4 files changed, 37 insertions, 17 deletions
diff --git a/compiler/rustc_serialize/Cargo.toml b/compiler/rustc_serialize/Cargo.toml
index dbc5c1519..3b0b3144f 100644
--- a/compiler/rustc_serialize/Cargo.toml
+++ b/compiler/rustc_serialize/Cargo.toml
@@ -6,6 +6,7 @@ edition = "2021"
 [dependencies]
 indexmap = "1.9.1"
 smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
+thin-vec = "0.2.8"
 
 [dev-dependencies]
 rustc_macros = { path = "../rustc_macros" }
diff --git a/compiler/rustc_serialize/src/collection_impls.rs b/compiler/rustc_serialize/src/collection_impls.rs
index 5e53f0b10..8f8c50411 100644
--- a/compiler/rustc_serialize/src/collection_impls.rs
+++ b/compiler/rustc_serialize/src/collection_impls.rs
@@ -1,13 +1,12 @@
 //! Implementations of serialization for structures found in liballoc
 
-use std::hash::{BuildHasher, Hash};
-
 use crate::{Decodable, Decoder, Encodable, Encoder};
+use smallvec::{Array, SmallVec};
 use std::collections::{BTreeMap, BTreeSet, HashMap, HashSet, LinkedList, VecDeque};
+use std::hash::{BuildHasher, Hash};
 use std::rc::Rc;
 use std::sync::Arc;
-
-use smallvec::{Array, SmallVec};
+use thin_vec::ThinVec;
 
 impl<S: Encoder, A: Array<Item: Encodable<S>>> Encodable<S> for SmallVec<A> {
     fn encode(&self, s: &mut S) {
@@ -23,6 +22,19 @@ impl<D: Decoder, A: Array<Item: Decodable<D>>> Decodable<D> for SmallVec<A> {
     }
 }
 
+impl<S: Encoder, T: Encodable<S>> Encodable<S> for ThinVec<T> {
+    fn encode(&self, s: &mut S) {
+        self.as_slice().encode(s);
+    }
+}
+
+impl<D: Decoder, T: Decodable<D>> Decodable<D> for ThinVec<T> {
+    fn decode(d: &mut D) -> ThinVec<T> {
+        let len = d.read_usize();
+        (0..len).map(|_| Decodable::decode(d)).collect()
+    }
+}
+
 impl<S: Encoder, T: Encodable<S>> Encodable<S> for LinkedList<T> {
     fn encode(&self, s: &mut S) {
         s.emit_usize(self.len());
diff --git a/compiler/rustc_serialize/src/lib.rs b/compiler/rustc_serialize/src/lib.rs
index e606f4273..fa9c7bd54 100644
--- a/compiler/rustc_serialize/src/lib.rs
+++ b/compiler/rustc_serialize/src/lib.rs
@@ -14,10 +14,13 @@ Core encoding and decoding interfaces.
 #![feature(min_specialization)]
 #![feature(core_intrinsics)]
 #![feature(maybe_uninit_slice)]
-#![feature(let_else)]
+#![cfg_attr(bootstrap, feature(let_else))]
 #![feature(new_uninit)]
+#![feature(allocator_api)]
 #![cfg_attr(test, feature(test))]
 #![allow(rustc::internal)]
+#![deny(rustc::untranslatable_diagnostic)]
+#![deny(rustc::diagnostic_outside_of_impl)]
 
 pub use self::serialize::{Decodable, Decoder, Encodable, Encoder};
 
diff --git a/compiler/rustc_serialize/src/serialize.rs b/compiler/rustc_serialize/src/serialize.rs
index 36585b8d7..751b209f1 100644
--- a/compiler/rustc_serialize/src/serialize.rs
+++ b/compiler/rustc_serialize/src/serialize.rs
@@ -4,6 +4,7 @@
 Core encoding and decoding interfaces.
 */
 
+use std::alloc::Allocator;
 use std::borrow::Cow;
 use std::cell::{Cell, RefCell};
 use std::marker::PhantomData;
@@ -229,9 +230,9 @@ impl<D: Decoder, T> Decodable<D> for PhantomData<T> {
     }
 }
 
-impl<D: Decoder, T: Decodable<D>> Decodable<D> for Box<[T]> {
-    fn decode(d: &mut D) -> Box<[T]> {
-        let v: Vec<T> = Decodable::decode(d);
+impl<D: Decoder, A: Allocator + Default, T: Decodable<D>> Decodable<D> for Box<[T], A> {
+    fn decode(d: &mut D) -> Box<[T], A> {
+        let v: Vec<T, A> = Decodable::decode(d);
         v.into_boxed_slice()
     }
 }
@@ -264,16 +265,17 @@ impl<S: Encoder, T: Encodable<S>> Encodable<S> for Vec<T> {
     }
 }
 
-impl<D: Decoder, T: Decodable<D>> Decodable<D> for Vec<T> {
-    default fn decode(d: &mut D) -> Vec<T> {
+impl<D: Decoder, T: Decodable<D>, A: Allocator + Default> Decodable<D> for Vec<T, A> {
+    default fn decode(d: &mut D) -> Vec<T, A> {
         let len = d.read_usize();
+        let allocator = A::default();
         // SAFETY: we set the capacity in advance, only write elements, and
         // only set the length at the end once the writing has succeeded.
-        let mut vec = Vec::with_capacity(len);
+        let mut vec = Vec::with_capacity_in(len, allocator);
         unsafe {
             let ptr: *mut T = vec.as_mut_ptr();
             for i in 0..len {
-                std::ptr::write(ptr.offset(i as isize), Decodable::decode(d));
+                std::ptr::write(ptr.add(i), Decodable::decode(d));
             }
             vec.set_len(len);
         }
@@ -457,13 +459,15 @@ impl<D: Decoder, T: Decodable<D>> Decodable<D> for Arc<T> {
     }
 }
 
-impl<S: Encoder, T: ?Sized + Encodable<S>> Encodable<S> for Box<T> {
+impl<S: Encoder, T: ?Sized + Encodable<S>, A: Allocator + Default> Encodable<S> for Box<T, A> {
     fn encode(&self, s: &mut S) {
-        (**self).encode(s);
+        (**self).encode(s)
     }
 }
-impl<D: Decoder, T: Decodable<D>> Decodable<D> for Box<T> {
-    fn decode(d: &mut D) -> Box<T> {
-        Box::new(Decodable::decode(d))
+
+impl<D: Decoder, A: Allocator + Default, T: Decodable<D>> Decodable<D> for Box<T, A> {
+    fn decode(d: &mut D) -> Box<T, A> {
+        let allocator = A::default();
+        Box::new_in(Decodable::decode(d), allocator)
     }
 }