fixed clippy errors

datafusion/physical-expr-common/src/sort_expr.rs

@@ -346,16 +346,18 @@ pub struct LexOrdering {
     pub inner: Vec<PhysicalSortExpr>,
 }
 
+impl AsRef<LexOrdering> for LexOrdering {
+    fn as_ref(&self) -> &LexOrdering {
+        self
+    }
+}
+
 impl LexOrdering {
     // Creates a new [`LexOrdering`] from a vector
     pub fn new(inner: Vec<PhysicalSortExpr>) -> Self {
         Self { inner }
     }
 
-    pub fn as_ref(&self) -> &LexOrdering {
-        self
-    }
-
     pub fn capacity(&self) -> usize {
         self.inner.capacity()
     }

datafusion/physical-expr/src/equivalence/ordering.rs

@@ -146,12 +146,7 @@ impl OrderingEquivalenceClass {
     /// Returns the concatenation of all the orderings. This enables merge
     /// operations to preserve all equivalent orderings simultaneously.
     pub fn output_ordering(&self) -> Option<LexOrdering> {
-        let output_ordering = self
-            .orderings
-            .iter()
-            .flat_map(|ordering| ordering.as_ref())
-            .cloned()
-            .collect();
+        let output_ordering = self.orderings.iter().flatten().cloned().collect();
         let output_ordering = collapse_lex_ordering(output_ordering);
         (!output_ordering.is_empty()).then_some(output_ordering)
     }