Check in codegen test expectations.

test/codegen/expect/map_keys.js

+dart_library.library('map_keys', null, /* Imports */[
+  'dart_sdk'
+], function load__map_keys(exports, dart_sdk) {
+  'use strict';
+  const core = dart_sdk.core;
+  const math = dart_sdk.math;
+  const dart = dart_sdk.dart;
+  const dartx = dart_sdk.dartx;
+  const map_keys = Object.create(null);
+  let VoidTodynamic = () => (VoidTodynamic = dart.constFn(dart.definiteFunctionType(dart.dynamic, [])))();
+  map_keys.main = function() {
+    core.print(dart.map({'1': 2, '3': 4, '5': 6}));
+    core.print(dart.map([1, 2, 3, 4, 5, 6]));
+    core.print(dart.map({'1': 2, [dart.str`${dart.notNull(math.Random.new().nextInt(2)) + 2}`]: 4, '5': 6}));
+    let x = '3';
+    core.print(dart.map(['1', 2, x, 4, '5', 6]));
+    core.print(dart.map(['1', 2, null, 4, '5', 6]));
+  };
+  dart.fn(map_keys.main, VoidTodynamic());
+  // Exports:
+  exports.map_keys = map_keys;
+});
+
+//# sourceMappingURL=map_keys.js.map