fix #27088, future then upwards inference

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 '../../../reflective_tests.dart';
 import 'strong_test_helper.dart';
 
 void main() {
@@ skipping 961 matching lines @@
         /*error:ARGUMENT_TYPE_NOT_ASSIGNABLE*/topTop,
         aa,
         /*error:ARGUMENT_TYPE_NOT_ASSIGNABLE*/aTop,
         botA,
         /*warning:DOWN_CAST_COMPOSITE*/botTop
                     );
     apply/*<BotA>*/(
         (dynamic x) => new A(),
         /*error:ARGUMENT_TYPE_NOT_ASSIGNABLE*/(dynamic x) => (x as Object),
         (A x) => x,
-        /*error:ARGUMENT_TYPE_NOT_ASSIGNABLE*/(A x) => (x as Object),
+        /*error:ARGUMENT_TYPE_NOT_ASSIGNABLE*/(A x) => (/*info:UNNECESSARY_CAST*/x as Object),
         botA,
         /*warning:DOWN_CAST_COMPOSITE*/botTop
                     );
   }
   {
     AA f;
     f = topA;
     f = /*error:INVALID_ASSIGNMENT*/topTop;
     f = aa;
     f = /*error:STATIC_TYPE_ERROR*/aTop; // known function
     f = /*warning:DOWN_CAST_COMPOSITE*/botA;
     f = /*warning:DOWN_CAST_COMPOSITE*/botTop;
     apply/*<AA>*/(
         topA,
         /*error:ARGUMENT_TYPE_NOT_ASSIGNABLE*/topTop,
         aa,
         /*error:STATIC_TYPE_ERROR*/aTop, // known function
         /*warning:DOWN_CAST_COMPOSITE*/botA,
         /*warning:DOWN_CAST_COMPOSITE*/botTop
                   );
     apply/*<AA>*/(
         (dynamic x) => new A(),
         /*error:ARGUMENT_TYPE_NOT_ASSIGNABLE*/(dynamic x) => (x as Object),
         (A x) => x,
-        /*error:STATIC_TYPE_ERROR*/(A x) => (x as Object), // known function
+        /*error:STATIC_TYPE_ERROR*/(A x) => (/*info:UNNECESSARY_CAST*/x as Object), // known function
         /*warning:DOWN_CAST_COMPOSITE*/botA,
         /*warning:DOWN_CAST_COMPOSITE*/botTop
                   );
   }
   {
     TopTop f;
     f = topA;
     f = topTop;
     f = /*error:INVALID_ASSIGNMENT*/aa;
     f = /*error:STATIC_TYPE_ERROR*/aTop; // known function
     f = /*error:INVALID_ASSIGNMENT*/botA;
     f = /*warning:DOWN_CAST_COMPOSITE*/botTop;
     apply/*<TopTop>*/(
         topA,
         topTop,
         /*error:ARGUMENT_TYPE_NOT_ASSIGNABLE*/aa,
         /*error:STATIC_TYPE_ERROR*/aTop, // known function
         /*error:ARGUMENT_TYPE_NOT_ASSIGNABLE*/botA,
         /*warning:DOWN_CAST_COMPOSITE*/botTop
                       );
     apply/*<TopTop>*/(
         (dynamic x) => new A(),
         (dynamic x) => (x as Object),
         /*error:ARGUMENT_TYPE_NOT_ASSIGNABLE*/(A x) => x,
-        /*error:STATIC_TYPE_ERROR*/(A x) => (x as Object), // known function
+        /*error:STATIC_TYPE_ERROR*/(A x) => (/*info:UNNECESSARY_CAST*/x as Object), // known function
         /*error:ARGUMENT_TYPE_NOT_ASSIGNABLE*/botA,
         /*warning:DOWN_CAST_COMPOSITE*/botTop
                       );
   }
   {
     TopA f;
     f = topA;
     f = /*error:STATIC_TYPE_ERROR*/topTop; // known function
     f = /*error:STATIC_TYPE_ERROR*/aa; // known function
     f = /*error:STATIC_TYPE_ERROR*/aTop; // known function
     f = /*warning:DOWN_CAST_COMPOSITE*/botA;
     f = /*warning:DOWN_CAST_COMPOSITE*/botTop;
     apply/*<TopA>*/(
         topA,
         /*error:STATIC_TYPE_ERROR*/topTop, // known function
         /*error:STATIC_TYPE_ERROR*/aa, // known function
         /*error:STATIC_TYPE_ERROR*/aTop, // known function
         /*warning:DOWN_CAST_COMPOSITE*/botA,
         /*warning:DOWN_CAST_COMPOSITE*/botTop
                     );
     apply/*<TopA>*/(
         (dynamic x) => new A(),
         /*error:STATIC_TYPE_ERROR*/(dynamic x) => (x as Object), // known function
         /*error:STATIC_TYPE_ERROR*/(A x) => x, // known function
-        /*error:STATIC_TYPE_ERROR*/(A x) => (x as Object), // known function
+        /*error:STATIC_TYPE_ERROR*/(A x) => (/*info:UNNECESSARY_CAST*/x as Object), // known function
         /*warning:DOWN_CAST_COMPOSITE*/botA,
         /*warning:DOWN_CAST_COMPOSITE*/botTop
                     );
   }
 }
 ''');
   }
 
