Remove fns {try_,}from_os_rng

Author: dhardy

README.md

@@ -91,7 +91,7 @@ compiler versions will be compatible. This is especially true of Rand's
 experimental `simd_support` feature.
 
 Rand supports limited functionality in `no_std` mode (enabled via
-`default-features = false`). In this case, `OsRng` and `from_os_rng` are
+`default-features = false`). In this case, `OsRng` is
 unavailable (unless `os_rng` is enabled), large parts of `seq` are
 unavailable (unless `alloc` is enabled), and `ThreadRng` is unavailable.
 

rand_core/src/lib.rs

@@ -490,48 +490,6 @@ pub trait SeedableRng: Sized {
         rng.try_fill_bytes(seed.as_mut())?;
         Ok(Self::from_seed(seed))
     }
-
-    /// Creates a new instance of the RNG seeded via [`getrandom`].
-    ///
-    /// This method is the recommended way to construct non-deterministic PRNGs
-    /// since it is convenient and secure.
-    ///
-    /// Note that this method may panic on (extremely unlikely) [`getrandom`] errors.
-    /// If it's not desirable, use the [`try_from_os_rng`] method instead.
-    ///
-    /// In case the overhead of using [`getrandom`] to seed *many* PRNGs is an
-    /// issue, one may prefer to seed from a local PRNG, e.g.
-    /// `from_rng(rand::rng()).unwrap()`.
-    ///
-    /// # Panics
-    ///
-    /// If [`getrandom`] is unable to provide secure entropy this method will panic.
-    ///
-    /// [`getrandom`]: https://docs.rs/getrandom
-    /// [`try_from_os_rng`]: SeedableRng::try_from_os_rng
-    #[cfg(feature = "os_rng")]
-    fn from_os_rng() -> Self {
-        match Self::try_from_os_rng() {
-            Ok(res) => res,
-            Err(err) => panic!("from_os_rng failed: {}", err),
-        }
-    }
-
-    /// Creates a new instance of the RNG seeded via [`getrandom`] without unwrapping
-    /// potential [`getrandom`] errors.
-    ///
-    /// In case the overhead of using [`getrandom`] to seed *many* PRNGs is an
-    /// issue, one may prefer to seed from a local PRNG, e.g.
-    /// `from_rng(&mut rand::rng()).unwrap()`.
-    ///
-    /// [`getrandom`]: https://docs.rs/getrandom
-    #[cfg(feature = "os_rng")]
-    fn try_from_os_rng() -> Result<Self, getrandom::Error> {
-        let mut seed = Self::Seed::default();
-        getrandom::fill(seed.as_mut())?;
-        let res = Self::from_seed(seed);
-        Ok(res)
-    }
 }
 
 #[cfg(test)]

src/rngs/small.rs

@@ -47,13 +47,6 @@ type Rng = super::xoshiro256plusplus::Xoshiro256PlusPlus;
 ///     let rng = SmallRng::from_rng(&mut rand::rng());
 ///     # let _: SmallRng = rng;
 ///     ```
-///     or [`SeedableRng::from_os_rng`]:
-///     ```
-///     # use rand::SeedableRng;
-///     # use rand::rngs::SmallRng;
-///     let rng = SmallRng::from_os_rng();
-///     # let _: SmallRng = rng;
-///     ```
 /// 2.  To use a deterministic integral seed, use `seed_from_u64`. This uses a
 ///     hash function internally to yield a (typically) good seed from any
 ///     input.

src/rngs/std.rs

@@ -39,8 +39,8 @@ use chacha20::ChaCha12Rng as Rng;
 ///
 /// Using a fresh seed **direct from the OS** is the most secure option:
 /// ```
-/// # use rand::{SeedableRng, rngs::StdRng};
-/// let rng = StdRng::from_os_rng();
+/// # use rand::{SeedableRng, rngs::{StdRng, OsRng}};
+/// let rng = StdRng::try_from_rng(&mut OsRng).unwrap();
 /// # let _: StdRng = rng;
 /// ```
 ///