Language/Variables/Evaluation_of_Implicit_Variable_Getters/definition_t06.dart

/*
 * Copyright (c) 2021, 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.
 */
/**
 * @assertion Let d be the declaration of a variable v.  If d is a local or
 * instance variable, then the invocation of the implicit getter of v
 * evaluates to the value stored in v.
 * If d is a static or library variable then the implicit getter method of v
 * executes as follows:
 * - Non-constant variable declaration with initializer. If d is of one of the 
 *   forms var v = e; , T v = e; , final v = e; , final T v = e; , static 
 *   v = e; , static T v = e; , static final v = e;  or static final T v = e; 
 *   and no value has yet been stored into v then the initializer expression 
 *   e is evaluated. If, during the evaluation of e, the getter  for v is 
 *   invoked, a CyclicInitializationError is thrown. If the evaluation 
 *   succeeded yielding an object o, let r = o, otherwise let r = null. In 
 *   any case, r is stored into v. The result of executing the getter is r.
 * - Constant variable declaration. If d is of one of the forms const v = e; ,
 *   const T v = e; , static const v = e;  or static const T v = e; the result
 *   of the getter is the value of the compile time constant e. Note that a
 *   compile time constant cannot depend on itself, so no cyclic references 
 *   can occur. Otherwise
 * - Variable declaration without initializer. The result of executing the
 *   getter method is the value stored in v.
 * @note NNBD Spec now reads: If a variable or field is read from during the
 * process of evaluating its own initializer expression, and no write to the
 * variable has occurred, the read is treated as a first read and the
 * initializer expression is evaluated again.
 *
 * A toplevel or static variable with an initializer is evaluated as if it was
 * marked [late]. Note that this is a change from pre-NNBD semantics in that:
 *
 * Throwing an exception during initializer evaluation no longer sets the
 * variable to [null]
 *
 * Reading the variable during initializer evaluation is no longer checked for,
 * and does not cause an error.
 *
 * @description Checks that if during the evaluation of [e], the getter for [v]
 * is invoked, a [CyclicInitializationError] is thrown
 * @author sgrekhov@unipro.ru
 */
f(func) {}

class C {
  static var sVar = f(() => sVar);
//           ^^^^
// [analyzer] unspecified
// [cfe] unspecified
  static final sFinal = f(() => sFinal);
//             ^^^^^^
// [analyzer] unspecified
// [cfe] unspecified}
}

main() {
  C? c;
}