   void test_functionTypingAndSubtyping_dynamicFunctions_clasuresAreNotFuzzy() {
     // Regression test for
@@ skipping 558 matching lines @@
 }
 int i2i(int x) => x;
 num n2n(num x) => x;
 void main() {
    {
      I2I f;
      f = new A();
      f = /*error:INVALID_ASSIGNMENT*/new B();
      f = i2i;
      f = /*error:INVALID_ASSIGNMENT*/n2n;
-     f = /*warning:DOWN_CAST_COMPOSITE*/i2i as Object;
-     f = /*warning:DOWN_CAST_COMPOSITE*/n2n as Function;
+     f = /*info:UNNECESSARY_CAST,warning:DOWN_CAST_COMPOSITE*/i2i as Object;
+     f = /*info:UNNECESSARY_CAST,warning:DOWN_CAST_COMPOSITE*/n2n as Function;
    }
    {
      N2N f;
      f = /*error:INVALID_ASSIGNMENT*/new A();
      f = new B();
      f = /*error:INVALID_ASSIGNMENT*/i2i;
      f = n2n;
-     f = /*warning:DOWN_CAST_COMPOSITE*/i2i as Object;
-     f = /*warning:DOWN_CAST_COMPOSITE*/n2n as Function;
+     f = /*info:UNNECESSARY_CAST,warning:DOWN_CAST_COMPOSITE*/i2i as Object;
+     f = /*info:UNNECESSARY_CAST,warning:DOWN_CAST_COMPOSITE*/n2n as Function;
    }
    {
      A f;
      f = new A();
      f = /*error:INVALID_ASSIGNMENT*/new B();
      f = /*error:INVALID_ASSIGNMENT*/i2i;
      f = /*error:INVALID_ASSIGNMENT*/n2n;
-     f = /*info:DOWN_CAST_IMPLICIT*/i2i as Object;
-     f = /*info:DOWN_CAST_IMPLICIT*/n2n as Function;
+     f = /*info:UNNECESSARY_CAST,info:DOWN_CAST_IMPLICIT*/i2i as Object;
+     f = /*info:UNNECESSARY_CAST,info:DOWN_CAST_IMPLICIT*/n2n as Function;
    }
    {
      B f;
      f = /*error:INVALID_ASSIGNMENT*/new A();
      f = new B();
      f = /*error:INVALID_ASSIGNMENT*/i2i;
      f = /*error:INVALID_ASSIGNMENT*/n2n;
-     f = /*info:DOWN_CAST_IMPLICIT*/i2i as Object;
-     f = /*info:DOWN_CAST_IMPLICIT*/n2n as Function;
+     f = /*info:UNNECESSARY_CAST,info:DOWN_CAST_IMPLICIT*/i2i as Object;
+     f = /*info:UNNECESSARY_CAST,info:DOWN_CAST_IMPLICIT*/n2n as Function;
    }
    {
      Function f;
      f = new A();
      f = new B();
      f = i2i;
      f = n2n;
-     f = /*info:DOWN_CAST_IMPLICIT*/i2i as Object;
-     f = (n2n as Function);
+     f = /*info:UNNECESSARY_CAST,info:DOWN_CAST_IMPLICIT*/i2i as Object;
+     f = /*info:UNNECESSARY_CAST*/n2n as Function;
    }
 }
 ''');
   }
 
   void test_functionTypingAndSubtyping_staticMethodVariance() {
     checkFile('''
 class A {}
 class B extends A {}
 
