Specify only that duplicates are discarded, not the order.

alloc/src/collections/btree/map.rs

@@ -2292,7 +2292,7 @@ impl<K: Ord, V> FromIterator<(K, V)> for BTreeMap<K, V> {
     /// Constructs a `BTreeMap<K, V>` from an iterator of key-value pairs.
     ///
     /// If the iterator produces any pairs with equal keys,
-    /// all but the last value for each such key are discarded.
+    /// all but one of the corresponding values will be dropped.
     fn from_iter<T: IntoIterator<Item = (K, V)>>(iter: T) -> BTreeMap<K, V> {
         let mut inputs: Vec<_> = iter.into_iter().collect();
 
@@ -2409,8 +2409,8 @@ where
 impl<K: Ord, V, const N: usize> From<[(K, V); N]> for BTreeMap<K, V> {
     /// Converts a `[(K, V); N]` into a `BTreeMap<K, V>`.
     ///
-    /// If any entries in the array have equal keys, all but the last entry for each such key
-    /// are discarded.
+    /// If any entries in the array have equal keys,
+    /// all but one of the corresponding values will be dropped.
     ///
     /// ```
     /// use std::collections::BTreeMap;

alloc/src/collections/btree/set.rs

@@ -1491,7 +1491,8 @@ impl<T: Ord, A: Allocator + Clone> BTreeSet<T, A> {
 impl<T: Ord, const N: usize> From<[T; N]> for BTreeSet<T> {
     /// Converts a `[T; N]` into a `BTreeSet<T>`.
     ///
-    /// If the array contains any equal values, all but the last instance of each are discarded.
+    /// If the array contains any equal values,
+    /// all but one will be dropped.
     ///
     /// # Examples
     ///

std/src/collections/hash/map.rs

@@ -1448,8 +1448,8 @@ where
 {
     /// Converts a `[(K, V); N]` into a `HashMap<K, V>`.
     ///
-    /// If any entries in the array have equal keys, all but the last entry for each such key
-    /// are discarded.
+    /// If any entries in the array have equal keys,
+    /// all but one of the corresponding values will be dropped.
     ///
     /// # Examples
     ///
@@ -3227,7 +3227,7 @@ where
     /// Constructs a `HashMap<K, V>` from an iterator of key-value pairs.
     ///
     /// If the iterator produces any pairs with equal keys,
-    /// all but the last value for each such key are discarded.
+    /// all but one of the corresponding values will be dropped.
     fn from_iter<T: IntoIterator<Item = (K, V)>>(iter: T) -> HashMap<K, V, S> {
         let mut map = HashMap::with_hasher(Default::default());
         map.extend(iter);

std/src/collections/hash/set.rs

@@ -1093,7 +1093,8 @@ where
 {
     /// Converts a `[T; N]` into a `HashSet<T>`.
     ///
-    /// If the array contains any equal values, all but the last instance of each are discarded.
+    /// If the array contains any equal values,
+    /// all but one will be dropped.
     ///
     /// # Examples
     ///