example in chapter `Ownership` seems not correct

[Gnosnay]

In Ownership chapter we give one example to indicate that variable will be dropped at the end of scope.

struct Point(i32, i32);

fn main() {
    {
        let p = Point(3, 4);
        println!("x: {}", p.0);
    }
    println!("y: {}", p.1);
}

But actually the rustc’s complaining is

    Blocking waiting for file lock on package cache
   Compiling exercise v0.1.0 (/home/coder/project/exercise)
error[E0425]: cannot find value `p` in this scope
 --> src/main.rs:8:23
  |
8 |     println!("y: {}", p.1);
  |                       ^ not found in this scope

For more information about this error, try `rustc --explain E0425`.
error: could not compile `exercise` due to previous error

I believe this example may cause confusion.

[Gnosnay]

I believe here we need to introduce what the end of scope is. E.g. the end of one code block, one pointer transfer to another function e.t.c

[mgeisler]

Hi @Yansongsongsong,

You are completely correct that the error message is about scopes and that the instructor will have to explain what a scope is at this point. That is normally super easy, though, since the course participants already know how to program. To my knowledge, a scope in Rust is the same as a scope in C++ (please correct me if I'm wrong?) and so I normally tell the students that.

To me, ownership is mostly a matter of who should deallocate this value when it goes out of scope? So that is why I start the discussion of borrowing and ownership with scopes.

We should eventually write something about this into speaker notes #53.

[Gnosnay]

Hi @Yansongsongsong,

You are completely correct that the error message is about scopes and that the instructor will have to explain what a scope is at this point. That is normally super easy, though, since the course participants already know how to program. To my knowledge, a scope in Rust is the same as a scope in C++ (please correct me if I'm wrong?) and so I normally tell the students that.

To me, ownership is mostly a matter of who should deallocate this value when it goes out of scope? So that is why I start the discussion of borrowing and ownership with scopes.

We should eventually write something about this into speaker notes #53.

hi @mgeisler , Thank you for your reply. That sounds great. Looking forward to new version with spears notes!

Feel free to close this issue at any time.

[mgeisler]

Thanks, I'll close it for now.