Add type inference for assignments to properties.

pkg/front_end/testcases/inference/infer_assign_to_implicit_this.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;
+
+class A {}
+
+class B extends A {
+  A operator +(C v) => null;
+  B operator -(int i) => null;
+  B operator *(B v) => null;
+  C operator &(A v) => null;
+}
+
+class C extends B {}
+
+T f<T>() => null;
+
+class Test {
+  B member;
+
+  void test() {
+    /*@target=Test::member*/ member = /*@typeArgs=B*/ f();
+    /*@target=Test::member*/ member ??= /*@typeArgs=B*/ f();
+    /*@target=Test::member*/ member += /*@typeArgs=dynamic*/ f();
+    /*@target=Test::member*/ member *= /*@typeArgs=dynamic*/ f();
+    /*@target=Test::member*/ member &= /*@typeArgs=dynamic*/ f();
+    -- /*@target=Test::member*/ member;
+    /*@target=Test::member*/ member--;
+    var /*@type=B*/ v1 = /*@target=Test::member*/ member = /*@typeArgs=B*/ f();
+    var /*@type=B*/ v2 = /*@target=Test::member*/ member ??= /*@typeArgs=B*/ f();
+    var /*@type=A*/ v3 = /*@target=Test::member*/ member += /*@typeArgs=dynamic*/ f();
+    var /*@type=B*/ v4 = /*@target=Test::member*/ member *= /*@typeArgs=dynamic*/ f();
+    var /*@type=C*/ v5 = /*@target=Test::member*/ member &= /*@typeArgs=dynamic*/ f();
+    var /*@type=B*/ v6 = -- /*@target=Test::member*/ member;
+    var /*@type=B*/ v7 = /*@target=Test::member*/ member--;
+  }
+}
+
+main() {}