Internal compiler error

[heartpunk]

➜  datastructures.rs git:(master) ✗ RUST_LOG="rustc=1;::rt::backtrace" rustc stack.rs &&./stack
rust: task failed at 'assertion failed: rp.is_none()', /private/tmp/rust-5o4g/rust-0.7/src/librustc/middle/typeck/collect.rs:1040
error: internal compiler error: unexpected failure
note: the compiler hit an unexpected failure path. this is a bug
note: try running with RUST_LOG=rustc=1,::rt::backtrace to get further details and report the results to github.com/mozilla/rust/issues
rust: task failed at 'explicit failure', /private/tmp/rust-5o4g/rust-0.7/src/librustc/rustc.rs:354
rust: domain main @0x7f9afc008410 root task failed

The code that caused it is:

trait ImmStack<T> {
    fn push(self, item : T) -> Self;
    fn pop(self) -> (Option<T>, Option<Self>);
    fn new() -> Self;
}

#[deriving(Eq, ToStr)]
enum Chain<T> {
    Link(T, ~Chain<T>),
    Break
}

//impl<T> ImmStack<T> for Chain<T> {
//    fn push(self, item : T) -> Chain<T> {
//        Link(item, ~self)
//    }
//    fn pop(self) -> (Option<T>, Option<Chain<T>>) {
//        match self {
//            Link(item, ~new_self) => return (Some(item), Some(new_self)),
//            Break => return (None, None)
//        }
//    }
//    fn new() -> Chain<T> {
//        Break
//    }
//}

fn push<'self, T>(stack : &'self mut Chain<T>, item : T) -> &'self mut Chain<T> {
    &mut Link(item, ~*stack)
}

fn pop<T>(stack : &mut Chain<T>) -> Option<T> {
    match *stack {
        Link(item, ~new_stack) => {
            stack = &mut new_stack;
            return Some(item);
        },
        Break => return None
    }
}

fn new<T>() -> &mut Chain<T> {
    &mut Break
}

fn main() {
    let mut b : &Chain<int> = ~Break;
    push(push(push(b, 1), 2), 3);
    println(b.to_str());
}

[heartpunk]

It's probably related to lifetimes, as I'd only added the lifetime stuff to push before this error happened.

[bblum]

What happens if you change 'self to 'a?

[heartpunk]

This happens:

immstack.rs:29:4: 30:1 error: borrowed value does not live long enough
immstack.rs:29     &mut Link(item, ~*stack)
immstack.rs:30 }
immstack.rs:28:71: 30:1 note: borrowed pointer must be valid for the lifetime &'a  as defined on the block at 28:71...
immstack.rs:28 fn push<'a, T>(stack : &'a mut Chain<T>, item : T) -> &'a mut Chain<T> {
immstack.rs:29     &mut Link(item, ~*stack)
immstack.rs:30 }
immstack.rs:28:71: 30:1 note: ...but borrowed value is only valid for the block at 28:71
immstack.rs:28 fn push<'a, T>(stack : &'a mut Chain<T>, item : T) -> &'a mut Chain<T> {
immstack.rs:29     &mut Link(item, ~*stack)
immstack.rs:30 }
immstack.rs:29:21: 29:27 error: cannot move out of dereference of & pointer
immstack.rs:29     &mut Link(item, ~*stack)
                                    ^~~~~~
immstack.rs:34:8: 34:30 error: cannot move out of dereference of & pointer
immstack.rs:34         Link(item, ~new_stack) => {
                       ^~~~~~~~~~~~~~~~~~~~~~
immstack.rs:34:19: 34:29 error: cannot move out of dereference of & pointer
immstack.rs:34         Link(item, ~new_stack) => {
                                  ^~~~~~~~~~
immstack.rs:35:20: 35:34 error: borrowed value does not live long enough
immstack.rs:35             stack = &mut new_stack;
                                   ^~~~~~~~~~~~~~
immstack.rs:32:46: 40:1 note: borrowed pointer must be valid for the anonymous lifetime #1 defined on the block at 32:46...
immstack.rs:32 fn pop<T>(stack : &mut Chain<T>) -> Option<T> {
immstack.rs:33     match *stack {
immstack.rs:34         Link(item, ~new_stack) => {
immstack.rs:35             stack = &mut new_stack;
immstack.rs:36             return Some(item);
immstack.rs:37         },
               ...
immstack.rs:33:4: 39:5 note: ...but borrowed value is only valid for the match at 33:4
immstack.rs:33     match *stack {
immstack.rs:34         Link(item, ~new_stack) => {
immstack.rs:35             stack = &mut new_stack;
immstack.rs:36             return Some(item);
immstack.rs:37         },
immstack.rs:38         Break => return None
               ...
immstack.rs:35:20: 35:34 error: cannot borrow immutable local variable as mutable
immstack.rs:35             stack = &mut new_stack;
                                   ^~~~~~~~~~~~~~
immstack.rs:35:12: 35:17 error: cannot assign to immutable argument
immstack.rs:35             stack = &mut new_stack;
                           ^~~~~
immstack.rs:43:4: 43:14 error: cannot borrow immutable static item as mutable
immstack.rs:43     &mut Break
                   ^~~~~~~~~~
immstack.rs:48:19: 48:20 error: cannot borrow immutable dereference of & pointer as mutable
immstack.rs:48     push(push(push(b, 1), 2), 3);
                                  ^
error: aborting due to 9 previous errors

Which seems like it's could be right, but I certainly don't understand well enough to judge yet.

[alexcrichton]

Closing as a duplicate of #7989. When the lifetime is changed from 'self to 'a the compiler errors are all legitimate.