Yeet `owning_ref`

Turns out
- `owning_ref` is unsound due to `Box` aliasing stuff
- `rustc` doesn't need 99% of the `owning_ref` API
- `rustc` can use a far simpler abstraction that is `OwnedSlice`

6 files changed, 1 insertions, 1971 deletions

diff --git a/compiler/rustc_data_structures/src/lib.rs b/compiler/rustc_data_structures/src/lib.rs
index 62e22127b77..47d8c84ba20 100644
--- a/compiler/rustc_data_structures/src/lib.rs
+++ b/compiler/rustc_data_structures/src/lib.rs
@@ -61,7 +61,6 @@ pub mod intern;
 pub mod jobserver;
 pub mod macros;
 pub mod obligation_forest;
-pub mod owning_ref;
 pub mod sip128;
 pub mod small_c_str;
 pub mod small_str;
diff --git a/compiler/rustc_data_structures/src/memmap.rs b/compiler/rustc_data_structures/src/memmap.rs
index 3d44e17f31d..1556873f597 100644
--- a/compiler/rustc_data_structures/src/memmap.rs
+++ b/compiler/rustc_data_structures/src/memmap.rs
@@ -2,9 +2,7 @@ use std::fs::File;
 use std::io;
 use std::ops::{Deref, DerefMut};
 
-use crate::owning_ref::StableAddress;
-
-/// A trivial wrapper for [`memmap2::Mmap`] that implements [`StableAddress`].
+/// A trivial wrapper for [`memmap2::Mmap`] (or `Vec<u8>` on WASM).
 #[cfg(not(target_arch = "wasm32"))]
 pub struct Mmap(memmap2::Mmap);
 
@@ -46,12 +44,6 @@ impl AsRef<[u8]> for Mmap {
     }
 }
 
-// SAFETY: On architectures other than WASM, mmap is used as backing storage. The address of this
-// memory map is stable. On WASM, `Vec<u8>` is used as backing storage. The `Mmap` type doesn't
-// export any function that can cause the `Vec` to be re-allocated. As such the address of the
-// bytes inside this `Vec` is stable.
-unsafe impl StableAddress for Mmap {}
-
 #[cfg(not(target_arch = "wasm32"))]
 pub struct MmapMut(memmap2::MmapMut);
 
diff --git a/compiler/rustc_data_structures/src/owning_ref/LICENSE b/compiler/rustc_data_structures/src/owning_ref/LICENSE
deleted file mode 100644
index dff72d1e432..00000000000
--- a/compiler/rustc_data_structures/src/owning_ref/LICENSE
+++ /dev/null
@@ -1,21 +0,0 @@
-The MIT License (MIT)
-
-Copyright (c) 2015 Marvin Löbel
-
-Permission is hereby granted, free of charge, to any person obtaining a copy
-of this software and associated documentation files (the "Software"), to deal
-in the Software without restriction, including without limitation the rights
-to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-copies of the Software, and to permit persons to whom the Software is
-furnished to do so, subject to the following conditions:
-
-The above copyright notice and this permission notice shall be included in all
-copies or substantial portions of the Software.
-
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-SOFTWARE.
diff --git a/compiler/rustc_data_structures/src/owning_ref/mod.rs b/compiler/rustc_data_structures/src/owning_ref/mod.rs
deleted file mode 100644
index d1d92b905b8..00000000000
--- a/compiler/rustc_data_structures/src/owning_ref/mod.rs
+++ /dev/null
@@ -1,1211 +0,0 @@
-#![warn(missing_docs)]
-
-/*!
-# An owning reference.
-
-This crate provides the _owning reference_ types `OwningRef` and `OwningRefMut`
-that enables it to bundle a reference together with the owner of the data it points to.
-This allows moving and dropping of an `OwningRef` without needing to recreate the reference.
-
-This can sometimes be useful because Rust borrowing rules normally prevent
-moving a type that has been moved from. For example, this kind of code gets rejected:
-
-```compile_fail,E0515
-fn return_owned_and_referenced<'a>() -> (Vec<u8>, &'a [u8]) {
-    let v = vec![1, 2, 3, 4];
-    let s = &v[1..3];
-    (v, s)
-}
-```
-
-Even though, from a memory-layout point of view, this can be entirely safe
-if the new location of the vector still lives longer than the lifetime `'a`
-of the reference because the backing allocation of the vector does not change.
-
-This library enables this safe usage by keeping the owner and the reference
-bundled together in a wrapper type that ensure that lifetime constraint:
-
-```
-# use rustc_data_structures::owning_ref::OwningRef;
-# fn main() {
-fn return_owned_and_referenced() -> OwningRef<Vec<u8>, [u8]> {
-    let v = vec![1, 2, 3, 4];
-    let or = OwningRef::new(v);
-    let or = or.map(|v| &v[1..3]);
-    or
-}
-# }
-```
-
-It works by requiring owner types to dereference to stable memory locations
-and preventing mutable access to root containers, which in practice requires heap allocation
-as provided by `Box<T>`, `Rc<T>`, etc.
-
-Also provided are typedefs for common owner type combinations,
-which allow for less verbose type signatures.
-For example, `BoxRef<T>` instead of `OwningRef<Box<T>, T>`.
-
-The crate also provides the more advanced `OwningHandle` type,
-which allows more freedom in bundling a dependent handle object
-along with the data it depends on, at the cost of some unsafe needed in the API.
-See the documentation around `OwningHandle` for more details.
-
-# Examples
-
-## Basics
-
-```
-use rustc_data_structures::owning_ref::BoxRef;
-
-fn main() {
-    // Create an array owned by a Box.
-    let arr = Box::new([1, 2, 3, 4]) as Box<[i32]>;
-
-    // Transfer into a BoxRef.
-    let arr: BoxRef<[i32]> = BoxRef::new(arr);
-    assert_eq!(&*arr, &[1, 2, 3, 4]);
-
-    // We can slice the array without losing ownership or changing type.
-    let arr: BoxRef<[i32]> = arr.map(|arr| &arr[1..3]);
-    assert_eq!(&*arr, &[2, 3]);
-
-    // Also works for Arc, Rc, String and Vec!
-}
-```
-
-## Caching a reference to a struct field
-
-```
-use rustc_data_structures::owning_ref::BoxRef;
-
-fn main() {
-    struct Foo {
-        tag: u32,
-        x: u16,
-        y: u16,
-        z: u16,
-    }
-    let foo = Foo { tag: 1, x: 100, y: 200, z: 300 };
-
-    let or = BoxRef::new(Box::new(foo)).map(|foo| {
-        match foo.tag {
-            0 => &foo.x,
-            1 => &foo.y,
-            2 => &foo.z,
-            _ => panic!(),
-        }
-    });
-
-    assert_eq!(*or, 200);
-}
-```
-
-## Caching a reference to an entry in a vector
-
-```
-use rustc_data_structures::owning_ref::VecRef;
-
-fn main() {
-    let v = VecRef::new(vec![1, 2, 3, 4, 5]).map(|v| &v[3]);
-    assert_eq!(*v, 4);
-}
-```
-
-## Caching a subslice of a String
-
-```
-use rustc_data_structures::owning_ref::StringRef;
-
-fn main() {
-    let s = StringRef::new("hello world".to_owned())
-        .map(|s| s.split(' ').nth(1).unwrap());
-
-    assert_eq!(&*s, "world");
-}
-```
-
-## Reference counted slices that share ownership of the backing storage
-
-```
-use rustc_data_structures::owning_ref::RcRef;
-use std::rc::Rc;
-
-fn main() {
-    let rc: RcRef<[i32]> = RcRef::new(Rc::new([1, 2, 3, 4]) as Rc<[i32]>);
-    assert_eq!(&*rc, &[1, 2, 3, 4]);
-
-    let rc_a: RcRef<[i32]> = rc.clone().map(|s| &s[0..2]);
-    let rc_b = rc.clone().map(|s| &s[1..3]);
-    let rc_c = rc.clone().map(|s| &s[2..4]);
-    assert_eq!(&*rc_a, &[1, 2]);
-    assert_eq!(&*rc_b, &[2, 3]);
-    assert_eq!(&*rc_c, &[3, 4]);
-
-    let rc_c_a = rc_c.clone().map(|s| &s[1]);
-    assert_eq!(&*rc_c_a, &4);
-}
-```
-
-## Atomic reference counted slices that share ownership of the backing storage
-
-```
-use rustc_data_structures::owning_ref::ArcRef;
-use std::sync::Arc;
-
-fn main() {
-    use std::thread;
-
-    fn par_sum(rc: ArcRef<[i32]>) -> i32 {
-        if rc.len() == 0 {
-            return 0;
-        } else if rc.len() == 1 {
-            return rc[0];
-        }
-        let mid = rc.len() / 2;
-        let left = rc.clone().map(|s| &s[..mid]);
-        let right = rc.map(|s| &s[mid..]);
-
-        let left = thread::spawn(move || par_sum(left));
-        let right = thread::spawn(move || par_sum(right));
-
-        left.join().unwrap() + right.join().unwrap()
-    }
-
-    let rc: Arc<[i32]> = Arc::new([1, 2, 3, 4]);
-    let rc: ArcRef<[i32]> = rc.into();
-
-    assert_eq!(par_sum(rc), 10);
-}
-```
-
-## References into RAII locks
-
-```
-use rustc_data_structures::owning_ref::RefRef;
-use std::cell::{RefCell, Ref};
-
-fn main() {
-    let refcell = RefCell::new((1, 2, 3, 4));
-    // Also works with Mutex and RwLock
-
-    let refref = {
-        let refref = RefRef::new(refcell.borrow()).map(|x| &x.3);
-        assert_eq!(*refref, 4);
-
-        // We move the RAII lock and the reference to one of
-        // the subfields in the data it guards here:
-        refref
-    };
-
-    assert_eq!(*refref, 4);
-
-    drop(refref);
-
-    assert_eq!(*refcell.borrow(), (1, 2, 3, 4));
-}
-```
-
-## Mutable reference
-
-When the owned container implements `DerefMut`, it is also possible to make
-a _mutable owning reference_. (e.g., with `Box`, `RefMut`, `MutexGuard`)
-
-```
-use rustc_data_structures::owning_ref::RefMutRefMut;
-use std::cell::{RefCell, RefMut};
-
-fn main() {
-    let refcell = RefCell::new((1, 2, 3, 4));
-
-    let mut refmut_refmut = {
-        let mut refmut_refmut = RefMutRefMut::new(refcell.borrow_mut()).map_mut(|x| &mut x.3);
-        assert_eq!(*refmut_refmut, 4);
-        *refmut_refmut *= 2;
-
-        refmut_refmut
-    };
-
-    assert_eq!(*refmut_refmut, 8);
-    *refmut_refmut *= 2;
-
-    drop(refmut_refmut);
-
-    assert_eq!(*refcell.borrow(), (1, 2, 3, 16));
-}
-```
-*/
-
-pub use stable_deref_trait::{
-    CloneStableDeref as CloneStableAddress, StableDeref as StableAddress,
-};
-use std::mem;
-
-/// An owning reference.
