Rollup merge of #130822 - bjoernager:non-null-from-ref, r=dtolnay

Add `from_ref` and `from_mut` constructors to `core::ptr::NonNull`. Relevant tracking issue: #130823 The `core::ptr::NonNull` type should have the convenience constructors `from_ref` and `from_mut` for parity with `core::ptr::from_ref` and `core::ptr::from_mut`. Although the type in question already implements `From<&T>` and `From<&mut T>`, these new functions also carry the ability to be used in constant expressions (due to not being behind a trait).
rust-lang · Oct 16, 2024 · 1817de6 · 1817de6
2 parents 0037048 + 94ab726
commit 1817de6
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Showing 8 changed files with 97 additions and 68 deletions.
diff --git a/library/core/src/lib.rs b/library/core/src/lib.rs
@@ -153,6 +153,7 @@
 #![feature(isqrt)]
 #![feature(lazy_get)]
 #![feature(link_cfg)]
+#![feature(non_null_from_ref)]
 #![feature(offset_of_enum)]
 #![feature(panic_internals)]
 #![feature(ptr_alignment_type)]

diff --git a/library/core/src/ptr/non_null.rs b/library/core/src/ptr/non_null.rs
@@ -230,6 +230,24 @@ impl<T: ?Sized> NonNull<T> {
         }
     }
 
+    /// Converts a reference to a `NonNull` pointer.
+    #[unstable(feature = "non_null_from_ref", issue = "130823")]
+    #[rustc_const_unstable(feature = "non_null_from_ref", issue = "130823")]
+    #[inline]
+    pub const fn from_ref(r: &T) -> Self {
+        // SAFETY: A reference cannot be null.
+        unsafe { NonNull { pointer: r as *const T } }
+    }
+
+    /// Converts a mutable reference to a `NonNull` pointer.
+    #[unstable(feature = "non_null_from_ref", issue = "130823")]
+    #[rustc_const_unstable(feature = "non_null_from_ref", issue = "130823")]
+    #[inline]
+    pub const fn from_mut(r: &mut T) -> Self {
+        // SAFETY: A mutable reference cannot be null.
+        unsafe { NonNull { pointer: r as *mut T } }
+    }
+
     /// Performs the same functionality as [`std::ptr::from_raw_parts`], except that a
     /// `NonNull` pointer is returned, as opposed to a raw `*const` pointer.
     ///
@@ -1753,9 +1771,8 @@ impl<T: ?Sized> From<&mut T> for NonNull<T> {
     ///
     /// This conversion is safe and infallible since references cannot be null.
     #[inline]
-    fn from(reference: &mut T) -> Self {
-        // SAFETY: A mutable reference cannot be null.
-        unsafe { NonNull { pointer: reference as *mut T } }
+    fn from(r: &mut T) -> Self {
+        NonNull::from_mut(r)
     }
 }
 
