Implement override-based inference of instance fields.

pkg/front_end/testcases/inference/infer_from_rhs_only_if_it_wont_conflict_with_overridden_fields.dart.strong.expect

Index: pkg/front_end/testcases/inference/infer_from_rhs_only_if_it_wont_conflict_with_overridden_fields.dart.strong.expect
diff --git a/pkg/front_end/testcases/inference/infer_from_rhs_only_if_it_wont_conflict_with_overridden_fields.dart.strong.expect b/pkg/front_end/testcases/inference/infer_from_rhs_only_if_it_wont_conflict_with_overridden_fields.dart.strong.expect
new file mode 100644
index 0000000000000000000000000000000000000000..a78fd93e8e9137dd136b5609b197f51865f613bd
--- /dev/null
+++ b/pkg/front_end/testcases/inference/infer_from_rhs_only_if_it_wont_conflict_with_overridden_fields.dart.strong.expect
@@ -0,0 +1,21 @@
+library test;
+import self as self;
+import "dart:core" as core;
+
+class A extends core::Object {
+  field dynamic x = null;
+  constructor •() → void
+    : super core::Object::•()
+    ;
+}
+class B extends core::Object implements self::A {
+  field dynamic x = 2;
+  constructor •() → void
+    : super core::Object::•()
+    ;
+}
+static method foo() → dynamic {
+  core::String y = new self::B::•().{self::B::x};
+  core::int z = new self::B::•().{self::B::x};
+}
+static method main() → dynamic {}