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test_switch.zig (1930B) - Raw

      1 const std = @import("std");
      2 const builtin = @import("builtin");
      3 const expect = std.testing.expect;
      4 
      5 test "switch simple" {
      6     const a: u64 = 10;
      7     const zz: u64 = 103;
      8 
      9     // All branches of a switch expression must be able to be coerced to a
     10     // common type.
     11     //
     12     // Branches cannot fallthrough. If fallthrough behavior is desired, combine
     13     // the cases and use an if.
     14     const b = switch (a) {
     15         // Multiple cases can be combined via a ','
     16         1, 2, 3 => 0,
     17 
     18         // Ranges can be specified using the ... syntax. These are inclusive
     19         // of both ends.
     20         5...100 => 1,
     21 
     22         // Branches can be arbitrarily complex.
     23         101 => blk: {
     24             const c: u64 = 5;
     25             break :blk c * 2 + 1;
     26         },
     27 
     28         // Switching on arbitrary expressions is allowed as long as the
     29         // expression is known at compile-time.
     30         zz => zz,
     31         blk: {
     32             const d: u32 = 5;
     33             const e: u32 = 100;
     34             break :blk d + e;
     35         } => 107,
     36 
     37         // The else branch catches everything not already captured.
     38         // Else branches are mandatory unless the entire range of values
     39         // is handled.
     40         else => 9,
     41     };
     42 
     43     try expect(b == 1);
     44 }
     45 
     46 // Switch expressions can be used outside a function:
     47 const os_msg = switch (builtin.target.os.tag) {
     48     .linux => "we found a linux user",
     49     else => "not a linux user",
     50 };
     51 
     52 // Inside a function, switch statements implicitly are compile-time
     53 // evaluated if the target expression is compile-time known.
     54 test "switch inside function" {
     55     switch (builtin.target.os.tag) {
     56         .fuchsia => {
     57             // On an OS other than fuchsia, block is not even analyzed,
     58             // so this compile error is not triggered.
     59             // On fuchsia this compile error would be triggered.
     60             @compileError("fuchsia not supported");
     61         },
     62         else => {},
     63     }
     64 }
     65 
     66 // test