Closed
Description
The compiler panics when referencing a captured variable inside a nested closure.
This happens on the playground nightly build "rustc 1.42.0-nightly (ed33453 2019-12-25) running on x86_64-unknown-linux-gnu" as well as MSVC stable "stable-x86_64-pc-windows-msvc updated - rustc 1.40.0 (73528e3 2019-12-16)".
This issue feels awfully related to #67252. But from what I gathered, its fix (#67289) went live a couple of days ago and should be in the playground version 1.42.0-nightly (ed33453 2019-12-25).
I tried this code (minimal-ish example):
https://gist.github.com/rust-play/362fc228ed152a41e5b216603e7c236f
fn main() {
let _ = vec![0]
.iter()
.flat_map(|a| vec![0].iter().map(|_| &a))
.collect::<Vec<_>>();
}I expected to see this happen: No compiler errors or warnings and especially no crash.
Meta
rustc --version --verbose:
rustc 1.40.0 (73528e3 2019-12-16)
binary: rustc
commit-hash: 73528e3
commit-date: 2019-12-16
host: x86_64-pc-windows-msvc
release: 1.40.0
LLVM version: 9.0
Backtrace (from the playground):
Standard Error
Compiling playground v0.0.1 (/playground)
error: internal compiler error: src/librustc/hir/map/mod.rs:955: no name for expr |a| <[_]>::into_vec(box [0]).iter().map(|_| &a) (hir_id=HirId { owner: DefIndex(3), local_id: 40 })
thread 'rustc' panicked at 'Box<Any>', src/librustc_errors/lib.rs:895:9
stack backtrace:
0: backtrace::backtrace::libunwind::trace
at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.40/src/backtrace/libunwind.rs:88
1: backtrace::backtrace::trace_unsynchronized
at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.40/src/backtrace/mod.rs:66
2: std::sys_common::backtrace::_print_fmt
at src/libstd/sys_common/backtrace.rs:77
3: <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt
at src/libstd/sys_common/backtrace.rs:59
4: core::fmt::write
at src/libcore/fmt/mod.rs:1057
5: std::io::Write::write_fmt
at src/libstd/io/mod.rs:1426
6: std::sys_common::backtrace::_print
at src/libstd/sys_common/backtrace.rs:62
7: std::sys_common::backtrace::print
at src/libstd/sys_common/backtrace.rs:49
8: std::panicking::default_hook::{{closure}}
at src/libstd/panicking.rs:195
9: std::panicking::default_hook
at src/libstd/panicking.rs:215
10: rustc_driver::report_ice
11: std::panicking::rust_panic_with_hook
at src/libstd/panicking.rs:476
12: std::panicking::begin_panic
13: rustc_errors::HandlerInner::bug
14: rustc_errors::Handler::bug
15: rustc::util::bug::opt_span_bug_fmt::{{closure}}
16: rustc::ty::context::tls::with_opt::{{closure}}
17: rustc::ty::context::tls::with_opt
18: rustc::util::bug::opt_span_bug_fmt
19: rustc::util::bug::bug_fmt
20: rustc::hir::map::Map::name
21: rustc_mir::borrow_check::diagnostics::conflict_errors::<impl rustc_mir::borrow_check::MirBorrowckCtxt>::report_borrowed_value_does_not_live_long_enough
22: rustc_mir::borrow_check::MirBorrowckCtxt::check_for_invalidation_at_exit
23: rustc_mir::borrow_check::flows::Flows::with_outgoing_borrows
24: <rustc_mir::borrow_check::MirBorrowckCtxt as rustc_mir::dataflow::DataflowResultsConsumer>::visit_terminator_entry
25: rustc_mir::borrow_check::do_mir_borrowck
26: rustc::ty::context::GlobalCtxt::enter_local
27: rustc_mir::borrow_check::mir_borrowck
28: rustc::ty::query::__query_compute::mir_borrowck
29: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::mir_borrowck>::compute
30: rustc::dep_graph::graph::DepGraph::with_task_impl
31: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
32: rustc_mir::borrow_check::type_check::TypeChecker::check_rvalue
33: rustc_mir::borrow_check::type_check::TypeChecker::typeck_mir
34: rustc_mir::borrow_check::type_check::type_check
35: rustc_mir::borrow_check::nll::compute_regions
36: rustc_mir::borrow_check::do_mir_borrowck
37: rustc::ty::context::GlobalCtxt::enter_local
38: rustc_mir::borrow_check::mir_borrowck
39: rustc::ty::query::__query_compute::mir_borrowck
40: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::mir_borrowck>::compute
41: rustc::dep_graph::graph::DepGraph::with_task_impl
42: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
43: rustc::ty::<impl rustc::ty::context::TyCtxt>::par_body_owners
44: rustc_interface::passes::analysis
45: rustc::ty::query::__query_compute::analysis
46: rustc::dep_graph::graph::DepGraph::with_task_impl
47: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
48: rustc::ty::context::tls::enter_global
49: rustc_interface::interface::run_compiler_in_existing_thread_pool
50: std::thread::local::LocalKey<T>::with
51: scoped_tls::ScopedKey<T>::set
52: syntax::with_globals
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
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 1.42.0-nightly (ed33453a3 2019-12-25) running on x86_64-unknown-linux-gnu
note: compiler flags: -C codegen-units=1 -C debuginfo=2 --crate-type bin
note: some of the compiler flags provided by cargo are hidden
query stack during panic:
#0 [mir_borrowck] processing `main::{{closure}}#0`
#1 [mir_borrowck] processing `main`
#2 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to previous error
error: could not compile `playground`.
To learn more, run the command again with --verbose.