Spec says empty namedArguments is const {}, not const <Symbol, dynamic>{}.

tests/language/invocation_mirror_empty_arguments_test.dart

+// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import "package:expect/expect.dart";
+
+class Getter {
+  noSuchMethod(invocation) {
+    Expect.isTrue(invocation.isGetter);
+    Expect.identical(const [], invocation.positionalArguments);
+    Expect.identical(const {}, invocation.namedArguments);
+  }
+}
+
+class Setter {
+  noSuchMethod(invocation) {
+    Expect.isTrue(invocation.isSetter);
+    Expect.identical(const {}, invocation.namedArguments);
+  }
+}
+
+class Method {
+  noSuchMethod(invocation) {
+    Expect.isTrue(invocation.isMethod);
+    Expect.identical(const [], invocation.positionalArguments);
+    Expect.identical(const {}, invocation.namedArguments);
+  }
+}
+
+class Operator {
+  noSuchMethod(invocation) {
+    Expect.isTrue(invocation.isMethod);
+    Expect.identical(const {}, invocation.namedArguments);
+  }
+}
+
+main() {
+  var g = new Getter();
+  print(g.getterThatDoesNotExist);
+  var s = new Setter();
+  print(s.setterThatDoesNotExist = 42);
+  var m = new Method();
+  print(m.methodThatDoesNotExist());
+  var o = new Operator();
+  print(o + 42); // Operator that does not exist.
+}