diff --git a/src/adaptors/mod.rs b/src/adaptors/mod.rs
index 095b08918..d717e5408 100644
--- a/src/adaptors/mod.rs
+++ b/src/adaptors/mod.rs
@@ -1108,9 +1108,7 @@ where
 
     fn next(&mut self) -> Option<Self::Item> {
         let f = &mut self.f;
-        // TODO: once MSRV >= 1.62, use `then_some`.
-        self.iter
-            .find_map(|(count, val)| if f(val) { Some(count) } else { None })
+        self.iter.find_map(|(count, val)| f(val).then_some(count))
     }
 
     fn size_hint(&self) -> (usize, Option<usize>) {
@@ -1138,11 +1136,10 @@ where
 {
     fn next_back(&mut self) -> Option<Self::Item> {
         let f = &mut self.f;
-        // TODO: once MSRV >= 1.62, use `then_some`.
         self.iter
             .by_ref()
             .rev()
-            .find_map(|(count, val)| if f(val) { Some(count) } else { None })
+            .find_map(|(count, val)| f(val).then_some(count))
     }
 
     fn rfold<B, G>(self, init: B, mut func: G) -> B
diff --git a/src/combinations_with_replacement.rs b/src/combinations_with_replacement.rs
index f363f9ba2..c17e75250 100644
--- a/src/combinations_with_replacement.rs
+++ b/src/combinations_with_replacement.rs
@@ -73,11 +73,7 @@ where
             Some((increment_from, increment_value)) => {
                 // We need to update the rightmost non-max value
                 // and all those to the right
-                for i in &mut self.indices[increment_from..] {
-                    *i = increment_value;
-                }
-                // TODO: once MSRV >= 1.50, use `fill` instead:
-                // self.indices[increment_from..].fill(increment_value);
+                self.indices[increment_from..].fill(increment_value);
                 false
             }
             // Otherwise, we're done
diff --git a/src/concat_impl.rs b/src/concat_impl.rs
index ec7b91c60..d13a2931d 100644
--- a/src/concat_impl.rs
+++ b/src/concat_impl.rs
@@ -1,8 +1,6 @@
-use crate::Itertools;
-
 /// Combine all an iterator's elements into one element by using [`Extend`].
 ///
-/// [`IntoIterator`]-enabled version of [`Itertools::concat`].
+/// [`IntoIterator`]-enabled version of [`crate::Itertools::concat`].
 ///
 /// This combinator will extend the first item with each of the rest of the
 /// items of the iterator. If the iterator is empty, the default value of
@@ -19,10 +17,9 @@ where
     I: IntoIterator,
     I::Item: Extend<<<I as IntoIterator>::Item as IntoIterator>::Item> + IntoIterator + Default,
 {
-    #[allow(deprecated)] //TODO: once msrv hits 1.51. replace `fold1` with `reduce`
     iterable
         .into_iter()
-        .fold1(|mut a, b| {
+        .reduce(|mut a, b| {
             a.extend(b);
             a
         })
diff --git a/src/kmerge_impl.rs b/src/kmerge_impl.rs
index 0be3840a1..698c75a6d 100644
--- a/src/kmerge_impl.rs
+++ b/src/kmerge_impl.rs
@@ -1,5 +1,4 @@
 use crate::size_hint;
-use crate::Itertools;
 
 use alloc::vec::Vec;
 use std::fmt;
@@ -128,7 +127,7 @@ impl<T, F: FnMut(&T, &T) -> bool> KMergePredicate<T> for F {
 /// Create an iterator that merges elements of the contained iterators using
 /// the ordering function.
 ///
-/// [`IntoIterator`] enabled version of [`Itertools::kmerge`].
+/// [`IntoIterator`] enabled version of [`crate::Itertools::kmerge`].
 ///
 /// ```
 /// use itertools::kmerge;
@@ -172,7 +171,7 @@ where
 
 /// Create an iterator that merges elements of the contained iterators.
 ///
-/// [`IntoIterator`] enabled version of [`Itertools::kmerge_by`].
+/// [`IntoIterator`] enabled version of [`crate::Itertools::kmerge_by`].
 pub fn kmerge_by<I, F>(
     iterable: I,
     mut less_than: F,
@@ -223,11 +222,10 @@ where
     }
 
     fn size_hint(&self) -> (usize, Option<usize>) {
-        #[allow(deprecated)] //TODO: once msrv hits 1.51. replace `fold1` with `reduce`
         self.heap
             .iter()
             .map(|i| i.size_hint())
-            .fold1(size_hint::add)
+            .reduce(size_hint::add)
             .unwrap_or((0, Some(0)))
     }
 }
diff --git a/tests/quick.rs b/tests/quick.rs
index 6fe6f6923..12b6b9d5a 100644
--- a/tests/quick.rs
+++ b/tests/quick.rs
@@ -1511,13 +1511,12 @@ quickcheck! {
                 acc + val
             });
 
-        // TODO: Swap `fold1` with stdlib's `reduce` when it's stabilized
         let group_map_lookup = a.iter()
             .map(|&b| b as u64)
             .map(|i| (i % modulo, i))
             .into_group_map()
             .into_iter()
-            .map(|(key, vals)| (key, vals.into_iter().fold1(|acc, val| acc + val).unwrap()))
+            .map(|(key, vals)| (key, vals.into_iter().reduce(|acc, val| acc + val).unwrap()))
             .collect::<HashMap<_,_>>();
         assert_eq!(lookup, group_map_lookup);