Can't find impl for type involving &

[jdm]

rusti> trait Tr { fn foo(&self); }
()
rusti>  impl Tr for &int { fn foo(&self) {} }
()
rusti> fn foo<T: Tr>(a: &T) { a.foo(); }
()
rusti> foo(&5);
<anon>:45:0: 45:3 error: failed to find an implementation of trait @main::Tr for <V1>

There are similarly confusing errors involving unsafe pointers, but I haven't figured out a good testcase yet.

[bstrie]

I'm not sure if this is a bug. Here's an updated test case:

trait Tr {
    fn foo(&self);
}

impl<'self> Tr for &'self int {
    fn foo(&self) {
        println("hello");
    }
}

fn foo<T: Tr>(a: &T) { a.foo(); }

fn main() {
    foo(&5);
}

...which fails to compile with error: failed to find an implementation of trait Tr for int.

However, if you change the foo(&5); to foo(& &5);, this prints "hello" as expected. Is this actually a bug, or is it just a complication of autoderef?

[nikomatsakis]

On Mon, May 06, 2013 at 12:40:38PM -0700, Ben Striegel wrote:

However, if you change the foo(&5); to foo(& &5);, this prints
"hello" as expected. Is this actually a bug, or is it just a
complication of autoderef?

I don't believe this is a bug. T here is &int, so an &&int is expected.
The correct way to do this is to impl Ty for int, not &int.

[alexcrichton]

It appears that the consensus is that this isn't a bug, so I'm closing for now.