Confusing error: 'method read has 1 parameters'

[brson]

I am trying to implement my own trait called Reader, but I accidentally had a different Reader trait in scope.

/home/brian/dev/rust/src/libcore/rt/io/comm_adapters.rs:20:4: 20:67 error: method `read` has 1 parameters 
but the trait has 2
/home/brian/dev/rust/src/libcore/rt/io/comm_adapters.rs:20     fn read(&mut self, _buf: &mut [u8]) -> Option<uint> { fail!() }
                                                               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

It took some time to figure out that rustc and I were looking at different traits. It could tell me the path to the trait it is trying to match. Even better, it could tell me about alternate traits with the same name.

[Xazax-hun]

The following code is working:

fn main() {
let x = 5;
let x = 6;
println(fmt!("%?",x));
}

Apparently the second x creates a new variable that hides the first x that is in the same scope. Is it intentional?
It looks like Rust does not seems to handle name collosions and in my opinion this can be the source of several errors.

[jdm]

@Xazax-hun, that's intentional behaviour, and unrelated to the original issue report.

[alexcrichton]

Here's a small code sample which exhibits this behavior:

use a::Reader;
use b::Reader;

mod a {
    pub trait Reader {
        fn foo(int);
    }
}

mod b {
    pub trait Reader {
        fn foo(int, int);
    }
}

struct A;

impl Reader for A {
    fn foo(_: int) {}
}

fn main() {
}

with the error

foo.rs:19:4: 19:21 error: method `foo` has 1 parameter but the trait has 2
foo.rs:19     fn foo(_: int) {}
              ^~~~~~~~~~~~~~~~~
error: aborting due to previous error

[jaeminMoon]

I think, is it intentional?
first Reader(mod a) is removed by second Reader(mod b).

use b::Reader;
use a::Reader;

If you change code, it will be done.

[sanxiyn]

The bug is about improving the error message. For example, instead of saying the trait, the error message could say the trait b::Reader``.