Fix VM crash when encountering an assignment expression in a case expression.

tests/language/case_expression_with_assignment_test.dart

Index: tests/language/case_expression_with_assignment_test.dart
diff --git a/tests/language/case_expression_with_assignment_test.dart b/tests/language/case_expression_with_assignment_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..aa78629597f6edec9fc3bb4e20bd7f00b11de7ff
--- /dev/null
+++ b/tests/language/case_expression_with_assignment_test.dart
@@ -0,0 +1,28 @@
+// 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.
+
+// Regression test for crash in VM parser (issue 29370).
+
+import "package:expect/expect.dart";
+
+const ERROR_A = 0;
+const ERROR_B = 1;
+
+errorToString(error) {
+  switch (error) {
+    case ERROR_A:
+      return "ERROR_A";
+    case ERROR_B = 1: //# 01: compile-time error
+    case ERROR_B: //# none: ok
+      return "ERROR_B";
+    default:
+      return "Unknown error";
+  }
+}
+
+main() {
+  Expect.equals(errorToString(ERROR_A), "ERROR_A");
+  Expect.equals(errorToString(ERROR_B), "ERROR_B");
+  Expect.equals(errorToString(55), "Unknown error");
+}