internal compiler error: expected object type

[tilpner]

Upon fixing an old project to compile under the latest Rust, I encountered:

/tmp/redox-tween/src/lib.rs:100:9: 100:30 error: internal compiler error: expected object type
/tmp/redox-tween/src/lib.rs:100         CellAccess::new(self) as Access<T>
                                        ^~~~~~~~~~~~~~~~~~~~~

Backtrace:

task 'rustc' failed at 'Box<Any>', /home/rustbuild/src/rust-buildbot/slave/nightly-linux/build/src/libsyntax/diagnostic.rs:113
stack backtrace:
   1:     0x7f68f2c93f00 - rt::backtrace::imp::write::hb40e767174eadc9blLq
   2:     0x7f68f2c970c0 - failure::on_fail::hab6209505fea7a58N6q
   3:     0x7f68f738af80 - unwind::begin_unwind_inner::h3a7e8417aad82c7eMTd
   4:     0x7f68f3a41450 - unwind::begin_unwind::h2392538768877619269
   5:     0x7f68f3a413d0 - diagnostic::SpanHandler::span_bug::he7781fbb688ed22cudF
   6:     0x7f68f7ba3650 - driver::session::Session::span_bug::h5c6ded0cb05eac01TPx
   7:     0x7f68f7ef83d0 - middle::typeck::check::vtable2::check_object_cast::ha7b33ce543eddd8aJ2K
   8:     0x7f68f7f60fa0 - middle::typeck::check::check_cast::h6b4ba42c32c12f0fRXT
   9:     0x7f68f7f8a2e0 - middle::typeck::check::check_expr_with_unifier::hbcb91288bec55a2csXV
  10:     0x7f68f7f52700 - middle::typeck::check::check_block_with_expected::h2574fbf2342efdb2hbY
  11:     0x7f68f7f4d890 - middle::typeck::check::check_fn::h41bca712826f247fmDS
  12:     0x7f68f7f4d6a0 - middle::typeck::check::check_bare_fn::h854b4341f0f8841bpsS
  13:     0x7f68f7f568a0 - middle::typeck::check::check_method_body::h0680613c351d794bLaT
  14:     0x7f68f7f47620 - middle::typeck::check::check_item::he10ec73ffea798b14ZS
  15:     0x7f68f7f4cf40 - middle::typeck::check::check_item_types::h757d0292ac6a701dnrS
  16:     0x7f68f79f37d0 - util::common::time::h7040980569714169789
  17:     0x7f68f81f6250 - middle::typeck::check_crate::h3c78e9fb1a6da400cDk
  18:     0x7f68f825fc10 - driver::driver::phase_3_run_analysis_passes::h01e80bc9274a9fc096w
  19:     0x7f68f825af50 - driver::driver::compile_input::h644c4bcdb8d4fa416Nw
  20:     0x7f68f82dce40 - driver::run_compiler::hd9154f69e0f25652kFA
  21:     0x7f68f82dcd20 - driver::main_args::closure.146572
  22:     0x7f68f7a0ce70 - task::TaskBuilder<S>::try_future::closure.101814
  23:     0x7f68f7a0cc60 - task::TaskBuilder<S>::spawn_internal::closure.101785
  24:     0x7f68f76da540 - task::spawn_opts::closure.8457
  25:     0x7f68f73e1390 - rust_try_inner
  26:     0x7f68f73e1380 - rust_try
  27:     0x7f68f7388580 - unwind::try::haa9a6e4d3a3bf10cuId
  28:     0x7f68f73883e0 - task::Task::run::h18e39631c20de002cYc
  29:     0x7f68f76da2b0 - task::spawn_opts::closure.8397
  30:     0x7f68f7389fd0 - thread::thread_start::hfdbefd9910b77f41rid
  31:     0x7f68f203c250 - start_thread
  32:     0x7f68f70623b9 - clone
  33:                0x0 - <unknown>

Reproduce with

git clone https://github.com/hoeppnertill/redox-tween && cd redox-tween && git reset --hard bba1bddfe7f70151aa65bf1cbbb5550cfa1b9e81 && env RUST_BACKTRACE=1 cargo build

(Oh, and there's no need to criticize the code quality yet. Maybe when it's refactored...)

[bkoropoff]

Reduced test case:

fn main() {
    let _foo = 5u as std::fmt::Show;
}

This looks DST-related to me. cc @nick29581

[bkoropoff]

I'll look into fixing this

[alexcrichton]

Closed by #17598