Rollup merge of #110958 - compiler-errors:stdlib-refinement, r=cuviper

Make sure that some stdlib method signatures aren't accidental refinements

In the process of implementing https://rust-lang.github.io/rfcs/3245-refined-impls.html, I found a bunch of stdlib implementations that accidentally "refined" their method signatures by dropping  (unnecessary) bounds.

This isn't currently a problem, but may become one if/when method  signature refining is stabilized in the future. Shouldn't hurt to make these signatures a bit more accurate anyways.

NOTE (just to be clear lol): This does not affect behavior at all, since we don't actually take advantage of refined implementations yet!

3 files changed, 65 insertions, 17 deletions

diff --git a/library/alloc/src/collections/btree/map.rs b/library/alloc/src/collections/btree/map.rs
index afdc998172d..efbbc1c2331 100644
--- a/library/alloc/src/collections/btree/map.rs
+++ b/library/alloc/src/collections/btree/map.rs
@@ -1543,11 +1543,17 @@ impl<'a, K: 'a, V: 'a> Iterator for Iter<'a, K, V> {
         self.next_back()
     }
 
-    fn min(mut self) -> Option<(&'a K, &'a V)> {
+    fn min(mut self) -> Option<(&'a K, &'a V)>
+    where
+        (&'a K, &'a V): Ord,
+    {
         self.next()
     }
 
-    fn max(mut self) -> Option<(&'a K, &'a V)> {
+    fn max(mut self) -> Option<(&'a K, &'a V)>
+    where
+        (&'a K, &'a V): Ord,
+    {
         self.next_back()
     }
 }
@@ -1612,11 +1618,17 @@ impl<'a, K, V> Iterator for IterMut<'a, K, V> {
         self.next_back()
     }
 
-    fn min(mut self) -> Option<(&'a K, &'a mut V)> {
+    fn min(mut self) -> Option<(&'a K, &'a mut V)>
+    where
+        (&'a K, &'a mut V): Ord,
+    {
         self.next()
     }
 
-    fn max(mut self) -> Option<(&'a K, &'a mut V)> {
+    fn max(mut self) -> Option<(&'a K, &'a mut V)>
+    where
+        (&'a K, &'a mut V): Ord,
+    {
         self.next_back()
     }
 }
@@ -1779,11 +1791,17 @@ impl<'a, K, V> Iterator for Keys<'a, K, V> {
         self.next_back()
     }
 
-    fn min(mut self) -> Option<&'a K> {
+    fn min(mut self) -> Option<&'a K>
+    where
+        &'a K: Ord,
+    {
         self.next()
     }
 
-    fn max(mut self) -> Option<&'a K> {
+    fn max(mut self) -> Option<&'a K>
+    where
+        &'a K: Ord,
+    {
         self.next_back()
     }
 }
@@ -2008,11 +2026,17 @@ impl<'a, K, V> Iterator for Range<'a, K, V> {
         self.next_back()
     }
 
-    fn min(mut self) -> Option<(&'a K, &'a V)> {
+    fn min(mut self) -> Option<(&'a K, &'a V)>
+    where
+        (&'a K, &'a V): Ord,
+    {
         self.next()
     }
 
-    fn max(mut self) -> Option<(&'a K, &'a V)> {
+    fn max(mut self) -> Option<(&'a K, &'a V)>
+    where
+        (&'a K, &'a V): Ord,
+    {
         self.next_back()
     }
 }
@@ -2081,11 +2105,17 @@ impl<K, V, A: Allocator + Clone> Iterator for IntoKeys<K, V, A> {
         self.next_back()
     }
 
-    fn min(mut self) -> Option<K> {
+    fn min(mut self) -> Option<K>
+    where
+        K: Ord,
+    {
         self.next()
     }
 
-    fn max(mut self) -> Option<K> {
+    fn max(mut self) -> Option<K>
+    where
+        K: Ord,
+    {
         self.next_back()
     }
 }
@@ -2204,11 +2234,17 @@ impl<'a, K, V> Iterator for RangeMut<'a, K, V> {
         self.next_back()
     }
 
-    fn min(mut self) -> Option<(&'a K, &'a mut V)> {
+    fn min(mut self) -> Option<(&'a K, &'a mut V)>
+    where
+        (&'a K, &'a mut V): Ord,
+    {
         self.next()
     }
 
-    fn max(mut self) -> Option<(&'a K, &'a mut V)> {
+    fn max(mut self) -> Option<(&'a K, &'a mut V)>
+    where
+        (&'a K, &'a mut V): Ord,
+    {
         self.next_back()
     }
 }
diff --git a/library/alloc/src/collections/btree/set.rs b/library/alloc/src/collections/btree/set.rs
index da952a13f1e..940fa30afb8 100644
--- a/library/alloc/src/collections/btree/set.rs
+++ b/library/alloc/src/collections/btree/set.rs
@@ -1501,11 +1501,17 @@ impl<'a, T> Iterator for Iter<'a, T> {
         self.next_back()
     }
 
-    fn min(mut self) -> Option<&'a T> {
+    fn min(mut self) -> Option<&'a T>
+    where
+        &'a T: Ord,
+    {
         self.next()
     }
 
-    fn max(mut self) -> Option<&'a T> {
+    fn max(mut self) -> Option<&'a T>
+    where
+        &'a T: Ord,
+    {
         self.next_back()
     }
 }
@@ -1604,11 +1610,17 @@ impl<'a, T> Iterator for Range<'a, T> {
         self.next_back()
     }
 
-    fn min(mut self) -> Option<&'a T> {
+    fn min(mut self) -> Option<&'a T>
+    where
+        &'a T: Ord,
+    {
         self.next()
     }
 
-    fn max(mut self) -> Option<&'a T> {
+    fn max(mut self) -> Option<&'a T>
+    where
+        &'a T: Ord,
+    {
         self.next_back()
     }
 }
diff --git a/library/alloc/src/collections/vec_deque/mod.rs b/library/alloc/src/collections/vec_deque/mod.rs
index 8916b42eda0..896da37f94c 100644
--- a/library/alloc/src/collections/vec_deque/mod.rs
+++ b/library/alloc/src/collections/vec_deque/mod.rs
@@ -2815,7 +2815,7 @@ impl<'a, T: 'a + Copy, A: Allocator> Extend<&'a T> for VecDeque<T, A> {
     }
 
     #[inline]
-    fn extend_one(&mut self, &elem: &T) {
+    fn extend_one(&mut self, &elem: &'a T) {
         self.push_back(elem);
     }