error: cannot assign to constant

problem.zig

pub const Data = struct {
    count: u8,

    pub fn init() Data {
        return Data{
            .count = 0,
        };
    }

    pub fn append(self: Data, value: u8) !void {
        if (self.count == 10)
            return error.Overflow;

        self.count += 1;
    }
};


pub fn main() !void {
    var data = Data.init();
    try data.append(2);
}