-///
-/// This wraps an owner `O` and a reference `&T` pointing
-/// at something reachable from `O::Target` while keeping
-/// the ability to move `self` around.
-///
-/// The owner is usually a pointer that points at some base type.
-///
-/// For more details and examples, see the module and method docs.
-pub struct OwningRef<O, T: ?Sized> {
-    owner: O,
-    reference: *const T,
-}
-
-/// An mutable owning reference.
-///
-/// This wraps an owner `O` and a reference `&mut T` pointing
-/// at something reachable from `O::Target` while keeping
-/// the ability to move `self` around.
-///
-/// The owner is usually a pointer that points at some base type.
-///
-/// For more details and examples, see the module and method docs.
-pub struct OwningRefMut<O, T: ?Sized> {
-    owner: O,
-    reference: *mut T,
-}
-
-/// Helper trait for an erased concrete type an owner dereferences to.
-/// This is used in form of a trait object for keeping
-/// something around to (virtually) call the destructor.
-pub trait Erased {}
-impl<T> Erased for T {}
-
-/// Helper trait for erasing the concrete type of what an owner dereferences to,
-/// for example `Box<T> -> Box<Erased>`. This would be unneeded with
-/// higher kinded types support in the language.
-#[allow(unused_lifetimes)]
-pub unsafe trait IntoErased<'a> {
-    /// Owner with the dereference type substituted to `Erased`.
-    type Erased;
-    /// Performs the type erasure.
-    fn into_erased(self) -> Self::Erased;
-}
-
-/// Helper trait for erasing the concrete type of what an owner dereferences to,
-/// for example `Box<T> -> Box<Erased + Send>`. This would be unneeded with
-/// higher kinded types support in the language.
-#[allow(unused_lifetimes)]
-pub unsafe trait IntoErasedSend<'a> {
-    /// Owner with the dereference type substituted to `Erased + Send`.
-    type Erased: Send;
-    /// Performs the type erasure.
-    fn into_erased_send(self) -> Self::Erased;
-}
-
-/// Helper trait for erasing the concrete type of what an owner dereferences to,
-/// for example `Box<T> -> Box<Erased + Send + Sync>`. This would be unneeded with
-/// higher kinded types support in the language.
-#[allow(unused_lifetimes)]
-pub unsafe trait IntoErasedSendSync<'a> {
-    /// Owner with the dereference type substituted to `Erased + Send + Sync`.
-    type Erased: Send + Sync;
-    /// Performs the type erasure.
-    fn into_erased_send_sync(self) -> Self::Erased;
-}
-
-/////////////////////////////////////////////////////////////////////////////
-// OwningRef
-/////////////////////////////////////////////////////////////////////////////
-
-impl<O, T: ?Sized> OwningRef<O, T> {
-    /// Creates a new owning reference from an owner
-    /// initialized to the direct dereference of it.
-    ///
-    /// # Example
-    /// ```
-    /// use rustc_data_structures::owning_ref::OwningRef;
-    ///
-    /// fn main() {
-    ///     let owning_ref = OwningRef::new(Box::new(42));
-    ///     assert_eq!(*owning_ref, 42);
-    /// }
-    /// ```
-    pub fn new(o: O) -> Self
-    where
-        O: StableAddress,
-        O: Deref<Target = T>,
-    {
-        OwningRef { reference: &*o, owner: o }
-    }
-
-    /// Like `new`, but doesn’t require `O` to implement the `StableAddress` trait.
-    /// Instead, the caller is responsible to make the same promises as implementing the trait.
-    ///
-    /// This is useful for cases where coherence rules prevents implementing the trait
-    /// without adding a dependency to this crate in a third-party library.
-    pub unsafe fn new_assert_stable_address(o: O) -> Self
-    where
-        O: Deref<Target = T>,
-    {
-        OwningRef { reference: &*o, owner: o }
-    }
-
-    /// Converts `self` into a new owning reference that points at something reachable
-    /// from the previous one.
-    ///
-    /// This can be a reference to a field of `U`, something reachable from a field of
-    /// `U`, or even something unrelated with a `'static` lifetime.
-    ///
-    /// # Example
-    /// ```
-    /// use rustc_data_structures::owning_ref::OwningRef;
-    ///
-    /// fn main() {
-    ///     let owning_ref = OwningRef::new(Box::new([1, 2, 3, 4]));
-    ///
-    ///     // create an owning reference that points at the
-    ///     // third element of the array.
-    ///     let owning_ref = owning_ref.map(|array| &array[2]);
-    ///     assert_eq!(*owning_ref, 3);
-    /// }
-    /// ```
-    pub fn map<F, U: ?Sized>(self, f: F) -> OwningRef<O, U>
-    where
-        O: StableAddress,
-        F: FnOnce(&T) -> &U,
-    {
-        OwningRef { reference: f(&self), owner: self.owner }
-    }
-
-    /// Tries to convert `self` into a new owning reference that points
-    /// at something reachable from the previous one.
-    ///
-    /// This can be a reference to a field of `U`, something reachable from a field of
-    /// `U`, or even something unrelated with a `'static` lifetime.
-    ///
-    /// # Example
-    /// ```
-    /// use rustc_data_structures::owning_ref::OwningRef;
-    ///
-    /// fn main() {
-    ///     let owning_ref = OwningRef::new(Box::new([1, 2, 3, 4]));
-    ///
-    ///     // create an owning reference that points at the
-    ///     // third element of the array.
-    ///     let owning_ref = owning_ref.try_map(|array| {
-    ///         if array[2] == 3 { Ok(&array[2]) } else { Err(()) }
-    ///     });
-    ///     assert_eq!(*owning_ref.unwrap(), 3);
-    /// }
-    /// ```
-    pub fn try_map<F, U: ?Sized, E>(self, f: F) -> Result<OwningRef<O, U>, E>
-    where
-        O: StableAddress,
-        F: FnOnce(&T) -> Result<&U, E>,
-    {
-        Ok(OwningRef { reference: f(&self)?, owner: self.owner })
-    }
-
-    /// Converts `self` into a new owning reference with a different owner type.
-    ///
-    /// The new owner type needs to still contain the original owner in some way
-    /// so that the reference into it remains valid. This function is marked unsafe
-    /// because the user needs to manually uphold this guarantee.
-    pub unsafe fn map_owner<F, P>(self, f: F) -> OwningRef<P, T>
-    where
-        O: StableAddress,
-        P: StableAddress,
-        F: FnOnce(O) -> P,
-    {
-        OwningRef { reference: self.reference, owner: f(self.owner) }
-    }
-
-    /// Converts `self` into a new owning reference where the owner is wrapped
-    /// in an additional `Box<O>`.
-    ///
-    /// This can be used to safely erase the owner of any `OwningRef<O, T>`
-    /// to an `OwningRef<Box<Erased>, T>`.
-    pub fn map_owner_box(self) -> OwningRef<Box<O>, T> {
-        OwningRef { reference: self.reference, owner: Box::new(self.owner) }
-    }
-
-    /// Erases the concrete base type of the owner with a trait object.
-    ///
-    /// This allows mixing of owned references with different owner base types.
-    ///
-    /// # Example
-    /// ```
-    /// use rustc_data_structures::owning_ref::{OwningRef, Erased};
-    ///
-    /// fn main() {
-    ///     // N.B., using the concrete types here for explicitness.
-    ///     // For less verbose code type aliases like `BoxRef` are provided.
-    ///
-    ///     let owning_ref_a: OwningRef<Box<[i32; 4]>, [i32; 4]>
-    ///         = OwningRef::new(Box::new([1, 2, 3, 4]));
-    ///
-    ///     let owning_ref_b: OwningRef<Box<Vec<(i32, bool)>>, Vec<(i32, bool)>>
-    ///         = OwningRef::new(Box::new(vec![(0, false), (1, true)]));
-    ///
-    ///     let owning_ref_a: OwningRef<Box<[i32; 4]>, i32>
-    ///         = owning_ref_a.map(|a| &a[0]);
-    ///
-    ///     let owning_ref_b: OwningRef<Box<Vec<(i32, bool)>>, i32>
-    ///         = owning_ref_b.map(|a| &a[1].0);
-    ///
-    ///     let owning_refs: [OwningRef<Box<dyn Erased>, i32>; 2]
-    ///         = [owning_ref_a.erase_owner(), owning_ref_b.erase_owner()];
-    ///
-    ///     assert_eq!(*owning_refs[0], 1);
-    ///     assert_eq!(*owning_refs[1], 1);
-    /// }
-    /// ```
-    pub fn erase_owner<'a>(self) -> OwningRef<O::Erased, T>
-    where
-        O: IntoErased<'a>,
-    {
-        OwningRef { reference: self.reference, owner: self.owner.into_erased() }
-    }
-
-    /// Erases the concrete base type of the owner with a trait object which implements `Send`.
