Handle mandatory arguments correctly in function type aliases.

pkg/front_end/test/fasta/typedef.dart

Index: pkg/front_end/test/fasta/typedef.dart
diff --git a/pkg/front_end/test/fasta/typedef.dart b/pkg/front_end/test/fasta/typedef.dart
new file mode 100644
index 0000000000000000000000000000000000000000..44de7221796b9b77cc2be3300cdaee36dd6194b4
--- /dev/null
+++ b/pkg/front_end/test/fasta/typedef.dart
@@ -0,0 +1,13 @@
+// Copyright (c) 2017, 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.
+
+typedef _NullaryFunction();
+typedef _UnaryFunction(args);
+typedef _BinaryFunction(args, message);
+
+main() {
+  print(main is _NullaryFunction);
+  print(main is _UnaryFunction);
+  print(main is _BinaryFunction);
+}