Support type promotion in dart2js.

tests/language/type_promotion_multiple_test.dart

Index: tests/language/type_promotion_multiple_test.dart
diff --git a/tests/language/type_promotion_multiple_test.dart b/tests/language/type_promotion_multiple_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..f692916c722bdbe27bd6f4449e9d8ff0b4d13363
--- /dev/null
+++ b/tests/language/type_promotion_multiple_test.dart
@@ -0,0 +1,96 @@
+// Copyright (c) 2013, 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.
+
+// Test type promotion of locals.
+
+class A {
+  var a = "a";
+}
+class B extends A {
+  var b = "b";
+}
+class C extends B {
+  var c = "c";
+}
+class D extends A {
+  var d = "d";
+}
+class E implements C, D {
+  var a = "";
+  var b = "";
+  var c = "";
+  var d = "";
+}
+
+void main() {
+  test(new E());
+}
+void test(A a1) {
+  A a2 = new E();
+  print(a1.a);
+  print(a1.b); /// 01: static type warning
+  print(a1.c); /// 02: static type warning
+  print(a1.d); /// 03: static type warning
+
+  print(a2.a);
+  print(a2.b); /// 04: static type warning
+  print(a2.c); /// 05: static type warning
+  print(a2.d); /// 06: static type warning
+
+  if (a1 is B && a2 is C) {
+    print(a1.a);
+    print(a1.b);
+    print(a1.c); /// 07: static type warning
+    print(a1.d); /// 08: static type warning
+
+    print(a2.a);
+    print(a2.b);
+    print(a2.c);
+    print(a2.d); /// 09: static type warning
+
+    if (a1 is C && a2 is D) {
+      print(a1.a);
+      print(a1.b);
+      print(a1.c);
+      print(a1.d); /// 10: static type warning
+
+      print(a2.a);
+      print(a2.b);
+      print(a2.c);
+      print(a2.d); /// 11: static type warning
+    }
+  }
+
+  var o1 = a1 is B  && a2 is C ?
+      '${a1.a}'
+      '${a1.b}'
+      '${a1.c}' /// 12: static type warning
+      '${a1.d}' /// 13: static type warning
+      '${a2.a}'
+      '${a2.b}'
+      '${a2.c}'
+      '${a2.d}' /// 14: static type warning
+      :
+      '${a1.a}'
+      '${a1.b}' /// 15: static type warning
+      '${a1.c}' /// 16: static type warning
+      '${a1.d}' /// 17: static type warning
+      '${a2.a}'
+      '${a2.b}' /// 18: static type warning
+      '${a2.c}' /// 19: static type warning
+      '${a2.d}' /// 20: static type warning
+      ;
+
+  if (a2 is C && a1 is B && a1 is C && a2 is B && a2 is D) {
+    print(a1.a);
+    print(a1.b);
+    print(a1.c);
+    print(a1.d); /// 21: static type warning
+
+    print(a2.a);
+    print(a2.b);
+    print(a2.c);
+    print(a2.d); /// 22: static type warning
+  }
+}