From a2cab3b1aca9b90037007bb2d69b7c1d7c8a43f7 Mon Sep 17 00:00:00 2001
From: Philippe-Cholet <44676486+Philippe-Cholet@users.noreply.github.com>
Date: Thu, 2 May 2024 11:11:26 +0200
Subject: [PATCH] `get`: when is it ESI and/or DEI

---
 src/lib.rs         |  5 +++--
 tests/test_core.rs | 22 ++++++++++++++++++++++
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index 37d64a160..c45f0cd07 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -515,8 +515,9 @@ pub trait Itertools: Iterator {
     ///
     /// It's a generalisation of [`Iterator::take`] and [`Iterator::skip`],
     /// and uses these under the hood.
-    /// Therefore, the resulting iterator is [`DoubleEndedIterator`]
-    /// and/or [`ExactSizeIterator`] if the adapted iterator is.
+    /// Therefore, the resulting iterator is:
+    /// - [`ExactSizeIterator`] if the adapted iterator is [`ExactSizeIterator`].
+    /// - [`DoubleEndedIterator`] if the adapted iterator is [`DoubleEndedIterator`] and [`ExactSizeIterator`].
     ///
     /// # Unspecified Behavior
     /// The result of indexing with an exhausted [`core::ops::RangeInclusive`] is unspecified.
diff --git a/tests/test_core.rs b/tests/test_core.rs
index b5826ef39..6f7dc1fda 100644
--- a/tests/test_core.rs
+++ b/tests/test_core.rs
@@ -18,6 +18,28 @@ use crate::it::Itertools;
 use core::iter;
 use itertools as it;
 
+#[allow(dead_code)]
+fn get_esi_then_esi<I: ExactSizeIterator + Clone>(it: I) {
+    fn is_esi(_: impl ExactSizeIterator) {}
+    is_esi(it.clone().get(1..4));
+    is_esi(it.clone().get(1..=4));
+    is_esi(it.clone().get(1..));
+    is_esi(it.clone().get(..4));
+    is_esi(it.clone().get(..=4));
+    is_esi(it.get(..));
+}
+
+#[allow(dead_code)]
+fn get_dei_esi_then_dei_esi<I: DoubleEndedIterator + ExactSizeIterator + Clone>(it: I) {
+    fn is_dei_esi(_: impl DoubleEndedIterator + ExactSizeIterator) {}
+    is_dei_esi(it.clone().get(1..4));
+    is_dei_esi(it.clone().get(1..=4));
+    is_dei_esi(it.clone().get(1..));
+    is_dei_esi(it.clone().get(..4));
+    is_dei_esi(it.clone().get(..=4));
+    is_dei_esi(it.get(..));
+}
+
 #[test]
 fn product0() {
     let mut prod = iproduct!();