#1401. Patterns execution. Assignment and switch statement tests (#1857)

Add tests about pattern matching execution, using pattern assignments and switch statements.

Author: sgrekhov

LanguageFeatures/Patterns/execution_pattern_assignment_A01_t01.dart

@@ -0,0 +1,63 @@
+// Copyright (c) 2023, 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
+/// Pattern assignment
+/// 1. Evaluate the right-hand side expression to a value v.
+/// 2. Match v against the pattern on the left. When matching a variable pattern
+///   against a value o, record that o will be the new value for the
+///   corresponding variable, but do not store the variable.
+/// 3. Once all destructuring and matching is done, store all of the assigned
+///   variables with their corresponding values.
+///
+/// @description Check that if matching fails then no values are assigned
+/// @author [email protected]
+
+// SharedOptions=--enable-experiment=patterns,records
+
+import "../../Utils/expect.dart";
+import "patterns_lib.dart";
+
+main() {
+  int v1 = 42;
+  Expect.throws(() {
+    (v1) = (3.14) as dynamic;
+  });
+  Expect.equals(42, v1);
+
+  int l1 = 42;
+  int l2 = 42;
+  Expect.throws(() {
+    dynamic pi = 3.14;
+    [l1, l2] = [0, pi];
+  });
+  Expect.equals(42, l1);
+  Expect.equals(42, l2);
+
+  int m1 = 42;
+  int m2 = 42;
+  Expect.throws(() {
+    dynamic pi = 3.14;
+    {"k1": m1, "k2": m2} = {"k1": 0, "k2": pi};
+  });
+  Expect.equals(42, m1);
+  Expect.equals(42, m2);
+
+  int r1 = 42;
+  int r2 = 42;
+  Expect.throws(() {
+    dynamic pi = 3.14;
+    (r1, r2) = (0, pi);
+  });
+  Expect.equals(42, r1);
+  Expect.equals(42, r2);
+
+  int o1 = 42;
+  int o2 = 42;
+  Expect.throws(() {
+    Circle(sizeAsInt: o1, areaAsDynamicDouble: o2) = Circle(1);
+  });
+  Expect.equals(42, o1);
+  Expect.equals(42, o2);
+}

LanguageFeatures/Patterns/execution_switch_statement_A01_t01.dart

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+// Copyright (c) 2023, 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 statement
+/// 1. Evaluate the switch value producing v.
+/// 2. For each case:
+///   i. Match the case's pattern against v. If the match fails then continue to
+///     the next case (or default clause or exit the switch if there are no
+///     other cases).
+///   ii. If there is a guard clause, evaluate it. If it does not evaluate to a
+///     Boolean, throw a runtime error. This can happen if the guard
+///     expression's type is dynamic. If it evaluates to false, continue to the
+///     next case (or default or exit).
+///   iii. Find the nearest non-empty case body at or following this case.
+///     You're allowed to have multiple empty cases where all preceding ones
+///     share the same body with the last case.
+///   iv. If the enclosing scope for the body is a shared case scope, then
+///     initialize all shared variables the values of the corresponding
+///     variables from the case scope. There will be no shared case scope and
+///     nothing to copy if the body is only used by a single case.
+///   v. Execute the body statement.
+///   vi. If execution of the body statement continues with a label, and that
+///     label is labeling a switch case of this switch, go to step 3 and
+///     continue from that label.
+///   vii. Otherwise the switch statement completes normally. An explicit break
+///     is no longer required.
+/// 3. If no case pattern matched and there is a default clause, execute the
+///   statements after it.
+/// 4. If the static type of v is an always-exhaustive type, no case matches,
+///   and there is no default clause, then throw a runtime error.
+///
+/// @description Check that if matching fails then execution continues to the
+/// next case or default (if any)
+/// @author [email protected]
+
+// SharedOptions=--enable-experiment=patterns
+
+import "../../Utils/expect.dart";
+
+main() {
+  String log = "";
+  var v = [42];
+  switch (v) {
+    case [String s]:
+      log += "case-1;";
+    case [bool b]:
+      log += "case-2;";
+      break;
+    case [1, 2]:
+      log += "case-3;";
+  }
+  Expect.equals("", log);
+
+  switch (v) {
+    case [_, 2]:
+      log += "case-1;";
+    case [bool _]:
+      log += "case-2;";
+      break;
+    case [1, _]:
+      log += "case-3;";
+    default:
+      log += "default";
+  }
+  Expect.equals("default", log);
+}

