noreturn

noreturn is the type of:

• break
• continue
• return
• unreachable
• while (true) {}

When resolving types together, such as if clauses or switch prongs, the noreturn type is compatible with every other type. Consider:

test_noreturn.zig

fn foo(condition: bool, b: u32) void {
    const a = if (condition) b else return;
    _ = a;
    @panic("do something with a");
}
test "noreturn" {
    foo(false, 1);
}

Shell

$ zig test test_noreturn.zig
1/1 test "noreturn"... OK
All 1 tests passed.

Another use case for noreturn is the exit function:

noreturn_from_exit.zig

const std = @import("std");
const builtin = @import("builtin");
const native_arch = builtin.cpu.arch;
const expect = std.testing.expect;
const WINAPI: std.builtin.CallingConvention = if (native_arch == .i386) .Stdcall else .C;
extern "kernel32" fn ExitProcess(exit_code: c_uint) callconv(WINAPI) noreturn;
test "foo" {
    const value = bar() catch ExitProcess(1);
    try expect(value == 1234);
}
fn bar() anyerror!u32 {
    return 1234;
}

Shell

$ zig test noreturn_from_exit.zig -target x86_64-windows --test-no-exec