Allow unsized BlockRngCore

Author: dhardy

rand-core/src/impls.rs

@@ -184,10 +184,10 @@ pub fn next_u64_via_fill<R: RngCore + ?Sized>(rng: &mut R) -> u64 {
 /// [`RngCore`]: ../RngCore.t.html
 /// [`SeedableRng`]: ../SeedableRng.t.html
 #[derive(Clone)]
-pub struct BlockRng<R: BlockRngCore> {
-    pub core: R,
+pub struct BlockRng<R: BlockRngCore + ?Sized> {
     pub results: R::Results,
     pub index: usize,
+    pub core: R,
 }
 
 // Custom Debug implementation that does not expose the contents of `results`.

rand-core/src/lib.rs

@@ -200,7 +200,7 @@ pub trait RngCore {
 /// // Final RNG.
 /// type MyRng = BlockRng<u32, MyRngCore>;
 /// ```
-pub trait BlockRngCore: Sized {
+pub trait BlockRngCore {
     /// Results element type, e.g. `u32`.
     type Item;