#3057. Add more reachability tests for && and || operators (#3104)

Add more reachability tests for && and || operators

Author: sgrekhov

TypeSystem/flow-analysis/reachability_A18_t04.dart

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+// Copyright (c) 2025, 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 - Shortcut and: If `N` is a shortcut "and" expression of the form
+/// `E1 && E2`, then:
+/// - Let `before(E1) = before(N)`.
+/// - Let `before(E2) = split(true(E1))`.
+/// - Let `true(N) = unsplit(true(E2))`.
+/// - Let `false(N) = merge(split(false(E1)), false(E2))`.
+///
+/// @description Checks that in an expression of the form `E1 && E2`, if `E1` is
+/// `false` and the static type of `E2` is `Never`, then the code after
+/// `E1 && E2` is not considered dead code.
+/// @author [email protected]
+
+Never foo() => throw "Never";
+
+main() {
+  late int i;
+  if (2 > 1) {
+    false && foo();
+    i = 42;
+  }
+  i; // Not definitely unassigned
+}

TypeSystem/flow-analysis/reachability_A18_t05.dart

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+// Copyright (c) 2025, 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 - Shortcut and: If `N` is a shortcut "and" expression of the form
+/// `E1 && E2`, then:
+/// - Let `before(E1) = before(N)`.
+/// - Let `before(E2) = split(true(E1))`.
+/// - Let `true(N) = unsplit(true(E2))`.
+/// - Let `false(N) = merge(split(false(E1)), false(E2))`.
+///
+/// @description Checks that in an expression of the form `E1 && E2` if `E1` is
+/// `true` then `E2` is always executed.
+/// @author [email protected]
+
+Never foo() => throw "Never";
+
+main() {
+  late int i;
+  if (1 > 2) {
+    true && foo();
+    i = 42;
+  }
+  i; // Definitely unassigned
+//^
+// [analyzer] unspecified
+// [cfe] unspecified
+}

TypeSystem/flow-analysis/reachability_A19_t04.dart

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+// Copyright (c) 2025, 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 - Shortcut or: If `N` is a shortcut "or" expression of the form
+/// `E1 || E2`, then:
+/// - Let `before(E1) = before(N)`.
+/// - Let `before(E2) = split(false(E1))`.
+/// - Let `false(N) = unsplit(false(E2))`.
+/// - Let `true(N) = merge(split(true(E1)), true(E2))`.
+///
+/// @description Checks that in an expression of the form `E1 || E2`, if `E1` is
+/// `true` and the static type of `E2` is `Never`, then the code after
+/// `E1 || E2` is not considered dead code.
+/// @author [email protected]
+
+Never foo() => throw "Never";
+
+main() {
+  late int i;
+  if (2 > 1) {
+    true || foo();
+    i = 42;
+  }
+  i; // Not definitely unassigned
+}

TypeSystem/flow-analysis/reachability_A19_t05.dart

@@ -0,0 +1,28 @@
+// Copyright (c) 2025, 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 - Shortcut or: If `N` is a shortcut "or" expression of the form
+/// `E1 || E2`, then:
+/// - Let `before(E1) = before(N)`.
+/// - Let `before(E2) = split(false(E1))`.
+/// - Let `false(N) = unsplit(false(E2))`.
+/// - Let `true(N) = merge(split(true(E1)), true(E2))`.
+///
+/// @description Checks that in an expression of the form `E1 || E2` if `E1` is
+/// `false` then `E2` is always executed.
+/// @author [email protected]
+
+Never foo() => throw "Never";
+
+main() {
+  late int i;
+  if (1 > 2) {
+    false || foo();
+    i = 42;
+  }
+  i; // Definitely unassigned
+//^
+// [analyzer] unspecified
+// [cfe] unspecified
+}