don't produce errors from inference for downward inferred type variables

pkg/analyzer/test/src/task/strong/checker_test.dart

 // Copyright (c) 2015, 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.
 
 library analyzer.test.src.task.strong.checker_test;
 
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import 'strong_test_helper.dart';
 
@@ skipping 2029 matching lines @@
 /*=T*/ foo/*<T>*/(/*=T*/ x, /*=T*/ y) => x;
 /*=T*/ bar/*<T>*/({/*=T*/ x, /*=T*/ y}) => x;
 
 main() {
   String x;
   // resolving these shouldn't crash.
   foo/*error:EXTRA_POSITIONAL_ARGUMENTS*/(1, 2, 3);
   x = foo/*error:EXTRA_POSITIONAL_ARGUMENTS*/('1', '2', '3');
   foo/*error:NOT_ENOUGH_REQUIRED_ARGUMENTS*/(1);
   x = foo/*error:NOT_ENOUGH_REQUIRED_ARGUMENTS*/('1');
-  x = /*error:COULD_NOT_INFER*/foo/*error:EXTRA_POSITIONAL_ARGUMENTS*/(/*error:ARGUMENT_TYPE_NOT_ASSIGNABLE*/1, /*error:ARGUMENT_TYPE_NOT_ASSIGNABLE*/2, 3);
-  x = /*error:COULD_NOT_INFER*/foo/*error:NOT_ENOUGH_REQUIRED_ARGUMENTS*/(/*error:ARGUMENT_TYPE_NOT_ASSIGNABLE*/1);
+  x = foo/*error:EXTRA_POSITIONAL_ARGUMENTS*/(/*error:ARGUMENT_TYPE_NOT_ASSIGNABLE*/1, /*error:ARGUMENT_TYPE_NOT_ASSIGNABLE*/2, 3);
+  x = foo/*error:NOT_ENOUGH_REQUIRED_ARGUMENTS*/(/*error:ARGUMENT_TYPE_NOT_ASSIGNABLE*/1);
 
   // named arguments
   bar(y: 1, x: 2, /*error:UNDEFINED_NAMED_PARAMETER*/z: 3);
   x = bar(/*error:UNDEFINED_NAMED_PARAMETER*/z: '1', x: '2', y: '3');
   bar(y: 1);
   x = bar(x: '1', /*error:UNDEFINED_NAMED_PARAMETER*/z: 42);
-  x = /*error:COULD_NOT_INFER*/bar(/*error:ARGUMENT_TYPE_NOT_ASSIGNABLE*/y: 1, /*error:ARGUMENT_TYPE_NOT_ASSIGNABLE*/x: 2, /*error:UNDEFINED_NAMED_PARAMETER*/z: 3);
-  x = /*error:COULD_NOT_INFER*/bar(/*error:ARGUMENT_TYPE_NOT_ASSIGNABLE*/x: 1);
+  x = bar(/*error:ARGUMENT_TYPE_NOT_ASSIGNABLE*/y: 1, /*error:ARGUMENT_TYPE_NOT_ASSIGNABLE*/x: 2, /*error:UNDEFINED_NAMED_PARAMETER*/z: 3);
+  x = bar(/*error:ARGUMENT_TYPE_NOT_ASSIGNABLE*/x: 1);
 }
 ''');
   }
 
   test_genericMethodOverride() async {
     await checkFile('''
 class Future<T> {
   /*=S*/ then/*<S>*/(/*=S*/ onValue(T t)) => null;
 }
 
@@ skipping 2068 matching lines @@
 class CheckerTest_Driver extends CheckerTest {
   @override
   bool get enableNewAnalysisDriver => true;
 
   @failingTest
   @override
   test_covariantOverride_fields() async {
     await super.test_covariantOverride_fields();
   }
 }