Fallout: add phantom data to librand

Author: nikomatsakis

src/librand/distributions/mod.rs

@@ -21,6 +21,7 @@
 
 use core::prelude::*;
 use core::num::{Float, Int};
+use core::marker::PhantomData;
 
 use {Rng, Rand};
 
@@ -56,7 +57,13 @@ pub trait IndependentSample<Support>: Sample<Support> {
 
 /// A wrapper for generating types that implement `Rand` via the
 /// `Sample` & `IndependentSample` traits.
-pub struct RandSample<Sup>;
+pub struct RandSample<Sup> { _marker: PhantomData<Sup> }
+
+impl<Sup> RandSample<Sup> {
+    pub fn new() -> RandSample<Sup> {
+        RandSample { _marker: PhantomData }
+    }
+}
 
 impl<Sup: Rand> Sample<Sup> for RandSample<Sup> {
     fn sample<R: Rng>(&mut self, rng: &mut R) -> Sup { self.ind_sample(rng) }
@@ -285,7 +292,7 @@ mod tests {
 
     #[test]
     fn test_rand_sample() {
-        let mut rand_sample = RandSample::<ConstRand>;
+        let mut rand_sample = RandSample::<ConstRand>::new();
 
         assert_eq!(rand_sample.sample(&mut ::test::rng()), ConstRand(0));
         assert_eq!(rand_sample.ind_sample(&mut ::test::rng()), ConstRand(0));

src/librand/lib.rs

@@ -41,6 +41,7 @@ extern crate core;
 #[cfg(test)] #[macro_use] extern crate log;
 
 use core::prelude::*;
+use core::marker::PhantomData;
 
 pub use isaac::{IsaacRng, Isaac64Rng};
 pub use chacha::ChaChaRng;
@@ -206,7 +207,7 @@ pub trait Rng : Sized {
     ///                     .collect::<Vec<(f64, bool)>>());
     /// ```
     fn gen_iter<'a, T: Rand>(&'a mut self) -> Generator<'a, T, Self> {
-        Generator { rng: self }
+        Generator { rng: self, _marker: PhantomData }
     }
 
     /// Generate a random value in the range [`low`, `high`).
@@ -317,6 +318,7 @@ pub trait Rng : Sized {
 /// This iterator is created via the `gen_iter` method on `Rng`.
 pub struct Generator<'a, T, R:'a> {
     rng: &'a mut R,
+    _marker: PhantomData<T>
 }
 
 impl<'a, T: Rand, R: Rng> Iterator for Generator<'a, T, R> {