Broken MIR with generators

[raviqqe]

Similar to #44184 but I'm not sure if they have the same cause or not.

#![feature(generators)]

fn main() {
    let x = (|_| {},);

    || {
        let x = x;

        x.0({
            yield;
        });
    };
}

Build log:

> RUST_BACKTRACE=full cargo build               
   Compiling rust-async-await-examples v0.1.0 (file:///home/raviqqe/src/github.com/raviqqe/rust-async-await-examples)
error: internal compiler error: librustc_mir/transform/generator.rs:495: Broken MIR: generator contains type &[closure@src/main.rs:4:14: 4:20] in MIR, but typeck only knows about {([closure@src/main.rs:4:14
: 4:20],), ()}                                                                                                                                
  --> src/main.rs:6:5                                                                                   
   |                                                                                                                                             
6  | /     || {                                                     
7  | |         let x = x;                                                                                                     
8  | |                                                                               
9  | |         x.0({                                                                  
10 | |             yield;                                                         
11 | |         });                                                       
12 | |     };                                                   
   | |_____^                                                                                  
                                           
thread 'rustc' panicked at 'Box<Any>', librustc_errors/lib.rs:482:9
stack backtrace:                                                             
   0: 0xb0df70b3 - std::sys::unix::backtrace::tracing::imp::unwind_backtrace::h0e675f09d0ea6efb
                       at libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1: 0xb0dee0d7 - std::sys_common::backtrace::_print::hab188ab7e2264fa5
                       at libstd/sys_common/backtrace.rs:71
   2: 0xb0df3b63 - std::panicking::default_hook::{{closure}}::h6de89401c7cfba88
                       at libstd/sys_common/backtrace.rs:59
                       at libstd/panicking.rs:380
   3: 0xb0df37a3 - std::panicking::default_hook::h77c5e57344ea1784                                               
                       at libstd/panicking.rs:396
   4: 0xb0df402b - std::panicking::rust_panic_with_hook::h25665bb68f9c33fc                
                       at libstd/panicking.rs:576
   5: 0xb03f0eff - std::panicking::begin_panic::hf4ea98dd652225c7
   6: 0xb03eb53b - rustc_errors::Handler::span_bug::he0e663394c58146e
   7: 0xb042ddc3 - rustc::session::opt_span_bug_fmt::{{closure}}::haf4055a290286ee8
   8: 0xb042dc97 - rustc::session::span_bug_fmt::hee67d12eca98dbd4
   9: 0xb0531463 - <rustc_mir::transform::generator::StateTransform as rustc_mir::transform::MirPass>::run_pass::had9d05b7ba1db7f2
  10: 0xb058f9c7 - rustc_mir::transform::optimized_mir::{{closure}}::h7ce2e52ae25ea6aa
  11: 0xb053a543 - rustc_mir::transform::optimized_mir::h445785565316d102
  12: 0xafe5977b - rustc::dep_graph::graph::DepGraph::with_task_impl::h3a29a7f629570871
  13: 0xb010f97b - rustc::ty::maps::<impl rustc::ty::maps::queries::optimized_mir<'tcx>>::force::h7b56c39bb8303000
  14: 0xb01100bf - rustc::ty::maps::<impl rustc::ty::maps::queries::optimized_mir<'tcx>>::try_get::h5633b7bfd050e56c
  15: 0xb01f8aa3 - rustc::ty::maps::TyCtxtAt::optimized_mir::h25db50b902f2c8d6
  16: 0xb01f618f - rustc::ty::maps::<impl rustc::ty::context::TyCtxt<'a, 'tcx, 'lcx>>::optimized_mir::h5882e75dd3b20368
  17: 0xb0500c2b - rustc_mir::shim::make_shim::hc8d2a6409593d7a0
  18: 0xafe6959b - rustc::dep_graph::graph::DepGraph::with_task_impl::h978a41a5ecd39563
  19: 0xb013917b - rustc::ty::maps::<impl rustc::ty::maps::queries::mir_shims<'tcx>>::force::hb539e45b421eb998
  20: 0xb0139a37 - rustc::ty::maps::<impl rustc::ty::maps::queries::mir_shims<'tcx>>::try_get::h89de7c175fc7a084
  21: 0xb01f9a77 - rustc::ty::maps::TyCtxtAt::mir_shims::hfd281ebae9f5e7f2
  22: 0xb0073247 - rustc::ty::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::instance_mir::h3beb5ac11f8f3252
  23: 0xb057eb9b - rustc_mir::monomorphize::collector::collect_items_rec::hedb90edba41840ef
  24: 0xb057f6f7 - rustc_mir::monomorphize::collector::collect_items_rec::hedb90edba41840ef
  25: 0xb057d8a3 - rustc_mir::monomorphize::collector::collect_crate_mono_items::h6c068d30b04615ad
  26: 0xac0f2bcb - rustc_trans::base::collect_and_partition_translation_items::he0b50da974cf616b
  27: 0xafe53203 - rustc::dep_graph::graph::DepGraph::with_task_impl::h175249ac280b602a
  28: 0xb01d60a3 - rustc::ty::maps::<impl rustc::ty::maps::queries::collect_and_partition_translation_items<'tcx>>::force::hc7f3cedff79b2e40
  29: 0xb01d687f - rustc::ty::maps::<impl rustc::ty::maps::queries::collect_and_partition_translation_items<'tcx>>::try_get::hc14bee7a47d847cc
  30: 0xb01fdb47 - rustc::ty::maps::TyCtxtAt::collect_and_partition_translation_items::hfe44aa4a7c757c20
  31: 0xb01f725b - rustc::ty::maps::<impl rustc::ty::context::TyCtxt<'a, 'tcx, 'lcx>>::collect_and_partition_translation_items::h3b09465602c4412e
  32: 0xac0ef0d3 - rustc_trans::base::trans_crate::h7d2492fa073d403b
  33: 0xac14bb93 - <rustc_trans::LlvmTransCrate as rustc_trans_utils::trans_crate::TransCrate>::trans_crate::h0375a1b8d27d3d45
  34: 0xb0f788cb - rustc_driver::driver::phase_4_translate_to_llvm::h1ef6b9e392ff1ffb
  35: 0xb0f73133 - rustc_driver::driver::compile_input::{{closure}}::h0c654196b84b4f55
  36: 0xb0f08637 - rustc::ty::context::TyCtxt::create_and_enter::h93711c24bd13b118
  37: 0xb0f71833 - rustc_driver::driver::compile_input::hd3b772952eb5ec6d
  38: 0xb0f88f4f - rustc_driver::run_compiler::hfc7537ef811b8b4e
  39: 0xb0ebf447 - std::sys_common::backtrace::__rust_begin_short_backtrace::h12654191a5e25e74
  40: 0xb0e085ef - __rust_maybe_catch_panic
                       at libpanic_unwind/lib.rs:102
  41: 0xb0ef5327 - <F as alloc::boxed::FnBox<A>>::call_box::h0c2113b4a6bfc4a2
  42: 0xb0e01bb7 - std::sys::unix::thread::Thread::new::thread_start::hb2b6d7bbaa9b84de
                       at /checkout/src/liballoc/boxed.rs:798
                       at libstd/sys_common/thread.rs:24
                       at libstd/sys/unix/thread.rs:90

