#1401. [Patterns] Switch expression tests (#1633)

* #1401. [Patterns] Switch expression tests added

* #1401. [Patterns] More switch expression tests added

* #1401. Implement review notes

* #1401. Fix spec_parser failures

Author: sgrekhov

LanguageFeatures/Patterns/switch_expression_A01_t01.dart

@@ -0,0 +1,57 @@
+// Copyright (c) 2022, 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
+/// primary                 ::= // Existing productions...
+///                           | switchExpression
+///
+/// switchExpression      ::= 'switch' '(' expression ')' '{'
+///                           switchExpressionCase ( ',' switchExpressionCase )*
+///                           ','? '}'
+/// switchExpressionCase  ::= guardedPattern '=>' expression
+///
+/// The body is a series of cases. Each case has a pattern, optional guard, and
+/// a single expression body. As with other expression forms containing a list
+/// of subelements (argument lists, collection literals), the cases are
+/// separated by commas with an optional trailing comma. Since the body of each
+/// case is a single expression with a known terminator, it's easy to tell when
+/// one case ends and the next begins. That lets us do away with the case
+/// keyword.
+///
+/// To keep the syntax small and light, we also disallow a default clause.
+/// Instead, you can use a shorter _ wildcard pattern to catch any remaining
+/// values.
+///
+/// @description Check that it is a compile-time error if a switch expression
+/// contains `case`, `default` or uses `;` as a separator
+/// @author [email protected]
+
+// SharedOptions=--enable-experiment=patterns
+
+main () {
+  int i = 42;
+  var x = switch(i) {
+    case 1 => "one"
+//  ^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+    _ => "any"
+  };
+
+  var y = switch(i) {
+    1 => "one",
+    default => "default"
+//  ^^^^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+  };
+
+  var z = switch(i) {
+    1 => "one";
+//            ^
+// [analyzer] unspecified
+// [cfe] unspecified
+    _ => "any"
+  };
+}

LanguageFeatures/Patterns/switch_expression_A01_t02.dart

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+// Copyright (c) 2022, 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
+/// primary                 ::= // Existing productions...
+///                           | switchExpression
+///
+/// switchExpression      ::= 'switch' '(' expression ')' '{'
+///                           switchExpressionCase ( ',' switchExpressionCase )*
+///                           ','? '}'
+/// switchExpressionCase  ::= guardedPattern '=>' expression
+///
+/// The body is a series of cases. Each case has a pattern, optional guard, and
+/// a single expression body. As with other expression forms containing a list
+/// of subelements (argument lists, collection literals), the cases are
+/// separated by commas with an optional trailing comma. Since the body of each
+/// case is a single expression with a known terminator, it's easy to tell when
+/// one case ends and the next begins. That lets us do away with the case
+/// keyword.
+///
+/// To keep the syntax small and light, we also disallow a default clause.
+/// Instead, you can use a shorter _ wildcard pattern to catch any remaining
+/// values.
+///
+/// @description Check that it is a compile-time error if a switch expression
+/// uses `:` instead of '=>'
+/// @author [email protected]
+
+// SharedOptions=--enable-experiment=patterns
+
+main () {
+  int i = 42;
+  var x = switch(i) {
+    1: "one"
+//   ^
+// [analyzer] unspecified
+// [cfe] unspecified
+    _ => "any"
+  };
+
+  var y = switch(i) {
+    1 => "one",
+    _: "zero"
+//   ^
+// [analyzer] unspecified
+// [cfe] unspecified
+  };
+
+  var z = switch(i) {
+    1: "one",
+//   ^
+// [analyzer] unspecified
+// [cfe] unspecified
+    _: "zero"
+//   ^
+// [analyzer] unspecified
+// [cfe] unspecified
+  };
+}

