fix #28008, fix #28009 implement FutureOr<T>

pkg/analyzer/test/src/summary/resynthesize_common.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 test.src.serialization.elements_test;
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/standard_resolution_map.dart';
 import 'package:analyzer/dart/constant/value.dart';
 import 'package:analyzer/dart/element/element.dart';
@@ skipping 3255 matching lines @@
 
   test_function_type_parameter_with_function_typed_parameter() {
     prepareAnalysisContext(createOptions());
     checkLibrary('void f<T, U>(T x(U u)) {}');
   }
 
   test_functions() {
     checkLibrary('f() {} g() {}');
   }
 
+  test_futureOr() {
+    var library = checkLibrary('import "dart:async"; FutureOr<int> x;');
+    var variables = library.definingCompilationUnit.topLevelVariables;
+    expect(variables, hasLength(1));
+    if (createOptions().strongMode) {
+      expect(variables[0].type.toString(), 'FutureOr<int>');
+    } else {
+      expect(variables[0].type.toString(), 'dynamic');
+    }
+  }
+
+  test_futureOr_const() {
+    var library = checkLibrary('import "dart:async"; const x = FutureOr;');
+    var variables = library.definingCompilationUnit.topLevelVariables;
+    expect(variables, hasLength(1));
+    var x = variables[0] as ConstTopLevelVariableElementImpl;
+    if (createOptions().strongMode) {
+      expect(x.type.toString(), 'Type');
+    } else {
+      expect(x.type.toString(), 'dynamic');
+    }
+    expect(x.constantInitializer.toString(), 'FutureOr');
+  }
+
+  test_futureOr_inferred() {
+    var library = checkLibrary('''
+import "dart:async";
+FutureOr<int> f() => null;
+var x = f();
+var y = x.then((z) => z.asDouble());
+''');
+    var variables = library.definingCompilationUnit.topLevelVariables;
+    expect(variables, hasLength(2));
+    var x = variables[0];
+    expect(x.name, 'x');
+    var y = variables[1];
+    expect(y.name, 'y');
+    if (createOptions().strongMode) {
+      expect(x.type.toString(), 'FutureOr<int>');
+      expect(y.type.toString(), 'dynamic');
+    } else {
+      expect(x.type.toString(), 'dynamic');
+      expect(y.type.toString(), 'dynamic');
+    }
+  }
+
   test_generic_gClass_gMethodStatic() {
     prepareAnalysisContext(createOptions());
     checkLibrary('''
 class C<T, U> {
   static void m<V, W>(V v, W w) {
     void f<X, Y>(V v, W w, X x, Y y) {
     }
   }
 }
 ''');
@@ skipping 1681 matching lines @@
       fail('Unexpectedly tried to get unlinked summary for $uri');
     }
     return serializedUnit;
   }
 
   @override
   bool hasLibrarySummary(String uri) {
     return true;
   }
 }