Don't allow statement-nodes in expression contexts.

tests/language/issue3806_test.dart

Index: tests/language/issue3806_test.dart
diff --git a/tests/language/issue3806_test.dart b/tests/language/issue3806_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..d6c3e20e3fd6be7e2165856aeb67d1f6ef304982
--- /dev/null
+++ b/tests/language/issue3806_test.dart
@@ -0,0 +1,22 @@
+// Copyright (c) 2012, 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.
+
+// Dart2js produced a statement in an expression context for this test.
+
+class A {
+  var foo = "foo";
+  bar(x) {
+    if (foo == 3) return;
+    var t = x;
+    if (x == 0 ) t = foo;
+    foo = t;
+  }
+  toto(x) => x;
+  titi() {
+    foo = 0;
+    for (int i = 0; i < 3; i++) bar(i);
+  }
+}
+
+main() => new A().titi();