Auto merge of #48648 - snf:fallible_allocation, r=Kimundi

Fallible allocation

Implementing RFC#2116 [Fallible Allocation](https://github.com/rust-lang/rust/issues/48043) .
Work in progress. Initially adding @Gankro's try_reserve for Vec.

1 files changed, 18 insertions, 0 deletions

diff --git a/src/liballoc/allocator.rs b/src/liballoc/allocator.rs
index 55e8c0b430f..fdc4efc66b9 100644
--- a/src/liballoc/allocator.rs
+++ b/src/liballoc/allocator.rs
@@ -373,6 +373,24 @@ impl fmt::Display for CannotReallocInPlace {
     }
 }
 
+/// Augments `AllocErr` with a CapacityOverflow variant.
+#[derive(Clone, PartialEq, Eq, Debug)]
+#[unstable(feature = "try_reserve", reason = "new API", issue="48043")]
+pub enum CollectionAllocErr {
+    /// Error due to the computed capacity exceeding the collection's maximum
+    /// (usually `isize::MAX` bytes).
+    CapacityOverflow,
+    /// Error due to the allocator (see the `AllocErr` type's docs).
+    AllocErr(AllocErr),
+}
+
+#[unstable(feature = "try_reserve", reason = "new API", issue="48043")]
+impl From<AllocErr> for CollectionAllocErr {
+    fn from(err: AllocErr) -> Self {
+        CollectionAllocErr::AllocErr(err)
+    }
+}
+
 /// An implementation of `Alloc` can allocate, reallocate, and
 /// deallocate arbitrary blocks of data described via `Layout`.
 ///