#3057. Add more try-catch(-finally) tests (#3149)

Author: sgrekhov

TypeSystem/flow-analysis/reachability_try_catch_A04_t01.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 try catch: If `N` is a try/catch statement of the form
+/// `try B alternatives` then:
+/// - Let `before(B) = before(N)`
+/// - For each catch block on `Ti Si` in alternatives:
+///   - Let
+///     `before(Si) = conservativeJoin(before(N), assignedIn(B), capturedIn(B))`
+/// - Let `after(N) = join(after(B), after(C0), ..., after(Ck))`
+///
+/// @description Checks that if `B` is empty then assignment in `alternatives`
+/// is not treated as unreachable.
+/// @author [email protected]
+
+test() {
+  late int i;
+  try {
+  } on Exception catch (_) {
+    i = 42;
+  }
+  i; // Possibly assigned
+}
+
+main() {
+  print(test);
+}

TypeSystem/flow-analysis/reachability_try_catch_A04_t02.dart

@@ -0,0 +1,29 @@
+// 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 try catch: If `N` is a try/catch statement of the form
+/// `try B alternatives` then:
+/// - Let `before(B) = before(N)`
+/// - For each catch block on `Ti Si` in alternatives:
+///   - Let
+///     `before(Si) = conservativeJoin(before(N), assignedIn(B), capturedIn(B))`
+/// - Let `after(N) = join(after(B), after(C0), ..., after(Ck))`
+///
+/// @description Checks that if `B` is empty and some promoted variable is
+/// captured in `alternatives` then this variable is demoted.
+/// @author [email protected]
+
+main() {
+  int? i = 1 > 2 ? 42 : null;
+  if (i != null) { // `i` promoted to `int`
+    try {
+    } on Exception catch (_) {
+      () {i = 42;}; // `i` demoted to `int?`
+    }
+    i.isEven;
+//    ^^^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+  }
+}

TypeSystem/flow-analysis/reachability_try_catch_finally_A03_t01.dart

@@ -0,0 +1,79 @@
+// 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 try catch finally: If `N` is a try/catch/finally statement of the
+/// form `try B1 alternatives finally F` then:
+/// - Let `before(B1) = before(N)`
+/// - Let `before(Si) = join(after(B1), conservativeJoin(before(N),
+///     assignedIn(B1), capturedIn(B1)))`, where `Si`
+///   is the body of the i'th alternative
+/// - Let
+///   `after(N) = join(attachFinally(after(B1), before(F), after(F)), M1 .. Mk)`
+///   where `Mj = attachFinally(after(Sj), before(F), after(F))`
+///
+/// @description Checks that if a type `T` is made a type of interest in
+/// `before(N)` then it can be promoted in `B1`, `Si`, `F` and `after(N)`.
+/// @author [email protected]
+
+class S {}
+
+class T extends S {
+  int answer() => 42;
+}
+
+class C {
+  T v;
+  C(this.v);
+}
+
+test1() {
+  S s = S();
+  if (s is T) {}  // make `T` a type of interest
+  try {
+    s = T();
+    s.answer();
+  } catch (_) {
+  } finally {
+  }
+}
+
+test2() {
+  S s = S();
+  if (s is T) {}
+  try {
+  } catch (_) {
+    (s,) = (T(),);
+    s.answer();
+  } finally {
+  }
+}
+
+test3() {
+  S s = S();
+  if (s is T) {}
+  try {
+  } catch (_) {
+  } finally {
+    (x: s) = (x: T());
+    s.answer();
+  }
+}
+
+test4() {
+  S s = S();
+  if (s is T) {}
+  try {
+  } catch (_) {
+  } finally {
+  }
+  C(v: s) = C(T());
+  s.answer();
+}
+
+main() {
+  print(test1);
+  print(test2);
+  print(test3);
+  print(test4);
+}