#2420. Add more exhaustiveness tests (#2513)

Add more exhaustiveness tests

Author: sgrekhov

LanguageFeatures/Extension-types/exhaustiveness_flow_analysis_A01_t01.dart

@@ -0,0 +1,30 @@
+// Copyright (c) 2024, 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 Extension type erasure is not used during flow analysis
+///
+/// @description Check that an extension type erasure is not used during flow
+/// analysis that isn't concerned with run-time type tests
+/// @author [email protected]
+
+// SharedOptions=--enable-experiment=inline-class
+
+extension type const ET1(int value) {
+  void confirmET1() {}
+}
+extension type const ET2(int value) implements int {
+  void confirmET2() {}
+}
+
+void main() {
+  int i = 42;
+  switch (i) {
+    case ET1 v:
+      v.confirmET1(); // This confirms that `ET1` is not erased to int
+  }
+  switch (i) {
+    case ET2 v:
+      v.confirmET2();
+  }
+}

LanguageFeatures/Extension-types/exhaustiveness_variable_A04_t01.dart

@@ -0,0 +1,36 @@
+// Copyright (c) 2024, 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 Exhaustiveness of a variable pattern is determined by the static
+/// type of the corresponding variable.
+///
+/// @description Check static type of a variable pattern
+/// @author [email protected]
+
+// SharedOptions=--enable-experiment=inline-class
+
+import '../../Utils/static_type_helper.dart';
+
+extension type ET(int i) {}
+extension type TO(int i) implements ET {}
+
+main() {
+  ET x = ET(1);
+  switch (x) {
+    case int y:
+      x.expectStaticType<Exactly<ET>>;
+      y.expectStaticType<Exactly<int>>;
+    case TO z: // Unreachable, it's Ok
+      x.expectStaticType<Exactly<TO>>;
+      z.expectStaticType<Exactly<TO>>;
+  }
+  switch (42) {
+    case ET y:
+      x.expectStaticType<Exactly<ET>>;
+      y.expectStaticType<Exactly<ET>>;
+    case TO z: // Unreachable, it's Ok
+      x.expectStaticType<Exactly<ET>>;
+      z.expectStaticType<Exactly<TO>>;
+  }
+}

LanguageFeatures/Patterns/Exhaustiveness/exhaustiveness_lib.dart

@@ -46,3 +46,7 @@ class LastPersonOnEarth<T> implements Jack<T>, Queen<T>, King<T> {
 
   LastPersonOnEarth(this.suit, {this.oneEyed = false});
 }
+
+sealed class SClass {}
+class B1Class extends SClass {}
+class B2Class extends SClass {}

LanguageFeatures/Patterns/Exhaustiveness/exhaustiveness_sealed_A02_t02.dart

@@ -6,7 +6,7 @@
 /// matched type are always exhaustive
 ///
 /// @description Check that it is a compile-time error if the matched value type
-/// of a switch expression or stetement is a sealed class and the set of cases
+/// of a switch expression or statement is a sealed class and the set of cases
 /// is not exhaustive
 /// @author [email protected]
 

LanguageFeatures/Patterns/Exhaustiveness/exhaustiveness_sealed_A03_t01.dart

@@ -0,0 +1,31 @@
+// Copyright (c) 2024, 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 Switch statements and expressions with a sealed class as a
+/// matched type are always exhaustive
+///
+/// @description Check that the flow analysis considers a case reachable even in
+/// the case where it accepts only objects of an unrelated type.
+/// @author [email protected]
+
+class A {}
+
+class B {}
+
+void main() {
+  int x;
+  A a = A();
+  switch (a) {
+    case B():
+      print(
+          '''x is not assigned here. This case looks impossible, but there can 
+          be a hidden subtype of A and B in some other library''');
+    case _:
+      x = 1;
+  }
+  print(x);
+//      ^
+// [analyzer] unspecified
+// [cfe] unspecified
+}

LanguageFeatures/Patterns/Exhaustiveness/exhaustiveness_sealed_A03_t02.dart

@@ -0,0 +1,32 @@
+// Copyright (c) 2024, 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 Switch statements and expressions with a sealed class as a
+/// matched type are always exhaustive
+///
+/// @description Check that the flow analysis considers a case reachable even in
+/// the case where it accepts only objects of an unrelated type.
+/// @author [email protected]
+
+import 'exhaustiveness_lib.dart';
+
+class C {}
+class D extends C implements B1Class {}
+
+void main() {
+  int x;
+  SClass s = D();
+  switch (s) {
+    case C():
+      print('x is not assigned here');
+    case B1Class():
+      x = 1;
+    case B2Class():
+      x = 2;
+  }
+  print(x);
+//      ^
+// [analyzer] unspecified
+// [cfe] unspecified
+}