ICE VtableImpl ... did not contain projection for Obligation

[tobgu]

My code is probably wrong in some way because I'm a real n00b to Rust but since the compiler output tells me to submit a bug report I will obey. Possible duplicate of #20347 but I know too little to be sure.

Compiler version info

rustc 0.13.0-nightly (c6c786671 2015-01-04 00:50:59 +0000)
binary: rustc
commit-hash: c6c786671d692d7b13c2e5c68a53001327b4b125
commit-date: 2015-01-04 00:50:59 +0000
host: x86_64-unknown-linux-gnu
release: 0.13.0-nightly
Initial: 0

Compiler output

p2.rs:12:1: 19:2 error: internal compiler error: impl `VtableImpl(impl_def_id=DefId { krate: 0, node: 21 }:Fibonacci.Iterator, substs=Substs[types=[[];[];[]], regions=[[];[];[]]], nested=[[];[];[]])` did not contain projection for `Obligation(predicate=<Fibonacci as TraitRef(Fibonacci, core::iter::Iterator)>::Item,depth=0)`
p2.rs:12 impl Iterator for Fibonacci {
p2.rs:13     fn next(&mut self) -> uint {
p2.rs:14         let curr = self.curr;
p2.rs:15         self.curr = self.next;
p2.rs:16         self.next = curr + self.next;
p2.rs:17         curr
         ...
note: the compiler unexpectedly panicked. this is a bug.
note: we would appreciate a bug report: http://doc.rust-lang.org/complement-bugreport.html
note: run with `RUST_BACKTRACE=1` for a backtrace
thread 'rustc' panicked at 'Box<Any>', /home/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libsyntax/diagnostic.rs:123

stack backtrace:
   1:     0x7fe8477b32d0 - sys::backtrace::write::h8532e701ef86014f4it
   2:     0x7fe8477d8b00 - failure::on_fail::h7532e1f79d134d5dzvz
   3:     0x7fe84773e1c0 - rt::unwind::begin_unwind_inner::h97b151606151d62deaz
   4:     0x7fe8425efc60 - rt::unwind::begin_unwind::h15809447133099964284
   5:     0x7fe8425efbf0 - diagnostic::SpanHandler::span_bug::he8142ababcc30c39DFF
   6:     0x7fe845aeee70 - middle::traits::project::project_type::h947eece142ef049d52P
   7:     0x7fe845aebfd0 - middle::traits::project::opt_normalize_projection_type::hb3defb9cc9365d1e8UP
   8:     0x7fe845ad9ba0 - middle::traits::project::normalize_projection_type::hdc293893275ee559JTP
   9:     0x7fe845aed470 - middle::traits::project::AssociatedTypeNormalizer<'a, 'b, 'tcx>.TypeFolder<'tcx>::fold_ty::h801cbd2cdff2eff1kSP
  10:     0x7fe846daa2e0 - middle::ty_fold::Rc<T>.TypeFoldable<'tcx>::fold_with::h6325524173844043840
  11:     0x7fe846daae90 - middle::ty_fold::VecPerParamSpace<T>.TypeFoldable<'tcx>::fold_with::h13884369302522804796
  12:     0x7fe846dc6280 - check::FnCtxt<'a, 'tcx>::instantiate_bounds::hed550a9659b70335Oll
  13:     0x7fe846ddefc0 - check::wf::CheckTypeWellFormedVisitor<'ccx, 'tcx>::check_impl::closure.29997
  14:     0x7fe846ddb430 - check::wf::CheckTypeWellFormedVisitor<'ccx, 'tcx>::with_fcx::hb1283961ed8977b7Gfi
  15:     0x7fe846de1d70 - check::wf::CheckTypeWellFormedVisitor<'ccx, 'tcx>.Visitor<'v>::visit_item::h001ababd87597e37soi
  16:     0x7fe846fcefe0 - check_crate::unboxed_closure.40162
  17:     0x7fe846fc9c30 - check_crate::h19fb6dea5733566ajsx
  18:     0x7fe847d04640 - driver::phase_3_run_analysis_passes::h46b1604d9f9f5633Tva
  19:     0x7fe847cf2ae0 - driver::compile_input::h68b8602933aad8d7wba
  20:     0x7fe847dbdeb0 - thunk::F.Invoke<A, R>::invoke::h18029802347644288836
  21:     0x7fe847dbcc60 - rt::unwind::try::try_fn::h6518866316425934196
  22:     0x7fe84783f400 - rust_try_inner
  23:     0x7fe84783f3f0 - rust_try
  24:     0x7fe847dbcfb0 - thunk::F.Invoke<A, R>::invoke::h15513809553472565307
  25:     0x7fe8477c4e40 - sys::thread::thread_start::h5ea7ba97235331d5a9v
  26:     0x7fe841e130c0 - start_thread
  27:     0x7fe8473e4ec9 - __clone
  28:                0x0 - <unknown>

uname --all

Linux <host>-Ubuntu 3.13.0-39-generic #66-Ubuntu SMP Tue Oct 28 13:30:27 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux

Source code

use std::iter::AdditiveIterator;

struct Fibonacci {
    curr: uint,
    next: uint,
}

fn fib() -> Fibonacci {
    Fibonacci {curr: 1, next: 2}
}

impl Iterator for Fibonacci {
    fn next(&mut self) -> uint {
        let curr = self.curr;
        self.curr = self.next;
        self.next = curr + self.next;
        curr
    }
}

fn initial() -> uint {
    fib().take(5).sum();
}

fn main() {
    println!("Initial: {}", initial());
}

[shepmaster]

@tobgu to get unstuck, you will want to change your code slightly:

impl Iterator<uint> for Fibonacci {
    fn next(&mut self) -> Option<uint> {

But there shouldn't be an ICE either way :-)

[tobgu]

Thanks, that was actually my initial try but it gave me the following compilation error:
p2.rs:17:6: 17:20 error: wrong number of type arguments: expected 0, found 1
p2.rs:17 impl Iterator for Fibonacci {

What helped me in the end was adding the uint as an associated type like so:
impl Iterator for Fibonacci {
type Item = uint;

This way things compile and works as intended. It feels slightly awkward though...

[huonw]

Closing as a dupe of #20347, thanks for filing!