1 files changed, 153 insertions, 0 deletions
diff --git a/third_party/rust/itertools/tests/specializations.rs b/third_party/rust/itertools/tests/specializations.rs
new file mode 100644
index 0000000000..057e11c9f6
--- /dev/null
+++ b/third_party/rust/itertools/tests/specializations.rs
@@ -0,0 +1,153 @@
+use itertools::Itertools;
+use std::fmt::Debug;
+use quickcheck::quickcheck;
+
+struct Unspecialized<I>(I);
+impl<I> Iterator for Unspecialized<I>
+where
+    I: Iterator,
+{
+    type Item = I::Item;
+
+    #[inline(always)]
+    fn next(&mut self) -> Option<Self::Item> {
+        self.0.next()
+    }
+}
+
+macro_rules! check_specialized {
+    ($src:expr, |$it:pat| $closure:expr) => {
+        let $it = $src.clone();
+        let v1 = $closure;
+
+        let $it = Unspecialized($src.clone());
+        let v2 = $closure;
+
+        assert_eq!(v1, v2);
+    }
+}
+
+fn test_specializations<IterItem, Iter>(
+    it: &Iter,
+) where
+    IterItem: Eq + Debug + Clone,
+    Iter: Iterator<Item = IterItem> + Clone,
+{
+    check_specialized!(it, |i| i.count());
+    check_specialized!(it, |i| i.last());
+    check_specialized!(it, |i| i.collect::<Vec<_>>());
+    check_specialized!(it, |i| {
+        let mut parameters_from_fold = vec![];
+        let fold_result = i.fold(vec![], |mut acc, v: IterItem| {
+            parameters_from_fold.push((acc.clone(), v.clone()));
+            acc.push(v);
+            acc
+        });
+        (parameters_from_fold, fold_result)
+    });
+    check_specialized!(it, |mut i| {
+        let mut parameters_from_all = vec![];
+        let first = i.next();
+        let all_result = i.all(|x| {
+            parameters_from_all.push(x.clone());
+            Some(x)==first
+        });
+        (parameters_from_all, all_result)
+    });
+    let size = it.clone().count();
+    for n in 0..size + 2 {
+        check_specialized!(it, |mut i| i.nth(n));
+    }
+    // size_hint is a bit harder to check
+    let mut it_sh = it.clone();
+    for n in 0..size + 2 {
+        let len = it_sh.clone().count();
+        let (min, max) = it_sh.size_hint();
+        assert_eq!(size - n.min(size), len);
+        assert!(min <= len);
+        if let Some(max) = max {
+            assert!(len <= max);
+        }
+        it_sh.next();
+    }
+}
+
+quickcheck! {
+    fn intersperse(v: Vec<u8>) -> () {
+        test_specializations(&v.into_iter().intersperse(0));
+    }
+}
+
+quickcheck! {
+    fn put_back_qc(test_vec: Vec<i32>) -> () {
+        test_specializations(&itertools::put_back(test_vec.iter()));
+        let mut pb = itertools::put_back(test_vec.into_iter());
+        pb.put_back(1);
+        test_specializations(&pb);
+    }
+}
+
+quickcheck! {
+    fn merge_join_by_qc(i1: Vec<usize>, i2: Vec<usize>) -> () {
+        test_specializations(&i1.into_iter().merge_join_by(i2.into_iter(), std::cmp::Ord::cmp));
+    }
+}
+
+quickcheck! {
+    fn map_into(v: Vec<u8>) -> () {
+        test_specializations(&v.into_iter().map_into::<u32>());
+    }
+}
+
+quickcheck! {
+    fn map_ok(v: Vec<Result<u8, char>>) -> () {
+        test_specializations(&v.into_iter().map_ok(|u| u.checked_add(1)));
+    }
+}
+
+quickcheck! {
+    fn process_results(v: Vec<Result<u8, u8>>) -> () {
+        helper(v.iter().copied());
+        helper(v.iter().copied().filter(Result::is_ok));
+
+        fn helper(it: impl Iterator<Item = Result<u8, u8>> + Clone) {
+            macro_rules! check_results_specialized {
+                ($src:expr, |$it:pat| $closure:expr) => {
+                    assert_eq!(
+                        itertools::process_results($src.clone(), |$it| $closure),
+                        itertools::process_results($src.clone(), |i| {
+                            let $it = Unspecialized(i);
+                            $closure
+                        }),
+                    )
+                }
+            }
+
+            check_results_specialized!(it, |i| i.count());
+            check_results_specialized!(it, |i| i.last());
+            check_results_specialized!(it, |i| i.collect::<Vec<_>>());
+            check_results_specialized!(it, |i| {
+                let mut parameters_from_fold = vec![];
+                let fold_result = i.fold(vec![], |mut acc, v| {
+                    parameters_from_fold.push((acc.clone(), v));
+                    acc.push(v);
+                    acc
+                });
+                (parameters_from_fold, fold_result)
+            });
+            check_results_specialized!(it, |mut i| {
+                let mut parameters_from_all = vec![];
+                let first = i.next();
+                let all_result = i.all(|x| {
+                    parameters_from_all.push(x);
+                    Some(x)==first
+                });
+                (parameters_from_all, all_result)
+            });
+            let size = it.clone().count();
+            for n in 0..size + 2 {
+                check_results_specialized!(it, |mut i| i.nth(n));
+            }
+        }
+    }
+}