Auto merge of #86810 - ojeda:alloc-gate, r=dtolnay

alloc: `no_global_oom_handling`: disable `new()`s, `pin()`s, etc.

They are infallible, and could not be actually used because
they will trigger an error when monomorphized, but it is better
to just remove them.

Link: Rust-for-Linux/linux#402
Suggested-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

library/alloc/src/rc.rs

@@ -262,6 +262,7 @@ use core::marker::{self, PhantomData, Unpin, Unsize};
 use core::mem::size_of_val;
 use core::mem::{self, align_of_val_raw, forget};
 use core::ops::{CoerceUnsized, Deref, DispatchFromDyn, Receiver};
+#[cfg(not(no_global_oom_handling))]
 use core::pin::Pin;
 use core::ptr::{self, NonNull};
 #[cfg(not(no_global_oom_handling))]
@@ -346,6 +347,7 @@ impl<T> Rc<T> {
     ///
     /// let five = Rc::new(5);
     /// ```
+    #[cfg(not(no_global_oom_handling))]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn new(value: T) -> Rc<T> {
         // There is an implicit weak pointer owned by all the strong
@@ -381,6 +383,7 @@ impl<T> Rc<T> {
     ///     }
     /// }
     /// ```
+    #[cfg(not(no_global_oom_handling))]
     #[unstable(feature = "arc_new_cyclic", issue = "75861")]
     pub fn new_cyclic(data_fn: impl FnOnce(&Weak<T>) -> T) -> Rc<T> {
         // Construct the inner in the "uninitialized" state with a single
@@ -577,6 +580,7 @@ impl<T> Rc<T> {
     }
     /// Constructs a new `Pin<Rc<T>>`. If `T` does not implement `Unpin`, then
     /// `value` will be pinned in memory and unable to be moved.
+    #[cfg(not(no_global_oom_handling))]
     #[stable(feature = "pin", since = "1.33.0")]
     pub fn pin(value: T) -> Pin<Rc<T>> {
         unsafe { Pin::new_unchecked(Rc::new(value)) }
@@ -1473,6 +1477,7 @@ impl<T: ?Sized> Clone for Rc<T> {
     }
 }
 
+#[cfg(not(no_global_oom_handling))]
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T: Default> Default for Rc<T> {
     /// Creates a new `Rc<T>`, with the `Default` value for `T`.
@@ -1731,6 +1736,7 @@ impl<T: ?Sized> fmt::Pointer for Rc<T> {
     }
 }
 
+#[cfg(not(no_global_oom_handling))]
 #[stable(feature = "from_for_ptrs", since = "1.6.0")]
 impl<T> From<T> for Rc<T> {
     /// Converts a generic type `T` into a `Rc<T>`

library/alloc/src/sync.rs

@@ -19,6 +19,7 @@ use core::marker::{PhantomData, Unpin, Unsize};
 use core::mem::size_of_val;
 use core::mem::{self, align_of_val_raw};
 use core::ops::{CoerceUnsized, Deref, DispatchFromDyn, Receiver};
+#[cfg(not(no_global_oom_handling))]
 use core::pin::Pin;
 use core::ptr::{self, NonNull};
 #[cfg(not(no_global_oom_handling))]
@@ -332,6 +333,7 @@ impl<T> Arc<T> {
     ///
     /// let five = Arc::new(5);
     /// ```
+    #[cfg(not(no_global_oom_handling))]
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn new(data: T) -> Arc<T> {
@@ -365,6 +367,7 @@ impl<T> Arc<T> {
     ///     me: me.clone(),
     /// });
     /// ```
+    #[cfg(not(no_global_oom_handling))]
     #[inline]
     #[unstable(feature = "arc_new_cyclic", issue = "75861")]
     pub fn new_cyclic(data_fn: impl FnOnce(&Weak<T>) -> T) -> Arc<T> {
@@ -485,6 +488,7 @@ impl<T> Arc<T> {
 
     /// Constructs a new `Pin<Arc<T>>`. If `T` does not implement `Unpin`, then
     /// `data` will be pinned in memory and unable to be moved.
+    #[cfg(not(no_global_oom_handling))]
     #[stable(feature = "pin", since = "1.33.0")]
     pub fn pin(data: T) -> Pin<Arc<T>> {
         unsafe { Pin::new_unchecked(Arc::new(data)) }
@@ -2274,6 +2278,7 @@ impl<T: ?Sized> fmt::Pointer for Arc<T> {
     }
 }
 
+#[cfg(not(no_global_oom_handling))]
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T: Default> Default for Arc<T> {
     /// Creates a new `Arc<T>`, with the `Default` value for `T`.
@@ -2298,6 +2303,7 @@ impl<T: ?Sized + Hash> Hash for Arc<T> {
     }
 }
 
+#[cfg(not(no_global_oom_handling))]
 #[stable(feature = "from_for_ptrs", since = "1.6.0")]
 impl<T> From<T> for Arc<T> {
     /// Converts a `T` into an `Arc<T>`