Port some improvements from rust-lang/rust#49000

src/iter.rs

@@ -1,7 +1,7 @@
 //! `GenericArray` iterator implementation.
 
 use super::{ArrayLength, GenericArray};
-use core::{cmp, ptr};
+use core::{cmp, ptr, fmt, mem};
 use core::mem::ManuallyDrop;
 
 /// An iterator that moves out of a `GenericArray`
@@ -26,6 +26,23 @@ mod test {
     }
 }
 
+impl<T, N> GenericArrayIter<T, N>
+where
+    N: ArrayLength<T>,
+{
+    /// Returns the remaining items of this iterator as a slice
+    #[inline]
+    pub fn as_slice(&self) -> &[T] {
+        &self.array.as_slice()[self.index..self.index_back]
+    }
+
+    /// Returns the remaining items of this iterator as a mutable slice
+    #[inline]
+    pub fn as_mut_slice(&mut self) -> &mut [T] {
+        &mut self.array.as_mut_slice()[self.index..self.index_back]
+    }
+}
+
 impl<T, N> IntoIterator for GenericArray<T, N>
 where
     N: ArrayLength<T>,
@@ -42,21 +59,58 @@ where
     }
 }
 
+// Based on work in rust-land/rust#49000
+impl<T: fmt::Debug, N> fmt::Debug for GenericArrayIter<T, N>
+where
+    N: ArrayLength<T>,
+{
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_tuple("GenericArrayIter")
+            .field(&self.as_slice())
+            .finish()
+    }
+}
+
 impl<T, N> Drop for GenericArrayIter<T, N>
 where
     N: ArrayLength<T>,
 {
     #[inline]
     fn drop(&mut self) {
         // Drop values that are still alive.
-        for p in &mut self.array[self.index..self.index_back] {
+        for p in self.as_mut_slice() {
             unsafe {
                 ptr::drop_in_place(p);
             }
         }
     }
 }
 
+impl<T: Clone, N> Clone for GenericArrayIter<T, N>
+where
+    N: ArrayLength<T>,
+{
+    fn clone(&self) -> Self {
+        // This places all cloned elements at the start of the new array iterator,
+        // not at their original indices.
+        unsafe {
+            let mut iter = GenericArrayIter {
+                array: ManuallyDrop::new(mem::uninitialized()),
+                index: 0,
+                index_back: 0,
+            };
+
+            for (dst, src) in iter.array.iter_mut().zip(self.as_slice()) {
+                ptr::write(dst, src.clone());
+
+                iter.index_back += 1;
+            }
+
+            iter
+        }
+    }
+}
+
 impl<T, N> Iterator for GenericArrayIter<T, N>
 where
     N: ArrayLength<T>,
@@ -90,8 +144,10 @@ where
     fn nth(&mut self, n: usize) -> Option<T> {
         // First consume values prior to the nth.
         let ndrop = cmp::min(n, self.len());
+
         for p in &mut self.array[self.index..self.index + ndrop] {
             self.index += 1;
+
             unsafe {
                 ptr::drop_in_place(p);
             }
@@ -129,3 +185,5 @@ where
         self.index_back - self.index
     }
 }
+
+// TODO: Implement `FusedIterator` and `TrustedLen` when stabilized

