Immovable generator issue

[andreytkachenko]

compiler fails with error when try compile the code:

#![feature(generators, generator_trait, conservative_impl_trait)]

extern crate futures;

use std::ops::{ Generator };
use futures::{ Future, Async };

fn tmp() -> impl Future<Item = u32, Error = ()> {
    futures::future::ok(123)
}

fn gen() -> impl Generator<Yield = Async<u32>, Return = ()> {
    unsafe {static move || {
        let dist = {
            let mut future = tmp();

            loop  {
                match Future::poll(&mut future) {
                    Ok(Async::Ready(e)) => {
                        break Ok(e)
                    }

                    Ok(Async::NotReady) => {}

                    Err(e) => {
                        break Err(e)
                    }
                }

                yield Async::NotReady
            }
        }.unwrap();
        
        match (&dist,) {
            (tmp,) => (),
        }
    }}
}

fn main() {
    let mut g = gen();
    
    println!("{:?}", g.resume());
    
}

and the error message:

error: internal compiler error: librustc_mir/transform/generator.rs:461: Broken MIR: generator contains type u32 in MIR, but typeck only knows about {impl futures::Future, futures::Async<u32>, ()}
  --> src/main.rs:13:13
   |
13 |       unsafe {static move || {
   |  _____________^
14 | |         let dist = {
15 | |             let mut future = tmp();
16 | |
...  |
36 | |         }
37 | |     }}
   | |_____^

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 (a0dcecff9 2018-01-24) running on x86_64-unknown-linux-gnu

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

thread 'rustc' panicked at 'Box<Any>', librustc_errors/lib.rs:456:9
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
stack backtrace:
   0: std::sys::unix::backtrace::tracing::imp::unwind_backtrace
             at libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1: std::sys_common::backtrace::print
             at libstd/sys_common/backtrace.rs:68
             at libstd/sys_common/backtrace.rs:57
   2: std::panicking::default_hook::{{closure}}
             at libstd/panicking.rs:380
   3: std::panicking::default_hook
             at libstd/panicking.rs:390
   4: std::panicking::rust_panic_with_hook
             at libstd/panicking.rs:576
   5: std::panicking::begin_panic
   6: rustc_errors::Handler::span_bug
   7: rustc::session::opt_span_bug_fmt::{{closure}}
   8: rustc::ty::context::tls::with_opt
   9: rustc::session::span_bug_fmt
  10: <rustc_mir::transform::generator::StateTransform as rustc_mir::transform::MirPass>::run_pass
  11: rustc_mir::transform::optimized_mir::{{closure}}
  12: rustc_mir::transform::optimized_mir
  13: rustc::ty::maps::<impl rustc::ty::maps::queries::optimized_mir<'tcx>>::compute_result
  14: rustc::dep_graph::graph::DepGraph::with_task_impl
  15: rustc_errors::Handler::track_diagnostics
  16: rustc::ty::maps::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::cycle_check
  17: rustc::ty::maps::<impl rustc::ty::maps::queries::optimized_mir<'tcx>>::force
  18: rustc::ty::maps::<impl rustc::ty::maps::queries::optimized_mir<'tcx>>::try_get
  19: rustc::ty::maps::TyCtxtAt::optimized_mir
  20: rustc::ty::sty::ClosureSubsts::field_tys
  21: rustc_mir::borrow_check::nll::type_check::TypeChecker::typeck_mir
  22: rustc_mir::borrow_check::nll::type_check::type_check_internal
  23: rustc::ty::context::tls::enter
  24: rustc::infer::InferCtxtBuilder::enter
  25: <rustc_mir::borrow_check::nll::type_check::TypeckMir as rustc_mir::transform::MirPass>::run_pass
  26: rustc_mir::transform::mir_const::{{closure}}
  27: rustc_mir::transform::mir_const
  28: rustc::ty::maps::<impl rustc::ty::maps::queries::mir_const<'tcx>>::compute_result
  29: rustc::dep_graph::graph::DepGraph::with_task_impl
  30: rustc_errors::Handler::track_diagnostics
  31: rustc::ty::maps::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::cycle_check
  32: rustc::ty::maps::<impl rustc::ty::maps::queries::mir_const<'tcx>>::force
  33: rustc::ty::maps::<impl rustc::ty::maps::queries::mir_const<'tcx>>::try_get
  34: rustc::ty::maps::TyCtxtAt::mir_const
  35: rustc::ty::maps::<impl rustc::ty::context::TyCtxt<'a, 'tcx, 'lcx>>::mir_const
  36: rustc_mir::transform::mir_validated
  37: rustc::ty::maps::<impl rustc::ty::maps::queries::mir_validated<'tcx>>::compute_result
  38: rustc::dep_graph::graph::DepGraph::with_task_impl
  39: rustc_errors::Handler::track_diagnostics
  40: rustc::ty::maps::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::cycle_check
  41: rustc::ty::maps::<impl rustc::ty::maps::queries::mir_validated<'tcx>>::force
  42: rustc::ty::maps::<impl rustc::ty::maps::queries::mir_validated<'tcx>>::try_get
  43: rustc::ty::maps::TyCtxtAt::mir_validated
  44: rustc::ty::maps::<impl rustc::ty::context::TyCtxt<'a, 'tcx, 'lcx>>::mir_validated
  45: rustc_borrowck::borrowck::borrowck
  46: rustc::dep_graph::graph::DepGraph::with_task_impl
  47: rustc_errors::Handler::track_diagnostics
  48: rustc::ty::maps::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::cycle_check
  49: rustc::ty::maps::<impl rustc::ty::maps::queries::borrowck<'tcx>>::force
  50: rustc::ty::maps::<impl rustc::ty::maps::queries::borrowck<'tcx>>::try_get
  51: rustc::ty::maps::TyCtxtAt::borrowck
  52: rustc::ty::maps::<impl rustc::ty::context::TyCtxt<'a, 'tcx, 'lcx>>::borrowck
  53: rustc_borrowck::borrowck::check_crate
  54: <std::thread::local::LocalKey<T>>::with
  55: <std::thread::local::LocalKey<T>>::with
  56: rustc_driver::driver::compile_input
  57: rustc_driver::run_compiler

[PaulGrandperrin]

I'm also hitting this bug