-    ///
-    /// This allows mixing of owned references with different owner base types.
-    pub fn erase_send_owner<'a>(self) -> OwningRef<O::Erased, T>
-    where
-        O: IntoErasedSend<'a>,
-    {
-        OwningRef { reference: self.reference, owner: self.owner.into_erased_send() }
-    }
-
-    /// Erases the concrete base type of the owner with a trait object
-    /// which implements `Send` and `Sync`.
-    ///
-    /// This allows mixing of owned references with different owner base types.
-    pub fn erase_send_sync_owner<'a>(self) -> OwningRef<O::Erased, T>
-    where
-        O: IntoErasedSendSync<'a>,
-    {
-        OwningRef { reference: self.reference, owner: self.owner.into_erased_send_sync() }
-    }
-
-    // UNIMPLEMENTED: wrap_owner
-
-    // FIXME: Naming convention?
-    /// A getter for the underlying owner.
-    pub fn owner(&self) -> &O {
-        &self.owner
-    }
-
-    // FIXME: Naming convention?
-    /// Discards the reference and retrieves the owner.
-    pub fn into_inner(self) -> O {
-        self.owner
-    }
-}
-
-impl<O, T: ?Sized> OwningRefMut<O, T> {
-    /// Creates a new owning reference from an owner
-    /// initialized to the direct dereference of it.
-    ///
-    /// # Example
-    /// ```
-    /// use rustc_data_structures::owning_ref::OwningRefMut;
-    ///
-    /// fn main() {
-    ///     let owning_ref_mut = OwningRefMut::new(Box::new(42));
-    ///     assert_eq!(*owning_ref_mut, 42);
-    /// }
-    /// ```
-    pub fn new(mut o: O) -> Self
-    where
-        O: StableAddress,
-        O: DerefMut<Target = T>,
-    {
-        OwningRefMut { reference: &mut *o, owner: o }
-    }
-
-    /// Like `new`, but doesn’t require `O` to implement the `StableAddress` trait.
-    /// Instead, the caller is responsible to make the same promises as implementing the trait.
-    ///
-    /// This is useful for cases where coherence rules prevents implementing the trait
-    /// without adding a dependency to this crate in a third-party library.
-    pub unsafe fn new_assert_stable_address(mut o: O) -> Self
-    where
-        O: DerefMut<Target = T>,
-    {
-        OwningRefMut { reference: &mut *o, owner: o }
-    }
-
-    /// Converts `self` into a new _shared_ owning reference that points at
-    /// something reachable from the previous one.
-    ///
-    /// This can be a reference to a field of `U`, something reachable from a field of
-    /// `U`, or even something unrelated with a `'static` lifetime.
-    ///
-    /// # Example
-    /// ```
-    /// use rustc_data_structures::owning_ref::OwningRefMut;
-    ///
-    /// fn main() {
-    ///     let owning_ref_mut = OwningRefMut::new(Box::new([1, 2, 3, 4]));
-    ///
-    ///     // create an owning reference that points at the
-    ///     // third element of the array.
-    ///     let owning_ref = owning_ref_mut.map(|array| &array[2]);
-    ///     assert_eq!(*owning_ref, 3);
-    /// }
-    /// ```
-    pub fn map<F, U: ?Sized>(mut self, f: F) -> OwningRef<O, U>
-    where
-        O: StableAddress,
-        F: FnOnce(&mut T) -> &U,
-    {
-        OwningRef { reference: f(&mut self), owner: self.owner }
-    }
-
-    /// Converts `self` into a new _mutable_ owning reference that points at
-    /// something reachable from the previous one.
-    ///
-    /// This can be a reference to a field of `U`, something reachable from a field of
-    /// `U`, or even something unrelated with a `'static` lifetime.
-    ///
-    /// # Example
-    /// ```
-    /// use rustc_data_structures::owning_ref::OwningRefMut;
-    ///
-    /// fn main() {
-    ///     let owning_ref_mut = OwningRefMut::new(Box::new([1, 2, 3, 4]));
-    ///
-    ///     // create an owning reference that points at the
-    ///     // third element of the array.
-    ///     let owning_ref_mut = owning_ref_mut.map_mut(|array| &mut array[2]);
-    ///     assert_eq!(*owning_ref_mut, 3);
-    /// }
-    /// ```
-    pub fn map_mut<F, U: ?Sized>(mut self, f: F) -> OwningRefMut<O, U>
-    where
-        O: StableAddress,
-        F: FnOnce(&mut T) -> &mut U,
-    {
-        OwningRefMut { reference: f(&mut self), owner: self.owner }
-    }
-
-    /// Tries to convert `self` into a new _shared_ owning reference that points
-    /// at something reachable from the previous one.
-    ///
-    /// This can be a reference to a field of `U`, something reachable from a field of
-    /// `U`, or even something unrelated with a `'static` lifetime.
-    ///
-    /// # Example
-    /// ```
-    /// use rustc_data_structures::owning_ref::OwningRefMut;
-    ///
-    /// fn main() {
-    ///     let owning_ref_mut = OwningRefMut::new(Box::new([1, 2, 3, 4]));
-    ///
-    ///     // create an owning reference that points at the
-    ///     // third element of the array.
-    ///     let owning_ref = owning_ref_mut.try_map(|array| {
-    ///         if array[2] == 3 { Ok(&array[2]) } else { Err(()) }
-    ///     });
-    ///     assert_eq!(*owning_ref.unwrap(), 3);
-    /// }
-    /// ```
-    pub fn try_map<F, U: ?Sized, E>(mut self, f: F) -> Result<OwningRef<O, U>, E>
-    where
-        O: StableAddress,
-        F: FnOnce(&mut T) -> Result<&U, E>,
-    {
-        Ok(OwningRef { reference: f(&mut self)?, owner: self.owner })
-    }
-
-    /// Tries to convert `self` into a new _mutable_ owning reference that points
-    /// at something reachable from the previous one.
-    ///
-    /// This can be a reference to a field of `U`, something reachable from a field of
-    /// `U`, or even something unrelated with a `'static` lifetime.
-    ///
-    /// # Example
-    /// ```
-    /// use rustc_data_structures::owning_ref::OwningRefMut;
-    ///
-    /// fn main() {
-    ///     let owning_ref_mut = OwningRefMut::new(Box::new([1, 2, 3, 4]));
-    ///
-    ///     // create an owning reference that points at the
-    ///     // third element of the array.
-    ///     let owning_ref_mut = owning_ref_mut.try_map_mut(|array| {
-    ///         if array[2] == 3 { Ok(&mut array[2]) } else { Err(()) }
-    ///     });
-    ///     assert_eq!(*owning_ref_mut.unwrap(), 3);
-    /// }
-    /// ```
-    pub fn try_map_mut<F, U: ?Sized, E>(mut self, f: F) -> Result<OwningRefMut<O, U>, E>
-    where
-        O: StableAddress,
-        F: FnOnce(&mut T) -> Result<&mut U, E>,
-    {
-        Ok(OwningRefMut { reference: f(&mut self)?, owner: self.owner })
-    }
-
-    /// Converts `self` into a new owning reference with a different owner type.
-    ///
-    /// The new owner type needs to still contain the original owner in some way
-    /// so that the reference into it remains valid. This function is marked unsafe
-    /// because the user needs to manually uphold this guarantee.
-    pub unsafe fn map_owner<F, P>(self, f: F) -> OwningRefMut<P, T>
-    where
-        O: StableAddress,
-        P: StableAddress,
-        F: FnOnce(O) -> P,
-    {
-        OwningRefMut { reference: self.reference, owner: f(self.owner) }
-    }
-
-    /// Converts `self` into a new owning reference where the owner is wrapped
-    /// in an additional `Box<O>`.
-    ///
-    /// This can be used to safely erase the owner of any `OwningRefMut<O, T>`
-    /// to an `OwningRefMut<Box<Erased>, T>`.
-    pub fn map_owner_box(self) -> OwningRefMut<Box<O>, T> {
-        OwningRefMut { reference: self.reference, owner: Box::new(self.owner) }
-    }
-
-    /// Erases the concrete base type of the owner with a trait object.
-    ///
-    /// This allows mixing of owned references with different owner base types.
-    ///
-    /// # Example
-    /// ```
-    /// use rustc_data_structures::owning_ref::{OwningRefMut, Erased};
-    ///
-    /// fn main() {
-    ///     // N.B., using the concrete types here for explicitness.
-    ///     // For less verbose code type aliases like `BoxRef` are provided.
