Add UnordMap::try_insert

compiler/rustc_data_structures/src/unord.rs

@@ -4,6 +4,7 @@
 
 use rustc_hash::{FxHashMap, FxHashSet};
 use rustc_macros::{Decodable_Generic, Encodable_Generic};
+use std::collections::hash_map::OccupiedError;
 use std::{
     borrow::{Borrow, BorrowMut},
     collections::hash_map::Entry,
@@ -469,6 +470,11 @@ impl<K: Eq + Hash, V> UnordMap<K, V> {
         self.inner.insert(k, v)
     }
 
+    #[inline]
+    pub fn try_insert(&mut self, k: K, v: V) -> Result<&mut V, OccupiedError<'_, K, V>> {
+        self.inner.try_insert(k, v)
+    }
+
     #[inline]
     pub fn contains_key<Q: ?Sized>(&self, k: &Q) -> bool
     where