From 5721f3774002bd5e4823d1e46e75a701dd607727 Mon Sep 17 00:00:00 2001
From: Easyoakland <97992568+Easyoakland@users.noreply.github.com>
Date: Sun, 6 Aug 2023 18:49:51 -0600
Subject: [PATCH 1/5] `try_len` method

---
 src/lib.rs       | 16 ++++++++++++++++
 src/size_hint.rs |  9 +++++++++
 2 files changed, 25 insertions(+)

diff --git a/src/lib.rs b/src/lib.rs
index c9bad16eb..2c9abba00 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -3840,6 +3840,22 @@ pub trait Itertools : Iterator {
     {
         MultiUnzip::multiunzip(self)
     }
+
+    /// Returns the length of the iterator if one exists.
+    ///
+    /// ```
+    /// use itertools::Itertools;
+    ///
+    /// assert_eq!([0; 10].into_iter().try_len(), Some(10));
+    /// assert_eq!((10..15).try_len(), Some(5));
+    /// assert_eq!((15..10).try_len(), Some(0));
+    /// assert_eq!((10..).try_len(), None);
+    /// ```
+    fn try_len(self) -> Option<usize>
+    where Self: Sized
+    {
+        size_hint::try_len(self)
+    }
 }
 
 impl<T: ?Sized> Itertools for T where T: Iterator { }
diff --git a/src/size_hint.rs b/src/size_hint.rs
index 71ea1412b..e329165c0 100644
--- a/src/size_hint.rs
+++ b/src/size_hint.rs
@@ -117,3 +117,12 @@ pub fn min(a: SizeHint, b: SizeHint) -> SizeHint {
     };
     (lower, upper)
 }
+
+/// Returns the length of the iterator if one exists.
+#[inline]
+pub fn try_len(it: impl Iterator) -> Option<usize> {
+    match it.size_hint() {
+        (lo, Some(hi)) if lo == hi => Some(lo),
+        _ => None
+    }
+}
\ No newline at end of file

From 6e54b0fa8b4615a799418dd50e0efc5ef1ff2c27 Mon Sep 17 00:00:00 2001
From: Easyoakland <97992568+Easyoakland@users.noreply.github.com>
Date: Sun, 6 Aug 2023 19:02:01 -0600
Subject: [PATCH 2/5] take by ref

---
 src/lib.rs       | 2 +-
 src/size_hint.rs | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index 2c9abba00..52a8f3e8a 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -3851,7 +3851,7 @@ pub trait Itertools : Iterator {
     /// assert_eq!((15..10).try_len(), Some(0));
     /// assert_eq!((10..).try_len(), None);
     /// ```
-    fn try_len(self) -> Option<usize>
+    fn try_len(&self) -> Option<usize>
     where Self: Sized
     {
         size_hint::try_len(self)
diff --git a/src/size_hint.rs b/src/size_hint.rs
index e329165c0..b221583f7 100644
--- a/src/size_hint.rs
+++ b/src/size_hint.rs
@@ -120,7 +120,7 @@ pub fn min(a: SizeHint, b: SizeHint) -> SizeHint {
 
 /// Returns the length of the iterator if one exists.
 #[inline]
-pub fn try_len(it: impl Iterator) -> Option<usize> {
+pub fn try_len(it: &impl Iterator) -> Option<usize> {
     match it.size_hint() {
         (lo, Some(hi)) if lo == hi => Some(lo),
         _ => None

From 952d8c4c87826a0413f0ae7ed8a5aee257d1c0a9 Mon Sep 17 00:00:00 2001
From: Easyoakland <97992568+Easyoakland@users.noreply.github.com>
Date: Mon, 7 Aug 2023 20:48:54 -0600
Subject: [PATCH 3/5] match other `sizehint` function conventions

---
 src/lib.rs       | 3 ++-
 src/size_hint.rs | 4 ++--
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index 52a8f3e8a..1244ab9a2 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -3842,6 +3842,7 @@ pub trait Itertools : Iterator {
     }
 
     /// Returns the length of the iterator if one exists.
+    /// Relies on the [`size_hint`] of the iterator being correct.
     ///
     /// ```
     /// use itertools::Itertools;
@@ -3854,7 +3855,7 @@ pub trait Itertools : Iterator {
     fn try_len(&self) -> Option<usize>
     where Self: Sized
     {
-        size_hint::try_len(self)
+        size_hint::try_len(self.size_hint())
     }
 }
 
diff --git a/src/size_hint.rs b/src/size_hint.rs
index b221583f7..dfe69d1d9 100644
--- a/src/size_hint.rs
+++ b/src/size_hint.rs
@@ -120,8 +120,8 @@ pub fn min(a: SizeHint, b: SizeHint) -> SizeHint {
 
