unstable(feature = "integer_sign_cast", issue = "125882")]
+        #[must_use = "this returns the result of the operation, \
+                      without modifying the original"]
+        #[inline(always)]
+        pub const fn cast_unsigned(self) -> NonZero<$Uint> {
+            // SAFETY: `self.get()` can't be zero
+            unsafe { NonZero::new_unchecked(self.get().cast_unsigned()) }
+        }
+
     };
 }
 
 nonzero_integer! {
     Self = NonZeroU8,
     Primitive = unsigned u8,
+    SignedPrimitive = i8,
     rot = 2,
     rot_op = "0x82",
     rot_result = "0xa",
@@ -2052,6 +2107,7 @@ nonzero_integer! {
 nonzero_integer! {
     Self = NonZeroU16,
     Primitive = unsigned u16,
+    SignedPrimitive = i16,
     rot = 4,
     rot_op = "0xa003",
     rot_result = "0x3a",
@@ -2063,6 +2119,7 @@ nonzero_integer! {
 nonzero_integer! {
     Self = NonZeroU32,
     Primitive = unsigned u32,
+    SignedPrimitive = i32,
     rot = 8,
     rot_op = "0x10000b3",
     rot_result = "0xb301",
@@ -2074,6 +2131,7 @@ nonzero_integer! {
 nonzero_integer! {
     Self = NonZeroU64,
     Primitive = unsigned u64,
+    SignedPrimitive = i64,
     rot = 12,
     rot_op = "0xaa00000000006e1",
     rot_result = "0x6e10aa",
@@ -2085,6 +2143,7 @@ nonzero_integer! {
 nonzero_integer! {
     Self = NonZeroU128,
     Primitive = unsigned u128,
+    SignedPrimitive = i128,
     rot = 16,
     rot_op = "0x13f40000000000000000000000004f76",
     rot_result = "0x4f7613f4",
@@ -2097,6 +2156,7 @@ nonzero_integer! {
 nonzero_integer! {
     Self = NonZeroUsize,
     Primitive = unsigned usize,
+    SignedPrimitive = isize,
     rot = 4,
     rot_op = "0xa003",
     rot_result = "0x3a",
@@ -2109,6 +2169,7 @@ nonzero_integer! {
 nonzero_integer! {
     Self = NonZeroUsize,
     Primitive = unsigned usize,
+    SignedPrimitive = isize,
     rot = 8,
     rot_op = "0x10000b3",
     rot_result = "0xb301",
@@ -2121,6 +2182,7 @@ nonzero_integer! {
 nonzero_integer! {
     Self = NonZeroUsize,
     Primitive = unsigned usize,
+    SignedPrimitive = isize,
     rot = 12,
     rot_op = "0xaa00000000006e1",
     rot_result = "0x6e10aa",

std/src/sys/pal/unix/fs.rs

@@ -740,29 +740,27 @@ impl Iterator for ReadDir {
                 // to `byte_offset` and thus does not require the full extent of `*entry_ptr`
                 // to be in bounds of the same allocation, only the offset of the field
                 // being referenced.
-                macro_rules! entry_field_ptr {
-                    ($field:ident) => {
-                        &raw const (*entry_ptr).$field
-                    };
-                }
 
                 // d_name is guaranteed to be null-terminated.
-                let name = CStr::from_ptr(entry_field_ptr!(d_name).cast());
+                let name = CStr::from_ptr((&raw const (*entry_ptr).d_name).cast());
                 let name_bytes = name.to_bytes();
                 if name_bytes == b"." || name_bytes == b".." {
                     continue;
                 }
 
+                // When loading from a field, we can skip the `&raw const`; `(*entry_ptr).d_ino` as
+                // a value expression will do the right thing: `byte_offset` to the field and then
+                // only access those bytes.
                 #[cfg(not(target_os = "vita"))]
                 let entry = dirent64_min {
-                    d_ino: *entry_field_ptr!(d_ino) as u64,
+                    d_ino: (*entry_ptr).d_ino as u64,
                     #[cfg(not(any(
                         target_os = "solaris",
                         target_os = "illumos",
                         target_os = "aix",
                         target_os = "nto",
                     )))]
-                    d_type: *entry_field_ptr!(d_type) as u8,
+                    d_type: (*entry_ptr).d_type as u8,
                 };
 
                 #[cfg(target_os = "vita")]