Make call methods definite.

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 1283 matching lines @@
         /*error:INVALID_CAST_FUNCTION_EXPR*/(A x) => (/*info:UNNECESSARY_CAST*/x as Object), // known function
         /*warning:DOWN_CAST_COMPOSITE*/botA,
         /*warning:DOWN_CAST_COMPOSITE*/botTop
                     );
   }
 }
 ''');
   }
 
   void test_functionTypingAndSubtyping_dynamicFunctions_closuresAreNotFuzzy() {
-    // Regression test for
+    // Regression test for definite function cases
     // https://github.com/dart-lang/sdk/issues/26118
     // https://github.com/dart-lang/sdk/issues/26156
+    // https://github.com/dart-lang/sdk/issues/28087
     checkFile('''
 void takesF(void f(int x)) {}
 
 typedef void TakesInt(int x);
 
 void update(_) {}
 void updateOpt([_]) {}
 void updateOptNum([num x]) {}
 
+class Callable {
+  void call(_) {}
+}
+
 class A {
   TakesInt f;
   A(TakesInt g) {
     f = update;
     f = updateOpt;
     f = updateOptNum;
+    f = new Callable();
   }
   TakesInt g(bool a, bool b) {
     if (a) {
       return update;
     } else if (b) {
       return updateOpt;
+    } else if (a) {
+      return updateOptNum;
     } else {
-      return updateOptNum;
+      return new Callable();
     }
   }
 }
 
 void test0() {
   takesF(update);
   takesF(updateOpt);
   takesF(updateOptNum);
+  takesF(new Callable());
   TakesInt f;
   f = update;
   f = updateOpt;
   f = updateOptNum;
+  f = new Callable();
   new A(update);
   new A(updateOpt);
   new A(updateOptNum);
+  new A(new Callable());
 }
 
 void test1() {
   void takesF(f(int x)) => null;
   takesF((dynamic y) => 3);
 }
 
 void test2() {
   int x;
   int f/*<T>*/(/*=T*/ t, callback(/*=T*/ x)) { return 3; }
@@ skipping 2661 matching lines @@
     // Regression test for https://github.com/dart-lang/sdk/issues/25069
     checkFile('''
 typedef int Foo();
 void foo() {}
 void main () {
   Foo x = /*error:INVALID_ASSIGNMENT,info:USE_OF_VOID_RESULT*/foo();
 }
 ''');
   }
 }