Move generic NonZero rustc_layout_scalar_valid_range_start attribute to inner type.

Author: reitermarkus

library/core/src/num/nonzero.rs

@@ -6,21 +6,12 @@ use crate::hash::{Hash, Hasher};
 use crate::intrinsics;
 use crate::marker::StructuralPartialEq;
 use crate::ops::{BitOr, BitOrAssign, Div, Neg, Rem};
+use crate::ptr;
 use crate::str::FromStr;
 
 use super::from_str_radix;
 use super::{IntErrorKind, ParseIntError};
 
-mod private {
-    #[unstable(
-        feature = "nonzero_internals",
-        reason = "implementation detail which may disappear or be replaced at any time",
-        issue = "none"
-    )]
-    #[const_trait]
-    pub trait Sealed {}
-}
-
 /// A marker trait for primitive types which can be zero.
 ///
 /// This is an implementation detail for <code>[NonZero]\<T></code> which may disappear or be replaced at any time.
@@ -34,38 +25,70 @@ mod private {
     issue = "none"
 )]
 #[const_trait]
-pub unsafe trait ZeroablePrimitive: Sized + Copy + private::Sealed {}
+pub unsafe trait ZeroablePrimitive: Sized + Copy + private::Sealed {
+    #[doc(hidden)]
+    type NonZeroInner: Sized + Copy;
+}
 
 macro_rules! impl_zeroable_primitive {
-    ($primitive:ty) => {
-        #[unstable(
-            feature = "nonzero_internals",
-            reason = "implementation detail which may disappear or be replaced at any time",
-            issue = "none"
-        )]
-        impl const private::Sealed for $primitive {}
-
-        #[unstable(
-            feature = "nonzero_internals",
-            reason = "implementation detail which may disappear or be replaced at any time",
-            issue = "none"
-        )]
-        unsafe impl const ZeroablePrimitive for $primitive {}
+    ($($NonZeroInner:ident ( $primitive:ty )),+ $(,)?) => {
+        mod private {
+            #[unstable(
+                feature = "nonzero_internals",
+                reason = "implementation detail which may disappear or be replaced at any time",
+                issue = "none"
+            )]
+            #[const_trait]
+            pub trait Sealed {}
+
+            $(
+                #[derive(Debug, Clone, Copy, PartialEq)]
+                #[repr(transparent)]
+                #[rustc_layout_scalar_valid_range_start(1)]
+                #[rustc_nonnull_optimization_guaranteed]
+                #[unstable(
+                    feature = "nonzero_internals",
+                    reason = "implementation detail which may disappear or be replaced at any time",
+                    issue = "none"
+                )]
+                pub struct $NonZeroInner($primitive);
+            )+
+        }
+
+        $(
+            #[unstable(
+                feature = "nonzero_internals",
+                reason = "implementation detail which may disappear or be replaced at any time",
+                issue = "none"
+            )]
+            impl const private::Sealed for $primitive {}
+
+            #[unstable(
+                feature = "nonzero_internals",
+                reason = "implementation detail which may disappear or be replaced at any time",
+                issue = "none"
+            )]
+            unsafe impl const ZeroablePrimitive for $primitive {
+                type NonZeroInner = private::$NonZeroInner;
+            }
+        )+
     };
 }
 
-impl_zeroable_primitive!(u8);
-impl_zeroable_primitive!(u16);
-impl_zeroable_primitive!(u32);
-impl_zeroable_primitive!(u64);
-impl_zeroable_primitive!(u128);
-impl_zeroable_primitive!(usize);
-impl_zeroable_primitive!(i8);
-impl_zeroable_primitive!(i16);
-impl_zeroable_primitive!(i32);
-impl_zeroable_primitive!(i64);
-impl_zeroable_primitive!(i128);
-impl_zeroable_primitive!(isize);
+impl_zeroable_primitive!(
+    NonZeroU8Inner(u8),
+    NonZeroU16Inner(u16),
+    NonZeroU32Inner(u32),
+    NonZeroU64Inner(u64),
+    NonZeroU128Inner(u128),
+    NonZeroUsizeInner(usize),
+    NonZeroI8Inner(i8),
+    NonZeroI16Inner(i16),
+    NonZeroI32Inner(i32),
+    NonZeroI64Inner(i64),
+    NonZeroI128Inner(i128),
+    NonZeroIsizeInner(isize),
+);
 
