Generated functions for returning queries return Iterable<_> instead of List<_> (#2044)

* fix for missing toList

* removed unnecessary toList

drift_dev/lib/src/writer/queries/query_writer.dart

@@ -222,7 +222,7 @@ class QueryWriter {
     } else {
       _buffer.write('rows.map(');
       _writeMappingLambda(update);
-      _buffer.write(')');
+      _buffer.write(').toList()');
     }
     _buffer.write(');\n}');
   }

drift_dev/test/writer/queries/query_writer_test.dart

@@ -82,6 +82,28 @@ void main() {
     );
   });
 
+  test('generates correct returning mapping', () async {
+    final state = TestState.withContent({
+      'a|lib/main.moor': '''
+        CREATE TABLE tbl (
+          id INTEGER,
+          text TEXT
+        );
+
+        query: INSERT INTO tbl (id, text) VALUES(10, "test") RETURNING id;
+      ''',
+    });
+    addTearDown(state.close);
+
+    final file = await state.analyze('package:a/main.moor');
+    final fileState = file.currentResult as ParsedDriftFile;
+
+    final writer = Writer(const DriftOptions.defaults());
+    QueryWriter(writer.child()).write(fileState.resolvedQueries!.single);
+
+    expect(writer.writeGenerated(), contains('.toList()'));
+  });
+
   group('generates correct code for expanded arrays', () {
     late TestState state;