[bankisan]

Regarding the example in your first point, you are still sending a reference `m` of the map. If you wanted to send an immutable type, you could declare the channel to only accept struct values (and not pointers to structs) and you'll get your desired behavior.

Here's a playground for reference:

https://play.golang.org/p/U2tYZVTtUf-

[simiones]

Given that there is no way to make a non-pointer map in Go, there is no workaround for the example they gave.

The broader point is that there is no way in Go to ensure that data passed over a channel will not be modified concurrently without modifying the type of the data specifically for the channel use case.

A deep_copy() primitive would fix this.

[bankisan]

Right, but they mentioned sending immutable structs which is why I gave the struct example. But you're right that every declared map is a just a pointer.

With respect to your second point, I see what you mean but I still don't think that's a negative of Go. You can pass in copied values without having to have a deep_copy() primitive (loop map values and copy to new map, dereferencing a pointer, etc.). Like other parts of Go, if you want to make your data immutable there is no syntactic sugar. You have to explicitly write it out.

[simiones]

> With respect to your second point, I see what you mean but I still don't think that's a negative of Go.

It is a negative of Go, because Go pushes you into the pit of failure by its design: it is much, much harder to do the right thing (send deep copies of objects over channels) than it is to do the wrong things (send pointers or shallow copies over channels).

[eru]

You'd have to roll your own deep_copy by hand (or code generation) for every single data type.

[eru]

Yes, either a deep_copy() or a way to declare things immutable. (Or both.)