 /// A value that is known not to equal zero.
 ///
@@ -80,10 +103,8 @@ impl_zeroable_primitive!(isize);
 /// ```
 #[unstable(feature = "generic_nonzero", issue = "120257")]
 #[repr(transparent)]
-#[rustc_layout_scalar_valid_range_start(1)]
-#[rustc_nonnull_optimization_guaranteed]
 #[rustc_diagnostic_item = "NonZero"]
-pub struct NonZero<T: ZeroablePrimitive>(T);
+pub struct NonZero<T: ZeroablePrimitive>(T::NonZeroInner);
 
 macro_rules! impl_nonzero_fmt {
     ($Trait:ident) => {
@@ -114,8 +135,7 @@ where
 {
     #[inline]
     fn clone(&self) -> Self {
-        // SAFETY: The contained value is non-zero.
-        unsafe { Self(self.0) }
+        Self(self.0)
     }
 }
 
@@ -188,19 +208,19 @@ where
     #[inline]
     fn max(self, other: Self) -> Self {
         // SAFETY: The maximum of two non-zero values is still non-zero.
-        unsafe { Self(self.get().max(other.get())) }
+        unsafe { Self::new_unchecked(self.get().max(other.get())) }
     }
 
     #[inline]
     fn min(self, other: Self) -> Self {
         // SAFETY: The minimum of two non-zero values is still non-zero.
-        unsafe { Self(self.get().min(other.get())) }
+        unsafe { Self::new_unchecked(self.get().min(other.get())) }
     }
 
     #[inline]
     fn clamp(self, min: Self, max: Self) -> Self {
         // SAFETY: A non-zero value clamped between two non-zero values is still non-zero.
-        unsafe { Self(self.get().clamp(min.get(), max.get())) }
+        unsafe { Self::new_unchecked(self.get().clamp(min.get(), max.get())) }
     }
 }
 
@@ -240,7 +260,7 @@ where
     #[inline]
     fn bitor(self, rhs: Self) -> Self::Output {
         // SAFETY: Bitwise OR of two non-zero values is still non-zero.
-        unsafe { Self(self.get() | rhs.get()) }
+        unsafe { Self::new_unchecked(self.get() | rhs.get()) }
     }
 }
 
@@ -254,7 +274,7 @@ where
     #[inline]
     fn bitor(self, rhs: T) -> Self::Output {
         // SAFETY: Bitwise OR of a non-zero value with anything is still non-zero.
-        unsafe { Self(self.get() | rhs) }
+        unsafe { Self::new_unchecked(self.get() | rhs) }
     }
 }
 
@@ -268,7 +288,7 @@ where
     #[inline]
     fn bitor(self, rhs: NonZero<T>) -> Self::Output {
         // SAFETY: Bitwise OR of anything with a non-zero value is still non-zero.
-        unsafe { NonZero(self | rhs.get()) }
+        unsafe { NonZero::new_unchecked(self | rhs.get()) }
     }
 }
 
@@ -346,7 +366,7 @@ where
     pub fn from_mut(n: &mut T) -> Option<&mut Self> {
         // SAFETY: Memory layout optimization guarantees that `Option<NonZero<T>>` has
         //         the same layout and size as `T`, with `0` representing `None`.
-        let opt_n = unsafe { &mut *(n as *mut T as *mut Option<Self>) };
+        let opt_n = unsafe { &mut *(ptr::from_mut(n).cast::<Option<Self>>()) };
 