@@ -1765,8 +1782,7 @@ impl<T: ?Sized> From<&T> for NonNull<T> {
     ///
     /// This conversion is safe and infallible since references cannot be null.
     #[inline]
-    fn from(reference: &T) -> Self {
-        // SAFETY: A reference cannot be null.
-        unsafe { NonNull { pointer: reference as *const T } }
+    fn from(r: &T) -> Self {
+        NonNull::from_ref(r)
     }
 }
diff --git a/tests/mir-opt/pre-codegen/slice_iter.enumerated_loop.PreCodegen.after.panic-abort.mir b/tests/mir-opt/pre-codegen/slice_iter.enumerated_loop.PreCodegen.after.panic-abort.mir
@@ -19,30 +19,30 @@ fn enumerated_loop(_1: &[T], _2: impl Fn(usize, &T)) -> () {
             debug i => _22;
             debug x => _23;
         }
-        scope 17 (inlined <Enumerate<std::slice::Iter<'_, T>> as Iterator>::next) {
+        scope 18 (inlined <Enumerate<std::slice::Iter<'_, T>> as Iterator>::next) {
             let mut _14: &mut std::slice::Iter<'_, T>;
             let mut _15: std::option::Option<&T>;
             let mut _19: (usize, bool);
             let mut _20: (usize, &T);
-            scope 18 {
+            scope 19 {
                 let _18: usize;
-                scope 23 {
+                scope 24 {
                 }
             }
-            scope 19 {
-                scope 20 {
-                    scope 26 (inlined <Option<(usize, &T)> as FromResidual<Option<Infallible>>>::from_residual) {
+            scope 20 {
+                scope 21 {
+                    scope 27 (inlined <Option<(usize, &T)> as FromResidual<Option<Infallible>>>::from_residual) {
                     }
                 }
             }
-            scope 21 {
-                scope 22 {
+            scope 22 {
+                scope 23 {
                 }
             }
-            scope 24 (inlined <Option<&T> as Try>::branch) {
+            scope 25 (inlined <Option<&T> as Try>::branch) {
                 let mut _16: isize;
                 let _17: &T;
-                scope 25 {
+                scope 26 {
                 }
             }
         }
@@ -59,29 +59,31 @@ fn enumerated_loop(_1: &[T], _2: impl Fn(usize, &T)) -> () {
                     let _9: *const T;
                     scope 7 {
                     }
-                    scope 11 (inlined without_provenance::<T>) {
+                    scope 12 (inlined without_provenance::<T>) {
                     }
-                    scope 12 (inlined NonNull::<T>::as_ptr) {
+                    scope 13 (inlined NonNull::<T>::as_ptr) {
                     }
-                    scope 13 (inlined std::ptr::mut_ptr::<impl *mut T>::add) {
+                    scope 14 (inlined std::ptr::mut_ptr::<impl *mut T>::add) {
                     }
                 }
                 scope 8 (inlined <NonNull<[T]> as From<&[T]>>::from) {
-                    let mut _4: *const [T];
+                    scope 9 (inlined NonNull::<[T]>::from_ref) {
+                        let mut _4: *const [T];
+                    }
                 }
-                scope 9 (inlined NonNull::<[T]>::cast::<T>) {
+                scope 10 (inlined NonNull::<[T]>::cast::<T>) {
                     let mut _5: *const T;
-                    scope 10 (inlined NonNull::<[T]>::as_ptr) {
+                    scope 11 (inlined NonNull::<[T]>::as_ptr) {
                     }
                 }
             }
         }
     }
-    scope 14 (inlined <std::slice::Iter<'_, T> as Iterator>::enumerate) {
-        scope 15 (inlined Enumerate::<std::slice::Iter<'_, T>>::new) {
+    scope 15 (inlined <std::slice::Iter<'_, T> as Iterator>::enumerate) {
+        scope 16 (inlined Enumerate::<std::slice::Iter<'_, T>>::new) {
         }
     }
-    scope 16 (inlined <Enumerate<std::slice::Iter<'_, T>> as IntoIterator>::into_iter) {
+    scope 17 (inlined <Enumerate<std::slice::Iter<'_, T>> as IntoIterator>::into_iter) {
     }
 
     bb0: {

diff --git a/tests/mir-opt/pre-codegen/slice_iter.enumerated_loop.PreCodegen.after.panic-unwind.mir b/tests/mir-opt/pre-codegen/slice_iter.enumerated_loop.PreCodegen.after.panic-unwind.mir
@@ -34,29 +34,31 @@ fn enumerated_loop(_1: &[T], _2: impl Fn(usize, &T)) -> () {
                     let _9: *const T;
                     scope 7 {
                     }
-                    scope 11 (inlined without_provenance::<T>) {
+                    scope 12 (inlined without_provenance::<T>) {
                     }
-                    scope 12 (inlined NonNull::<T>::as_ptr) {
+                    scope 13 (inlined NonNull::<T>::as_ptr) {
                     }
-                    scope 13 (inlined std::ptr::mut_ptr::<impl *mut T>::add) {
+                    scope 14 (inlined std::ptr::mut_ptr::<impl *mut T>::add) {
                     }
                 }
                 scope 8 (inlined <NonNull<[T]> as From<&[T]>>::from) {
-                    let mut _4: *const [T];
+                    scope 9 (inlined NonNull::<[T]>::from_ref) {
+                        let mut _4: *const [T];
+                    }
                 }
-                scope 9 (inlined NonNull::<[T]>::cast::<T>) {
+                scope 10 (inlined NonNull::<[T]>::cast::<T>) {
                     let mut _5: *const T;
-                    scope 10 (inlined NonNull::<[T]>::as_ptr) {
+                    scope 11 (inlined NonNull::<[T]>::as_ptr) {
                     }
                 }
             }
         }
     }
-    scope 14 (inlined <std::slice::Iter<'_, T> as Iterator>::enumerate) {
-        scope 15 (inlined Enumerate::<std::slice::Iter<'_, T>>::new) {
+    scope 15 (inlined <std::slice::Iter<'_, T> as Iterator>::enumerate) {
+        scope 16 (inlined Enumerate::<std::slice::Iter<'_, T>>::new) {
         }
     }
-    scope 16 (inlined <Enumerate<std::slice::Iter<'_, T>> as IntoIterator>::into_iter) {
+    scope 17 (inlined <Enumerate<std::slice::Iter<'_, T>> as IntoIterator>::into_iter) {
     }
 
