Explicitly pass find arguments down the predicate so coercions can apply

compiler/rustc_data_structures/src/vec_map.rs

@@ -33,11 +33,11 @@ where
         self.0.iter().find(|(key, _)| k == key.borrow()).map(|elem| &elem.1)
     }
 
-    pub fn get_by<P>(&self, predicate: P) -> Option<&V>
+    pub fn get_by<P>(&self, mut predicate: P) -> Option<&V>
     where
         for<'b> P: FnMut(&'b &(K, V)) -> bool,
     {
-        self.0.iter().find(predicate).map(|elem| &elem.1)
+        self.0.iter().find(|kv| predicate(kv)).map(|elem| &elem.1)
     }
 
     pub fn contains_key<Q: ?Sized>(&self, k: &Q) -> bool