Relax Sized requirements for blanket impls

Author: fjarri

rand_core/CHANGELOG.md

@@ -4,6 +4,10 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## Unreleased
+### API changes
+- Relax `Sized` bound on blanket impls for `TryRngCore`, `TryCryptoRng`, `UnwrapErr`, and `UnwrapMut` (#1593)
+
 ## [0.9.1] - 2025-02-16
 ### API changes
 - Add `TryRngCore::unwrap_mut`, providing an impl of `RngCore` over `&mut rng` (#1589)

rand_core/src/lib.rs

@@ -254,7 +254,7 @@ pub trait TryRngCore {
 // Note that, unfortunately, this blanket impl prevents us from implementing
 // `TryRngCore` for types which can be dereferenced to `TryRngCore`, i.e. `TryRngCore`
 // will not be automatically implemented for `&mut R`, `Box<R>`, etc.
-impl<R: RngCore> TryRngCore for R {
+impl<R: RngCore + ?Sized> TryRngCore for R {
     type Error = core::convert::Infallible;
 
     #[inline]
@@ -290,14 +290,14 @@ impl<R: RngCore> TryRngCore for R {
 /// (like [`OsRng`]) or if the `default()` instance uses a strong, fresh seed.
 pub trait TryCryptoRng: TryRngCore {}
 
-impl<R: CryptoRng> TryCryptoRng for R {}
+impl<R: CryptoRng + ?Sized> TryCryptoRng for R {}
 
 /// Wrapper around [`TryRngCore`] implementation which implements [`RngCore`]
 /// by panicking on potential errors.
 #[derive(Debug, Default, Clone, Copy, Eq, PartialEq, Hash)]
-pub struct UnwrapErr<R: TryRngCore>(pub R);
+pub struct UnwrapErr<R: TryRngCore + ?Sized>(pub R);
 
-impl<R: TryRngCore> RngCore for UnwrapErr<R> {
+impl<R: TryRngCore + ?Sized> RngCore for UnwrapErr<R> {
     #[inline]
     fn next_u32(&mut self) -> u32 {
         self.0.try_next_u32().unwrap()
@@ -314,14 +314,14 @@ impl<R: TryRngCore> RngCore for UnwrapErr<R> {
     }
 }
 
-impl<R: TryCryptoRng> CryptoRng for UnwrapErr<R> {}
+impl<R: TryCryptoRng + ?Sized> CryptoRng for UnwrapErr<R> {}
 
 /// Wrapper around [`TryRngCore`] implementation which implements [`RngCore`]
 /// by panicking on potential errors.
 #[derive(Debug, Eq, PartialEq, Hash)]
 pub struct UnwrapMut<'r, R: TryRngCore + ?Sized>(pub &'r mut R);
 
-impl<R: TryRngCore> RngCore for UnwrapMut<'_, R> {
+impl<R: TryRngCore + ?Sized> RngCore for UnwrapMut<'_, R> {
     #[inline]
     fn next_u32(&mut self) -> u32 {
         self.0.try_next_u32().unwrap()
@@ -338,7 +338,7 @@ impl<R: TryRngCore> RngCore for UnwrapMut<'_, R> {
     }
 }
 
-impl<R: TryCryptoRng> CryptoRng for UnwrapMut<'_, R> {}
+impl<R: TryCryptoRng + ?Sized> CryptoRng for UnwrapMut<'_, R> {}
 
 /// A random number generator that can be explicitly seeded.
 ///