tests/language/external_abstract_fields/abstract_fields_error_test.dart

// Copyright (c) 2020, 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.

// Check that abstract instance variable declarations are abstract and
// do not allow more than they should.

// Check that abstract declarations are abstract.
class Abstract1 {
//    ^
// [cfe] The non-abstract class 'Abstract1' is missing implementations for these members:

  // The class is not abstract and does not have an implementation of `x`.
  abstract int x;
  //           ^
  // [analyzer] unspecified
}

// Check that class has expected interface.
abstract class Abstract2 {
  // Getter only.
  abstract final int x;
  // Getter and setter.
  abstract covariant String y;

  static void staticTest(Abstract2 a) {
    int x = a.x;

    // Cannot assign to final field.
    a.x = 42;
    //^
    // [cfe] The setter 'x' isn't defined for the class 'Abstract2'.
    //  ^
    // [analyzer] unspecified

    String y = a.y;
    a.y = "ab";

    // Cannot assign something of wrong type, even if covariant.
    a.y = Object();
    //    ^^^^^^^^
    // [analyzer] unspecified
    // [cfe] A value of type 'Object' can't be assigned to a variable of type 'String'.
  }

  void test() {
    int x = this.x;

    // Cannot assign to final field.
    this.x = 42;
    //   ^
    // [cfe] The setter 'x' isn't defined for the class 'Abstract2'.
    //     ^
    // [analyzer] unspecified

    String y = this.y;
    this.y = "ab";

    // Cannot assign something of wrong type, even if covariant.
    this.y = Object();
    //       ^^^^^^^^
    // [analyzer] unspecified
    // [cfe] A value of type 'Object' can't be assigned to a variable of type 'String'.
  }
}

class Concrete2 extends Abstract2 {
  final int x = 0;
  String y = '';
}

void main() {
  Abstract2.staticTest(throw 0);
  Concrete2().test();
}