| // 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 We extend switch statements to allow patterns in cases: |
| /// |
| /// switchStatement ::= 'switch' '(' expression ')' |
| /// '{' switchStatementCase* switchStatementDefault? '}' |
| /// switchStatementCase ::= label* 'case' guardedPattern ':' statements |
| /// guardedPattern ::= pattern ( 'when' expression )? |
| /// switchStatementDefault ::= label* 'default' ':' statements |
| /// ... |
| /// Many constant expressions are subsumed by the new pattern syntax so most |
| /// existing switch cases have the same semantics under this proposal. However, |
| /// patterns are not a strict superset of constant expressions and some switches |
| /// may be broken. |
| /// ... |
| /// Other constant expressions. Constant patterns allow simple literals and |
| /// references to named constants to be used directly as patterns, which covers |
| /// the majority of all existing switch cases. Also a constant constructor |
| /// explicitly prefixed with const is a valid constant expression pattern. But |
| /// some more complex expressions are valid constant expressions but not valid |
| /// constant patterns. |
| /// |
| /// @description Checks that old-style constant expressions are not valid |
| /// constant patterns now and produce a compile-time error |
| /// @author sgrekhov22@gmail.com |
| |
| String test(Object value) { |
| switch (value) { |
| case 1 + 2: |
| // ^ |
| // [analyzer] unspecified |
| // [cfe] unspecified |
| return "case =3"; |
| case 2 - 1: |
| // ^ |
| // [analyzer] unspecified |
| // [cfe] unspecified |
| return "case =1"; |
| case 2 * 2: |
| // ^ |
| // [analyzer] unspecified |
| // [cfe] unspecified |
| return "case =4"; |
| case 30 ^ 2: |
| // ^ |
| // [analyzer] unspecified |
| // [cfe] unspecified |
| return "case =28"; |
| case 1 | 4: |
| // ^ |
| // [analyzer] unspecified |
| // [cfe] unspecified |
| return "case =5"; |
| case 1 & 4: |
| // ^ |
| // [analyzer] unspecified |
| // [cfe] unspecified |
| return "case =0"; |
| case 15 % 8: |
| // ^ |
| // [analyzer] unspecified |
| // [cfe] unspecified |
| return "case =7"; |
| case 19 ~/ 8: |
| // ^^ |
| // [analyzer] unspecified |
| // [cfe] unspecified |
| return "case =2"; |
| case 19 >> 1: |
| // ^^ |
| // [analyzer] unspecified |
| // [cfe] unspecified |
| return "case =9"; |
| case 87 >>> 1: |
| // ^^^ |
| // [analyzer] unspecified |
| // [cfe] unspecified |
| return "case =43"; |
| case 19 << 1: |
| // ^^ |
| // [analyzer] unspecified |
| // [cfe] unspecified |
| return "case =38"; |
| case -1 > 2: |
| // ^ |
| // [analyzer] unspecified |
| // [cfe] unspecified |
| return "case =false"; |
| case -1 < 2: |
| // ^ |
| // [analyzer] unspecified |
| // [cfe] unspecified |
| return "case =true"; |
| case 1 >= 2: |
| // ^^ |
| // [analyzer] unspecified |
| // [cfe] unspecified |
| return "case =false2"; |
| case -1 <= 2: |
| // ^^ |
| // [analyzer] unspecified |
| // [cfe] unspecified |
| return "case =true2"; |
| case 1 == -2: |
| // ^^ |
| // [analyzer] unspecified |
| // [cfe] unspecified |
| return "case =false3"; |
| case 1 != 2: |
| // ^^ |
| // [analyzer] unspecified |
| // [cfe] unspecified |
| return "case =true3"; |
| case "Lily" + " " "was" " " + "here": |
| // ^ |
| // [analyzer] unspecified |
| // [cfe] unspecified |
| return "case String"; |
| case List<int>: |
| // ^^^^^^^^^ |
| // [analyzer] unspecified |
| // [cfe] unspecified |
| return "case =type"; |
| default: |
| return "default"; |
| } |
| } |
| |
| main() { |
| test(42); |
| } |
