Fix: preserve column quoting in DISTINCT ON elimination

sqlglot/transforms.py

@@ -205,7 +205,8 @@ def eliminate_distinct_on(expression: exp.Expression) -> exp.Expression:
 
             if not isinstance(select, exp.Alias):
                 alias = find_new_name(taken_names, select.output_name or "_col")
-                select = select.replace(exp.alias_(select, alias))
+                quoted = select.this.args.get("quoted") if isinstance(select, exp.Column) else None
+                select = select.replace(exp.alias_(select, alias, quoted=quoted))
 
             taken_names.add(select.output_name)
             new_selects.append(select.args["alias"])

tests/test_transforms.py

@@ -102,6 +102,11 @@ def test_eliminate_distinct_on(self):
             'SELECT DISTINCT ON (a) a AS "A", b FROM x ORDER BY c DESC',
             'SELECT "A", b FROM (SELECT a AS "A", b AS b, ROW_NUMBER() OVER (PARTITION BY a ORDER BY c DESC) AS _row_number FROM x) AS _t WHERE _row_number = 1',
         )
+        self.validate(
+            eliminate_distinct_on,
+            'SELECT DISTINCT ON (a) "A", b FROM x ORDER BY c DESC',
+            'SELECT "A", b FROM (SELECT "A" AS "A", b AS b, ROW_NUMBER() OVER (PARTITION BY a ORDER BY c DESC) AS _row_number FROM x) AS _t WHERE _row_number = 1',
+        )
 
     def test_eliminate_qualify(self):
         self.validate(