-    ///
-    ///     let owning_ref_mut_a: OwningRefMut<Box<[i32; 4]>, [i32; 4]>
-    ///         = OwningRefMut::new(Box::new([1, 2, 3, 4]));
-    ///
-    ///     let owning_ref_mut_b: OwningRefMut<Box<Vec<(i32, bool)>>, Vec<(i32, bool)>>
-    ///         = OwningRefMut::new(Box::new(vec![(0, false), (1, true)]));
-    ///
-    ///     let owning_ref_mut_a: OwningRefMut<Box<[i32; 4]>, i32>
-    ///         = owning_ref_mut_a.map_mut(|a| &mut a[0]);
-    ///
-    ///     let owning_ref_mut_b: OwningRefMut<Box<Vec<(i32, bool)>>, i32>
-    ///         = owning_ref_mut_b.map_mut(|a| &mut a[1].0);
-    ///
-    ///     let owning_refs_mut: [OwningRefMut<Box<dyn Erased>, i32>; 2]
-    ///         = [owning_ref_mut_a.erase_owner(), owning_ref_mut_b.erase_owner()];
-    ///
-    ///     assert_eq!(*owning_refs_mut[0], 1);
-    ///     assert_eq!(*owning_refs_mut[1], 1);
-    /// }
-    /// ```
-    pub fn erase_owner<'a>(self) -> OwningRefMut<O::Erased, T>
-    where
-        O: IntoErased<'a>,
-    {
-        OwningRefMut { reference: self.reference, owner: self.owner.into_erased() }
-    }
-
-    // UNIMPLEMENTED: wrap_owner
-
-    // FIXME: Naming convention?
-    /// A getter for the underlying owner.
-    pub fn owner(&self) -> &O {
-        &self.owner
-    }
-
-    // FIXME: Naming convention?
-    /// Discards the reference and retrieves the owner.
-    pub fn into_inner(self) -> O {
-        self.owner
-    }
-}
-
-/////////////////////////////////////////////////////////////////////////////
-// OwningHandle
-/////////////////////////////////////////////////////////////////////////////
-
-use std::ops::{Deref, DerefMut};
-
-/// `OwningHandle` is a complement to `OwningRef`. Where `OwningRef` allows
-/// consumers to pass around an owned object and a dependent reference,
-/// `OwningHandle` contains an owned object and a dependent _object_.
-///
-/// `OwningHandle` can encapsulate a `RefMut` along with its associated
-/// `RefCell`, or an `RwLockReadGuard` along with its associated `RwLock`.
-/// However, the API is completely generic and there are no restrictions on
-/// what types of owning and dependent objects may be used.
-///
-/// `OwningHandle` is created by passing an owner object (which dereferences
-/// to a stable address) along with a callback which receives a pointer to
-/// that stable location. The callback may then dereference the pointer and
-/// mint a dependent object, with the guarantee that the returned object will
-/// not outlive the referent of the pointer.
-///
-/// Since the callback needs to dereference a raw pointer, it requires `unsafe`
-/// code. To avoid forcing this unsafety on most callers, the `ToHandle` trait is
-/// implemented for common data structures. Types that implement `ToHandle` can
-/// be wrapped into an `OwningHandle` without passing a callback.
-pub struct OwningHandle<O, H>
-where
-    O: StableAddress,
-    H: Deref,
-{
-    handle: H,
-    _owner: O,
-}
-
-impl<O, H> Deref for OwningHandle<O, H>
-where
-    O: StableAddress,
-    H: Deref,
-{
-    type Target = H::Target;
-    fn deref(&self) -> &H::Target {
-        self.handle.deref()
-    }
-}
-
-unsafe impl<O, H> StableAddress for OwningHandle<O, H>
-where
-    O: StableAddress,
-    H: StableAddress,
-{
-}
-
-impl<O, H> DerefMut for OwningHandle<O, H>
-where
-    O: StableAddress,
-    H: DerefMut,
-{
-    fn deref_mut(&mut self) -> &mut H::Target {
-        self.handle.deref_mut()
-    }
-}
-
-/// Trait to implement the conversion of owner to handle for common types.
-pub trait ToHandle {
-    /// The type of handle to be encapsulated by the OwningHandle.
-    type Handle: Deref;
-
-    /// Given an appropriately-long-lived pointer to ourselves, create a
-    /// handle to be encapsulated by the `OwningHandle`.
-    unsafe fn to_handle(x: *const Self) -> Self::Handle;
-}
-
-/// Trait to implement the conversion of owner to mutable handle for common types.
-pub trait ToHandleMut {
-    /// The type of handle to be encapsulated by the OwningHandle.
-    type HandleMut: DerefMut;
-
-    /// Given an appropriately-long-lived pointer to ourselves, create a
-    /// mutable handle to be encapsulated by the `OwningHandle`.
-    unsafe fn to_handle_mut(x: *const Self) -> Self::HandleMut;
-}
-
-impl<O, H> OwningHandle<O, H>
-where
-    O: StableAddress<Target: ToHandle<Handle = H>>,
-    H: Deref,
-{
-    /// Creates a new `OwningHandle` for a type that implements `ToHandle`. For types
-    /// that don't implement `ToHandle`, callers may invoke `new_with_fn`, which accepts
-    /// a callback to perform the conversion.
-    pub fn new(o: O) -> Self {
-        OwningHandle::new_with_fn(o, |x| unsafe { O::Target::to_handle(x) })
-    }
-}
-
-impl<O, H> OwningHandle<O, H>
-where
-    O: StableAddress<Target: ToHandleMut<HandleMut = H>>,
-    H: DerefMut,
-{
-    /// Creates a new mutable `OwningHandle` for a type that implements `ToHandleMut`.
-    pub fn new_mut(o: O) -> Self {
-        OwningHandle::new_with_fn(o, |x| unsafe { O::Target::to_handle_mut(x) })
-    }
-}
-
-impl<O, H> OwningHandle<O, H>
-where
-    O: StableAddress,
-    H: Deref,
-{
-    /// Creates a new OwningHandle. The provided callback will be invoked with
-    /// a pointer to the object owned by `o`, and the returned value is stored
-    /// as the object to which this `OwningHandle` will forward `Deref` and
-    /// `DerefMut`.
-    pub fn new_with_fn<F>(o: O, f: F) -> Self
-    where
-        F: FnOnce(*const O::Target) -> H,
-    {
-        let h: H;
-        {
-            h = f(o.deref() as *const O::Target);
-        }
-
-        OwningHandle { handle: h, _owner: o }
-    }
-
-    /// Creates a new OwningHandle. The provided callback will be invoked with
-    /// a pointer to the object owned by `o`, and the returned value is stored
-    /// as the object to which this `OwningHandle` will forward `Deref` and
-    /// `DerefMut`.
-    pub fn try_new<F, E>(o: O, f: F) -> Result<Self, E>
-    where
-        F: FnOnce(*const O::Target) -> Result<H, E>,
-    {
-        let h: H;
-        {
-            h = f(o.deref() as *const O::Target)?;
-        }
-
-        Ok(OwningHandle { handle: h, _owner: o })
-    }
-}
-
-/////////////////////////////////////////////////////////////////////////////
-// std traits
-/////////////////////////////////////////////////////////////////////////////
-
-use std::borrow::Borrow;
-use std::cmp::Ordering;
-use std::fmt::{self, Debug};
-use std::hash::{Hash, Hasher};
-
-impl<O, T: ?Sized> Deref for OwningRef<O, T> {
-    type Target = T;
-
-    fn deref(&self) -> &T {
-        unsafe { &*self.reference }
-    }
-}
-
-impl<O, T: ?Sized> Deref for OwningRefMut<O, T> {
-    type Target = T;
-
-    fn deref(&self) -> &T {
-        unsafe { &*self.reference }
-    }
-}
-
-impl<O, T: ?Sized> DerefMut for OwningRefMut<O, T> {
-    fn deref_mut(&mut self) -> &mut T {
-        unsafe { &mut *self.reference }
-    }
-}
-
-unsafe impl<O, T: ?Sized> StableAddress for OwningRef<O, T> {}
-
-impl<O, T: ?Sized> AsRef<T> for OwningRef<O, T> {
-    fn as_ref(&self) -> &T {
-        self
-    }
-}
-
-impl<O, T: ?Sized> AsRef<T> for OwningRefMut<O, T> {
-    fn as_ref(&self) -> &T {
-        self
-    }
-}
-
-impl<O, T: ?Sized> AsMut<T> for OwningRefMut<O, T> {
-    fn as_mut(&mut self) -> &mut T {
-        self
-    }
-}
-
-impl<O, T: ?Sized> Borrow<T> for OwningRef<O, T> {
-    fn borrow(&self) -> &T {
-        self
-    }
-}
-
-impl<O, T: ?Sized> From<O> for OwningRef<O, T>
-where
-    O: StableAddress,
-    O: Deref<Target = T>,
-{
-    fn from(owner: O) -> Self {
-        OwningRef::new(owner)
-    }
-}
-
-impl<O, T: ?Sized> From<O> for OwningRefMut<O, T>
-where
-    O: StableAddress,
-    O: DerefMut<Target = T>,
-{
-    fn from(owner: O) -> Self {
-        OwningRefMut::new(owner)
-    }
-}
-
-impl<O, T: ?Sized> From<OwningRefMut<O, T>> for OwningRef<O, T>
-where
-    O: StableAddress,
-    O: DerefMut<Target = T>,
-{
-    fn from(other: OwningRefMut<O, T>) -> Self {
-        OwningRef { owner: other.owner, reference: other.reference }
-    }
-}
-
-// ^ FIXME: Is an Into impl for calling into_inner() possible as well?
