std: Remove `rand` crate and module

This commit removes the `rand` crate from the standard library facade as
well as the `__rand` module in the standard library. Neither of these
were used in any meaningful way in the standard library itself. The only
need for randomness in libstd is to initialize the thread-local keys of
a `HashMap`, and that unconditionally used `OsRng` defined in the
standard library anyway.

The cruft of the `rand` crate and the extra `rand` support in the
standard library makes libstd slightly more difficult to port to new
platforms, namely WebAssembly which doesn't have any randomness at all
(without interfacing with JS). The purpose of this commit is to clarify
and streamline randomness in libstd, focusing on how it's only required
in one location, hashmap seeds.

Note that the `rand` crate out of tree has almost always been a drop-in
replacement for the `rand` crate in-tree, so any usage (accidental or
purposeful) of the crate in-tree should switch to the `rand` crate on
crates.io. This then also has the further benefit of avoiding
duplication (mostly) between the two crates!

5 files changed, 10 insertions, 2 deletions

diff --git a/src/liballoc/Cargo.toml b/src/liballoc/Cargo.toml
index 686e5681d12..0a265ee1376 100644
--- a/src/liballoc/Cargo.toml
+++ b/src/liballoc/Cargo.toml
@@ -11,6 +11,9 @@ path = "lib.rs"
 core = { path = "../libcore" }
 std_unicode = { path = "../libstd_unicode" }
 
+[dev-dependencies]
+rand = "0.3"
+
 [[test]]
 name = "collectionstests"
 path = "../liballoc/tests/lib.rs"
diff --git a/src/liballoc/lib.rs b/src/liballoc/lib.rs
index a40ed060604..3cc3ea46796 100644
--- a/src/liballoc/lib.rs
+++ b/src/liballoc/lib.rs
@@ -135,6 +135,8 @@
 extern crate std;
 #[cfg(test)]
 extern crate test;
+#[cfg(test)]
+extern crate rand;
 
 extern crate std_unicode;
 
diff --git a/src/liballoc/linked_list.rs b/src/liballoc/linked_list.rs
index f897feb7afa..fac6acaca61 100644
--- a/src/liballoc/linked_list.rs
+++ b/src/liballoc/linked_list.rs
@@ -1269,10 +1269,11 @@ unsafe impl<'a, T: Sync> Sync for IterMut<'a, T> {}
 
 #[cfg(test)]
 mod tests {
-    use std::__rand::{thread_rng, Rng};
     use std::thread;
     use std::vec::Vec;
 
+    use rand::{thread_rng, Rng};
+
     use super::{LinkedList, Node};
 
     #[cfg(test)]
diff --git a/src/liballoc/tests/lib.rs b/src/liballoc/tests/lib.rs
index c5beb63d12e..00ebd88d464 100644
--- a/src/liballoc/tests/lib.rs
+++ b/src/liballoc/tests/lib.rs
@@ -30,6 +30,7 @@
 #![feature(unicode)]
 
 extern crate std_unicode;
+extern crate rand;
 
 use std::hash::{Hash, Hasher};
 use std::collections::hash_map::DefaultHasher;
diff --git a/src/liballoc/tests/slice.rs b/src/liballoc/tests/slice.rs
index c53bf15f1bf..85d5ce304b8 100644
--- a/src/liballoc/tests/slice.rs
+++ b/src/liballoc/tests/slice.rs
@@ -10,9 +10,10 @@
 
 use std::cmp::Ordering::{Equal, Greater, Less};
 use std::mem;
-use std::__rand::{Rng, thread_rng};
 use std::rc::Rc;
 
+use rand::{Rng, thread_rng};
+
 fn square(n: usize) -> usize {
     n * n
 }