@@ skipping 297 matching lines @@
   /*=T*/ g/*<T>*/() => null;
 
   /*error:IMPLICIT_DYNAMIC_FUNCTION*/f(d);
   f(42);
   /*error:IMPLICIT_DYNAMIC_FUNCTION*/g();
   d = /*error:IMPLICIT_DYNAMIC_FUNCTION*/g();
   i = g();
 
   /*error:IMPLICIT_DYNAMIC_INVOKE*/(/*<T>*/(/*=T*/ t) => t)(d);
   (/*<T>*/(/*=T*/ t) => t)(42);
-  (/*<T>*/() => null as dynamic/*=T*/)/*<int>*/();
+  (/*<T>*/() => /*info:UNNECESSARY_CAST*/null as dynamic/*=T*/)/*<int>*/();
 }
     ''');
     check(implicitDynamic: false);
   }
   void test_implicitDynamic_listLiteral() {
     addFile(r'''
 
 var l0 = /*error:IMPLICIT_DYNAMIC_LIST_LITERAL*/[];
 List l1 = /*error:IMPLICIT_DYNAMIC_LIST_LITERAL*/[];
 List<dynamic> l2 = /*error:IMPLICIT_DYNAMIC_LIST_LITERAL*/[];
@@ skipping 546 matching lines @@
   b = /*info:NON_GROUND_TYPE_CHECK_INFO*/bar is DI2I;
   b = /*info:NON_GROUND_TYPE_CHECK_INFO*/bar is ID2I;
   b = /*info:NON_GROUND_TYPE_CHECK_INFO*/bar is II2D;
   b = /*info:NON_GROUND_TYPE_CHECK_INFO*/bar is DD2I;
   b = /*info:NON_GROUND_TYPE_CHECK_INFO*/bar is DI2D;
   b = /*info:NON_GROUND_TYPE_CHECK_INFO*/bar is ID2D;
   b = bar is DD2D;
 
   // For as, the validity of checks is deferred to runtime.
   Function f;
-  f = foo as I2I;
-  f = foo as D2I;
-  f = foo as I2D;
-  f = foo as D2D;
+  f = /*info:UNNECESSARY_CAST*/foo as I2I;
+  f = /*info:UNNECESSARY_CAST*/foo as D2I;
+  f = /*info:UNNECESSARY_CAST*/foo as I2D;
+  f = /*info:UNNECESSARY_CAST*/foo as D2D;
 
-  f = bar as II2I;
-  f = bar as DI2I;
-  f = bar as ID2I;
-  f = bar as II2D;
-  f = bar as DD2I;
-  f = bar as DI2D;
-  f = bar as ID2D;
-  f = bar as DD2D;
+  f = /*info:UNNECESSARY_CAST*/bar as II2I;
+  f = /*info:UNNECESSARY_CAST*/bar as DI2I;
+  f = /*info:UNNECESSARY_CAST*/bar as ID2I;
+  f = /*info:UNNECESSARY_CAST*/bar as II2D;
+  f = /*info:UNNECESSARY_CAST*/bar as DD2I;
+  f = /*info:UNNECESSARY_CAST*/bar as DI2D;
+  f = /*info:UNNECESSARY_CAST*/bar as ID2D;
+  f = /*info:UNNECESSARY_CAST*/bar as DD2D;
 }
 ''');
   }
 
   void test_leastUpperBounds() {
     checkFile('''
 typedef T Returns<T>();
 
 // regression test for https://github.com/dart-lang/sdk/issues/26094
 class A <S extends  Returns<S>, T extends Returns<T>> {
@@ skipping 1166 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();
 }
 ''');
   }
 }