-
-impl<O, T: ?Sized> Debug for OwningRef<O, T>
-where
-    O: Debug,
-    T: Debug,
-{
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "OwningRef {{ owner: {:?}, reference: {:?} }}", self.owner(), &**self)
-    }
-}
-
-impl<O, T: ?Sized> Debug for OwningRefMut<O, T>
-where
-    O: Debug,
-    T: Debug,
-{
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "OwningRefMut {{ owner: {:?}, reference: {:?} }}", self.owner(), &**self)
-    }
-}
-
-impl<O, T: ?Sized> Clone for OwningRef<O, T>
-where
-    O: CloneStableAddress,
-{
-    fn clone(&self) -> Self {
-        OwningRef { owner: self.owner.clone(), reference: self.reference }
-    }
-}
-
-unsafe impl<O, T: ?Sized> CloneStableAddress for OwningRef<O, T> where O: CloneStableAddress {}
-
-unsafe impl<O, T: ?Sized> Send for OwningRef<O, T>
-where
-    O: Send,
-    for<'a> &'a T: Send,
-{
-}
-unsafe impl<O, T: ?Sized> Sync for OwningRef<O, T>
-where
-    O: Sync,
-    for<'a> &'a T: Sync,
-{
-}
-
-unsafe impl<O, T: ?Sized> Send for OwningRefMut<O, T>
-where
-    O: Send,
-    for<'a> &'a mut T: Send,
-{
-}
-unsafe impl<O, T: ?Sized> Sync for OwningRefMut<O, T>
-where
-    O: Sync,
-    for<'a> &'a mut T: Sync,
-{
-}
-
-impl Debug for dyn Erased {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "<Erased>",)
-    }
-}
-
-impl<O, T: ?Sized> PartialEq for OwningRef<O, T>
-where
-    T: PartialEq,
-{
-    fn eq(&self, other: &Self) -> bool {
-        self.deref().eq(other.deref())
-    }
-}
-
-impl<O, T: ?Sized> Eq for OwningRef<O, T> where T: Eq {}
-
-impl<O, T: ?Sized> PartialOrd for OwningRef<O, T>
-where
-    T: PartialOrd,
-{
-    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
-        self.deref().partial_cmp(other.deref())
-    }
-}
-
-impl<O, T: ?Sized> Ord for OwningRef<O, T>
-where
-    T: Ord,
-{
-    fn cmp(&self, other: &Self) -> Ordering {
-        self.deref().cmp(other.deref())
-    }
-}
-
-impl<O, T: ?Sized> Hash for OwningRef<O, T>
-where
-    T: Hash,
-{
-    fn hash<H: Hasher>(&self, state: &mut H) {
-        self.deref().hash(state);
-    }
-}
-
-impl<O, T: ?Sized> PartialEq for OwningRefMut<O, T>
-where
-    T: PartialEq,
-{
-    fn eq(&self, other: &Self) -> bool {
-        self.deref().eq(other.deref())
-    }
-}
-
-impl<O, T: ?Sized> Eq for OwningRefMut<O, T> where T: Eq {}
-
-impl<O, T: ?Sized> PartialOrd for OwningRefMut<O, T>
-where
-    T: PartialOrd,
-{
-    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
-        self.deref().partial_cmp(other.deref())
-    }
-}
-
-impl<O, T: ?Sized> Ord for OwningRefMut<O, T>
-where
-    T: Ord,
-{
-    fn cmp(&self, other: &Self) -> Ordering {
-        self.deref().cmp(other.deref())
-    }
-}
-
-impl<O, T: ?Sized> Hash for OwningRefMut<O, T>
-where
-    T: Hash,
-{
-    fn hash<H: Hasher>(&self, state: &mut H) {
-        self.deref().hash(state);
-    }
-}
-
-/////////////////////////////////////////////////////////////////////////////
-// std types integration and convenience type defs
-/////////////////////////////////////////////////////////////////////////////
-
-use std::cell::{Ref, RefCell, RefMut};
-use std::rc::Rc;
-use std::sync::Arc;
-use std::sync::{MutexGuard, RwLockReadGuard, RwLockWriteGuard};
-
-impl<T: 'static> ToHandle for RefCell<T> {
-    type Handle = Ref<'static, T>;
-    unsafe fn to_handle(x: *const Self) -> Self::Handle {
-        (*x).borrow()
-    }
-}
-
-impl<T: 'static> ToHandleMut for RefCell<T> {
-    type HandleMut = RefMut<'static, T>;
-    unsafe fn to_handle_mut(x: *const Self) -> Self::HandleMut {
-        (*x).borrow_mut()
-    }
-}
-
-// N.B., implementing ToHandle{,Mut} for Mutex and RwLock requires a decision
-// about which handle creation to use (i.e., read() vs try_read()) as well as
-// what to do with error results.
-
-/// Typedef of an owning reference that uses a `Box` as the owner.
-pub type BoxRef<T, U = T> = OwningRef<Box<T>, U>;
-/// Typedef of an owning reference that uses a `Vec` as the owner.
-pub type VecRef<T, U = T> = OwningRef<Vec<T>, U>;
-/// Typedef of an owning reference that uses a `String` as the owner.
-pub type StringRef = OwningRef<String, str>;
-
-/// Typedef of an owning reference that uses an `Rc` as the owner.
-pub type RcRef<T, U = T> = OwningRef<Rc<T>, U>;
-/// Typedef of an owning reference that uses an `Arc` as the owner.
-pub type ArcRef<T, U = T> = OwningRef<Arc<T>, U>;
-
-/// Typedef of an owning reference that uses a `Ref` as the owner.
-pub type RefRef<'a, T, U = T> = OwningRef<Ref<'a, T>, U>;
-/// Typedef of an owning reference that uses a `RefMut` as the owner.
-pub type RefMutRef<'a, T, U = T> = OwningRef<RefMut<'a, T>, U>;
-/// Typedef of an owning reference that uses a `MutexGuard` as the owner.
-pub type MutexGuardRef<'a, T, U = T> = OwningRef<MutexGuard<'a, T>, U>;
-/// Typedef of an owning reference that uses an `RwLockReadGuard` as the owner.
-pub type RwLockReadGuardRef<'a, T, U = T> = OwningRef<RwLockReadGuard<'a, T>, U>;
-/// Typedef of an owning reference that uses an `RwLockWriteGuard` as the owner.
-pub type RwLockWriteGuardRef<'a, T, U = T> = OwningRef<RwLockWriteGuard<'a, T>, U>;
-
-/// Typedef of a mutable owning reference that uses a `Box` as the owner.
-pub type BoxRefMut<T, U = T> = OwningRefMut<Box<T>, U>;
-/// Typedef of a mutable owning reference that uses a `Vec` as the owner.
-pub type VecRefMut<T, U = T> = OwningRefMut<Vec<T>, U>;
-/// Typedef of a mutable owning reference that uses a `String` as the owner.
-pub type StringRefMut = OwningRefMut<String, str>;
-
-/// Typedef of a mutable owning reference that uses a `RefMut` as the owner.
-pub type RefMutRefMut<'a, T, U = T> = OwningRefMut<RefMut<'a, T>, U>;
-/// Typedef of a mutable owning reference that uses a `MutexGuard` as the owner.
-pub type MutexGuardRefMut<'a, T, U = T> = OwningRefMut<MutexGuard<'a, T>, U>;
-/// Typedef of a mutable owning reference that uses an `RwLockWriteGuard` as the owner.
-pub type RwLockWriteGuardRefMut<'a, T, U = T> = OwningRef<RwLockWriteGuard<'a, T>, U>;
-
-unsafe impl<'a, T: 'a> IntoErased<'a> for Box<T> {
-    type Erased = Box<dyn Erased + 'a>;
-    fn into_erased(self) -> Self::Erased {
-        self
-    }
-}
-unsafe impl<'a, T: 'a> IntoErased<'a> for Rc<T> {
-    type Erased = Rc<dyn Erased + 'a>;
-    fn into_erased(self) -> Self::Erased {
-        self
-    }
-}
-unsafe impl<'a, T: 'a> IntoErased<'a> for Arc<T> {
-    type Erased = Arc<dyn Erased + 'a>;
-    fn into_erased(self) -> Self::Erased {
-        self
-    }
-}
-
-unsafe impl<'a, T: Send + 'a> IntoErasedSend<'a> for Box<T> {
-    type Erased = Box<dyn Erased + Send + 'a>;
-    fn into_erased_send(self) -> Self::Erased {
-        self
-    }
-}
-
-unsafe impl<'a, T: Send + 'a> IntoErasedSendSync<'a> for Box<T> {
-    type Erased = Box<dyn Erased + Sync + Send + 'a>;
-    fn into_erased_send_sync(self) -> Self::Erased {
-        let result: Box<dyn Erased + Send + 'a> = self;
-        // This is safe since Erased can always implement Sync
-        // Only the destructor is available and it takes &mut self
-        unsafe { mem::transmute(result) }
-    }
-}
-
-unsafe impl<'a, T: Send + Sync + 'a> IntoErasedSendSync<'a> for Arc<T> {
-    type Erased = Arc<dyn Erased + Send + Sync + 'a>;
-    fn into_erased_send_sync(self) -> Self::Erased {
-        self
-    }
-}
-
-/// Typedef of an owning reference that uses an erased `Box` as the owner.
-pub type ErasedBoxRef<U> = OwningRef<Box<dyn Erased>, U>;
-/// Typedef of an owning reference that uses an erased `Rc` as the owner.
-pub type ErasedRcRef<U> = OwningRef<Rc<dyn Erased>, U>;
-/// Typedef of an owning reference that uses an erased `Arc` as the owner.
-pub type ErasedArcRef<U> = OwningRef<Arc<dyn Erased>, U>;
-
-/// Typedef of a mutable owning reference that uses an erased `Box` as the owner.
-pub type ErasedBoxRefMut<U> = OwningRefMut<Box<dyn Erased>, U>;
-
-#[cfg(test)]
-mod tests;
diff --git a/compiler/rustc_data_structures/src/owning_ref/tests.rs b/compiler/rustc_data_structures/src/owning_ref/tests.rs
deleted file mode 100644
index a9b187c4ce0..00000000000
--- a/compiler/rustc_data_structures/src/owning_ref/tests.rs
+++ /dev/null
@@ -1,711 +0,0 @@
-// FIXME: owning_ref is not sound under stacked borrows. Preferably, get rid of it.