tests/iter.rs

@@ -0,0 +1,164 @@
+#[macro_use]
+extern crate generic_array;
+
+use std::cell::Cell;
+use std::ops::Drop;
+
+use generic_array::GenericArray;
+use generic_array::typenum::consts::U5;
+
+#[test]
+fn test_into_iter_as_slice() {
+    let array = arr![char; 'a', 'b', 'c'];
+    let mut into_iter = array.into_iter();
+    assert_eq!(into_iter.as_slice(), &['a', 'b', 'c']);
+    let _ = into_iter.next().unwrap();
+    assert_eq!(into_iter.as_slice(), &['b', 'c']);
+    let _ = into_iter.next().unwrap();
+    let _ = into_iter.next().unwrap();
+    assert_eq!(into_iter.as_slice(), &[]);
+}
+
+#[test]
+fn test_into_iter_as_mut_slice() {
+    let array = arr![char; 'a', 'b', 'c'];
+    let mut into_iter = array.into_iter();
+    assert_eq!(into_iter.as_slice(), &['a', 'b', 'c']);
+    into_iter.as_mut_slice()[0] = 'x';
+    into_iter.as_mut_slice()[1] = 'y';
+    assert_eq!(into_iter.next().unwrap(), 'x');
+    assert_eq!(into_iter.as_slice(), &['y', 'c']);
+}
+
+#[test]
+fn test_into_iter_debug() {
+    let array = arr![char; 'a', 'b', 'c'];
+    let into_iter = array.into_iter();
+    let debug = format!("{:?}", into_iter);
+    assert_eq!(debug, "GenericArrayIter(['a', 'b', 'c'])");
+}
+
+#[test]
+fn test_into_iter_clone() {
+    fn iter_equal<I: Iterator<Item = i32>>(it: I, slice: &[i32]) {
+        let v: Vec<i32> = it.collect();
+        assert_eq!(&v[..], slice);
+    }
+    let mut it = arr![i32; 1, 2, 3].into_iter();
+    iter_equal(it.clone(), &[1, 2, 3]);
+    assert_eq!(it.next(), Some(1));
+    let mut it = it.rev();
+    iter_equal(it.clone(), &[3, 2]);
+    assert_eq!(it.next(), Some(3));
+    iter_equal(it.clone(), &[2]);
+    assert_eq!(it.next(), Some(2));
+    iter_equal(it.clone(), &[]);
+    assert_eq!(it.next(), None);
+}
+
+#[test]
+fn test_into_iter_nth() {
+    let v = arr![i32; 0, 1, 2, 3, 4];
+    for i in 0..v.len() {
+        assert_eq!(v.clone().into_iter().nth(i).unwrap(), v[i]);
+    }
+    assert_eq!(v.clone().into_iter().nth(v.len()), None);
+
+    let mut iter = v.into_iter();
+    assert_eq!(iter.nth(2).unwrap(), v[2]);
+    assert_eq!(iter.nth(1).unwrap(), v[4]);
+}
+
+#[test]
+fn test_into_iter_last() {
+    let v = arr![i32; 0, 1, 2, 3, 4];
+    assert_eq!(v.into_iter().last().unwrap(), 4);
+    assert_eq!(arr![i32; 0].into_iter().last().unwrap(), 0);
+}
+
+#[test]
+fn test_into_iter_count() {
+    let v = arr![i32; 0, 1, 2, 3, 4];
+    assert_eq!(v.clone().into_iter().count(), 5);
+
+    let mut iter2 = v.into_iter();
+    iter2.next();
+    iter2.next();
+    assert_eq!(iter2.count(), 3);
+}
+
+#[test]
+fn test_into_iter_flat_map() {
+    assert!((0..5).flat_map(|i| arr![i32; 2 * i, 2 * i + 1]).eq(0..10));
+}
+
+#[test]
+fn test_into_iter_drops() {
+    struct R<'a> {
+       i: &'a Cell<usize>,
+    }
+
+    impl<'a> Drop for R<'a> {
+       fn drop(&mut self) {
+            self.i.set(self.i.get() + 1);
+        }
+    }
+
+    fn r(i: &Cell<usize>) -> R {
+        R {
+            i: i
+        }
+    }
+
+    fn v(i: &Cell<usize>) -> GenericArray<R, U5> {
+        arr![R; r(i), r(i), r(i), r(i), r(i)]
+    }
+
+    let i = Cell::new(0);
+    {
+        v(&i).into_iter();
+    }
+    assert_eq!(i.get(), 5);
+
+    let i = Cell::new(0);
+    {
+        let mut iter = v(&i).into_iter();
+        let _x = iter.next();
+        assert_eq!(i.get(), 0);
+        assert_eq!(iter.count(), 4);
+        assert_eq!(i.get(), 4);
+    }
+    assert_eq!(i.get(), 5);
+
+    let i = Cell::new(0);
+    {
+        let mut iter = v(&i).into_iter();
+        let _x = iter.nth(2);
+        assert_eq!(i.get(), 2);
+        let _y = iter.last();
+        assert_eq!(i.get(), 3);
+    }
+    assert_eq!(i.get(), 5);
+
+    let i = Cell::new(0);
+    for (index, _x) in v(&i).into_iter().enumerate() {
+        assert_eq!(i.get(), index);
+    }
+    assert_eq!(i.get(), 5);
+
+    let i = Cell::new(0);
+    for (index, _x) in v(&i).into_iter().rev().enumerate() {
+        assert_eq!(i.get(), index);
+    }
+    assert_eq!(i.get(), 5);
+}
+
+/*
+//TODO: Cover this
+#[allow(dead_code)]
+fn assert_covariance() {
+    fn into_iter<'new>(i: GenericArrayIter<&'static str, U10>) -> GenericArrayIter<&'new str, U10> {
+        i
+    }
+}
+*/

tests/mod.rs

@@ -57,11 +57,6 @@ fn test_copy() {
     assert_eq!(test2[0], 1);
 }
 
-#[test]
-fn test_iter_flat_map() {
-    assert!((0..5).flat_map(|i| arr![i32; 2 * i, 2 * i + 1]).eq(0..10));
-}
-
 #[derive(Debug, PartialEq, Eq)]
 struct NoClone<T>(T);