 /// Returns the length of the iterator if one exists.
 #[inline]
-pub fn try_len(it: &impl Iterator) -> Option<usize> {
-    match it.size_hint() {
+pub fn try_len(sh: SizeHint) -> Option<usize> {
+    match sh {
         (lo, Some(hi)) if lo == hi => Some(lo),
         _ => None
     }

From 87ad574a88b93e01b7ccbd8e62c85cf7f1cc43cf Mon Sep 17 00:00:00 2001
From: Easyoakland <97992568+Easyoakland@users.noreply.github.com>
Date: Tue, 8 Aug 2023 19:54:26 -0600
Subject: [PATCH 4/5] Result not Option, inline, no Sized bound, improve docs

---
 src/lib.rs       | 19 ++++++++++++-------
 src/size_hint.rs |  6 +++---
 2 files changed, 15 insertions(+), 10 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index 1244ab9a2..08bc2e059 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -3842,18 +3842,23 @@ pub trait Itertools : Iterator {
     }
 
     /// Returns the length of the iterator if one exists.
-    /// Relies on the [`size_hint`] of the iterator being correct.
+    /// Otherwise return `self.size_hint()`.
+    ///
+    /// Fallible [`ExactSizeIterator::len`].
+    ///
+    /// Inherits guarantees and restrictions from [`Iterator::size_hint`].
     ///
     /// ```
     /// use itertools::Itertools;
     ///
-    /// assert_eq!([0; 10].into_iter().try_len(), Some(10));
-    /// assert_eq!((10..15).try_len(), Some(5));
-    /// assert_eq!((15..10).try_len(), Some(0));
-    /// assert_eq!((10..).try_len(), None);
+    /// assert_eq!([0; 10].iter().try_len(), Ok(10));
+    /// assert_eq!((10..15).try_len(), Ok(5));
+    /// assert_eq!((15..10).try_len(), Ok(0));
+    /// assert_eq!((10..).try_len(), Err((usize::MAX, None)));
+    /// assert_eq!((10..15).filter(|x| x % 2 == 0).try_len(), Err((0, Some(5))));
     /// ```
-    fn try_len(&self) -> Option<usize>
-    where Self: Sized
+    #[inline]
+    fn try_len(&self) -> Result<usize, size_hint::SizeHint>
     {
         size_hint::try_len(self.size_hint())
     }
diff --git a/src/size_hint.rs b/src/size_hint.rs
index dfe69d1d9..dbd5624e6 100644
--- a/src/size_hint.rs
+++ b/src/size_hint.rs
@@ -120,9 +120,9 @@ pub fn min(a: SizeHint, b: SizeHint) -> SizeHint {
 
 /// Returns the length of the iterator if one exists.
 #[inline]
-pub fn try_len(sh: SizeHint) -> Option<usize> {
+pub fn try_len(sh: SizeHint) -> Result<usize, SizeHint> {
     match sh {
-        (lo, Some(hi)) if lo == hi => Some(lo),
-        _ => None
+        (lo, Some(hi)) if lo == hi => Ok(lo),
+        _ => Err(sh)
     }
 }
\ No newline at end of file

From 068de35d95d345ea6bf112ecdf8de504cdb3b334 Mon Sep 17 00:00:00 2001
From: Easyoakland <97992568+Easyoakland@users.noreply.github.com>
Date: Tue, 8 Aug 2023 23:21:03 -0600
Subject: [PATCH 5/5] inline function source code and remove annotation

---
 src/lib.rs       | 10 ++++++----
 src/size_hint.rs |  9 ---------
 2 files changed, 6 insertions(+), 13 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index 08bc2e059..41bedfcab 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -3857,10 +3857,12 @@ pub trait Itertools : Iterator {
     /// assert_eq!((10..).try_len(), Err((usize::MAX, None)));
     /// assert_eq!((10..15).filter(|x| x % 2 == 0).try_len(), Err((0, Some(5))));
     /// ```
-    #[inline]
-    fn try_len(&self) -> Result<usize, size_hint::SizeHint>
-    {
-        size_hint::try_len(self.size_hint())
+    fn try_len(&self) -> Result<usize, size_hint::SizeHint> {
+        let sh = self.size_hint();
+        match sh {
+            (lo, Some(hi)) if lo == hi => Ok(lo),
+            _ => Err(sh),
+        }
     }
 }
 
diff --git a/src/size_hint.rs b/src/size_hint.rs
index dbd5624e6..71ea1412b 100644
--- a/src/size_hint.rs
+++ b/src/size_hint.rs
@@ -117,12 +117,3 @@ pub fn min(a: SizeHint, b: SizeHint) -> SizeHint {
     };
     (lower, upper)
 }
-
-/// Returns the length of the iterator if one exists.
-#[inline]
-pub fn try_len(sh: SizeHint) -> Result<usize, SizeHint> {
-    match sh {
-        (lo, Some(hi)) if lo == hi => Ok(lo),
-        _ => Err(sh)
-    }
-}
\ No newline at end of file