sdk/tests/language/null_aware/invocation_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.

// Verify semantics of the ?. operator when it is used to invoke a method.

import "package:expect/expect.dart";
import "conditional_access_helper.dart" as h;

bad() {
  Expect.fail('Should not be executed');
}

class B {}

class C extends B {
  f(callback()?) => callback!();
  int? g(int? callback()) => callback();
  static staticF(callback()) => callback();
  static int? staticG(int? callback()) => callback();
}

C? nullC() => null;

main() {
  var c = C() as C?;

  // Make sure the "none" test fails if method invocation using "?." is not
  // implemented.  This makes status files easier to maintain.
  nullC()?.f(null);

  // o?.m(...) is equivalent to ((x) => x == null ? null : x.m(...))(o).
  Expect.equals(null, nullC()?.f(bad()));
  Expect.equals(1, c?.f(() => 1));

  // C?.m(...) is equivalent to C.m(...).
  Expect.equals(1, C?.staticF(() => 1));
  //                ^^
  // [analyzer] STATIC_WARNING.INVALID_NULL_AWARE_OPERATOR
  Expect.equals(1, h.C?.staticF(() => 1));
  //                  ^^
  // [analyzer] STATIC_WARNING.INVALID_NULL_AWARE_OPERATOR

  // The static type of o?.m(...) is the same as the static type of
  // o.m(...).
  {
    int? i = nullC()?.g(bad());
    Expect.equals(null, i);
  }
  {
    int? i = c?.g(() => 1);
    Expect.equals(1, i);
  }
  {
    String? s = nullC()?.g(bad());
    //          ^^^^^^^^^^^^^^^^^
    // [analyzer] COMPILE_TIME_ERROR.INVALID_ASSIGNMENT
    // [cfe] A value of type 'int?' can't be assigned to a variable of type 'String?'.
    Expect.equals(null, s);
  }
  {
    String? s = c?.g(() => null);
    //          ^^^^^^^^^^^^^^^^
    // [analyzer] COMPILE_TIME_ERROR.INVALID_ASSIGNMENT
    // [cfe] A value of type 'int?' can't be assigned to a variable of type 'String?'.
    Expect.equals(null, s);
  }
  {
    int? i = C?.staticG(() => 1);
    //        ^^
    // [analyzer] STATIC_WARNING.INVALID_NULL_AWARE_OPERATOR
    Expect.equals(1, i);
  }
  {
    int? i = h.C?.staticG(() => 1);
    //          ^^
    // [analyzer] STATIC_WARNING.INVALID_NULL_AWARE_OPERATOR
    Expect.equals(1, i);
  }
  {
    String? s = C?.staticG(() => null);
    //          ^^^^^^^^^^^^^^^^^^^^^^
    // [analyzer] COMPILE_TIME_ERROR.INVALID_ASSIGNMENT
    //           ^^
    // [analyzer] STATIC_WARNING.INVALID_NULL_AWARE_OPERATOR
    //             ^
    // [cfe] A value of type 'int?' can't be assigned to a variable of type 'String?'.
    Expect.equals(null, s);
  }
  {
    String? s = h.C?.staticG(() => null);
    //          ^^^^^^^^^^^^^^^^^^^^^^^^
    // [analyzer] COMPILE_TIME_ERROR.INVALID_ASSIGNMENT
    //             ^^
    // [analyzer] STATIC_WARNING.INVALID_NULL_AWARE_OPERATOR
    //               ^
    // [cfe] A value of type 'int?' can't be assigned to a variable of type 'String?'.
    Expect.equals(null, s);
  }

  // Let T be the static type of o and let y be a fresh variable of type T.
  // Exactly the same static warnings that would be caused by y.m(...) are also
  // generated in the case of o?.m(...).
  {
    var b = new C() as B?;
    Expect.equals(1, b?.f(() => 1));
    //                  ^
    // [analyzer] COMPILE_TIME_ERROR.UNDEFINED_METHOD
    // [cfe] The method 'f' isn't defined for the type 'B'.
  }
  {
    var i = 1 as int?;
    Expect.equals(null, nullC()?.f(i));
    //                             ^
    // [analyzer] COMPILE_TIME_ERROR.ARGUMENT_TYPE_NOT_ASSIGNABLE
    // [cfe] The argument type 'int?' can't be assigned to the parameter type 'dynamic Function()?'.
  }

  // '?.' can't be used to access toplevel functions in libraries imported via
  // prefix.
  h?.topLevelFunction();
  // [error column 3, length 1]
  // [analyzer] COMPILE_TIME_ERROR.PREFIX_IDENTIFIER_NOT_FOLLOWED_BY_DOT
  // [cfe] A prefix can't be used with null-aware operators.

  // Nor can it be used to access the toString method on the class Type.
  Expect.throwsNoSuchMethodError(() => C?.toString());
  //                                    ^^
  // [analyzer] STATIC_WARNING.INVALID_NULL_AWARE_OPERATOR
  //                                      ^^^^^^^^
  // [analyzer] COMPILE_TIME_ERROR.UNDEFINED_METHOD
  // [cfe] Method not found: 'C.toString'.
  Expect.throwsNoSuchMethodError(() => h.C?.toString());
  //                                      ^^
  // [analyzer] STATIC_WARNING.INVALID_NULL_AWARE_OPERATOR
  //                                        ^^^^^^^^
  // [analyzer] COMPILE_TIME_ERROR.UNDEFINED_METHOD
  // [cfe] Method not found: 'C.toString'.
}