     bb0: {

diff --git a/tests/mir-opt/pre-codegen/slice_iter.forward_loop.PreCodegen.after.panic-abort.mir b/tests/mir-opt/pre-codegen/slice_iter.forward_loop.PreCodegen.after.panic-abort.mir
@@ -31,25 +31,27 @@ fn forward_loop(_1: &[T], _2: impl Fn(&T)) -> () {
                     let _9: *const T;
                     scope 7 {
                     }
-                    scope 11 (inlined without_provenance::<T>) {
+                    scope 12 (inlined without_provenance::<T>) {
                     }
-                    scope 12 (inlined NonNull::<T>::as_ptr) {
+                    scope 13 (inlined NonNull::<T>::as_ptr) {
                     }
-                    scope 13 (inlined std::ptr::mut_ptr::<impl *mut T>::add) {
+                    scope 14 (inlined std::ptr::mut_ptr::<impl *mut T>::add) {
                     }
                 }
                 scope 8 (inlined <NonNull<[T]> as From<&[T]>>::from) {
-                    let mut _4: *const [T];
+                    scope 9 (inlined NonNull::<[T]>::from_ref) {
+                        let mut _4: *const [T];
+                    }
                 }
-                scope 9 (inlined NonNull::<[T]>::cast::<T>) {
+                scope 10 (inlined NonNull::<[T]>::cast::<T>) {
                     let mut _5: *const T;
-                    scope 10 (inlined NonNull::<[T]>::as_ptr) {
+                    scope 11 (inlined NonNull::<[T]>::as_ptr) {
                     }
                 }
             }
         }
     }
-    scope 14 (inlined <std::slice::Iter<'_, T> as IntoIterator>::into_iter) {
+    scope 15 (inlined <std::slice::Iter<'_, T> as IntoIterator>::into_iter) {
     }
 
     bb0: {

diff --git a/tests/mir-opt/pre-codegen/slice_iter.forward_loop.PreCodegen.after.panic-unwind.mir b/tests/mir-opt/pre-codegen/slice_iter.forward_loop.PreCodegen.after.panic-unwind.mir
@@ -31,25 +31,27 @@ fn forward_loop(_1: &[T], _2: impl Fn(&T)) -> () {
                     let _9: *const T;
                     scope 7 {
                     }
-                    scope 11 (inlined without_provenance::<T>) {
+                    scope 12 (inlined without_provenance::<T>) {
                     }
-                    scope 12 (inlined NonNull::<T>::as_ptr) {
+                    scope 13 (inlined NonNull::<T>::as_ptr) {
                     }
-                    scope 13 (inlined std::ptr::mut_ptr::<impl *mut T>::add) {
+                    scope 14 (inlined std::ptr::mut_ptr::<impl *mut T>::add) {
                     }
                 }
                 scope 8 (inlined <NonNull<[T]> as From<&[T]>>::from) {
-                    let mut _4: *const [T];
+                    scope 9 (inlined NonNull::<[T]>::from_ref) {
+                        let mut _4: *const [T];
+                    }
                 }
-                scope 9 (inlined NonNull::<[T]>::cast::<T>) {
+                scope 10 (inlined NonNull::<[T]>::cast::<T>) {
                     let mut _5: *const T;
-                    scope 10 (inlined NonNull::<[T]>::as_ptr) {
+                    scope 11 (inlined NonNull::<[T]>::as_ptr) {
                     }
                 }
             }
         }
     }
-    scope 14 (inlined <std::slice::Iter<'_, T> as IntoIterator>::into_iter) {
+    scope 15 (inlined <std::slice::Iter<'_, T> as IntoIterator>::into_iter) {
     }
 