LanguageFeatures/Patterns/execution_switch_statement_A02_t01.dart

@@ -0,0 +1,63 @@
+// Copyright (c) 2023, 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 statement
+/// 1. Evaluate the switch value producing v.
+/// 2. For each case:
+///   i. Match the case's pattern against v. If the match fails then continue to
+///     the next case (or default clause or exit the switch if there are no
+///     other cases).
+///   ii. If there is a guard clause, evaluate it. If it does not evaluate to a
+///     Boolean, throw a runtime error. This can happen if the guard
+///     expression's type is dynamic. If it evaluates to false, continue to the
+///     next case (or default or exit).
+///   iii. Find the nearest non-empty case body at or following this case.
+///     You're allowed to have multiple empty cases where all preceding ones
+///     share the same body with the last case.
+///   iv. If the enclosing scope for the body is a shared case scope, then
+///     initialize all shared variables the values of the corresponding
+///     variables from the case scope. There will be no shared case scope and
+///     nothing to copy if the body is only used by a single case.
+///   v. Execute the body statement.
+///   vi. If execution of the body statement continues with a label, and that
+///     label is labeling a switch case of this switch, go to step 3 and
+///     continue from that label.
+///   vii. Otherwise the switch statement completes normally. An explicit break
+///     is no longer required.
+/// 3. If no case pattern matched and there is a default clause, execute the
+///   statements after it.
+/// 4. If the static type of v is an always-exhaustive type, no case matches,
+///   and there is no default clause, then throw a runtime error.
+///
+/// @description Check that if there is a guard clause, it is evaluated if match
+/// success
+/// @author [email protected]
+
+// SharedOptions=--enable-experiment=patterns
+
+import "../../Utils/expect.dart";
+
+String log = "";
+
+bool guard(int v) {
+  log += "guard($v);";
+  return v == 42;
+}
+
+main() {
+  var v = [0, 42];
+  switch (v) {
+    case [int v1, var v2] when guard(v1):
+      log += "case-1;";
+    case [1, final v3] when guard(v3):
+      log += "case-2";
+      break;
+    case [0, var v4] when guard(v4):
+      log += "case-3;";
+    default:
+      log += "default";
+  }
+  Expect.equals("guard(0);guard(42);case-3;", log);
+}

LanguageFeatures/Patterns/execution_switch_statement_A02_t02.dart

@@ -0,0 +1,57 @@
+// Copyright (c) 2023, 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 statement
+/// 1. Evaluate the switch value producing v.
+/// 2. For each case:
+///   i. Match the case's pattern against v. If the match fails then continue to
+///     the next case (or default clause or exit the switch if there are no
+///     other cases).
+///   ii. If there is a guard clause, evaluate it. If it does not evaluate to a
+///     Boolean, throw a runtime error. This can happen if the guard
+///     expression's type is dynamic. If it evaluates to false, continue to the
+///     next case (or default or exit).
+///   iii. Find the nearest non-empty case body at or following this case.
+///     You're allowed to have multiple empty cases where all preceding ones
+///     share the same body with the last case.
+///   iv. If the enclosing scope for the body is a shared case scope, then
+///     initialize all shared variables the values of the corresponding
+///     variables from the case scope. There will be no shared case scope and
+///     nothing to copy if the body is only used by a single case.
+///   v. Execute the body statement.
+///   vi. If execution of the body statement continues with a label, and that
+///     label is labeling a switch case of this switch, go to step 3 and
+///     continue from that label.
+///   vii. Otherwise the switch statement completes normally. An explicit break
+///     is no longer required.
+/// 3. If no case pattern matched and there is a default clause, execute the
+///   statements after it.
+/// 4. If the static type of v is an always-exhaustive type, no case matches,
+///   and there is no default clause, then throw a runtime error.
+///
+/// @description Check that it is a runtime error if guard value is not
+/// assignable to bool
+/// @author [email protected]
+
+// SharedOptions=--enable-experiment=patterns
+
+import "../../Utils/expect.dart";
+
+dynamic guard(v) => v;
+
+String test(v) {
+  switch(42) {
+    case 42 when guard(v):
+      return "Case body";
+    default:
+      return "default";
+  }
+}
+
+main() {
+  Expect.equals("Case body", test(true));
+  Expect.equals("default", test(false));
+  Expect.throws(() {test(42);});
+}

