When the following codes are compiled, the compile error is generated.

----------------------------------------------------------------
async void func() {
    switch (0) {
    case 0:
        int tmp;
        break;
    case 1:
        int tmp;
        break;
    }
}

void main() {
    func();
}
----------------------------------------------------------------

$ valac --pkg gio-2.0 bug3.vala
bug3.vala:7.13-7.15: warning: local variable `tmp' declared but never used
        int tmp;
            ^^^
bug3.vala:10.13-10.15: warning: local variable `tmp' declared but never used
        int tmp;
            ^^^
/home/kentaro/work/VALA/bug3.vala.c:19:7: error: duplicate member ‘tmp’
error: cc exited with status 256
Compilation failed: 1 error(s), 2 warning(s)