         opt_n.as_mut()
     }
@@ -390,12 +410,17 @@ where
         // memory somewhere. If the value of `self` was from by-value argument
         // of some not-inlined function, LLVM don't have range metadata
         // to understand that the value cannot be zero.
-        match Self::new(self.0) {
-            Some(Self(n)) => n,
+        //
+        // SAFETY: `Self` is guaranteed to have the same layout as `Option<Self>`.
+        match unsafe { intrinsics::transmute_unchecked(self) } {
             None => {
                 // SAFETY: `NonZero` is guaranteed to only contain non-zero values, so this is unreachable.
                 unsafe { intrinsics::unreachable() }
             }
+            Some(Self(inner)) => {
+                // SAFETY: `T::NonZeroInner` is guaranteed to have the same layout as `T`.
+                unsafe { intrinsics::transmute_unchecked(inner) }
+            }
         }
     }
 }

tests/ui/consts/const-eval/raw-bytes.32bit.stderr

@@ -68,7 +68,7 @@ error[E0080]: it is undefined behavior to use this value
   --> $DIR/raw-bytes.rs:59:1
    |
 LL | const NULL_U8: NonZero<u8> = unsafe { mem::transmute(0u8) };
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value: encountered 0, but expected something greater or equal to 1
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value at .0: encountered 0, but expected something greater or equal to 1
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
    = note: the raw bytes of the constant (size: 1, align: 1) {
@@ -79,7 +79,7 @@ error[E0080]: it is undefined behavior to use this value
   --> $DIR/raw-bytes.rs:61:1
    |
 LL | const NULL_USIZE: NonZero<usize> = unsafe { mem::transmute(0usize) };
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value: encountered 0, but expected something greater or equal to 1
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value at .0: encountered 0, but expected something greater or equal to 1
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
    = note: the raw bytes of the constant (size: 4, align: 4) {

tests/ui/consts/const-eval/raw-bytes.64bit.stderr

@@ -68,7 +68,7 @@ error[E0080]: it is undefined behavior to use this value
   --> $DIR/raw-bytes.rs:59:1
    |
 LL | const NULL_U8: NonZero<u8> = unsafe { mem::transmute(0u8) };
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value: encountered 0, but expected something greater or equal to 1
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value at .0: encountered 0, but expected something greater or equal to 1
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
    = note: the raw bytes of the constant (size: 1, align: 1) {
@@ -79,7 +79,7 @@ error[E0080]: it is undefined behavior to use this value
   --> $DIR/raw-bytes.rs:61:1
    |
 LL | const NULL_USIZE: NonZero<usize> = unsafe { mem::transmute(0usize) };
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value: encountered 0, but expected something greater or equal to 1
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value at .0: encountered 0, but expected something greater or equal to 1
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
    = note: the raw bytes of the constant (size: 8, align: 8) {

tests/ui/consts/const-eval/ub-nonnull.stderr

@@ -19,7 +19,7 @@ error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-nonnull.rs:24:1
    |
 LL | const NULL_U8: NonZero<u8> = unsafe { mem::transmute(0u8) };
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value: encountered 0, but expected something greater or equal to 1
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value at .0: encountered 0, but expected something greater or equal to 1
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
    = note: the raw bytes of the constant (size: $SIZE, align: $ALIGN) {
@@ -30,7 +30,7 @@ error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-nonnull.rs:26:1
    |
 LL | const NULL_USIZE: NonZero<usize> = unsafe { mem::transmute(0usize) };
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value: encountered 0, but expected something greater or equal to 1
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value at .0: encountered 0, but expected something greater or equal to 1
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
    = note: the raw bytes of the constant (size: $SIZE, align: $ALIGN) {

