Remove Clone for StdRng, new bound for ReseedingRng (#1677)

Author: dhardy

CHANGELOG.md

@@ -17,6 +17,7 @@ You may also find the [Upgrade Guide](https://rust-random.github.io/book/update.
 - Fix `OsError::raw_os_error` on UEFI targets by returning `Option<usize>` (#1665)
 - Replace fn `TryRngCore::read_adapter(..) -> RngReadAdapter` with simpler struct `RngReader` (#1669)
 - Remove fns `SeedableRng::from_os_rng`, `try_from_os_rng` (#1674)
+- Remove `Clone` support for `StdRng`, `ReseedingRng` (#1677)
 
 ### Additions
 - Add fns `IndexedRandom::choose_iter`, `choose_weighted_iter` (#1632)

src/rngs/reseeding.rs

@@ -21,7 +21,6 @@ use rand_core::{CryptoRng, RngCore, SeedableRng, TryCryptoRng, TryRngCore};
 /// `ReseedingRng` reseeds the underlying PRNG in the following cases:
 ///
 /// - On a manual call to [`reseed()`].
-/// - After `clone()`, the clone will be reseeded on first use.
 /// - After the PRNG has generated a configurable number of random bytes.
 ///
 /// # When should reseeding after a fixed number of generated bytes be used?
@@ -62,9 +61,6 @@ use rand_core::{CryptoRng, RngCore, SeedableRng, TryCryptoRng, TryRngCore};
 /// let mut reseeding_rng = ReseedingRng::<ChaCha20Core, _>::new(0, OsRng).unwrap();
 ///
 /// println!("{}", reseeding_rng.random::<u64>());
-///
-/// let mut cloned_rng = reseeding_rng.clone();
-/// assert!(reseeding_rng.random::<u64>() != cloned_rng.random::<u64>());
 /// ```
 ///
 /// [`BlockRngCore`]: rand_core::block::BlockRngCore
@@ -124,18 +120,6 @@ where
     }
 }
 
-impl<R, Rsdr> Clone for ReseedingRng<R, Rsdr>
-where
-    R: BlockRngCore + SeedableRng + Clone,
-    Rsdr: TryRngCore + Clone,
-{
-    fn clone(&self) -> ReseedingRng<R, Rsdr> {
-        // Recreating `BlockRng` seems easier than cloning it and resetting
-        // the index.
-        ReseedingRng(BlockRng::new(self.0.core.clone()))
-    }
-}
-
 impl<R, Rsdr> CryptoRng for ReseedingRng<R, Rsdr>
 where
     R: BlockRngCore<Item = u32> + SeedableRng + CryptoBlockRng,
@@ -228,21 +212,6 @@ where
     }
 }
 
-impl<R, Rsdr> Clone for ReseedingCore<R, Rsdr>
-where
-    R: BlockRngCore + SeedableRng + Clone,
-    Rsdr: TryRngCore + Clone,
-{
-    fn clone(&self) -> ReseedingCore<R, Rsdr> {
-        ReseedingCore {
-            inner: self.inner.clone(),
-            reseeder: self.reseeder.clone(),
-            threshold: self.threshold,
-            bytes_until_reseed: 0, // reseed clone on first use
-        }
-    }
-}
-
 impl<R, Rsdr> CryptoBlockRng for ReseedingCore<R, Rsdr>
 where
     R: BlockRngCore<Item = u32> + SeedableRng + CryptoBlockRng,
@@ -277,19 +246,4 @@ mod test {
             assert_eq!(buf, seq);
         }
     }
-
-    #[test]
-    #[allow(clippy::redundant_clone)]
-    fn test_clone_reseeding() {
-        let zero = const_rng(0);
-        let mut rng1 = ReseedingRng::<Core, _>::new(32 * 4, zero).unwrap();
-
-        let first: u32 = rng1.random();
-        for _ in 0..10 {
-            let _ = rng1.random::<u32>();
-        }
-
-        let mut rng2 = rng1.clone();
-        assert_eq!(first, rng2.random::<u32>());
-    }
 }

src/rngs/std.rs

@@ -66,7 +66,7 @@ use chacha20::ChaCha12Rng as Rng;
 /// [CSPRNG]: https://rust-random.github.io/book/guide-gen.html#cryptographically-secure-pseudo-random-number-generator
 /// [rand_chacha]: https://crates.io/crates/rand_chacha
 /// [rand issue]: https://github.com/rust-random/rand/issues/932
-#[derive(Clone, Debug, PartialEq, Eq)]
+#[derive(Debug, PartialEq, Eq)]
 pub struct StdRng(Rng);
 
 impl RngCore for StdRng {