Initial commit

crates/std/src/arena/intern/hasher.rs

@@ -0,0 +1,22 @@
+use std::hash::Hasher;
+
+#[derive(Default, Clone, Copy, PartialEq, Eq)]
+pub struct NoHash(Option<u64>);
+
+impl Hasher for NoHash {
+    fn write_u64(&mut self, i: u64) {
+        if self.0.is_some() {
+            panic!("called write_u64 twice")
+        } else {
+            self.0 = Some(i);
+        }
+    }
+
+    fn write(&mut self, _: &[u8]) {
+        unreachable!()
+    }
+
+    fn finish(&self) -> u64 {
+        self.0.unwrap()
+    }
+}