Error snake for moving out of an &-pointer is wrong sometimes

[Manishearth]

Minimal-ish working example:

use std::string::String;
struct Foo {
 a: String,
 b: String,
 // Possibly some more fields here
}
struct FooThing(Vec<Foo>);
impl FooThing {
  fn filter(&mut self, bar: &Foo) {
    let FooThing(ref buf) = self.clone(); // Oops. Shouldn't be a `ref` there
    let new_buf: Vec<Foo> = buf.move_iter().filter(|f| f.a == bar.a && f.b == bar.b).collect();
  }
}
fn main() {

}

The usage of ref buf means that buf.move_iter won't work, since buf is an &-pointer now. An error is expected.

However, the error shown is:

test.rs:12:53: 12:56 error: the type of this value must be known in this context
test.rs:12  let new_buf: Vec<Foo> = buf.move_iter().filter(|f| f.a == bar.a && f.b == bar.b).collect();
                                                               ^~~

For some reason, the red caret points at f.a. Swapping f.a and bar.a, it still points at f.a. Swapping the two equality checks, it now points at f.b. I don't know what the difference was, but in my real-world case it was the second equality check that had the pointer on it.

The error snake goes to buf.move_iter() correctly if you replace self.clone() with *self.

[nham]

I made an attempt at reproducing this. Here is the updated code:

use std::string::String;

#[derive(Clone)]
struct Foo {
 a: String,
 b: String,
 // Possibly some more fields here
}

#[derive(Clone)]
struct FooThing(Vec<Foo>);

impl FooThing {
    fn filter(&mut self, bar: &Foo) {
        // Oops. Shouldn't be a `ref` there
        let FooThing(ref buf) = self.clone();

        let new_buf: Vec<Foo> = buf.into_iter()
                                   .filter(|f| f.a == bar.a && f.b == bar.b)
                                   .collect();
    }
}

fn main() {}

This fails to compile now, but with this error:

test_15479.rs:18:33: 18:36 error: cannot move out of borrowed content
test_15479.rs:18         let new_buf: Vec<Foo> = buf.into_iter()
                                                 ^~~
error: aborting due to previous error

(Version is rustc 1.0.0-nightly (07560d233 2015-04-20) (built 2015-04-20))

This appears to not have the problem described above.

[steveklabnik]

The error now says that error: the traitcore::iter::FromIterator<&Foo>is not implemented for the typecollections::vec::Vec[E0277], so I think this is basically fixed. @Manishearth , if you can come up with a different reproduction of this squiggle being wrong, let me know.