Language/Statements/Try/exception_handler_t01.dart

/*
 * Copyright (c) 2011, 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 A try statement try s1 on − catch1 ... on − catchn finally sf
 * defines an exception handler h that executes as follows:
 *   The on-catch clauses are examined in order, starting with catch1, until
 * either an on-catch clause that matches the current exception is found,
 * or the list of on-catch clauses has been exhausted. If an on-catch clause
 * on−catchk is found, then pk1 is bound to the current exception, pk2, if
 * declared, is bound to the active stack trace, and then catchk is executed.
 * If no on-catch clause is found, the finally clause is executed. Then,
 * execution resumes at the end of the try statement.
 *   A finally clause finally s defines an exception handler h that executes
 * as follows:
 *   Let r be the current return value. Then the current return value becomes
 * undefined. Any open streams associated with any asynchronous for loops and
 * yield-each statements executing within the dynamic scope of h are canceled,
 * in the order of their nesting, innermost first.
 *   Streams left open by for loops that were escaped for whatever reason would
 * be canceled at function termination, but it is best to cancel them as soon as
 * possible.
 *   Then the finally clause is executed. Let m be the immediately enclosing
 * function. If r is defined then the current return value is set to r and then:
 *  • if there is a dynamically enclosing error handler g defined by a finally
 *    clause in m, control is transferred to g.
 *  • Otherwise m terminates.
 *  Otherwise, execution resumes at the end of the try statement.
 * @description Checks that the catch clauses are examined in order, starting
 * with catch1, until a catch clause that matches the current exception is
 * found.
 * @author vasya
 */
import '../../../Utils/expect.dart';

class T1 { }
class T2 { }
class T3 { }

main() {
  bool ok = false;
  try {
    throw new T1();
  } on T1 catch (p1) {
    ok = true;
  } on T2 catch (p2) {
    Expect.fail("This clause shouldn't be executed");
  } on T3 catch (p3) {
    Expect.fail("This clause shouldn't be executed");
  }

  Expect.isTrue(ok, "Correct catch clause was not executed!");
  ok = false;

  try {
    throw new T2();
  } on T1 catch (p1) {
    Expect.fail("This clause shouldn't be executed");
  } on T2 catch (p2) {
    ok = true;
  } on T3 catch (p3) {
    Expect.fail("This clause shouldn't be executed");
  }
  Expect.isTrue(ok, "Correct catch clause was not executed!");
  ok = false;

  try {
    throw new T3();
  } on T1 catch (p1) {
    Expect.fail("This clause shouldn't be executed");
  } on T2 catch (p2) {
    Expect.fail("This clause shouldn't be executed");
  } on T3 catch (p3) {
    ok = true;
  }
  Expect.isTrue(ok, "Correct catch clause was not executed!");
  ok = false;

  try {
    throw "";
  } on T1 catch (p1) {
    Expect.fail("This clause shouldn't be executed");
  } on T2 catch (p2) {
    Expect.fail("This clause shouldn't be executed");
  } on T3 catch (p3) {
    Expect.fail("This clause shouldn't be executed");
  } catch (ex) {
    ok = true;
  }
  Expect.isTrue(ok, "Correct catch clause was not executed!");
  ok = false;
}