Add more FusedIterator

Mark FusedIterator to WhileSome, RcIter, PadUsing, TupleWindows,
TupleCombinations, RepeatN, Powerset, CombinationsWithReplacement,
WithPosition, KMergeBy

src/adaptors/mod.rs

@@ -728,6 +728,11 @@ impl<I, T> Iterator for TupleCombinations<I, T>
     }
 }
 
+impl<I, T> FusedIterator for TupleCombinations<I, T>
+    where I: FusedIterator,
+          T: HasCombination<I>,
+{}
+
 #[derive(Clone, Debug)]
 pub struct Tuple1Combination<I> {
     iter: I,

src/combinations_with_replacement.rs

@@ -1,5 +1,6 @@
 use alloc::vec::Vec;
 use std::fmt;
+use std::iter::FusedIterator;
 
 use super::lazy_buffer::LazyBuffer;
 
@@ -100,3 +101,9 @@ where
         }
     }
 }
+
+impl<I> FusedIterator for CombinationsWithReplacement<I>
+where
+    I: Iterator,
+    I::Item: Clone,
+{}

src/kmerge_impl.rs

@@ -2,6 +2,7 @@ use crate::size_hint;
 use crate::Itertools;
 
 use alloc::vec::Vec;
+use std::iter::FusedIterator;
 use std::mem::replace;
 use std::fmt;
 
@@ -219,3 +220,8 @@ impl<I, F> Iterator for KMergeBy<I, F>
                  .unwrap_or((0, Some(0)))
     }
 }
+
+impl<I, F> FusedIterator for KMergeBy<I, F>
+    where I: Iterator,
+          F: KMergePredicate<I::Item>
+{}

src/pad_tail.rs

@@ -1,4 +1,4 @@
-use std::iter::Fuse;
+use std::iter::{Fuse, FusedIterator};
 use crate::size_hint;
 
 /// An iterator adaptor that pads a sequence to a minimum length by filling
@@ -81,3 +81,9 @@ impl<I, F> ExactSizeIterator for PadUsing<I, F>
     where I: ExactSizeIterator,
           F: FnMut(usize) -> I::Item
 {}
+
+
+impl<I, F> FusedIterator for PadUsing<I, F>
+    where I: FusedIterator,
+          F: FnMut(usize) -> I::Item
+{}

src/powerset.rs

@@ -1,4 +1,5 @@
 use std::fmt;
+use std::iter::FusedIterator;
 use std::usize;
 use alloc::vec::Vec;
 
@@ -81,3 +82,9 @@ impl<I> Iterator for Powerset<I>
         }
     }
 }
+
+impl<I> FusedIterator for Powerset<I>
+    where
+        I: Iterator,
+        I::Item: Clone,
+{}

src/rciter_impl.rs

@@ -1,5 +1,5 @@
 
-use std::iter::IntoIterator;
+use std::iter::{FusedIterator, IntoIterator};
 use alloc::rc::Rc;
 use std::cell::RefCell;
 
@@ -93,3 +93,8 @@ impl<'a, I> IntoIterator for &'a RcIter<I>
         self.clone()
     }
 }
+
+
+impl<A, I> FusedIterator for RcIter<I>
+    where I: FusedIterator<Item = A>
+{}

src/repeatn.rs

@@ -1,3 +1,4 @@
+use std::iter::FusedIterator;
 
 /// An iterator that produces *n* repetitions of an element.
 ///
@@ -52,3 +53,7 @@ impl<A> DoubleEndedIterator for RepeatN<A>
 impl<A> ExactSizeIterator for RepeatN<A>
     where A: Clone
 {}
+
+impl<A> FusedIterator for RepeatN<A>
+    where A: Clone
+{}

src/tuple_impl.rs

@@ -1,6 +1,7 @@
 //! Some iterator that produces tuples
 
 use std::iter::Fuse;
+use std::iter::FusedIterator;
 use std::iter::Take;
 use std::iter::Cycle;
 use std::marker::PhantomData;
@@ -187,6 +188,12 @@ impl<I, T> Iterator for TupleWindows<I, T>
     }
 }
 
+impl<I, T> FusedIterator for TupleWindows<I, T>
+    where I: FusedIterator<Item = T::Item>,
+          T: HomogeneousTuple + Clone,
+          T::Item: Clone
+{}
+
 /// An iterator over all windows,wrapping back to the first elements when the
 /// window would otherwise exceed the length of the iterator, producing tuples
 /// of a specific size.

src/with_position.rs

@@ -1,4 +1,4 @@
-use std::iter::{Fuse,Peekable};
+use std::iter::{Fuse,Peekable, FusedIterator};
 
 /// An iterator adaptor that wraps each element in an [`Position`].
 ///
@@ -95,3 +95,6 @@ impl<I: Iterator> Iterator for WithPosition<I> {
 impl<I> ExactSizeIterator for WithPosition<I>
     where I: ExactSizeIterator,
 { }
+
+impl<I: Iterator> FusedIterator for WithPosition<I> 
+{}

tests/quick.rs

@@ -1618,6 +1618,18 @@ quickcheck! {
         is_fused(a.combinations(3))
     }
 
+    fn fused_combination_with_replacement(a: Iter<i16>) -> bool
+    {
+        is_fused(a.clone().combinations_with_replacement(1)) &&
+        is_fused(a.combinations_with_replacement(3))
+    }
+
+    fn fused_tuple_combination(a: Iter<i16>) -> bool
+    {
+        is_fused(a.clone().fuse().tuple_combinations::<(_,)>()) &&
+        is_fused(a.fuse().tuple_combinations::<(_,_,_)>())
+    }
+
     fn fused_unique(a: Iter<i16>) -> bool
     {
         is_fused(a.fuse().unique())
@@ -1669,5 +1681,15 @@ quickcheck! {
         !is_fused(a.clone().update(|x|*x+=1)) &&
         is_fused(a.fuse().update(|x|*x+=1))
     }
+
+    fn fused_tuple_windows(a: Iter<i16>) -> bool
+    {
+        is_fused(a.fuse().tuple_windows::<(_,_)>())
+    }
+
+    fn fused_pad_using(a: Iter<i16>) -> bool
+    {
+        is_fused(a.fuse().pad_using(100,|_|0))
+    }
 }