Switch to using rand_core and rand_chacha directly

And run `rustfmt`.

Author: LegNeato

crates/bevy_entropy/Cargo.toml

@@ -17,7 +17,8 @@ keywords = ["bevy", "random", "entropy"]
 bevy_app = { path = "../bevy_app", version = "0.8.0-dev" }
 bevy_utils = { path = "../bevy_utils", version = "0.8.0-dev" }
 # other
-rand = { version = "0.8", features = ["std_rng"] }
+rand_core = { version = "0.6.3" }
+rand_chacha = { version = "0.3.1" }
 
 [dev-dependencies]
 bevy_internal = { path = "../bevy_internal", version = "0.8.0-dev" }

crates/bevy_entropy/src/lib.rs

@@ -1,6 +1,7 @@
 use bevy_app::{App, Plugin};
 use bevy_utils::tracing::{debug, trace};
-use rand::{rngs::StdRng, RngCore, SeedableRng};
+use rand_chacha::ChaCha12Rng;
+use rand_core::{RngCore, SeedableRng};
 
 pub mod prelude {
     #[doc(hidden)]
@@ -25,14 +26,14 @@ impl Plugin for EntropyPlugin {
 }
 
 /// A resource that provides entropy.
-pub struct Entropy(StdRng);
+pub struct Entropy(ChaCha12Rng);
 
 impl Default for Entropy {
     /// The default entropy source is non-deterministic and seeded from the operating system.
     /// For a deterministic source, use [`Entropy::from`].
     fn default() -> Self {
         debug!("Entropy created via the operating system");
-        let rng = StdRng::from_entropy();
+        let rng = ChaCha12Rng::from_entropy();
         Entropy(rng)
     }
 }
@@ -43,7 +44,7 @@ impl Entropy {
     /// If determinism is not required, use [`Entropy::default`].
     pub fn from(seed: [u8; 32]) -> Self {
         debug!("Entropy created via seed: {:?} ", seed);
-        let rng = StdRng::from_seed(seed);
+        let rng = ChaCha12Rng::from_seed(seed);
         Entropy(rng)
     }
 

crates/bevy_internal/src/prelude.rs

@@ -1,9 +1,9 @@
 #[doc(hidden)]
 pub use crate::{
-    app::prelude::*, asset::prelude::*, core::prelude::*, ecs::prelude::*, entropy::prelude::*, hierarchy::prelude::*,
-    input::prelude::*, log::prelude::*, math::prelude::*, reflect::prelude::*, scene::prelude::*,
-    time::prelude::*, transform::prelude::*, utils::prelude::*, window::prelude::*, DefaultPlugins,
-    MinimalPlugins,
+    app::prelude::*, asset::prelude::*, core::prelude::*, ecs::prelude::*, entropy::prelude::*,
+    hierarchy::prelude::*, input::prelude::*, log::prelude::*, math::prelude::*,
+    reflect::prelude::*, scene::prelude::*, time::prelude::*, transform::prelude::*,
+    utils::prelude::*, window::prelude::*, DefaultPlugins, MinimalPlugins,
 };
 
 pub use bevy_derive::{bevy_main, Deref, DerefMut};