Fix compilation error

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/optimizer/PhysicalPlanOptimizer.java

@@ -139,7 +139,7 @@ public class PhysicalPlanOptimizer extends ParameterizedRuleExecutor<PhysicalPla
                             // to avoid the block from being trimmed
                             if (output.isEmpty()) {
                                 var alias = new Alias(logicalFragment.source(), "<all-fields-projected>", null, Literal.NULL, null, true);
-                                List<NamedExpression> fields = singletonList(alias);
+                                List<Alias> fields = singletonList(alias);
                                 logicalFragment = new Eval(logicalFragment.source(), logicalFragment, fields);
                                 output = Expressions.asAttributes(fields);
                             }