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;
}