-#[cfg(not(miri))]
-mod owning_ref {
-    use super::super::OwningRef;
-    use super::super::{BoxRef, Erased, ErasedBoxRef, RcRef};
-    use std::cmp::Ordering;
-    use std::collections::hash_map::DefaultHasher;
-    use std::collections::HashMap;
-    use std::hash::{Hash, Hasher};
-    use std::rc::Rc;
-
-    #[derive(Debug, PartialEq)]
-    struct Example(u32, String, [u8; 3]);
-    fn example() -> Example {
-        Example(42, "hello world".to_string(), [1, 2, 3])
-    }
-
-    #[test]
-    fn new_deref() {
-        let or: OwningRef<Box<()>, ()> = OwningRef::new(Box::new(()));
-        assert_eq!(&*or, &());
-    }
-
-    #[test]
-    fn into() {
-        let or: OwningRef<Box<()>, ()> = Box::new(()).into();
-        assert_eq!(&*or, &());
-    }
-
-    #[test]
-    fn map_offset_ref() {
-        let or: BoxRef<Example> = Box::new(example()).into();
-        let or: BoxRef<_, u32> = or.map(|x| &x.0);
-        assert_eq!(&*or, &42);
-
-        let or: BoxRef<Example> = Box::new(example()).into();
-        let or: BoxRef<_, u8> = or.map(|x| &x.2[1]);
-        assert_eq!(&*or, &2);
-    }
-
-    #[test]
-    fn map_heap_ref() {
-        let or: BoxRef<Example> = Box::new(example()).into();
-        let or: BoxRef<_, str> = or.map(|x| &x.1[..5]);
-        assert_eq!(&*or, "hello");
-    }
-
-    #[test]
-    fn map_static_ref() {
-        let or: BoxRef<()> = Box::new(()).into();
-        let or: BoxRef<_, str> = or.map(|_| "hello");
-        assert_eq!(&*or, "hello");
-    }
-
-    #[test]
-    fn map_chained() {
-        let or: BoxRef<String> = Box::new(example().1).into();
-        let or: BoxRef<_, str> = or.map(|x| &x[1..5]);
-        let or: BoxRef<_, str> = or.map(|x| &x[..2]);
-        assert_eq!(&*or, "el");
-    }
-
-    #[test]
-    fn map_chained_inference() {
-        let or = BoxRef::new(Box::new(example().1)).map(|x| &x[..5]).map(|x| &x[1..3]);
-        assert_eq!(&*or, "el");
-    }
-
-    #[test]
-    fn owner() {
-        let or: BoxRef<String> = Box::new(example().1).into();
-        let or = or.map(|x| &x[..5]);
-        assert_eq!(&*or, "hello");
-        assert_eq!(&**or.owner(), "hello world");
-    }
-
-    #[test]
-    fn into_inner() {
-        let or: BoxRef<String> = Box::new(example().1).into();
-        let or = or.map(|x| &x[..5]);
-        assert_eq!(&*or, "hello");
-        let s = *or.into_inner();
-        assert_eq!(&s, "hello world");
-    }
-
-    #[test]
-    fn fmt_debug() {
-        let or: BoxRef<String> = Box::new(example().1).into();
-        let or = or.map(|x| &x[..5]);
-        let s = format!("{:?}", or);
-        assert_eq!(&s, "OwningRef { owner: \"hello world\", reference: \"hello\" }");
-    }
-
-    #[test]
-    fn erased_owner() {
-        let o1: BoxRef<Example, str> = BoxRef::new(Box::new(example())).map(|x| &x.1[..]);
-
-        let o2: BoxRef<String, str> = BoxRef::new(Box::new(example().1)).map(|x| &x[..]);
-
-        let os: Vec<ErasedBoxRef<str>> = vec![o1.erase_owner(), o2.erase_owner()];
-        assert!(os.iter().all(|e| &e[..] == "hello world"));
-    }
-
-    #[test]
-    fn raii_locks() {
-        use super::super::{MutexGuardRef, RwLockReadGuardRef, RwLockWriteGuardRef};
-        use super::super::{RefMutRef, RefRef};
-        use std::cell::RefCell;
-        use std::sync::{Mutex, RwLock};
-
-        {
-            let a = RefCell::new(1);
-            let a = {
-                let a = RefRef::new(a.borrow());
-                assert_eq!(*a, 1);
-                a
-            };
-            assert_eq!(*a, 1);
-            drop(a);
-        }
-        {
-            let a = RefCell::new(1);
-            let a = {
-                let a = RefMutRef::new(a.borrow_mut());
-                assert_eq!(*a, 1);
-                a
-            };
-            assert_eq!(*a, 1);
-            drop(a);
-        }
-        {
-            let a = Mutex::new(1);
-            let a = {
-                let a = MutexGuardRef::new(a.lock().unwrap());
-                assert_eq!(*a, 1);
-                a
-            };
-            assert_eq!(*a, 1);
-            drop(a);
-        }
-        {
-            let a = RwLock::new(1);
-            let a = {
-                let a = RwLockReadGuardRef::new(a.read().unwrap());
-                assert_eq!(*a, 1);
-                a
-            };
-            assert_eq!(*a, 1);
-            drop(a);
-        }
-        {
-            let a = RwLock::new(1);
-            let a = {
-                let a = RwLockWriteGuardRef::new(a.write().unwrap());
-                assert_eq!(*a, 1);
-                a
-            };
-            assert_eq!(*a, 1);
-            drop(a);
-        }
-    }
-
-    #[test]
-    fn eq() {
-        let or1: BoxRef<[u8]> = BoxRef::new(vec![1, 2, 3].into_boxed_slice());
-        let or2: BoxRef<[u8]> = BoxRef::new(vec![1, 2, 3].into_boxed_slice());
-        assert_eq!(or1.eq(&or2), true);
-    }
-
-    #[test]
-    fn cmp() {
-        let or1: BoxRef<[u8]> = BoxRef::new(vec![1, 2, 3].into_boxed_slice());
-        let or2: BoxRef<[u8]> = BoxRef::new(vec![4, 5, 6].into_boxed_slice());
-        assert_eq!(or1.cmp(&or2), Ordering::Less);
-    }
-
-    #[test]
-    fn partial_cmp() {
-        let or1: BoxRef<[u8]> = BoxRef::new(vec![4, 5, 6].into_boxed_slice());
-        let or2: BoxRef<[u8]> = BoxRef::new(vec![1, 2, 3].into_boxed_slice());
-        assert_eq!(or1.partial_cmp(&or2), Some(Ordering::Greater));
-    }
-
-    #[test]
-    fn hash() {
-        let mut h1 = DefaultHasher::new();
-        let mut h2 = DefaultHasher::new();
-
-        let or1: BoxRef<[u8]> = BoxRef::new(vec![1, 2, 3].into_boxed_slice());
-        let or2: BoxRef<[u8]> = BoxRef::new(vec![1, 2, 3].into_boxed_slice());
-
-        or1.hash(&mut h1);
-        or2.hash(&mut h2);
-
-        assert_eq!(h1.finish(), h2.finish());
-    }
-
-    #[test]
-    fn borrow() {
-        let mut hash = HashMap::new();
-        let key = RcRef::<String>::new(Rc::new("foo-bar".to_string())).map(|s| &s[..]);
-
-        hash.insert(key.clone().map(|s| &s[..3]), 42);
-        hash.insert(key.clone().map(|s| &s[4..]), 23);
-
-        assert_eq!(hash.get("foo"), Some(&42));
-        assert_eq!(hash.get("bar"), Some(&23));
-    }
-
-    #[test]
-    fn total_erase() {
-        let a: OwningRef<Vec<u8>, [u8]> = OwningRef::new(vec![]).map(|x| &x[..]);
-        let b: OwningRef<Box<[u8]>, [u8]> =
-            OwningRef::new(vec![].into_boxed_slice()).map(|x| &x[..]);
-
-        let c: OwningRef<Rc<Vec<u8>>, [u8]> = unsafe { a.map_owner(Rc::new) };
-        let d: OwningRef<Rc<Box<[u8]>>, [u8]> = unsafe { b.map_owner(Rc::new) };
-
-        let e: OwningRef<Rc<dyn Erased>, [u8]> = c.erase_owner();
-        let f: OwningRef<Rc<dyn Erased>, [u8]> = d.erase_owner();
-
-        let _g = e.clone();
-        let _h = f.clone();
-    }
-
-    #[test]
-    fn total_erase_box() {
-        let a: OwningRef<Vec<u8>, [u8]> = OwningRef::new(vec![]).map(|x| &x[..]);
-        let b: OwningRef<Box<[u8]>, [u8]> =
-            OwningRef::new(vec![].into_boxed_slice()).map(|x| &x[..]);
-
-        let c: OwningRef<Box<Vec<u8>>, [u8]> = a.map_owner_box();
-        let d: OwningRef<Box<Box<[u8]>>, [u8]> = b.map_owner_box();
-
-        let _e: OwningRef<Box<dyn Erased>, [u8]> = c.erase_owner();
-        let _f: OwningRef<Box<dyn Erased>, [u8]> = d.erase_owner();
-    }
-
-    #[test]
-    fn try_map1() {
-        use std::any::Any;
-
-        let x = Box::new(123_i32);
-        let y: Box<dyn Any> = x;
-
-        assert!(OwningRef::new(y).try_map(|x| x.downcast_ref::<i32>().ok_or(())).is_ok());
-    }
-
-    #[test]
-    fn try_map2() {
-        use std::any::Any;
-
-        let x = Box::new(123_i32);
-        let y: Box<dyn Any> = x;
-
-        assert!(!OwningRef::new(y).try_map(|x| x.downcast_ref::<i32>().ok_or(())).is_err());