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: rustc 1.25.0-nightly (29c8276ce 2018-02-07) running on armv7-unknown-linux-gnueabihf

error: Could not compile `rust-async-await-examples`.

To learn more, run the command again with --verbose.

Workaround

Define a temporary variable explicitly.

#![feature(generators)]

fn main() {
    let x = (|_| {},);

    || {
        let x = x;

        let f = x.0;

        f({
            yield;
        });
    };
}

Meta

rustc --version --verbose

rustc 1.25.0-nightly (29c8276ce 2018-02-07)
binary: rustc
commit-hash: 29c8276cee4a0eab7e0634ff25c6b47bd9f87c6c
commit-date: 2018-02-07
host: armv7-unknown-linux-gnueabihf
release: 1.25.0-nightly
LLVM version: 4.0

cat /etc/os-release

NAME="Ubuntu"
VERSION="16.04.3 LTS (Xenial Xerus)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 16.04.3 LTS"
VERSION_ID="16.04"
HOME_URL="http://www.ubuntu.com/"
SUPPORT_URL="http://help.ubuntu.com/"
BUG_REPORT_URL="http://bugs.launchpad.net/ubuntu/"
VERSION_CODENAME=xenial
UBUNTU_CODENAME=xenial

uname -a

Linux localhost 3.14.0 #1 SMP PREEMPT Mon Jan 8 23:10:11 PST 2018 armv7l GNU/Linux

[eddyb]

cc @Zoxc @nikomatsakis