From fa9bfebfc9256369c03cbe8bba2e737de3cb38fc Mon Sep 17 00:00:00 2001
From: Stein Somers <git@steinsomers.be>
Date: Tue, 4 Feb 2020 22:19:05 +0100
Subject: [PATCH] Fix and test implementation of BTreeMap's first_entry,
 last_entry, pop_first, pop_last

---
 src/liballoc/collections/btree/map.rs | 24 ++++++++++++++----------
 src/liballoc/tests/btree/map.rs       |  5 +++++
 src/liballoc/tests/btree/set.rs       | 27 ++++++++++++++++-----------
 3 files changed, 35 insertions(+), 21 deletions(-)

diff --git a/src/liballoc/collections/btree/map.rs b/src/liballoc/collections/btree/map.rs
index 8eabc177304..c1778f2065d 100644
--- a/src/liballoc/collections/btree/map.rs
+++ b/src/liballoc/collections/btree/map.rs
@@ -675,13 +675,15 @@ impl<K: Ord, V> BTreeMap<K, V> {
         T: Ord,
         K: Borrow<T>,
     {
-        match self.length {
-            0 => None,
-            _ => Some(OccupiedEntry {
-                handle: self.root.as_mut().first_kv(),
+        let front = self.root.as_mut().first_leaf_edge();
+        if let Ok(kv) = front.right_kv() {
+            Some(OccupiedEntry {
+                handle: kv.forget_node_type(),
                 length: &mut self.length,
                 _marker: PhantomData,
-            }),
+            })
+        } else {
+            None
         }
     }
 
@@ -736,13 +738,15 @@ impl<K: Ord, V> BTreeMap<K, V> {
         T: Ord,
         K: Borrow<T>,
     {
-        match self.length {
-            0 => None,
-            _ => Some(OccupiedEntry {
-                handle: self.root.as_mut().last_kv(),
+        let back = self.root.as_mut().last_leaf_edge();
+        if let Ok(kv) = back.left_kv() {
+            Some(OccupiedEntry {
+                handle: kv.forget_node_type(),
                 length: &mut self.length,
                 _marker: PhantomData,
-            }),
+            })
+        } else {
+            None
         }
     }
 
diff --git a/src/liballoc/tests/btree/map.rs b/src/liballoc/tests/btree/map.rs
index 0d009507fc7..0a26d7bf427 100644
--- a/src/liballoc/tests/btree/map.rs
+++ b/src/liballoc/tests/btree/map.rs
@@ -23,6 +23,11 @@ fn test_basic_large() {
         assert_eq!(map.len(), i + 1);
     }
 
+    assert_eq!(map.first_key_value(), Some((&0, &0)));
+    assert_eq!(map.last_key_value(), Some((&(size - 1), &(10 * (size - 1)))));
+    assert_eq!(map.first_entry().unwrap().key(), &0);
+    assert_eq!(map.last_entry().unwrap().key(), &(size - 1));
+
     for i in 0..size {
         assert_eq!(map.get(&i).unwrap(), &(i * 10));
     }
diff --git a/src/liballoc/tests/btree/set.rs b/src/liballoc/tests/btree/set.rs
index 265ef758cc5..1a2b62d026b 100644
--- a/src/liballoc/tests/btree/set.rs
+++ b/src/liballoc/tests/btree/set.rs
@@ -487,21 +487,26 @@ fn test_first_last() {
     a.insert(2);
     assert_eq!(a.first(), Some(&1));
     assert_eq!(a.last(), Some(&2));
-    a.insert(3);
+    for i in 3..=12 {
+        a.insert(i);
+    }
     assert_eq!(a.first(), Some(&1));
-    assert_eq!(a.last(), Some(&3));
-
-    assert_eq!(a.len(), 3);
+    assert_eq!(a.last(), Some(&12));
     assert_eq!(a.pop_first(), Some(1));
-    assert_eq!(a.len(), 2);
-    assert_eq!(a.pop_last(), Some(3));
-    assert_eq!(a.len(), 1);
+    assert_eq!(a.pop_last(), Some(12));
     assert_eq!(a.pop_first(), Some(2));
-    assert_eq!(a.len(), 0);
-    assert_eq!(a.pop_last(), None);
-    assert_eq!(a.len(), 0);
+    assert_eq!(a.pop_last(), Some(11));
+    assert_eq!(a.pop_first(), Some(3));
+    assert_eq!(a.pop_last(), Some(10));
+    assert_eq!(a.pop_first(), Some(4));
+    assert_eq!(a.pop_first(), Some(5));
+    assert_eq!(a.pop_first(), Some(6));
+    assert_eq!(a.pop_first(), Some(7));
+    assert_eq!(a.pop_first(), Some(8));
+    assert_eq!(a.clone().pop_last(), Some(9));
+    assert_eq!(a.pop_first(), Some(9));
     assert_eq!(a.pop_first(), None);
-    assert_eq!(a.len(), 0);
+    assert_eq!(a.pop_last(), None);
 }
 
 fn rand_data(len: usize) -> Vec<u32> {