mv compiler to compiler/

compiler/rustc_data_structures/src/ptr_key.rs

@@ -0,0 +1,37 @@
+use std::ops::Deref;
+use std::{hash, ptr};
+
+/// 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>(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
+    }
+}