fix clippy warnings

Signed-off-by: Ruihang Xia <waynestxia@gmail.com>

Author: waynexia

datafusion/optimizer/src/rewrite_set_comparison.rs

@@ -38,7 +38,7 @@ use datafusion_expr::utils::merge_schema;
 pub struct RewriteSetComparison;
 
 impl RewriteSetComparison {
-    #[allow(missing_docs)]
+    /// Create a new `RewriteSetComparison` optimizer rule.
     pub fn new() -> Self {
         Self
     }

datafusion/sql/src/expr/subquery.rs

@@ -178,10 +178,10 @@ impl<S: ContextProvider> SqlToRel<'_, S> {
         let mut spans = Spans::new();
         if let SetExpr::Select(select) = subquery.body.as_ref() {
             for item in &select.projection {
-                if let SelectItem::ExprWithAlias { alias, .. } = item {
-                    if let Some(span) = Span::try_from_sqlparser_span(alias.span) {
-                        spans.add_span(span);
-                    }
+                if let SelectItem::ExprWithAlias { alias, .. } = item
+                    && let Some(span) = Span::try_from_sqlparser_span(alias.span)
+                {
+                    spans.add_span(span);
                 }
             }
         }