Rustc panics during build with `cannot convert `ReScope(Destruction(847))` to a region vid`

[nemosupremo]

I was trying to compile my application - and unfortunately I've made a large number of changes between the last time I could get it to build so figuring out that is going on will be tough (I'm also newer with Rust). I'll take a look at #51351 and see if I have any similar constructs in my program

I am simply running this command:

RUST_BACKTRACE=1 cargo build

Meta

rustc --version --verbose:

rustc 1.34.2 (6c2484dc3 2019-05-13)
binary: rustc
commit-hash: 6c2484dc3c532c052f159264e970278d8b77cdc9
commit-date: 2019-05-13
host: x86_64-apple-darwin
release: 1.34.2
LLVM version: 8.0

Backtrace:

error: internal compiler error: src/librustc_mir/borrow_check/nll/universal_regions.rs:745: cannot convert `ReScope(Destruction(847))` to a region vid

thread 'rustc' panicked at 'Box<Any>', src/librustc_errors/lib.rs:620:9
stack backtrace:
   0: std::sys::unix::backtrace::tracing::imp::unwind_backtrace
   1: std::sys_common::backtrace::_print
   2: std::panicking::default_hook::{{closure}}
   3: std::panicking::default_hook
   4: rustc::util::common::panic_hook
   5: std::panicking::rust_panic_with_hook
   6: std::panicking::begin_panic
   7: rustc_errors::Handler::bug
   8: rustc::util::bug::opt_span_bug_fmt::{{closure}}
   9: rustc::ty::context::tls::with_opt::{{closure}}
  10: rustc::ty::context::tls::with_context_opt
  11: rustc::ty::context::tls::with_opt
  12: rustc::util::bug::opt_span_bug_fmt
  13: rustc::util::bug::bug_fmt
  14: rustc_mir::borrow_check::nll::universal_regions::UniversalRegionIndices::to_region_vid::{{closure}}
  15: rustc_mir::borrow_check::nll::universal_regions::UniversalRegionIndices::to_region_vid
  16: rustc_mir::borrow_check::nll::type_check::constraint_conversion::ConstraintConversion::convert_all
  17: rustc_mir::borrow_check::nll::type_check::TypeChecker::prove_predicate
  18: rustc_mir::borrow_check::nll::type_check::TypeChecker::normalize_and_prove_instantiated_predicates
  19: <rustc_mir::borrow_check::nll::type_check::TypeVerifier<'a, 'b, 'gcx, 'tcx> as rustc::mir::visit::Visitor<'tcx>>::visit_constant
  20: <rustc_mir::borrow_check::nll::type_check::TypeVerifier<'a, 'b, 'gcx, 'tcx> as rustc::mir::visit::Visitor<'tcx>>::visit_mir
  21: rustc_mir::borrow_check::nll::type_check::type_check
  22: rustc_mir::borrow_check::nll::compute_regions
  23: rustc_mir::borrow_check::do_mir_borrowck
  24: rustc::ty::context::GlobalCtxt::enter_local
  25: rustc_mir::borrow_check::mir_borrowck
  26: rustc::ty::query::__query_compute::mir_borrowck
  27: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors<'tcx> for rustc::ty::query::queries::mir_borrowck<'tcx>>::compute
  28: rustc::dep_graph::graph::DepGraph::with_task_impl
  29: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::get_query
  30: rustc::ty::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::par_body_owners
  31: rustc::util::common::time
  32: <std::thread::local::LocalKey<T>>::with
  33: rustc::ty::context::TyCtxt::create_and_enter
  34: rustc_driver::driver::compile_input
  35: rustc_driver::run_compiler_with_pool
  36: <scoped_tls::ScopedKey<T>>::set
  37: rustc_driver::run_compiler
  38: syntax::with_globals
  39: __rust_maybe_catch_panic
  40: <F as alloc::boxed::FnBox<A>>::call_box
  41: std::sys::unix::thread::Thread::new::thread_start
  42: _pthread_body
  43: _pthread_start
query stack during panic:
#0 [mir_borrowck] processing `run`
end of query stack
error: aborting due to previous error

[Centril]

cc @matthewjasper @pnkfelix

[matthewjasper]

Does this still fail on nightly/beta? (1.36.0)

[nemosupremo]

I apologize - I don't think this report is very useful. I should have tested nightly first. What ended up happening is I decided to comment out modules, one by one in my code base to see if I could isolate the piece of code that was causing this error. Once I commented out the first module, I began getting borrow check errors in another separate module preventing my from compiling the program (basic stuff like using the reference in two separate closures). Once I fixed the problem module, my program compiled. I then thought the error was in the first module I commented it, but to make sure I uncommented out the module and now my program compiles :(. I neglected to save the code base which caused this error and I can't seem to Ctrl+Z enough to reproduce it.

[matthewjasper]

Closing as inactionable.
@nemosupremo please open a new issue of you run into this again.