tests/ui/lint/clashing-extern-fn.stderr

@@ -1,3 +1,31 @@
+warning: `extern` block uses type `Option<NonZero<usize>>`, which is not FFI-safe
+  --> $DIR/clashing-extern-fn.rs:369:43
+   |
+LL |             fn option_non_zero_usize() -> Option<core::num::NonZero<usize>>;
+   |                                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
+   |
+   = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum
+   = note: enum has no representation hint
+   = note: `#[warn(improper_ctypes)]` on by default
+
+warning: `extern` block uses type `Option<NonZero<isize>>`, which is not FFI-safe
+  --> $DIR/clashing-extern-fn.rs:370:43
+   |
+LL |             fn option_non_zero_isize() -> Option<core::num::NonZero<isize>>;
+   |                                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
+   |
+   = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum
+   = note: enum has no representation hint
+
+warning: `extern` block uses type `Option<Transparent>`, which is not FFI-safe
+  --> $DIR/clashing-extern-fn.rs:428:46
+   |
+LL |             fn hidden_niche_transparent() -> Option<Transparent>;
+   |                                              ^^^^^^^^^^^^^^^^^^^ not FFI-safe
+   |
+   = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum
+   = note: enum has no representation hint
+
 warning: `extern` block uses type `Option<TransparentNoNiche>`, which is not FFI-safe
   --> $DIR/clashing-extern-fn.rs:430:55
    |
@@ -6,7 +34,6 @@ LL |             fn hidden_niche_transparent_no_niche() -> Option<TransparentNoN
    |
    = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum
    = note: enum has no representation hint
-   = note: `#[warn(improper_ctypes)]` on by default
 
 warning: `extern` block uses type `Option<UnsafeCell<NonZero<usize>>>`, which is not FFI-safe
   --> $DIR/clashing-extern-fn.rs:434:46
@@ -178,6 +205,30 @@ LL |             fn non_null_ptr() -> *const usize;
    = note: expected `unsafe extern "C" fn() -> NonNull<usize>`
               found `unsafe extern "C" fn() -> *const usize`
 
+warning: `option_non_zero_usize` redeclared with a different signature
+  --> $DIR/clashing-extern-fn.rs:369:13
+   |
+LL |             fn option_non_zero_usize() -> usize;
+   |             ----------------------------------- `option_non_zero_usize` previously declared here
+...
+LL |             fn option_non_zero_usize() -> Option<core::num::NonZero<usize>>;
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ this signature doesn't match the previous declaration
+   |
+   = note: expected `unsafe extern "C" fn() -> usize`
+              found `unsafe extern "C" fn() -> Option<NonZero<usize>>`
+
+warning: `option_non_zero_isize` redeclared with a different signature
+  --> $DIR/clashing-extern-fn.rs:370:13
+   |
+LL |             fn option_non_zero_isize() -> isize;
+   |             ----------------------------------- `option_non_zero_isize` previously declared here
+...
+LL |             fn option_non_zero_isize() -> Option<core::num::NonZero<isize>>;
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ this signature doesn't match the previous declaration
+   |
+   = note: expected `unsafe extern "C" fn() -> isize`
+              found `unsafe extern "C" fn() -> Option<NonZero<isize>>`
+
 warning: `option_non_zero_usize_incorrect` redeclared with a different signature
   --> $DIR/clashing-extern-fn.rs:374:13
    |
@@ -202,6 +253,18 @@ LL |             fn option_non_null_ptr_incorrect() -> *const isize;
    = note: expected `unsafe extern "C" fn() -> *const usize`
               found `unsafe extern "C" fn() -> *const isize`
 
+warning: `hidden_niche_transparent` redeclared with a different signature
+  --> $DIR/clashing-extern-fn.rs:428:13
+   |
+LL |             fn hidden_niche_transparent() -> usize;
+   |             -------------------------------------- `hidden_niche_transparent` previously declared here
+...
+LL |             fn hidden_niche_transparent() -> Option<Transparent>;
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ this signature doesn't match the previous declaration
+   |
+   = note: expected `unsafe extern "C" fn() -> usize`
+              found `unsafe extern "C" fn() -> Option<Transparent>`
+
 warning: `hidden_niche_transparent_no_niche` redeclared with a different signature
   --> $DIR/clashing-extern-fn.rs:430:13
    |
@@ -226,5 +289,5 @@ LL |             fn hidden_niche_unsafe_cell() -> Option<UnsafeCell<NonZero<usiz
    = note: expected `unsafe extern "C" fn() -> usize`
               found `unsafe extern "C" fn() -> Option<UnsafeCell<NonZero<usize>>>`
 
-warning: 19 warnings emitted
+warning: 25 warnings emitted