Use DerefMut instead of Box/&mut to re-implement RngCore

src/lib.rs

@@ -272,7 +272,7 @@ extern crate stdweb;
 
 
 use core::{marker, mem, slice};
-#[cfg(all(feature="alloc", not(feature="std")))] use alloc::boxed::Box;
+use core::ops::DerefMut;
 
 // external rngs
 pub use jitter::JitterRng;
@@ -740,30 +740,7 @@ pub trait Rng: RngCore {
 
 impl<R: RngCore> Rng for R {}
 
-impl<'a, R: RngCore + ?Sized> RngCore for &'a mut R {
-    #[inline]
-    fn next_u32(&mut self) -> u32 {
-        (**self).next_u32()
-    }
-
-    #[inline]
-    fn next_u64(&mut self) -> u64 {
-        (**self).next_u64()
-    }
-
-    #[inline]
-    fn fill_bytes(&mut self, dest: &mut [u8]) {
-        (**self).fill_bytes(dest)
-    }
-
-    #[inline]
-    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
-        (**self).try_fill_bytes(dest)
-    }
-}
-
-#[cfg(any(feature="std", feature="alloc"))]
-impl<R: RngCore + ?Sized> RngCore for Box<R> {
+impl<R: RngCore + ?Sized, T: DerefMut<Target = R>> RngCore for T {
     #[inline]
     fn next_u32(&mut self) -> u32 {
         (**self).next_u32()