LanguageFeatures/Patterns/switch_expression_A01_t03.dart

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+// Copyright (c) 2022, 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
+/// primary                 ::= // Existing productions...
+///                           | switchExpression
+///
+/// switchExpression      ::= 'switch' '(' expression ')' '{'
+///                           switchExpressionCase ( ',' switchExpressionCase )*
+///                           ','? '}'
+/// switchExpressionCase  ::= guardedPattern '=>' expression
+///
+/// The body is a series of cases. Each case has a pattern, optional guard, and
+/// a single expression body. As with other expression forms containing a list
+/// of subelements (argument lists, collection literals), the cases are
+/// separated by commas with an optional trailing comma. Since the body of each
+/// case is a single expression with a known terminator, it's easy to tell when
+/// one case ends and the next begins. That lets us do away with the case
+/// keyword.
+///
+/// To keep the syntax small and light, we also disallow a default clause.
+/// Instead, you can use a shorter _ wildcard pattern to catch any remaining
+/// values.
+///
+/// @description Check that it is a compile-time error if a case expressions in
+/// a switch expression are not separated by comma
+/// @author [email protected]
+
+// SharedOptions=--enable-experiment=patterns
+
+main () {
+  int i = 42;
+  var x = switch(i) {
+    1 => "one"
+//           ^
+// [analyzer] unspecified
+// [cfe] unspecified
+    2 => "two"
+//           ^
+// [analyzer] unspecified
+// [cfe] unspecified
+    _ => "any"
+  };
+}

LanguageFeatures/Patterns/switch_expression_A01_t04.dart

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+// Copyright (c) 2022, 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
+/// primary                 ::= // Existing productions...
+///                           | switchExpression
+///
+/// switchExpression      ::= 'switch' '(' expression ')' '{'
+///                           switchExpressionCase ( ',' switchExpressionCase )*
+///                           ','? '}'
+/// switchExpressionCase  ::= guardedPattern '=>' expression
+///
+/// The body is a series of cases. Each case has a pattern, optional guard, and
+/// a single expression body. As with other expression forms containing a list
+/// of subelements (argument lists, collection literals), the cases are
+/// separated by commas with an optional trailing comma. Since the body of each
+/// case is a single expression with a known terminator, it's easy to tell when
+/// one case ends and the next begins. That lets us do away with the case
+/// keyword.
+///
+/// To keep the syntax small and light, we also disallow a default clause.
+/// Instead, you can use a shorter _ wildcard pattern to catch any remaining
+/// values.
+///
+/// @description Check that it is not an error if a trailing comma is not
+/// omitted
+/// @author [email protected]
+
+// SharedOptions=--enable-experiment=patterns
+
+import "../../Utils/expect.dart";
+
+main () {
+  int i = 2;
+  var x = switch(i) {
+    1 => "one",
+    2 => "two",
+    _ => "any",
+  };
+  Expect.equals("two", x);
+}

