data_structures: Add a reference wrapper for pointer-indexed maps/sets

Use `ptr::eq` for comparing pointers

2 files changed, 56 insertions, 10 deletions

diff --git a/src/librustc_data_structures/lib.rs b/src/librustc_data_structures/lib.rs
index b386f887d77..ef0d57c7b7c 100644
--- a/src/librustc_data_structures/lib.rs
+++ b/src/librustc_data_structures/lib.rs
@@ -56,29 +56,30 @@ extern crate rustc_cratesio_shim;
 
 pub use rustc_serialize::hex::ToHex;
 
-pub mod array_vec;
 pub mod accumulate_vec;
-pub mod small_vec;
+pub mod array_vec;
 pub mod base_n;
 pub mod bitslice;
 pub mod bitvec;
+pub mod flock;
+pub mod fx;
+pub mod graph;
 pub mod indexed_set;
 pub mod indexed_vec;
 pub mod obligation_forest;
+pub mod owning_ref;
+pub mod ptr_key;
 pub mod sip128;
+pub mod small_vec;
 pub mod snapshot_map;
 pub use ena::snapshot_vec;
+pub mod sorted_map;
 pub mod stable_hasher;
-pub mod transitive_relation;
-pub use ena::unify;
-pub mod fx;
-pub mod tuple_slice;
-pub mod graph;
-pub mod flock;
 pub mod sync;
-pub mod owning_ref;
 pub mod tiny_list;
-pub mod sorted_map;
+pub mod transitive_relation;
+pub mod tuple_slice;
+pub use ena::unify;
 pub mod work_queue;
 
 pub struct OnDrop<F: Fn()>(pub F);
diff --git a/src/librustc_data_structures/ptr_key.rs b/src/librustc_data_structures/ptr_key.rs
new file mode 100644
index 00000000000..6835dab38df
--- /dev/null
+++ b/src/librustc_data_structures/ptr_key.rs
@@ -0,0 +1,45 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use std::{hash, ptr};
+use std::ops::Deref;
+
+/// A wrapper around reference that compares and hashes like a pointer.
+/// Can be used as a key in sets/maps indexed by pointers to avoid `unsafe`.
+#[derive(Debug)]
+pub struct PtrKey<'a, T: 'a>(pub &'a T);
+
+impl<'a, T> Clone for PtrKey<'a, T> {
+    fn clone(&self) -> Self { *self }
+}
+
+impl<'a, T> Copy for PtrKey<'a, T> {}
+
+impl<'a, T> PartialEq for PtrKey<'a, T> {
+    fn eq(&self, rhs: &Self) -> bool {
+        ptr::eq(self.0, rhs.0)
+    }
+}
+
+impl<'a, T> Eq for PtrKey<'a, T> {}
+
+impl<'a, T> hash::Hash for PtrKey<'a, T> {
+    fn hash<H: hash::Hasher>(&self, hasher: &mut H) {
+        (self.0 as *const T).hash(hasher)
+    }
+}
+
+impl<'a, T> Deref for PtrKey<'a, T> {
+    type Target = T;
+
+    fn deref(&self) -> &Self::Target {
+        self.0
+    }
+}