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#3057. Add more reachability tests for true and false literals (#3072)
* #3057. Add more reachability tests for `true` and `false` literals * Excessive requirements removed * Apply review suggestions.
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‎TypeSystem/flow-analysis/reachability_A01_t26.dart

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// Copyright (c) 2025, the Dart project authors. Please see the AUTHORS file
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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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/// @assertion
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/// - Variable or getter: If `N` is an expression of the form `x` where the
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/// type of `x` is `T` then:
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/// If `T <: Never` then:
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/// - Let `after(N) = unreachable(before(N))`.
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/// Otherwise:
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/// - Let `after(N) = before(N)`.
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///
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/// @description Checks that the code is unreachable after a variable of type
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/// `Never`. Test a for-in statement in collection literals.
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/// @author [email protected]
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void test1(Never n) {
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late int i;
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bool b = (() => true)();
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if (b) {
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[
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for (var x in n) // The code after this point is unreachable
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i = 42 // Variable is initialized in a dead code. This leaves it definitely unassigned
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];
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}
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i; // It is an error to read a local late variable when it is definitely unassigned.
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//^
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// [analyzer] unspecified
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// [cfe] unspecified
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}
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void test2(Never n) {
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late int i;
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bool b = (() => true)();
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if (b) {
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<int>{
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for (var x in n) // The code after this point is unreachable
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i = 42 // Variable is initialized in a dead code. This leaves it definitely unassigned
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};
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}
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i; // It is an error to read a local late variable when it is definitely unassigned.
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//^
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// [analyzer] unspecified
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// [cfe] unspecified
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}
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void test3(Never n) {
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late int i;
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bool b = (() => true)();
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if (b) {
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<int, int>{
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for (var x in n) // The code after this point is unreachable
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1: i = 42 // Variable is initialized in a dead code. This leaves it definitely unassigned
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};
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}
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i; // It is an error to read a local late variable when it is definitely unassigned.
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//^
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// [analyzer] unspecified
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// [cfe] unspecified
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}
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main() {
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print(test1);
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print(test2);
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print(test3);
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}

‎TypeSystem/flow-analysis/reachability_A02_t01.dart

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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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/// @assertion True literal: If N is the literal true, then:
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/// Let true(N) = before(N).
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/// Let false(N) = unreachable(before(N)).
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/// @assertion True literal: If `N` is the literal `true`, then:
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/// Let `true(N) = before(N)`.
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/// Let `false(N) = unreachable(before(N))`.
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///
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/// @description Checks reachability after true literal
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/// @description Checks reachability after `true` literal
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/// @author [email protected]
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main() {

‎TypeSystem/flow-analysis/reachability_A02_t02.dart

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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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/// @assertion True literal: If N is the literal true, then:
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/// Let true(N) = before(N).
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/// Let false(N) = unreachable(before(N)).
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/// @assertion True literal: If `N` is the literal `true`, then:
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/// Let `true(N) = before(N)`.
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/// Let `false(N) = unreachable(before(N))`.
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///
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/// @description Checks reachability after true literal
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/// @description Checks reachability after `true` literal
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/// @author [email protected]
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main() {

‎TypeSystem/flow-analysis/reachability_A02_t03.dart

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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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/// @assertion True literal: If N is the literal true, then:
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/// Let true(N) = before(N).
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/// Let false(N) = unreachable(before(N)).
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/// @assertion True literal: If `N` is the literal `true`, then:
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/// Let `true(N) = before(N)`.
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/// Let `false(N) = unreachable(before(N))`.
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///
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/// @description Checks reachability after true literal
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/// @description Checks reachability after `true` literal
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/// @author [email protected]
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main() {

‎TypeSystem/flow-analysis/reachability_A02_t04.dart

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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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/// @assertion True literal: If N is the literal true, then:
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/// Let true(N) = before(N).
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/// Let false(N) = unreachable(before(N)).
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/// @assertion True literal: If `N` is the literal `true`, then:
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/// Let `true(N) = before(N)`.
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/// Let `false(N) = unreachable(before(N))`.
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///
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/// @description Checks reachability after true literal
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/// @description Checks reachability after `true` literal
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/// @author [email protected]
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main() {

‎TypeSystem/flow-analysis/reachability_A02_t05.dart

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// Copyright (c) 2025, the Dart project authors. Please see the AUTHORS file
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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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/// @assertion True literal: If `N` is the literal `true`, then:
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/// Let `true(N) = before(N)`.
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/// Let `false(N) = unreachable(before(N))`.
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///
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/// @description Checks reachability after `true` literal in collection literals
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/// @author [email protected]
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void test1() {
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int i;
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[
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if (true)
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i = 42
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];
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i; // Definitely assigned, not an error
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}
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void test2() {
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int i;
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<int>{
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if (true)
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i = 42
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};
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i; // Definitely assigned, not an error
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}
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void test3() {
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int i;
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<int, int>{
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if (true)
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1: i = 42
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};
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i; // Definitely assigned, not an error
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}
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main() {
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test1();
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test2();
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test3();
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}

‎TypeSystem/flow-analysis/reachability_A03_t01.dart

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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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/// @assertion False literal: If N is the literal false, then:
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/// Let true(N) = unreachable(before(N)).
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/// Let false(N) = before(N)
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/// @description Checks reachability after false literal
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/// @assertion False literal: If `N` is the literal `false`, then:
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/// Let `true(N) = unreachable(before(N))`.
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/// Let `false(N) = before(N)`
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///
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/// @description Checks reachability after `false` literal
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/// @author [email protected]
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main() {

‎TypeSystem/flow-analysis/reachability_A03_t02.dart

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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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/// @assertion False literal: If N is the literal false, then:
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/// Let true(N) = unreachable(before(N)).
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/// Let false(N) = before(N)
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/// @assertion False literal: If `N` is the literal `false`, then:
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/// Let `true(N) = unreachable(before(N))`.
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/// Let `false(N) = before(N)`
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///
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/// @description Checks reachability after false literal
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/// @description Checks reachability after `false` literal
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/// @author [email protected]
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main() {

‎TypeSystem/flow-analysis/reachability_A03_t03.dart

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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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/// @assertion False literal: If N is the literal false, then:
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/// Let true(N) = unreachable(before(N)).
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/// Let false(N) = before(N)
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/// @assertion False literal: If `N` is the literal `false`, then:
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/// Let `true(N) = unreachable(before(N))`.
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/// Let `false(N) = before(N)`
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///
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/// @description Checks reachability after false literal
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/// @description Checks reachability after `false` literal
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/// @author [email protected]
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main() {

‎TypeSystem/flow-analysis/reachability_A03_t04.dart

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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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/// @assertion False literal: If N is the literal false, then:
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/// Let true(N) = unreachable(before(N)).
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/// Let false(N) = before(N)
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/// @assertion False literal: If `N` is the literal `false`, then:
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/// Let `true(N) = unreachable(before(N))`.
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/// Let `false(N) = before(N)`
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///
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/// @description Checks reachability after false literal
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/// @description Checks reachability after `false` literal
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/// @author [email protected]
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main() {

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