LanguageFeatures/Patterns/switch_expression_A02_t01.dart

@@ -0,0 +1,166 @@
+// Copyright (c) 2022, 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
+/// primary                 ::= // Existing productions...
+///                           | switchExpression
+///
+/// switchExpression      ::= 'switch' '(' expression ')' '{'
+///                           switchExpressionCase ( ',' switchExpressionCase )*
+///                           ','? '}'
+/// switchExpressionCase  ::= guardedPattern '=>' expression
+///
+/// The body is a series of cases. Each case has a pattern, optional guard, and
+/// a single expression body. As with other expression forms containing a list
+/// of subelements (argument lists, collection literals), the cases are
+/// separated by commas with an optional trailing comma. Since the body of each
+/// case is a single expression with a known terminator, it's easy to tell when
+/// one case ends and the next begins. That lets us do away with the case
+/// keyword.
+///
+/// To keep the syntax small and light, we also disallow a default clause.
+/// Instead, you can use a shorter _ wildcard pattern to catch any remaining
+/// values.
+///
+/// Slotting into primary means it can be used anywhere any expression can
+/// appear, even as operands to unary and binary operators. Many of these uses
+/// are ugly, but not any more problematic than using a collection literal in
+/// the same context since a switch expression is always delimited by a switch
+/// and }.
+///
+/// @description Checks a switch expression with different subpatterns and a
+/// guard expression
+/// @author [email protected]
+
+// SharedOptions=--enable-experiment=patterns,records
+
+import "../../Utils/expect.dart";
+import "patterns_lib.dart";
+
+String test(int value) =>
+  switch (value) {
+    var a1 && 0 || var a1 && 1 when a1 == 0 => "logical-or-1",
+    1 || 2 => "logical-or-2",
+    var a2 && > 10 && var b2 && < 15 when a2 == 14 => "logical-and-1",
+    > 12 && < 17 => "logical-and-2",
+    < 25 when false => "relational-1",
+    <= 25 when true => "relational-2",
+    30 when 1 > 2 => "constant-1",
+    30 when 1 < 2 => "constant-2",
+    (var a3 && 40) when a3 == 42 => "parenthesized-1",
+    (40) => "parenthesized-2",
+    _ => "default"
+  };
+
+String testCast(num value) =>
+  switch (value) {
+    var c1 as int when c1 == 42 => "cast-1 =$c1",
+    var c2 as double when c2 > 4 => "cast-2 =${c2.toStringAsFixed(2)}",
+    _ => "default"
+  };
+
+String testNullCheck(int? value) =>
+  switch (value) {
+    var a1? when a1 > 0 => "null-check-1",
+    var a2? => "null-check-2",
+    _ => "default"
+  };
+
+String testNullAssert(int? value) {
+  switch (value) {
+    var a1! when a1 > 0 => "null-assert-1",
+    var a2! => "null-assert-2",
+    _ => "default"
+  };
+
+String testVariable(int value) =>
+  switch (value) {
+    var a1 when a1 > 0 => "variable-1",
+    var a2 when a2 < 0 => "variable-2",
+    _ => "default"
+  };
+
+String testList(List<int> list) =>
+  switch (list) {
+    [1, var a] when a > 0 => "list-1",
+    [1, final b, ...] when b < 0 => "list-2",
+    [1, _, ...r] when !r.isEmpty => "list-3",
+    _ => "default"
+  };
+
+String testMap(Map<String, int> map) {
+  switch (map) {
+    {"key1": 1, "key2": var a} when a > 0 => "map-1",
+    {"key1": 1, "key2": final b} when b < 0 => "map-2",
+    _ => "default"
+  };
+
+String testRecord(Record record) {
+  switch (record) {
+    (1, var a) when a > 0 => "record-1",
+    (1, final b) when b < 0 => "record-2",
+    (1, 2, n: var c) when c > 0 => "record-3",
+    (1, 2, n: final d) when d < 0 => "record-4",
+    _ => "default"
+  };
+
+String testObject(Shape shape) =>
+  switch (shape) {
+    Square(sizeAsInt: var a) when a > 2 => "object-1",
+    Square(areaAsInt: final b) when b < 4 => "object-2",
+    Circle(sizeAsInt: var c) when c > 1 => "object-3",
+    Circle(sizeAsInt: final d) when d < 1 => "object-4",
+    _ => "default"
+  };
+
+main() {
+  Expect.equals("logical-or-1", test(0));
+  Expect.equals("logical-or-2", test(1));
+  Expect.equals("logical-and-1", test(14));
+  Expect.equals("logical-and-2", test(13));
+  Expect.equals("default", test(24));
+  Expect.equals("relational-2", test(23));
+  Expect.equals("constant-2", test(30));
+  Expect.equals("parenthesized-2", test(40));
+  Expect.equals("default", test(100));
+
+  Expect.equals("cast-1 =42", testCast(42));
+  Expect.equals("cast-2 =41.00", testCast(41));
+  Expect.equals("default", testCast(3));
+
+  Expect.equals("null-check-2", testNullCheck(0));
+  Expect.equals("null-check-1", testNullCheck(1));
+  Expect.equals("default", testNullCheck(null));
+
+  Expect.equals("null-assert-1", testNullAssert(1));
+  Expect.equals("null-assert-2", testNullAssert(0));
+  Expect.throws(() {testNullAssert(null);});
+
+  Expect.equals("variable-1", testVariable(1));
+  Expect.equals("variable-2", testVariable(-1));
+  Expect.equals("default", testVariable(0));
+
+  Expect.equals("list-1", testList([1, 2]));
+  Expect.equals("list-2", testList([1, -1]));
+  Expect.equals("list-3", testList([1, 0, 3]));
+  Expect.equals("default", testList([1, 0]));
+
+  Expect.equals("map-1", testMap({"key1": 1, "key2": 2}));
+  Expect.equals("map-2", testMap({"key1": 1, "key2": -3}));
+  Expect.equals("default", testMap({"key1": 1, "key2": 0}));
+
+  Expect.equals("record-1", testRecord((1, 2)));
+  Expect.equals("record-2", testRecord((1, -3)));
+  Expect.equals("record-3", testRecord((1, 2, n: 3)));
+  Expect.equals("record-4", testRecord((1, 2, n: -4)));
+  Expect.equals("default", testRecord((1, 0)));
+  Expect.equals("default", testRecord((1, 2, n: 0)));
+
+  Expect.equals("object-1", testObject(Square(3)));
+  Expect.equals("object-2", testObject(Square(1)));
+  Expect.equals("default", testObject(Square(0)));
+  Expect.equals("object-3", testObject(Circle(2)));
+  Expect.equals("object-4", testObject(Circle(0.5)));
+  Expect.equals("default", testObject(Circle(1)));
+}