Add non-null types list to StrongModeOptions

pkg/analyzer/test/src/task/strong/non_null_checker_test.dart

 // Copyright (c) 2016, 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.
 
 // These tests are for an experimental feature that treats Dart primitive types
 // (int, bool, double, etc.) as non-nullable. This file is not evidence for an
 // intention to officially support non-nullable primitives in Dart (or general
 // NNBD, for that matter) so don't get too crazy about it.
 
 library analyzer.test.src.task.non_null_primitives.checker_test;
@@ skipping 24 matching lines @@
 }
 
 main() {
   var languages = new MyList();
   for (int i = 0; i < languages.length; ++i) {
     print(languages[i]);
   }
 }
 ''');
   }
+
+  void test_nullableTypes() {
+    // By default x can be set to null.
+    addFile('''int x = null;''');
+    check();
+  }
+
+  @failingTest
+  void test_nonnullableTypes() {
+    // If `int`s are non-nullable, then this code should throw an error.
+    addFile('''int x = /*error:INVALID_ASSIGNMENT*/null;''');
+    check(nonnullableTypes: <String>['int']);

[Jennifer Messerly, 2016/08/02 16:18:51]

to build on Brian's comment, consider qualifying it with an import URI, e.g.
'dart:core,int'

[Brian Wilkerson, 2016/08/02 16:25:18]

Unless this is intended to be a general purpose mechanism (I want to be able to
declare that my 'Point' class can never be null) that seems like overkill. I was
guessing that this is just to allow the translator to not have to wrap instances
of classes that could otherwise be converted to Java primitive types. But I
probably don't have the full picture, so your call.

[stanm, 2016/08/02 16:56:05]

I agree it's a bit of an overkill, but it actually makes implementing this
experimental feature easier (after adding the import URI, as John mentioned),
since then I can directly do a `contains` check whenever I need to handle
non-nullable types in a special way.

Also, I don't plan to make this user-visible: the actual compiler option will be
something like '--non-nullable-primitives' and will enable a preset collection
of non-nullable classes.

Also, I will add to the commit message that this CL is based on previous work
from Vijay:
https://github.com/dart-lang/dev_compiler/commit/9e124ba8d47963eb378d757ed54d...

(ironically, this is the commit that undoes it : )

+  }
 }