Add type inference for assignments to properties.

pkg/front_end/testcases/inference/infer_assign_to_implicit_this_upwards.dart

+// 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.
+
+/*@testedFeatures=inference*/
+library test;
+
+int getInt() => 0;
+num getNum() => 0;
+double getDouble() => 0.0;
+
+class Test1 {
+  int t;
+
+  void test() {
+    var /*@type=int*/ v1 = /*@target=Test1::t*/ t = getInt();
+    var /*@type=num*/ v2 = /*@target=Test1::t*/ t = getNum();
+    var /*@type=int*/ v4 = /*@target=Test1::t*/ t ??= getInt();
+    var /*@type=num*/ v5 = /*@target=Test1::t*/ t ??= getNum();
+    var /*@type=int*/ v7 = /*@target=Test1::t*/ t += getInt();
+    var /*@type=num*/ v8 = /*@target=Test1::t*/ t += getNum();
+    var /*@type=int*/ v10 = ++ /*@target=Test1::t*/ t;
+    var /*@type=int*/ v11 = /*@target=Test1::t*/ t++;
+  }
+}
+
+class Test2 {
+  num t;
+
+  void test() {
+    var /*@type=int*/ v1 = /*@target=Test2::t*/ t = getInt();
+    var /*@type=num*/ v2 = /*@target=Test2::t*/ t = getNum();
+    var /*@type=double*/ v3 = /*@target=Test2::t*/ t = getDouble();
+    var /*@type=num*/ v4 = /*@target=Test2::t*/ t ??= getInt();
+    var /*@type=num*/ v5 = /*@target=Test2::t*/ t ??= getNum();
+    var /*@type=num*/ v6 = /*@target=Test2::t*/ t ??= getDouble();
+    var /*@type=num*/ v7 = /*@target=Test2::t*/ t += getInt();
+    var /*@type=num*/ v8 = /*@target=Test2::t*/ t += getNum();
+    var /*@type=num*/ v9 = /*@target=Test2::t*/ t += getDouble();
+    var /*@type=num*/ v10 = ++ /*@target=Test2::t*/ t;
+    var /*@type=num*/ v11 = /*@target=Test2::t*/ t++;
+  }
+}
+
+class Test3 {
+  double t;
+
+  void test3() {
+    var /*@type=num*/ v2 = /*@target=Test3::t*/ t = getNum();
+    var /*@type=double*/ v3 = /*@target=Test3::t*/ t = getDouble();
+    var /*@type=num*/ v5 = /*@target=Test3::t*/ t ??= getNum();
+    var /*@type=double*/ v6 = /*@target=Test3::t*/ t ??= getDouble();
+    var /*@type=double*/ v7 = /*@target=Test3::t*/ t += getInt();
+    var /*@type=double*/ v8 = /*@target=Test3::t*/ t += getNum();
+    var /*@type=double*/ v9 = /*@target=Test3::t*/ t += getDouble();
+    var /*@type=double*/ v10 = ++ /*@target=Test3::t*/ t;
+    var /*@type=double*/ v11 = /*@target=Test3::t*/ t++;
+  }
+}
+
+main() {}