Auto merge of #107136 - petrochenkov:dochidden, r=cjgillot

[rust.git] / library / std / src / lib.rs

diff --git a/library/std/src/lib.rs b/library/std/src/lib.rs
index 6575cc71b051429cd6ac4a0c46c5d0628a96b219..99cc01863104850f21f1aba37334021cc8cba5f6 100644 (file)
--- a/library/std/src/lib.rs
+++ b/library/std/src/lib.rs
@@ -238,7 +238,6 @@
 #![feature(allocator_internals)]
 #![feature(allow_internal_unsafe)]
 #![feature(allow_internal_unstable)]
-#![feature(box_syntax)]
 #![feature(c_unwind)]
 #![feature(cfg_target_thread_local)]
 #![feature(concat_idents)]
@@ -652,3 +651,30 @@ mod sealed {
     #[unstable(feature = "sealed", issue = "none")]
     pub trait Sealed {}
 }
+
+#[cfg(test)]
+#[allow(dead_code)] // Not used in all configurations.
+pub(crate) mod test_helpers {
+    /// Test-only replacement for `rand::thread_rng()`, which is unusable for
+    /// us, as we want to allow running stdlib tests on tier-3 targets which may
+    /// not have `getrandom` support.
+    ///
+    /// Does a bit of a song and dance to ensure that the seed is different on
+    /// each call (as some tests sadly rely on this), but doesn't try that hard.
+    ///
+    /// This is duplicated in the `core`, `alloc` test suites (as well as
+    /// `std`'s integration tests), but figuring out a mechanism to share these
+    /// seems far more painful than copy-pasting a 7 line function a couple
+    /// times, given that even under a perma-unstable feature, I don't think we
+    /// want to expose types from `rand` from `std`.
+    #[track_caller]
+    pub(crate) fn test_rng() -> rand_xorshift::XorShiftRng {
+        use core::hash::{BuildHasher, Hash, Hasher};
+        let mut hasher = crate::collections::hash_map::RandomState::new().build_hasher();
+        core::panic::Location::caller().hash(&mut hasher);
+        let hc64 = hasher.finish();
+        let seed_vec = hc64.to_le_bytes().into_iter().chain(0u8..8).collect::<Vec<u8>>();
+        let seed: [u8; 16] = seed_vec.as_slice().try_into().unwrap();
+        rand::SeedableRng::from_seed(seed)
+    }
+}