tests/language_2/nnbd/syntax/late_modifier_final_field_test.dart

// Copyright (c) 2019, 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.

// SharedOptions=--enable-experiment=non-nullable
import 'package:expect/expect.dart';

int initCalls = 0;
int init() {
  ++initCalls;
  return 123;
}

class Base {
  late final int fieldWithInit;
}

// A inherits from Base to bypass the compile time error caused by assigning to
// a late final field that has an initializer. This allows us to test the
// runtime exception.
class A extends Base {
  late final int fieldWithInit = init();
}

class B {
  late final int fieldWithNoInit;
}

main() {
  Base a = A();
  Expect.equals(0, initCalls);
  Expect.equals(123, a.fieldWithInit);
  Expect.equals(1, initCalls);
  Expect.equals(123, a.fieldWithInit);
  Expect.equals(1, initCalls);
  Expect.throws(() => {a.fieldWithInit = 456},
      (error) => error is LateInitializationError);
  Expect.equals(1, initCalls);
  Expect.equals(123, a.fieldWithInit);
  Expect.equals(1, initCalls);
  initCalls = 0;

  Base a2 = A();
  Expect.equals(0, initCalls);
  Expect.throws(() => {a2.fieldWithInit = 456},
      (error) => error is LateInitializationError);
  Expect.equals(0, initCalls);
  Expect.equals(123, a2.fieldWithInit);
  Expect.equals(1, initCalls);

  B b = B();
  Expect.throws(
      () => b.fieldWithNoInit, (error) => error is LateInitializationError);
  b.fieldWithNoInit = 123;
  Expect.equals(123, b.fieldWithNoInit);
  Expect.throws(() => {b.fieldWithNoInit = 456},
      (error) => error is LateInitializationError);
  Expect.equals(123, b.fieldWithNoInit);
}