Migrate ff to rand_core 0.3 (used by rand 0.5)

Cargo.toml

@@ -10,7 +10,7 @@ repository = "https://github.com/ebfull/ff"
 
 [dependencies]
 byteorder = "1"
-rand = "0.4"
+rand_core = "0.3"
 ff_derive = { version = "0.3.0", path = "ff_derive", optional = true }
 
 [features]

ff_derive/src/lib.rs

@@ -136,13 +136,6 @@ fn prime_field_repr_impl(repr: &syn::Ident, limbs: usize) -> proc_macro2::TokenS
             }
         }
 
-        impl ::rand::Rand for #repr {
-            #[inline(always)]
-            fn rand<R: ::rand::Rng>(rng: &mut R) -> Self {
-                #repr(rng.gen())
-            }
-        }
-
         impl ::std::fmt::Display for #repr {
             fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
                 try!(write!(f, "0x"));
@@ -839,22 +832,6 @@ fn prime_field_impl(
             }
         }
 
-        impl ::rand::Rand for #name {
-            /// Computes a uniformly random element using rejection sampling.
-            fn rand<R: ::rand::Rng>(rng: &mut R) -> Self {
-                loop {
-                    let mut tmp = #name(#repr::rand(rng));
-
-                    // Mask away the unused bits at the beginning.
-                    tmp.0.as_mut()[#top_limb_index] &= 0xffffffffffffffff >> REPR_SHAVE_BITS;
-
-                    if tmp.is_valid() {
-                        return tmp
-                    }
-                }
-            }
-        }
-
         impl From<#name> for #repr {
             fn from(e: #name) -> #repr {
                 e.into_repr()
@@ -904,6 +881,26 @@ fn prime_field_impl(
         }
 
         impl ::ff::Field for #name {
+            /// Computes a uniformly random element using rejection sampling.
+            fn random<R: ::rand_core::RngCore>(rng: &mut R) -> Self {
+                loop {
+                    let mut tmp = {
+                        let mut repr = [0u64; #limbs];
+                        for i in 0..#limbs {
+                            repr[i] = rng.next_u64();
+                        }
+                        #name(#repr(repr))
+                    };
+
+                    // Mask away the unused bits at the beginning.
+                    tmp.0.as_mut()[#top_limb_index] &= 0xffffffffffffffff >> REPR_SHAVE_BITS;
+
+                    if tmp.is_valid() {
+                        return tmp
+                    }
+                }
+            }
+
             #[inline]
             fn zero() -> Self {
                 #name(#repr::from(0))

src/lib.rs

@@ -1,7 +1,7 @@
 #![allow(unused_imports)]
 
 extern crate byteorder;
-extern crate rand;
+extern crate rand_core;
 
 #[cfg(feature = "derive")]
 #[macro_use]
@@ -10,14 +10,18 @@ extern crate ff_derive;
 #[cfg(feature = "derive")]
 pub use ff_derive::*;
 
+use rand_core::RngCore;
 use std::error::Error;
 use std::fmt;
 use std::io::{self, Read, Write};
 
 /// This trait represents an element of a field.
 pub trait Field:
-    Sized + Eq + Copy + Clone + Send + Sync + fmt::Debug + fmt::Display + 'static + rand::Rand
+    Sized + Eq + Copy + Clone + Send + Sync + fmt::Debug + fmt::Display + 'static
 {
+    /// Returns an element chosen uniformly at random using a user-provided RNG.
+    fn random<R: RngCore>(rng: &mut R) -> Self;
+
     /// Returns the zero element of the field, the additive identity.
     fn zero() -> Self;
 
@@ -100,7 +104,6 @@ pub trait PrimeFieldRepr:
     + fmt::Debug
     + fmt::Display
     + 'static
-    + rand::Rand
     + AsRef<[u64]>
     + AsMut<[u64]>
     + From<u64>