Begin writing tests of the runtime checks needed for Dart 2.0 soundness.

pkg/front_end/testcases/runtime_checks/contravariant_generic_return.dart.direct.expect

+library test;
+import self as self;
+import "dart:core" as core;
+
+typedef F<T extends core::Object> = (T) → void;
+class C<T extends core::Object> extends core::Object {
+  default constructor •() → void
+    : super core::Object::•()
+    ;
+  method f1() → (self::C::T) → void {}
+  method f2() → core::List<(self::C::T) → void> {
+    return <dynamic>[this.f1()];
+  }
+}
+static method g1(self::C<core::num> c) → void {
+  dynamic x = c.f1();
+  core::print("hello");
+  x.call(1.5);
+}
+static method g2(self::C<core::num> c) → void {
+  (core::int) → void x = c.f1();
+  x.call(1);
+}
+static method g3(self::C<core::num> c) → void {
+  dynamic x = c.f2();
+}
+static method main() → void {}