ICE in ensure_public

[nagisa]

error: internal compiler error: unexpected panic
note: the compiler unexpectedly panicked. this is a bug.
note: we would appreciate a bug report: https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#bug-reports
thread 'rustc' panicked at 'called `Option::unwrap()` on a `None` value', ../src/libcore/option.rs:365
stack backtrace:
   1:     0x7fd8bfe28940 - sys::backtrace::tracing::imp::write::he27ef2eb40e30753Plt
   2:     0x7fd8bfe2f215 - panicking::log_panic::_<closure>::closure.39316
   3:     0x7fd8bfe2ec85 - panicking::log_panic::h20a17353a34447751lx
   4:     0x7fd8bfdf3783 - sys_common::unwind::begin_unwind_inner::hf876a8bedc1a7d89gds
   5:     0x7fd8bfdf40e8 - sys_common::unwind::begin_unwind_fmt::h69a2566a09092307mcs
   6:     0x7fd8bfe26801 - rust_begin_unwind
   7:     0x7fd8bfe79a7f - panicking::panic_fmt::h4197e07a6c9f36b2dMK
   8:     0x7fd8bfe73fb8 - panicking::panic::h14dc0798a39fe65fKKK
   9:     0x7fd8bf09823a - _<impl>::ensure_public::hde035fa84af6435dh0a
  10:     0x7fd8bf099244 - _<impl>::check_path::_<closure>::_<closure>::closure.12246
  11:     0x7fd8bf098c88 - _<impl>::check_path::_<closure>::closure.12244
  12:     0x7fd8bf09895b - _<impl>::check_path::h708120903b3b4e28Kbb
  13:     0x7fd8bf099b9a - _<impl>::visit_path::hdfda786dba7d0ea3jtb
  14:     0x7fd8bf09aef5 - _<impl>::visit_expr::h2d55fa99aaddc54awkb
  15:     0x7fd8bf09ae93 - _<impl>::visit_expr::h2d55fa99aaddc54awkb
  16:     0x7fd8bf0995e5 - visit::walk_item::walk_item::h16273349179620707161
  17:     0x7fd8bf09fe85 - check_crate::ha75a8757309cbaacuXb
  18:     0x7fd8c02f80da - driver::phase_3_run_analysis_passes::_<closure>::closure.21793
  19:     0x7fd8c02debf1 - middle::ty::context::_<impl>::create_and_enter::create_and_enter::h13642880013250108432
  20:     0x7fd8c02da02a - driver::phase_3_run_analysis_passes::h18429705411053108892
  21:     0x7fd8c02b8b64 - driver::compile_input::h8be95b88a1576d993ba
  22:     0x7fd8c041304b - run_compiler::h83cbc3300765328cysc
  23:     0x7fd8c04108d6 - boxed::_<impl>::call_box::call_box::h17940959236498258992
  24:     0x7fd8c04101e4 - sys_common::unwind::try::try_fn::try_fn::h12133114510587347876
  25:     0x7fd8bfe26668 - __rust_try
  26:     0x7fd8bfe1adeb - sys_common::unwind::try::inner_try::hbe46f56ef602f07cO9r
  27:     0x7fd8c041037e - boxed::_<impl>::call_box::call_box::h2880662908038604228
  28:     0x7fd8bfe2dce3 - sys::thread::_<impl>::new::thread_start::h13325138c3b56c4cdEw
  29:     0x7fd8b94fa4a3 - start_thread
  30:     0x7fd8bfabb13c - clone
  31:                0x0 - <unknown>

Trying to make the test case now.

[nagisa]

mod a {
    struct A;

    impl Default for A {
        pub fn default() -> A {
            A;
        }
    }
}


fn main() {
    a::A::default();
}

[nagisa]

Works on current beta. Does not work on current nightly.

[nikomatsakis]

triage: P-high

[nikomatsakis]

The unwrap seems to be from trying to get a def-id from a node-id that is not registered.

[nikomatsakis]

Problem seems to be that the def-id is not local to the current crate.

[nikomatsakis]

OK, the problem is that when doing the def-id conversion, I converted this code:

.. if id == source_did.unwrap_or(to_check).node ..

into this:

        let def_id = source_did.unwrap_or(to_check);
        debug!("ensure_public: def_id = {:?}", def_id);
        let node_id = self.tcx.map.as_local_node_id(def_id).unwrap();

In particular, I used an unwrap when converting to a local node-id because the original code accessed the node field without checking the crate, which is only really valid if the def-id is local. In other words, I blame the original commit :P

But I'm trying now to figure out what is SUPPOSED to happen here. I still don't quite understand the flow of this code. In particular I don't know what source_did represents or why it is external here.

[nikomatsakis]

Probably the right fix is just to keep the Option:

        let def_id = source_did.unwrap_or(to_check);
        debug!("ensure_public: def_id = {:?}", def_id);
        let node_id = self.tcx.map.as_local_node_id(def_id);
        let (err_span, err_msg) = if Some(id) == node_id {