rustc panics unexpectedly when passing phantomdata to hierarchical trait arguments

[iankronquist]

rustc panics unexpectedly when passing phantomdata to hierarchical trait arguments

I tried this code:

// wonderful tutorial: http://os.phil-opp.com/modifying-page-tables.html
// It's a really slick way to use Rust's type system to express the page
// tables.

use std::marker::PhantomData;
use std::boxed::Box;

pub trait PageTableLevel {}

trait HierarchicalLevel: PageTableLevel {
    type NextLevel: PageTableLevel;
}

pub struct PageTable<L: PageTableLevel> {
    level: PhantomData<L>,
}

impl<L: HierarchicalLevel> PageTable<L> {
    pub fn next_layer_create(&mut self, index: usize) -> Option<&mut PageTable<L::NextLevel>>
    {
        let address = allocate_page(L::NextLevel);
        None
    }
}

pub fn allocate_page(level: PageTableLevel) -> u64 {
    let page: &PageTable<PageTableLevel> = Box::new(Default::default);
    page as u64
}

I expected to see this happen: It shouldn't compile, and should give me lots of red errors and yellow warnings.

Instead, this happened: rustc panics.

Meta

rustc --version --verbose: rustc 1.16.0-nightly (1a2ed98 2017-01-13)
binary: rustc
commit-hash: 1a2ed98
commit-date: 2017-01-13
host: x86_64-unknown-linux-gnu
release: 1.16.0-nightly
LLVM version: 3.9

Backtrace:

error: main function not found

error: internal compiler error: /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc_typeck/check/mod.rs:4376: unexpected definition: AssociatedTy(DefId { krate: CrateNum(0), node: DefIndex(7) => repro/4089d7c8b778d88cec885baf7b69e6df-exe::HierarchicalLevel[0]::NextLevel[0] })

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

note: run with `RUST_BACKTRACE=1` for a backtrace

thread 'rustc' panicked at 'Box<Any>', /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc_errors/lib.rs:423
stack backtrace:
   1:     0x7f0dbe5680fc - std::sys::imp::backtrace::tracing::imp::write::h9c41d2f69e5caabf
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:42
   2:     0x7f0dbe57657e - std::panicking::default_hook::{{closure}}::h1f61f3c769fffe7a
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libstd/panicking.rs:351
   3:     0x7f0dbe576123 - std::panicking::default_hook::hd5bda4e453dfb4be
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libstd/panicking.rs:361
   4:     0x7f0dbe576a1b - std::panicking::rust_panic_with_hook::hffbc74969c7b5d87
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libstd/panicking.rs:555
   5:     0x7f0db6b81a57 - std::panicking::begin_panic::h74ad4f050841c998
   6:     0x7f0db6b971c9 - rustc_errors::Handler::bug::h7088c6afc4a008fb
   7:     0x7f0dbb8b87fa - rustc::session::opt_span_bug_fmt::{{closure}}::h8e30a0fda5e6d8ea
   8:     0x7f0dbb8b8605 - rustc::session::opt_span_bug_fmt::h4fd6d943719c63ae
   9:     0x7f0dbb8b8262 - rustc::session::bug_fmt::he01375c3004c5cfe
  10:     0x7f0dbca204e3 - rustc_typeck::check::FnCtxt::instantiate_value_path::hfcd1421ef04f3e81
  11:     0x7f0dbca0d858 - rustc_typeck::check::FnCtxt::check_expr_kind::h7172316f2afc3db4
  12:     0x7f0dbca0c05d - rustc_typeck::check::FnCtxt::check_expr_with_expectation_and_lvalue_pref::h58cbaadb2bb31008
  13:     0x7f0dbca00af6 - rustc_typeck::check::FnCtxt::check_argument_types::h222b4f6520160c8e
  14:     0x7f0dbc9da3b1 - rustc_typeck::check::callee::<impl rustc_typeck::check::FnCtxt<'a, 'gcx, 'tcx>>::confirm_builtin_call::h49b04582f1c761e4
  15:     0x7f0dbc9d9266 - rustc_typeck::check::callee::<impl rustc_typeck::check::FnCtxt<'a, 'gcx, 'tcx>>::check_call::h388fc4549b25dc5a
  16:     0x7f0dbca0d244 - rustc_typeck::check::FnCtxt::check_expr_kind::h7172316f2afc3db4
  17:     0x7f0dbca0c05d - rustc_typeck::check::FnCtxt::check_expr_with_expectation_and_lvalue_pref::h58cbaadb2bb31008
  18:     0x7f0dbca1e8fd - rustc_typeck::check::FnCtxt::check_decl_initializer::h406e808c34510780
  19:     0x7f0dbca1ea04 - rustc_typeck::check::FnCtxt::check_decl_local::ha21dda48446cfd7f
  20:     0x7f0dbca1ed36 - rustc_typeck::check::FnCtxt::check_stmt::h5f0c409d0347ada0
  21:     0x7f0dbca1f08e - rustc_typeck::check::FnCtxt::check_block_with_expected::h5fabdeff5662cd10
  22:     0x7f0dbca0c4c7 - rustc_typeck::check::FnCtxt::check_expr_kind::h7172316f2afc3db4
  23:     0x7f0dbca0c05d - rustc_typeck::check::FnCtxt::check_expr_with_expectation_and_lvalue_pref::h58cbaadb2bb31008
  24:     0x7f0dbc9f1eb1 - rustc_typeck::check::check_fn::h7512874de533d1c6
  25:     0x7f0dbc9f0ec4 - rustc_typeck::check::check_bare_fn::hff8cbad9cd9ca12c
  26:     0x7f0dbc9f3920 - rustc_typeck::check::check_item_body::h2a877e8ee0d16484
  27:     0x7f0dbc9ee08a - rustc_typeck::check::check_item_bodies::hf9c5a615b1a27ce2
  28:     0x7f0dbca60217 - rustc_typeck::check_crate::h93455a3168487f9e
  29:     0x7f0dbe91fc87 - rustc_driver::driver::phase_3_run_analysis_passes::{{closure}}::haccf5097991f72ff
  30:     0x7f0dbe8812b9 - rustc::ty::context::TyCtxt::create_and_enter::hc186c58b8fad7ff4
  31:     0x7f0dbe8ffe20 - rustc_driver::driver::compile_input::h44853ffed84a12cb
  32:     0x7f0dbe9450a2 - rustc_driver::run_compiler::hdc4bb0fcf7d0917a
  33:     0x7f0dbe849b4b - std::panicking::try::do_call::ha583797d32a865bd
  34:     0x7f0dbe57f89a - __rust_maybe_catch_panic
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libpanic_unwind/lib.rs:98
  35:     0x7f0dbe873852 - <F as alloc::boxed::FnBox<A>>::call_box::h6903719257a678be
  36:     0x7f0dbe5753d4 - std::sys::imp::thread::Thread::new::thread_start::h76badbf9b0ecaf58
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/liballoc/boxed.rs:615
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libstd/sys_common/thread.rs:21
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libstd/sys/unix/thread.rs:84
  37:     0x7f0db632c453 - start_thread
  38:     0x7f0dbe2397de - __GI___clone
  39:                0x0 - <unknown>

[petrochenkov]

This looks like a duplicate of #38919 and should be fixed in #39019.
Could you check the code on the latest nightly?

[iankronquist]

Looks like it's been fixed.