#3057. Add more flow analysis tests for while loop (#3141)

Author: sgrekhov

TypeSystem/flow-analysis/reachability_while_A04_t01.dart

@@ -0,0 +1,77 @@
+// 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 while statement: If `N` is a while statement of the form
+/// `while (E) S` then:
+/// - Let `before(E) = conservativeJoin(before(N), assignedIn(N), capturedIn(N))`
+/// - Let `before(S) = split(true(E))`.
+/// - Let `after(N) = inheritTested(join(false(E), unsplit(break(S))), after(S))`
+///
+/// @description Checks that if a promoted variable is captured in `S` it is
+/// demoted in `E`.
+/// @author sgrekhov22@gmail.com
+
+class C {
+  int v;
+  C(this.v);
+}
+
+test1(int? n) {
+  if (n != null) { // `n` promoted to `int`
+    while (n.isEven) {
+//           ^^^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+      () {
+        n = 42; // `n` demoted to `int?`
+      };
+    }
+  }
+}
+
+test2(int? n) {
+  if (n != null) {
+    while (n.isEven) {
+//           ^^^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+    () {
+        (n,) = (42,);
+      };
+    }
+  }
+}
+
+test3(int? n) {
+  if (n != null) {
+    while (n.isEven) {
+//           ^^^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+    () {
+        (x: n) = (x: 42);
+      };
+    }
+  }
+}
+
+test4(int? n) {
+  if (n != null) {
+    while (n.isEven) {
+//           ^^^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+    () {
+        C(v: n) = C(42);
+      };
+    }
+  }
+}
+
+main() {
+  print(test1);
+  print(test2);
+  print(test3);
+  print(test4);
+}

TypeSystem/flow-analysis/reachability_while_A04_t02.dart

@@ -0,0 +1,69 @@
+// 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 while statement: If `N` is a while statement of the form
+/// `while (E) S` then:
+/// - Let `before(E) = conservativeJoin(before(N), assignedIn(N), capturedIn(N))`
+/// - Let `before(S) = split(true(E))`.
+/// - Let `after(N) = inheritTested(join(false(E), unsplit(break(S))), after(S))`
+///
+/// @description Checks that if a promoted variable is captured in `E` it is
+/// demoted in `S`.
+/// @author sgrekhov22@gmail.com
+
+class C {
+  int v;
+  C(this.v);
+}
+
+test1(int? n) {
+  if (n != null) { // `n` promoted to `int`
+    while ((){n = 42; return false;}()) { // `n` demoted to `int?`
+      n.isEven;
+//      ^^^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+    }
+  }
+}
+
+test2(int? n) {
+  if (n != null) {
+    while ((){(n,) = (42,); return false;}()) {
+      n.isEven;
+//      ^^^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+    }
+  }
+}
+
+test3(int? n) {
+  if (n != null) {
+    while ((){(x: n) = (x: 42); return false;}()) {
+      n.isEven;
+//      ^^^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+    }
+  }
+}
+
+test4(int? n) {
+  if (n != null) {
+    while ((){C(v: n) = C(42); return false;}()) {
+      n.isEven;
+//      ^^^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+    }
+  }
+}
+
+main() {
+  print(test1);
+  print(test2);
+  print(test3);
+  print(test4);
+}

TypeSystem/flow-analysis/reachability_while_A05_t01.dart

@@ -0,0 +1,49 @@
+// 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 while statement: If `N` is a while statement of the form
+/// `while (E) S` then:
+/// - Let `before(E) = conservativeJoin(before(N), assignedIn(N), capturedIn(N))`
+/// - Let `before(S) = split(true(E))`.
+/// - Let `after(N) = inheritTested(join(false(E), unsplit(break(S))), after(S))`
+///
+/// @description Checks that if a type `T` is made a type of interest in
+/// `before(N)` then it can be promoted in `E`, `S` and `after(N)`.
+/// @author sgrekhov22@gmail.com
+
+class S {}
+
+class T extends S {
+  int answer() => 42;
+}
+
+test1() {
+  S s = S();
+  if (s is T) {} // make `T` a type of interest
+  while ([s = T(), s.answer()] == []) {}
+}
+
+test2() {
+  S s = S();
+  if (s is T) {}
+  while (1 > 2) {
+    s = T(); // No error
+    s.answer();
+  }
+}
+
+test3() {
+  S s = S();
+  if (s is T) {} // Make T a type of interest
+  while (1 > 2) {
+  }
+  s = T();
+  s.answer();
+}
+
+main() {
+  test1();
+  test2();
+  test3();
+}

TypeSystem/flow-analysis/reachability_while_A05_t02.dart

@@ -0,0 +1,40 @@
+// 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 while statement: If `N` is a while statement of the form
+/// `while (E) S` then:
+/// - Let `before(E) = conservativeJoin(before(N), assignedIn(N), capturedIn(N))`
+/// - Let `before(S) = split(true(E))`.
+/// - Let `after(N) = inheritTested(join(false(E), unsplit(break(S))), after(S))`
+///
+/// @description Checks that if a type `T` is made a type of interest in `E`
+/// then it can be promoted in `S` and `after(N)`.
+/// @author sgrekhov22@gmail.com
+
+class S {}
+
+class T extends S {
+  int answer() => 42;
+}
+
+test1() {
+  S s = S();
+  while (s is T) { // make `T` a type of interest
+    s = T();
+    s.answer();
+  }
+}
+
+test2() {
+  S s = S();
+  while (s is T) {
+  }
+  s = T();
+  s.answer();
+}
+
+main() {
+  test1();
+  test2();
+}

TypeSystem/flow-analysis/reachability_while_A05_t03.dart

@@ -0,0 +1,30 @@
+// 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 while statement: If `N` is a while statement of the form
+/// `while (E) S` then:
+/// - Let `before(E) = conservativeJoin(before(N), assignedIn(N), capturedIn(N))`
+/// - Let `before(S) = split(true(E))`.
+/// - Let `after(N) = inheritTested(join(false(E), unsplit(break(S))), after(S))`
+///
+/// @description Checks that if a type `T` is made a type of interest in `S`
+/// then it cannot be promoted in `E`.
+/// @author sgrekhov22@gmail.com
+
+class S {}
+
+class T extends S {
+  int answer() => 42;
+}
+
+
+main() {
+  S s = S();
+  while ([s = T(), s.answer()] == []) {
+//                   ^^^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+    if (s is T) {} // make `T` a type of interest
+  }
+}

TypeSystem/flow-analysis/reachability_while_A05_t04.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 while statement: If `N` is a while statement of the form
+/// `while (E) S` then:
+/// - Let `before(E) = conservativeJoin(before(N), assignedIn(N), capturedIn(N))`
+/// - Let `before(S) = split(true(E))`.
+/// - Let `after(N) = inheritTested(join(false(E), unsplit(break(S))), after(S))`
+///
+/// @description Checks that if a type `T` is made a type of interest in `S`
+/// then it can be promoted in `after(N)`.
+/// @author sgrekhov22@gmail.com
+
+class S {}
+
+class T extends S {
+  int answer() => 42;
+}
+
+main() {
+  S s = S();
+  while (1 > 2) {
+    if (s is T) {}
+  }
+  s = T();
+  s.answer();
+}