-    }
-}
-
-mod owning_handle {
-    use super::super::OwningHandle;
-    use super::super::RcRef;
-    use std::cell::RefCell;
-    use std::rc::Rc;
-    use std::sync::Arc;
-    use std::sync::RwLock;
-
-    #[test]
-    fn owning_handle() {
-        use std::cell::RefCell;
-        let cell = Rc::new(RefCell::new(2));
-        let cell_ref = RcRef::new(cell);
-        let mut handle =
-            OwningHandle::new_with_fn(cell_ref, |x| unsafe { x.as_ref() }.unwrap().borrow_mut());
-        assert_eq!(*handle, 2);
-        *handle = 3;
-        assert_eq!(*handle, 3);
-    }
-
-    #[test]
-    fn try_owning_handle_ok() {
-        use std::cell::RefCell;
-        let cell = Rc::new(RefCell::new(2));
-        let cell_ref = RcRef::new(cell);
-        let mut handle = OwningHandle::try_new::<_, ()>(cell_ref, |x| {
-            Ok(unsafe { x.as_ref() }.unwrap().borrow_mut())
-        })
-        .unwrap();
-        assert_eq!(*handle, 2);
-        *handle = 3;
-        assert_eq!(*handle, 3);
-    }
-
-    #[test]
-    fn try_owning_handle_err() {
-        use std::cell::RefCell;
-        let cell = Rc::new(RefCell::new(2));
-        let cell_ref = RcRef::new(cell);
-        let handle = OwningHandle::try_new::<_, ()>(cell_ref, |x| {
-            if false {
-                return Ok(unsafe { x.as_ref() }.unwrap().borrow_mut());
-            }
-            Err(())
-        });
-        assert!(handle.is_err());
-    }
-
-    #[test]
-    fn nested() {
-        use std::cell::RefCell;
-        use std::sync::{Arc, RwLock};
-
-        let result = {
-            let complex = Rc::new(RefCell::new(Arc::new(RwLock::new("someString"))));
-            let curr = RcRef::new(complex);
-            let curr =
-                OwningHandle::new_with_fn(curr, |x| unsafe { x.as_ref() }.unwrap().borrow_mut());
-            let mut curr = OwningHandle::new_with_fn(curr, |x| {
-                unsafe { x.as_ref() }.unwrap().try_write().unwrap()
-            });
-            assert_eq!(*curr, "someString");
-            *curr = "someOtherString";
-            curr
-        };
-        assert_eq!(*result, "someOtherString");
-    }
-
-    #[test]
-    fn owning_handle_safe() {
-        use std::cell::RefCell;
-        let cell = Rc::new(RefCell::new(2));
-        let cell_ref = RcRef::new(cell);
-        let handle = OwningHandle::new(cell_ref);
-        assert_eq!(*handle, 2);
-    }
-
-    #[test]
-    fn owning_handle_mut_safe() {
-        use std::cell::RefCell;
-        let cell = Rc::new(RefCell::new(2));
-        let cell_ref = RcRef::new(cell);
-        let mut handle = OwningHandle::new_mut(cell_ref);
-        assert_eq!(*handle, 2);
-        *handle = 3;
-        assert_eq!(*handle, 3);
-    }
-
-    #[test]
-    fn owning_handle_safe_2() {
-        let result = {
-            let complex = Rc::new(RefCell::new(Arc::new(RwLock::new("someString"))));
-            let curr = RcRef::new(complex);
-            let curr =
-                OwningHandle::new_with_fn(curr, |x| unsafe { x.as_ref() }.unwrap().borrow_mut());
-            let mut curr = OwningHandle::new_with_fn(curr, |x| {
-                unsafe { x.as_ref() }.unwrap().try_write().unwrap()
-            });
-            assert_eq!(*curr, "someString");
-            *curr = "someOtherString";
-            curr
-        };
-        assert_eq!(*result, "someOtherString");
-    }
-}
-
-// FIXME: owning_ref is not sound under stacked borrows. Preferably, get rid of it.
-#[cfg(not(miri))]
-mod owning_ref_mut {
-    use super::super::BoxRef;
-    use super::super::{BoxRefMut, Erased, ErasedBoxRefMut, OwningRefMut};
-    use std::cmp::Ordering;
-    use std::collections::hash_map::DefaultHasher;
-    use std::collections::HashMap;
-    use std::hash::{Hash, Hasher};
-
-    #[derive(Debug, PartialEq)]
-    struct Example(u32, String, [u8; 3]);
-    fn example() -> Example {
-        Example(42, "hello world".to_string(), [1, 2, 3])
-    }
-
-    #[test]
-    fn new_deref() {
-        let or: OwningRefMut<Box<()>, ()> = OwningRefMut::new(Box::new(()));
-        assert_eq!(&*or, &());
-    }
-
-    #[test]
-    fn new_deref_mut() {
-        let mut or: OwningRefMut<Box<()>, ()> = OwningRefMut::new(Box::new(()));
-        assert_eq!(&mut *or, &mut ());
-    }
-
-    #[test]
-    fn mutate() {
-        let mut or: OwningRefMut<Box<usize>, usize> = OwningRefMut::new(Box::new(0));
-        assert_eq!(&*or, &0);
-        *or = 1;
-        assert_eq!(&*or, &1);
-    }
-
-    #[test]
-    fn into() {
-        let or: OwningRefMut<Box<()>, ()> = Box::new(()).into();
-        assert_eq!(&*or, &());
-    }
-
-    #[test]
-    fn map_offset_ref() {
-        let or: BoxRefMut<Example> = Box::new(example()).into();
-        let or: BoxRef<_, u32> = or.map(|x| &mut x.0);
-        assert_eq!(&*or, &42);
-
-        let or: BoxRefMut<Example> = Box::new(example()).into();
-        let or: BoxRef<_, u8> = or.map(|x| &mut x.2[1]);
-        assert_eq!(&*or, &2);
-    }
-
-    #[test]
-    fn map_heap_ref() {
-        let or: BoxRefMut<Example> = Box::new(example()).into();
-        let or: BoxRef<_, str> = or.map(|x| &mut x.1[..5]);
-        assert_eq!(&*or, "hello");
-    }
-
-    #[test]
-    fn map_static_ref() {
-        let or: BoxRefMut<()> = Box::new(()).into();
-        let or: BoxRef<_, str> = or.map(|_| "hello");
-        assert_eq!(&*or, "hello");
-    }
-
-    #[test]
-    fn map_mut_offset_ref() {
-        let or: BoxRefMut<Example> = Box::new(example()).into();
-        let or: BoxRefMut<_, u32> = or.map_mut(|x| &mut x.0);
-        assert_eq!(&*or, &42);
-
-        let or: BoxRefMut<Example> = Box::new(example()).into();
-        let or: BoxRefMut<_, u8> = or.map_mut(|x| &mut x.2[1]);
-        assert_eq!(&*or, &2);
-    }
-
-    #[test]
-    fn map_mut_heap_ref() {
-        let or: BoxRefMut<Example> = Box::new(example()).into();
-        let or: BoxRefMut<_, str> = or.map_mut(|x| &mut x.1[..5]);
-        assert_eq!(&*or, "hello");
-    }
-
-    #[test]
-    fn map_mut_static_ref() {
-        static mut MUT_S: [u8; 5] = *b"hello";
-
-        let mut_s: &'static mut [u8] = unsafe { &mut MUT_S };
-
-        let or: BoxRefMut<()> = Box::new(()).into();
-        let or: BoxRefMut<_, [u8]> = or.map_mut(move |_| mut_s);
-        assert_eq!(&*or, b"hello");
-    }
-
-    #[test]
-    fn map_mut_chained() {
-        let or: BoxRefMut<String> = Box::new(example().1).into();
-        let or: BoxRefMut<_, str> = or.map_mut(|x| &mut x[1..5]);
-        let or: BoxRefMut<_, str> = or.map_mut(|x| &mut x[..2]);
-        assert_eq!(&*or, "el");
-    }
-
-    #[test]
-    fn map_chained_inference() {
-        let or = BoxRefMut::new(Box::new(example().1))
-            .map_mut(|x| &mut x[..5])
-            .map_mut(|x| &mut x[1..3]);
-        assert_eq!(&*or, "el");
-    }
-
-    #[test]
-    fn try_map_mut() {
-        let or: BoxRefMut<String> = Box::new(example().1).into();
-        let or: Result<BoxRefMut<_, str>, ()> = or.try_map_mut(|x| Ok(&mut x[1..5]));
-        assert_eq!(&*or.unwrap(), "ello");
-
-        let or: BoxRefMut<String> = Box::new(example().1).into();
-        let or: Result<BoxRefMut<_, str>, ()> = or.try_map_mut(|_| Err(()));
-        assert!(or.is_err());
-    }
-
-    #[test]
-    fn owner() {
-        let or: BoxRefMut<String> = Box::new(example().1).into();
-        let or = or.map_mut(|x| &mut x[..5]);
-        assert_eq!(&*or, "hello");
-        assert_eq!(&**or.owner(), "hello world");
-    }
-
-    #[test]
-    fn into_inner() {
-        let or: BoxRefMut<String> = Box::new(example().1).into();
-        let or = or.map_mut(|x| &mut x[..5]);
-        assert_eq!(&*or, "hello");
-        let s = *or.into_inner();
-        assert_eq!(&s, "hello world");
-    }
-
-    #[test]
