fallible allocation experiment 2

library/alloc/src/alloc.rs

@@ -12,6 +12,9 @@ use core::ptr::{self, NonNull};
 #[doc(inline)]
 pub use core::alloc::*;
 
+#[unstable(feature = "allocator_api", issue = "32838")]
+pub mod failure_handling;
+
 #[cfg(test)]
 mod tests;
 

library/alloc/src/alloc/failure_handling.rs

@@ -0,0 +1,39 @@
+//! TBD
+//! 
+
+mod sealed {
+    pub trait Sealed {}
+}
+
+/// Describes the handling behavior in case of allocation failure.
+pub trait FailureHandling: sealed::Sealed + Send + Sync + Unpin {
+    /// The type returned by allocating functions.
+    /// 
+    /// `Fallible` functions will return `Result<T, E>`,
+    /// but `Fatal` functions will return `T`.
+    type Result<T, E>;
+}
+
+/// Handle allocation failure globally by panicking / aborting.
+#[derive(Debug)]
+pub struct Fatal;
+
+impl sealed::Sealed for Fatal {}
+impl FailureHandling for Fatal {
+    type Result<T, E> = T;
+}
+
+/// Handle allocation failure falliblyby returning a `Result`.
+#[derive(Debug)]
+pub struct Fallible;
+
+impl sealed::Sealed for Fallible {}
+impl FailureHandling for Fallible {
+    type Result<T, E> = Result<T, E>;
+}
+
+/// Type parameter default `FailureHandling` for use in containers.
+#[cfg(not(no_global_oom_handling))]
+pub type DefaultFailureHandling = Fatal;
+#[cfg(no_global_oom_handling)]
+pub type DefaultFailureHandling = Fallible;

library/alloc/src/boxed.rs

@@ -165,6 +165,8 @@ use core::pin::Pin;
 use core::ptr::{self, NonNull, Unique};
 use core::task::{Context, Poll};
 
+use crate::alloc::failure_handling::Fallible;
+
 #[cfg(not(no_global_oom_handling))]
 use crate::alloc::{handle_alloc_error, WriteCloneIntoRaw};
 use crate::alloc::{AllocError, Allocator, Global, Layout};
@@ -692,7 +694,7 @@ impl<T> Box<[T]> {
             };
             Global.allocate(layout)?.cast()
         };
-        unsafe { Ok(RawVec::from_raw_parts_in(ptr.as_ptr(), len, Global).into_box(len)) }
+        unsafe { Ok(RawVec::<_, _, Fallible>::from_raw_parts_in(ptr.as_ptr(), len, Global).into_box(len)) }
     }
 
     /// Constructs a new boxed slice with uninitialized contents, with the memory
@@ -726,7 +728,7 @@ impl<T> Box<[T]> {
             };
             Global.allocate_zeroed(layout)?.cast()
         };
-        unsafe { Ok(RawVec::from_raw_parts_in(ptr.as_ptr(), len, Global).into_box(len)) }
+        unsafe { Ok(RawVec::<_, _, Fallible>::from_raw_parts_in(ptr.as_ptr(), len, Global).into_box(len)) }
     }
 }
 

library/alloc/src/collections/vec_deque/mod.rs

@@ -22,6 +22,7 @@ use core::slice;
 #[allow(unused_imports)]
 use core::mem;
 
+use crate::alloc::failure_handling::Fatal;
 use crate::alloc::{Allocator, Global};
 use crate::collections::TryReserveError;
 use crate::collections::TryReserveErrorKind;
@@ -102,7 +103,7 @@ pub struct VecDeque<
     // if `len == 0`, the exact value of `head` is unimportant.
     // if `T` is zero-Sized, then `self.len <= usize::MAX`, otherwise `self.len <= isize::MAX as usize`.
     len: usize,
-    buf: RawVec<T, A>,
+    buf: RawVec<T, A, Fatal>,
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]

library/alloc/src/lib.rs

@@ -263,6 +263,27 @@ pub mod __export {
     pub use core::format_args;
 }
 
+// HACK: so `std::vec::Vec` doesn't inherit the third `FailureHandling` parameter
+#[cfg(not(test))]
+#[doc(hidden)]
+#[unstable(feature = "std_internals", issue = "none", reason = "implementation detail")]
+pub mod std_vec {
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub mod __export {
+        // FIXME: include `vec` module docs here
+
+        #[stable(feature = "rust1", since = "1.0.0")]
+        pub use crate::vec::*;
+
+        // FIXME: include `Vec` docs here
+        #[stable(feature = "rust1", since = "1.0.0")]
+        pub type Vec<T, #[unstable(feature = "allocator_api", issue = "32838")] A = crate::alloc::Global> = crate::vec::Vec<T, A, crate::alloc::failure_handling::DefaultFailureHandling>;
+    }
+
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub use vec as __export;
+}
+
 #[cfg(test)]
 #[allow(dead_code)] // Not used in all configurations
 pub(crate) mod test_helpers {