Implement override-based type inference for instance methods.

pkg/front_end/testcases/inference/downwards_inference_on_list_literals_infer_if_value_types_match_context.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 DartType {}
 
 typedef void Asserter<T>(T type);
 typedef Asserter<T> AsserterBuilder<S, T>(S arg);
 
 Asserter<DartType> _isInt;
 Asserter<DartType> _isString;
 
 abstract class C {
   static AsserterBuilder<List<Asserter<DartType>>, DartType> assertBOf;
   static AsserterBuilder<List<Asserter<DartType>>, DartType> get assertCOf =>
       null;
 
   AsserterBuilder<List<Asserter<DartType>>, DartType> assertAOf;
   AsserterBuilder<List<Asserter<DartType>>, DartType> get assertDOf;
 
-  method(AsserterBuilder<List<Asserter<DartType>>, DartType> assertEOf) {
+  /*@topType=dynamic*/ method(
+      AsserterBuilder<List<Asserter<DartType>>, DartType> assertEOf) {
     /*@target=C::assertAOf*/ assertAOf(
         /*@typeArgs=(DartType) -> void*/ [_isInt, _isString]);
     assertBOf(
         /*@typeArgs=(DartType) -> void*/ [_isInt, _isString]);
     assertCOf(
         /*@typeArgs=(DartType) -> void*/ [_isInt, _isString]);
     /*@target=C::assertDOf*/ assertDOf(
         /*@typeArgs=(DartType) -> void*/ [_isInt, _isString]);
     assertEOf(
         /*@typeArgs=(DartType) -> void*/ [_isInt, _isString]);
   }
 }
 
 abstract class G<T> {
   AsserterBuilder<List<Asserter<DartType>>, DartType> assertAOf;
   AsserterBuilder<List<Asserter<DartType>>, DartType> get assertDOf;
 
-  method(AsserterBuilder<List<Asserter<DartType>>, DartType> assertEOf) {
+  /*@topType=dynamic*/ method(
+      AsserterBuilder<List<Asserter<DartType>>, DartType> assertEOf) {
     /*@target=G::assertAOf*/ assertAOf(
         /*@typeArgs=(DartType) -> void*/ [_isInt, _isString]);
     this. /*@target=G::assertAOf*/ assertAOf(
         /*@typeArgs=(DartType) -> void*/ [_isInt, _isString]);
     this. /*@target=G::assertDOf*/ assertDOf(
         /*@typeArgs=(DartType) -> void*/ [_isInt, _isString]);
     assertEOf(
         /*@typeArgs=(DartType) -> void*/ [_isInt, _isString]);
   }
 }
@@ skipping 21 matching lines @@
       /*@typeArgs=(DartType) -> void*/ [_isInt, _isString]);
 
   G<int> g;
   g. /*@target=G::assertAOf*/ assertAOf(
       /*@typeArgs=(DartType) -> void*/ [_isInt, _isString]);
   g. /*@target=G::assertDOf*/ assertDOf(
       /*@typeArgs=(DartType) -> void*/ [_isInt, _isString]);
 }
 
 main() {}