The first time I found that Rust compiler can be stupid

It’s not me, it’s not me, finally!

I got an error, which has a solution which is verbose and dumb. And I believe it’s a compiler’s fault.

Look at the structure:

struct ThreadCommands {
    control_tx: [Option<Sender<ControlCommand>>;8],
    draw_rx: [Option<Receiver<DrawCommand>>;8]
}

When I try to initialize it:

let mut control = ThreadCommands {
        control_tx: [None;8],
        draw_rx: [None;8]
 };

It all falls apart:

the trait `std::marker::Copy` is not implemented for `std::option::Option<std::sync::mpsc::Sender<ControlCommand>>`

There is a big reason why there is no Copy trait for Sender. It’s explicitly forbidden, as mpsc channel allows only one Sender.

But array initialization is requires Copy. This is stupid thing number one. Can’t we just pretend it’s in the code N times without writing it explicitly?

Second: Even if Some<Sender> must not be copied, the None should be trivially copied. I do not agree here with compiler and it forces me to write this:

ThreadCommands {
    control_tx: [None,None,None,None, None,None,None,None],
    draw_rx: [None,None,None,None, None,None,None,None]
}

Which is less than bright for a compiler.

Forum was nice enough to point me to the Default trait.

#[derive(Default)]
struct ThreadCommands {
    control_tx: [Option<Sender<ControlCommand>>;8],
    draw_rx: [Option<Receiver<DrawCommand>>;8]
}
...
let mut control:ThreadCommands = Default::default();

It worked. But I still disappointed, as Rust wasn’t that smart to see through types.

UPD: No, it’s not stupid, it’s old.

steffahn from Rust forum was very helpful and provided with few workarounds, and, more importantly, s/he said that nightly Rust now can do copy for None, even Some<Type> is copy-forbidden. It’s just wasn’t stabilized yet.