LanguageFeatures/Patterns/execution_switch_statement_A03_t01.dart

@@ -0,0 +1,81 @@
+// Copyright (c) 2023, 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 statement
+/// 1. Evaluate the switch value producing v.
+/// 2. For each case:
+///   i. Match the case's pattern against v. If the match fails then continue to
+///     the next case (or default clause or exit the switch if there are no
+///     other cases).
+///   ii. If there is a guard clause, evaluate it. If it does not evaluate to a
+///     Boolean, throw a runtime error. This can happen if the guard
+///     expression's type is dynamic. If it evaluates to false, continue to the
+///     next case (or default or exit).
+///   iii. Find the nearest non-empty case body at or following this case.
+///     You're allowed to have multiple empty cases where all preceding ones
+///     share the same body with the last case.
+///   iv. If the enclosing scope for the body is a shared case scope, then
+///     initialize all shared variables the values of the corresponding
+///     variables from the case scope. There will be no shared case scope and
+///     nothing to copy if the body is only used by a single case.
+///   v. Execute the body statement.
+///   vi. If execution of the body statement continues with a label, and that
+///     label is labeling a switch case of this switch, go to step 3 and
+///     continue from that label.
+///   vii. Otherwise the switch statement completes normally. An explicit break
+///     is no longer required.
+/// 3. If no case pattern matched and there is a default clause, execute the
+///   statements after it.
+/// 4. If the static type of v is an always-exhaustive type, no case matches,
+///   and there is no default clause, then throw a runtime error.
+///
+/// @description Check that body of the matched case is executed
+/// @author [email protected]
+
+// SharedOptions=--enable-experiment=patterns
+
+import "../../Utils/expect.dart";
+
+String log = "";
+
+bool guard(int n, bool b) {
+  log += "guard$n($b);";
+  return b;
+}
+
+void test(List<int> list) {
+  log = "";
+  switch (list) {
+    case [1, var v1] when guard(1, v1 == 1):
+    case [2, final v2] when guard(2, v2 == 2):
+    case [3, var v3] when guard(3, v3 == 3):
+      log += "shared body;";
+    case [4, var v4] when guard(4, v4 == 4):
+      log += "not shared body;";
+    default:
+      log += "default;";
+  }
+}
+
+main() {
+  test([1, 1]);
+  Expect.equals("guard1(true);shared body;", log);
+  test([2, 2]);
+  Expect.equals("guard2(true);shared body;", log);
+  test([3, 3]);
+  Expect.equals("guard3(true);shared body;", log);
+  test([4, 4]);
+  Expect.equals("guard4(true);not shared body;", log);
+  test([1, 42]);
+  Expect.equals("guard1(false);default;", log);
+  test([2, 42]);
+  Expect.equals("guard2(false);default;", log);
+  test([3, 42]);
+  Expect.equals("guard3(false);default;", log);
+  test([4, 42]);
+  Expect.equals("guard4(false);default;", log);
+  test([]);
+  Expect.equals("default;", log);
+}