-    fn fmt_debug() {
-        let or: BoxRefMut<String> = Box::new(example().1).into();
-        let or = or.map_mut(|x| &mut x[..5]);
-        let s = format!("{:?}", or);
-        assert_eq!(&s, "OwningRefMut { owner: \"hello world\", reference: \"hello\" }");
-    }
-
-    #[test]
-    fn erased_owner() {
-        let o1: BoxRefMut<Example, str> =
-            BoxRefMut::new(Box::new(example())).map_mut(|x| &mut x.1[..]);
-
-        let o2: BoxRefMut<String, str> =
-            BoxRefMut::new(Box::new(example().1)).map_mut(|x| &mut x[..]);
-
-        let os: Vec<ErasedBoxRefMut<str>> = vec![o1.erase_owner(), o2.erase_owner()];
-        assert!(os.iter().all(|e| &e[..] == "hello world"));
-    }
-
-    #[test]
-    fn raii_locks() {
-        use super::super::RefMutRefMut;
-        use super::super::{MutexGuardRefMut, RwLockWriteGuardRefMut};
-        use std::cell::RefCell;
-        use std::sync::{Mutex, RwLock};
-
-        {
-            let a = RefCell::new(1);
-            let a = {
-                let a = RefMutRefMut::new(a.borrow_mut());
-                assert_eq!(*a, 1);
-                a
-            };
-            assert_eq!(*a, 1);
-            drop(a);
-        }
-        {
-            let a = Mutex::new(1);
-            let a = {
-                let a = MutexGuardRefMut::new(a.lock().unwrap());
-                assert_eq!(*a, 1);
-                a
-            };
-            assert_eq!(*a, 1);
-            drop(a);
-        }
-        {
-            let a = RwLock::new(1);
-            let a = {
-                let a = RwLockWriteGuardRefMut::new(a.write().unwrap());
-                assert_eq!(*a, 1);
-                a
-            };
-            assert_eq!(*a, 1);
-            drop(a);
-        }
-    }
-
-    #[test]
-    fn eq() {
-        let or1: BoxRefMut<[u8]> = BoxRefMut::new(vec![1, 2, 3].into_boxed_slice());
-        let or2: BoxRefMut<[u8]> = BoxRefMut::new(vec![1, 2, 3].into_boxed_slice());
-        assert_eq!(or1.eq(&or2), true);
-    }
-
-    #[test]
-    fn cmp() {
-        let or1: BoxRefMut<[u8]> = BoxRefMut::new(vec![1, 2, 3].into_boxed_slice());
-        let or2: BoxRefMut<[u8]> = BoxRefMut::new(vec![4, 5, 6].into_boxed_slice());
-        assert_eq!(or1.cmp(&or2), Ordering::Less);
-    }
-
-    #[test]
-    fn partial_cmp() {
-        let or1: BoxRefMut<[u8]> = BoxRefMut::new(vec![4, 5, 6].into_boxed_slice());
-        let or2: BoxRefMut<[u8]> = BoxRefMut::new(vec![1, 2, 3].into_boxed_slice());
-        assert_eq!(or1.partial_cmp(&or2), Some(Ordering::Greater));
-    }
-
-    #[test]
-    fn hash() {
-        let mut h1 = DefaultHasher::new();
-        let mut h2 = DefaultHasher::new();
-
-        let or1: BoxRefMut<[u8]> = BoxRefMut::new(vec![1, 2, 3].into_boxed_slice());
-        let or2: BoxRefMut<[u8]> = BoxRefMut::new(vec![1, 2, 3].into_boxed_slice());
-
-        or1.hash(&mut h1);
-        or2.hash(&mut h2);
-
-        assert_eq!(h1.finish(), h2.finish());
-    }
-
-    #[test]
-    fn borrow() {
-        let mut hash = HashMap::new();
-        let key1 = BoxRefMut::<String>::new(Box::new("foo".to_string())).map(|s| &s[..]);
-        let key2 = BoxRefMut::<String>::new(Box::new("bar".to_string())).map(|s| &s[..]);
-
-        hash.insert(key1, 42);
-        hash.insert(key2, 23);
-
-        assert_eq!(hash.get("foo"), Some(&42));
-        assert_eq!(hash.get("bar"), Some(&23));
-    }
-
-    #[test]
-    fn total_erase() {
-        let a: OwningRefMut<Vec<u8>, [u8]> = OwningRefMut::new(vec![]).map_mut(|x| &mut x[..]);
-        let b: OwningRefMut<Box<[u8]>, [u8]> =
-            OwningRefMut::new(vec![].into_boxed_slice()).map_mut(|x| &mut x[..]);
-
-        let c: OwningRefMut<Box<Vec<u8>>, [u8]> = unsafe { a.map_owner(Box::new) };
-        let d: OwningRefMut<Box<Box<[u8]>>, [u8]> = unsafe { b.map_owner(Box::new) };
-
-        let _e: OwningRefMut<Box<dyn Erased>, [u8]> = c.erase_owner();
-        let _f: OwningRefMut<Box<dyn Erased>, [u8]> = d.erase_owner();
-    }
-
-    #[test]
-    fn total_erase_box() {
-        let a: OwningRefMut<Vec<u8>, [u8]> = OwningRefMut::new(vec![]).map_mut(|x| &mut x[..]);
-        let b: OwningRefMut<Box<[u8]>, [u8]> =
-            OwningRefMut::new(vec![].into_boxed_slice()).map_mut(|x| &mut x[..]);
-
-        let c: OwningRefMut<Box<Vec<u8>>, [u8]> = a.map_owner_box();
-        let d: OwningRefMut<Box<Box<[u8]>>, [u8]> = b.map_owner_box();
-
-        let _e: OwningRefMut<Box<dyn Erased>, [u8]> = c.erase_owner();
-        let _f: OwningRefMut<Box<dyn Erased>, [u8]> = d.erase_owner();
-    }
-
-    #[test]
-    fn try_map1() {
-        use std::any::Any;
-
-        let x = Box::new(123_i32);
-        let y: Box<dyn Any> = x;
-
-        assert!(OwningRefMut::new(y).try_map_mut(|x| x.downcast_mut::<i32>().ok_or(())).is_ok());
-    }
-
-    #[test]
-    fn try_map2() {
-        use std::any::Any;
-
-        let x = Box::new(123_i32);
-        let y: Box<dyn Any> = x;
-
-        assert!(!OwningRefMut::new(y).try_map_mut(|x| x.downcast_mut::<i32>().ok_or(())).is_err());
-    }
-
-    #[test]
-    fn try_map3() {
-        use std::any::Any;
-
-        let x = Box::new(123_i32);
-        let y: Box<dyn Any> = x;
-
-        assert!(OwningRefMut::new(y).try_map(|x| x.downcast_ref::<i32>().ok_or(())).is_ok());
-    }
-
-    #[test]
-    fn try_map4() {
-        use std::any::Any;
-
-        let x = Box::new(123_i32);
-        let y: Box<dyn Any> = x;
-
-        assert!(!OwningRefMut::new(y).try_map(|x| x.downcast_ref::<i32>().ok_or(())).is_err());
-    }
-
-    #[test]
-    fn into_owning_ref() {
-        use super::super::BoxRef;
-
-        let or: BoxRefMut<()> = Box::new(()).into();
-        let or: BoxRef<()> = or.into();
-        assert_eq!(&*or, &());
-    }
-
-    struct Foo {
-        u: u32,
-    }
-    struct Bar {
-        f: Foo,
-    }
-
-    #[test]
-    fn ref_mut() {
-        use std::cell::RefCell;
-
-        let a = RefCell::new(Bar { f: Foo { u: 42 } });
-        let mut b = OwningRefMut::new(a.borrow_mut());
-        assert_eq!(b.f.u, 42);
-        b.f.u = 43;
-        let mut c = b.map_mut(|x| &mut x.f);
-        assert_eq!(c.u, 43);
-        c.u = 44;
-        let mut d = c.map_mut(|x| &mut x.u);
-        assert_eq!(*d, 44);
-        *d = 45;
-        assert_eq!(*d, 45);
-    }
-}
diff --git a/compiler/rustc_data_structures/src/sync.rs b/compiler/rustc_data_structures/src/sync.rs
index 855a7eb331f..215b8088741 100644
--- a/compiler/rustc_data_structures/src/sync.rs
+++ b/compiler/rustc_data_structures/src/sync.rs
@@ -7,9 +7,6 @@
 //! while the serial versions degenerate straightforwardly to serial execution.
 //! The operations include `join`, `parallel`, `par_iter`, and `par_for_each`.
 //!
-//! `rustc_erase_owner!` erases an `OwningRef` owner into `Erased` for the
-//! serial version and `Erased + Send + Sync` for the parallel version.
-//!
 //! Types
 //! -----
 //! The parallel versions of types provide various kinds of synchronization,
@@ -60,12 +57,6 @@ cfg_if! {
         pub unsafe auto trait Send {}
         pub unsafe auto trait Sync {}
 
-        #[macro_export]
-        macro_rules! rustc_erase_owner {
-            ($v:expr) => {
-                $v.erase_owner()
-            }
-        }
         unsafe impl<T> Send for T {}
         unsafe impl<T> Sync for T {}
 
@@ -376,15 +367,6 @@ cfg_if! {
         /// This makes locks panic if they are already held.
         /// It is only useful when you are running in a single thread
         const ERROR_CHECKING: bool = false;
-
-        #[macro_export]
-        macro_rules! rustc_erase_owner {
-            ($v:expr) => {{
-                let v = $v;
-                ::rustc_data_structures::sync::assert_send_val(&v);
-                v.erase_send_sync_owner()
-            }}
-        }
     }
 }