     bb0: {

diff --git a/tests/mir-opt/pre-codegen/slice_iter.reverse_loop.PreCodegen.after.panic-abort.mir b/tests/mir-opt/pre-codegen/slice_iter.reverse_loop.PreCodegen.after.panic-abort.mir
@@ -18,7 +18,7 @@ fn reverse_loop(_1: &[T], _2: impl Fn(&T)) -> () {
         scope 2 {
             debug x => _17;
         }
-        scope 17 (inlined <Rev<std::slice::Iter<'_, T>> as Iterator>::next) {
+        scope 18 (inlined <Rev<std::slice::Iter<'_, T>> as Iterator>::next) {
             let mut _14: &mut std::slice::Iter<'_, T>;
         }
     }
@@ -34,29 +34,31 @@ fn reverse_loop(_1: &[T], _2: impl Fn(&T)) -> () {
                     let _9: *const T;
                     scope 7 {
                     }
-                    scope 11 (inlined without_provenance::<T>) {
+                    scope 12 (inlined without_provenance::<T>) {
                     }
-                    scope 12 (inlined NonNull::<T>::as_ptr) {
+                    scope 13 (inlined NonNull::<T>::as_ptr) {
                     }
-                    scope 13 (inlined std::ptr::mut_ptr::<impl *mut T>::add) {
+                    scope 14 (inlined std::ptr::mut_ptr::<impl *mut T>::add) {
                     }
                 }
                 scope 8 (inlined <NonNull<[T]> as From<&[T]>>::from) {
-                    let mut _4: *const [T];
+                    scope 9 (inlined NonNull::<[T]>::from_ref) {
+                        let mut _4: *const [T];
+                    }
                 }
-                scope 9 (inlined NonNull::<[T]>::cast::<T>) {
+                scope 10 (inlined NonNull::<[T]>::cast::<T>) {
                     let mut _5: *const T;
-                    scope 10 (inlined NonNull::<[T]>::as_ptr) {
+                    scope 11 (inlined NonNull::<[T]>::as_ptr) {
                     }
                 }
             }
         }
     }
-    scope 14 (inlined <std::slice::Iter<'_, T> as Iterator>::rev) {
-        scope 15 (inlined Rev::<std::slice::Iter<'_, T>>::new) {
+    scope 15 (inlined <std::slice::Iter<'_, T> as Iterator>::rev) {
+        scope 16 (inlined Rev::<std::slice::Iter<'_, T>>::new) {
         }
     }
-    scope 16 (inlined <Rev<std::slice::Iter<'_, T>> as IntoIterator>::into_iter) {
+    scope 17 (inlined <Rev<std::slice::Iter<'_, T>> as IntoIterator>::into_iter) {
     }
 
     bb0: {

diff --git a/tests/mir-opt/pre-codegen/slice_iter.reverse_loop.PreCodegen.after.panic-unwind.mir b/tests/mir-opt/pre-codegen/slice_iter.reverse_loop.PreCodegen.after.panic-unwind.mir
@@ -18,7 +18,7 @@ fn reverse_loop(_1: &[T], _2: impl Fn(&T)) -> () {
         scope 2 {
             debug x => _17;
         }
-        scope 17 (inlined <Rev<std::slice::Iter<'_, T>> as Iterator>::next) {
+        scope 18 (inlined <Rev<std::slice::Iter<'_, T>> as Iterator>::next) {
             let mut _14: &mut std::slice::Iter<'_, T>;
         }
     }
@@ -34,29 +34,31 @@ fn reverse_loop(_1: &[T], _2: impl Fn(&T)) -> () {
                     let _9: *const T;
                     scope 7 {
                     }
-                    scope 11 (inlined without_provenance::<T>) {
+                    scope 12 (inlined without_provenance::<T>) {
                     }
-                    scope 12 (inlined NonNull::<T>::as_ptr) {
+                    scope 13 (inlined NonNull::<T>::as_ptr) {
                     }
-                    scope 13 (inlined std::ptr::mut_ptr::<impl *mut T>::add) {
+                    scope 14 (inlined std::ptr::mut_ptr::<impl *mut T>::add) {
                     }
                 }
                 scope 8 (inlined <NonNull<[T]> as From<&[T]>>::from) {
-                    let mut _4: *const [T];
+                    scope 9 (inlined NonNull::<[T]>::from_ref) {
+                        let mut _4: *const [T];
+                    }
                 }
-                scope 9 (inlined NonNull::<[T]>::cast::<T>) {
+                scope 10 (inlined NonNull::<[T]>::cast::<T>) {
                     let mut _5: *const T;
-                    scope 10 (inlined NonNull::<[T]>::as_ptr) {
+                    scope 11 (inlined NonNull::<[T]>::as_ptr) {
                     }
                 }
             }
         }
     }
-    scope 14 (inlined <std::slice::Iter<'_, T> as Iterator>::rev) {
-        scope 15 (inlined Rev::<std::slice::Iter<'_, T>>::new) {
+    scope 15 (inlined <std::slice::Iter<'_, T> as Iterator>::rev) {
+        scope 16 (inlined Rev::<std::slice::Iter<'_, T>>::new) {
         }
     }
-    scope 16 (inlined <Rev<std::slice::Iter<'_, T>> as IntoIterator>::into_iter) {
+    scope 17 (inlined <Rev<std::slice::Iter<'_, T>> as IntoIterator>::into_iter) {
     }
 
     bb0: {