From 3a8ae170c678caf9d6ebacc04256c1e90631e50d Mon Sep 17 00:00:00 2001
From: Paul Dicker <pitdicker@gmail.com>
Date: Sun, 29 Apr 2018 16:10:59 +0200
Subject: [PATCH] Require AsMut for BlockRngCore::Results

---
 rand_core/CHANGELOG.md  | 1 +
 rand_core/src/impls.rs  | 4 ++--
 rand_core/src/lib.rs    | 2 +-
 src/prng/isaac_array.rs | 7 +++++++
 src/reseeding.rs        | 2 +-
 5 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/rand_core/CHANGELOG.md b/rand_core/CHANGELOG.md
index ebde39eca60..79603a4f438 100644
--- a/rand_core/CHANGELOG.md
+++ b/rand_core/CHANGELOG.md
@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Enable the `std` feature by default. (#409)
 - Change `BlockRng64::inner` and add `BlockRng64::inner_mut` to mirror `BlockRng`. (#419)
 - Add `BlockRng{64}::index` and `BlockRng{64}::generate_and_set`. (#374, #419)
+- Change `BlockRngCore::Results` bound to also require `AsMut<[Self::Item]>`. (#419)
 
 ## [0.1.0] - 2018-04-17
 (Split out of the Rand crate, changes here are relative to rand 0.4.2)
diff --git a/rand_core/src/impls.rs b/rand_core/src/impls.rs
index 46166de5b97..54b122e07b9 100644
--- a/rand_core/src/impls.rs
+++ b/rand_core/src/impls.rs
@@ -249,7 +249,7 @@ impl<R: BlockRngCore> BlockRng<R> {
 }
 
 impl<R: BlockRngCore<Item=u32>> RngCore for BlockRng<R>
-where <R as BlockRngCore>::Results: AsRef<[u32]>
+where <R as BlockRngCore>::Results: AsRef<[u32]> + AsMut<[u32]>
 {
     #[inline(always)]
     fn next_u32(&mut self) -> u32 {
@@ -448,7 +448,7 @@ impl<R: BlockRngCore> BlockRng64<R> {
 }
 
 impl<R: BlockRngCore<Item=u64>> RngCore for BlockRng64<R>
-where <R as BlockRngCore>::Results: AsRef<[u64]>
+where <R as BlockRngCore>::Results: AsRef<[u64]> + AsMut<[u64]>
 {
     #[inline(always)]
     fn next_u32(&mut self) -> u32 {
diff --git a/rand_core/src/lib.rs b/rand_core/src/lib.rs
index 4d2f997967b..fc8c419eeb3 100644
--- a/rand_core/src/lib.rs
+++ b/rand_core/src/lib.rs
@@ -238,7 +238,7 @@ pub trait BlockRngCore {
     
     /// Results type. This is the 'block' an RNG implementing `BlockRngCore`
     /// generates, which will usually be an array like `[u32; 16]`.
-    type Results: AsRef<[Self::Item]> + Default;
+    type Results: AsRef<[Self::Item]> + AsMut<[Self::Item]> + Default;
 
     /// Generate a new block of results.
     fn generate(&mut self, results: &mut Self::Results);
diff --git a/src/prng/isaac_array.rs b/src/prng/isaac_array.rs
index 327cfbf5bcf..3ebf828c684 100644
--- a/src/prng/isaac_array.rs
+++ b/src/prng/isaac_array.rs
@@ -38,6 +38,13 @@ impl<T> ::core::convert::AsRef<[T]> for IsaacArray<T> {
     }
 }
 
+impl<T> ::core::convert::AsMut<[T]> for IsaacArray<T> {
+    #[inline(always)]
+    fn as_mut(&mut self) -> &mut [T] {
+        &mut self.inner[..]
+    }
+}
+
 impl<T> ::core::ops::Deref for IsaacArray<T> {
     type Target = [T; RAND_SIZE];
     #[inline(always)]
diff --git a/src/reseeding.rs b/src/reseeding.rs
index 0f7f049429a..c74862cbdde 100644
--- a/src/reseeding.rs
+++ b/src/reseeding.rs
@@ -84,7 +84,7 @@ where R: BlockRngCore + SeedableRng,
 // implements RngCore, but we can't specify that because ReseedingCore is private
 impl<R, Rsdr: RngCore> RngCore for ReseedingRng<R, Rsdr>
 where R: BlockRngCore<Item = u32> + SeedableRng,
-    <R as BlockRngCore>::Results: AsRef<[u32]>
+    <R as BlockRngCore>::Results: AsRef<[u32]> + AsMut<[u32]>
 {
     #[inline(always)]
     fn next_u32(&mut self) -> u32 {