fixes #27586, prefer context type in generic inference

tests/language_strong/recursive_inheritance_test.dart

Index: tests/language_strong/recursive_inheritance_test.dart
diff --git a/tests/language_strong/recursive_inheritance_test.dart b/tests/language_strong/recursive_inheritance_test.dart
index 1d513ae5a3a156ddd297c4fd5d55813e95a0a1e0..0f5f05362e3761e185af94f18fea35fc41ef6490 100644
--- a/tests/language_strong/recursive_inheritance_test.dart
+++ b/tests/language_strong/recursive_inheritance_test.dart
@@ -6,16 +6,21 @@ import "package:expect/expect.dart";
 
 // Regression test for recursive inheritance patterns
 abstract class Comparable<T> {
-  int compare(T a);
-}
-class MI<T extends MI<T>> {
+  int compareTo(T a);
 }
+class MI<T extends MI<T>> {}
+
+class _MI extends MI<_MI> {}
 
 class PMI<T extends Comparable<T>> extends MI<PMI<T>> {}
 
+class _PMI extends PMI<_PMI> implements Comparable<_PMI> {
+  int compareTo(_PMI other) => throw new UnimplementedError();
+}
+
 void main() {
-  var a = new MI();
-  var b = new PMI();
+  MI a = new MI<_MI>();
+  PMI b = new PMI<_PMI>();
   a = b;
   Expect.isTrue(a is MI);
   Expect.isTrue(b is PMI);