Document CTFE behavior of methods that call is_null

(cherry picked from commit e6efbb2)

Author: theemathas

library/core/src/ptr/const_ptr.rs

@@ -258,6 +258,13 @@ impl<T: ?Sized> *const T {
     /// When calling this method, you have to ensure that *either* the pointer is null *or*
     /// the pointer is [convertible to a reference](crate::ptr#pointer-to-reference-conversion).
     ///
+    /// # Panics during const evaluation
+    ///
+    /// This method will panic during const evaluation if the pointer cannot be
+    /// determined to be null or not. See [`is_null`] for more information.
+    ///
+    /// [`is_null`]: #method.is_null
+    ///
     /// # Examples
     ///
     /// ```
@@ -335,6 +342,13 @@ impl<T: ?Sized> *const T {
     /// When calling this method, you have to ensure that *either* the pointer is null *or*
     /// the pointer is [convertible to a reference](crate::ptr#pointer-to-reference-conversion).
     ///
+    /// # Panics during const evaluation
+    ///
+    /// This method will panic during const evaluation if the pointer cannot be
+    /// determined to be null or not. See [`is_null`] for more information.
+    ///
+    /// [`is_null`]: #method.is_null
+    ///
     /// # Examples
     ///
     /// ```
@@ -1595,6 +1609,13 @@ impl<T> *const [T] {
     ///
     /// [valid]: crate::ptr#safety
     /// [allocated object]: crate::ptr#allocated-object
+    ///
+    /// # Panics during const evaluation
+    ///
+    /// This method will panic during const evaluation if the pointer cannot be
+    /// determined to be null or not. See [`is_null`] for more information.
+    ///
+    /// [`is_null`]: #method.is_null
     #[inline]
     #[unstable(feature = "ptr_as_uninit", issue = "75402")]
     #[rustc_const_unstable(feature = "ptr_as_uninit", issue = "75402")]

library/core/src/ptr/mut_ptr.rs

@@ -247,6 +247,13 @@ impl<T: ?Sized> *mut T {
     /// When calling this method, you have to ensure that *either* the pointer is null *or*
     /// the pointer is [convertible to a reference](crate::ptr#pointer-to-reference-conversion).
     ///
+    /// # Panics during const evaluation
+    ///
+    /// This method will panic during const evaluation if the pointer cannot be
+    /// determined to be null or not. See [`is_null`] for more information.
+    ///
+    /// [`is_null`]: #method.is_null-1
+    ///
     /// # Examples
     ///
     /// ```
@@ -331,6 +338,13 @@ impl<T: ?Sized> *mut T {
     /// Note that because the created reference is to `MaybeUninit<T>`, the
     /// source pointer can point to uninitialized memory.
     ///
+    /// # Panics during const evaluation
+    ///
+    /// This method will panic during const evaluation if the pointer cannot be
+    /// determined to be null or not. See [`is_null`] for more information.
+    ///
+    /// [`is_null`]: #method.is_null-1
+    ///
     /// # Examples
     ///
     /// ```
@@ -595,6 +609,12 @@ impl<T: ?Sized> *mut T {
     /// the pointer is null *or*
     /// the pointer is [convertible to a reference](crate::ptr#pointer-to-reference-conversion).
     ///
+    /// # Panics during const evaluation
+    ///
+    /// This method will panic during const evaluation if the pointer cannot be
+    /// determined to be null or not. See [`is_null`] for more information.
+    ///
+    /// [`is_null`]: #method.is_null-1
     ///
     /// # Examples
     ///
@@ -678,6 +698,13 @@ impl<T: ?Sized> *mut T {
     ///
     /// When calling this method, you have to ensure that *either* the pointer is null *or*
     /// the pointer is [convertible to a reference](crate::ptr#pointer-to-reference-conversion).
+    ///
+    /// # Panics during const evaluation
+    ///
+    /// This method will panic during const evaluation if the pointer cannot be
+    /// determined to be null or not. See [`is_null`] for more information.
+    ///
+    /// [`is_null`]: #method.is_null-1
     #[inline]
     #[unstable(feature = "ptr_as_uninit", issue = "75402")]
     #[rustc_const_unstable(feature = "ptr_as_uninit", issue = "75402")]
@@ -1950,6 +1977,13 @@ impl<T> *mut [T] {
     ///
     /// [valid]: crate::ptr#safety
     /// [allocated object]: crate::ptr#allocated-object
+    ///
+    /// # Panics during const evaluation
+    ///
+    /// This method will panic during const evaluation if the pointer cannot be
+    /// determined to be null or not. See [`is_null`] for more information.
+    ///
+    /// [`is_null`]: #method.is_null-1
     #[inline]
     #[unstable(feature = "ptr_as_uninit", issue = "75402")]
     #[rustc_const_unstable(feature = "ptr_as_uninit", issue = "75402")]
@@ -2002,6 +2036,13 @@ impl<T> *mut [T] {
     ///
     /// [valid]: crate::ptr#safety
     /// [allocated object]: crate::ptr#allocated-object
+    ///
+    /// # Panics during const evaluation
+    ///
+    /// This method will panic during const evaluation if the pointer cannot be
+    /// determined to be null or not. See [`is_null`] for more information.
+    ///
+    /// [`is_null`]: #method.is_null-1
     #[inline]
     #[unstable(feature = "ptr_as_uninit", issue = "75402")]
     #[rustc_const_unstable(feature = "ptr_as_uninit", issue = "75402")]

library/core/src/ptr/non_null.rs

@@ -202,6 +202,13 @@ impl<T: ?Sized> NonNull<T> {
 
     /// Creates a new `NonNull` if `ptr` is non-null.
     ///
+    /// # Panics during const evaluation
+    ///
+    /// This method will panic during const evaluation if the pointer cannot be
+    /// determined to be null or not. See [`is_null`] for more information.
+    ///
+    /// [`is_null`]: ../primitive.pointer.html#method.is_null-1
+    ///
     /// # Examples
     ///
     /// ```