ICE on improperly implemented TryFrom

[sbosnick]

rustc lib.rs --edition=2018 --crate-type lib produces an ICE for the code given below. This code should produce
an error (the TryFrom implementation is missing associated items).

Code

(UPDATED: Here's MCVE: #74047 (comment))

use std::convert::{TryFrom, TryInto};
use std::io;
use std::os::unix::net::UnixStream;
use std::path::Path;

pub struct MyStream { }

impl MyStream {
    pub async fn connect(path: impl AsRef<Path>) -> io::Result<MyStream> {
        let socket = Socket::new()?;

        let stream: MyStream = socket.into_unix_stream().try_into()?;

        loop {}
    }

}

impl TryFrom<UnixStream> for MyStream {
}

pub struct Socket { }

impl Socket {
    pub fn new() -> io::Result<Socket> {
        loop {}
    }

    pub fn into_unix_stream(self) -> UnixStream {
        loop {}
    }
}

Meta

rustc --version --verbose:

rustc 1.44.1 (c7087fe00 2020-06-17)
binary: rustc
commit-hash: c7087fe00d2ba919df1d813c040a5d47e43b0fe7
commit-date: 2020-06-17
host: x86_64-unknown-linux-gnu
release: 1.44.1
LLVM version: 9.0

Error also occurs on beta and nightly.

Error output

thread 'rustc' panicked at 'no entry found for key', src/librustc_mir_build/build/mod.rs:345:9
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

error: internal compiler error: unexpected panic

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 1.44.1 (c7087fe00 2020-06-17) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type lib

error: internal compiler error: cat_expr Errd
  --> src/lib.rs:12:32
   |
12 |         let stream: MyStream = socket.into_unix_stream().try_into()?;
   |                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: internal compiler error: cat_expr Errd
  --> src/lib.rs:12:32
   |
12 |         let stream: MyStream = socket.into_unix_stream().try_into()?;
   |                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: internal compiler error: cat_expr Errd
  --> src/lib.rs:12:68
   |
12 |         let stream: MyStream = socket.into_unix_stream().try_into()?;
   |                                                                    ^

thread 'rustc' panicked at 'no errors encountered even though `delay_span_bug` issued', src/librustc_errors/lib.rs:366:17
stack backtrace:
   0:     0x7f129fb65ab4 - backtrace::backtrace::libunwind::trace::h812748238d609e46
                               at /cargo/registry/src/gh.neting.cc-1ecc6299db9ec823/backtrace-0.3.46/src/backtrace/libunwind.rs:86
   1:     0x7f129fb65ab4 - backtrace::backtrace::trace_unsynchronized::h7c97e818aebf09c8
                               at /cargo/registry/src/gh.neting.cc-1ecc6299db9ec823/backtrace-0.3.46/src/backtrace/mod.rs:66
   2:     0x7f129fb65ab4 - std::sys_common::backtrace::_print_fmt::h60d914263b0ccd71
                               at src/libstd/sys_common/backtrace.rs:78
   3:     0x7f129fb65ab4 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::hf78227137afc7565
                               at src/libstd/sys_common/backtrace.rs:59
   4:     0x7f129fba3bac - core::fmt::write::h543cdf60775f89bf
                               at src/libcore/fmt/mod.rs:1069
   5:     0x7f129fb574d3 - std::io::Write::write_fmt::h0c7f3ce24c679426
                               at src/libstd/io/mod.rs:1504
   6:     0x7f129fb6aab5 - std::sys_common::backtrace::_print::h80e55e24be231368
                               at src/libstd/sys_common/backtrace.rs:62
   7:     0x7f129fb6aab5 - std::sys_common::backtrace::print::h3b197b9c1261c865
                               at src/libstd/sys_common/backtrace.rs:49
   8:     0x7f129fb6aab5 - std::panicking::default_hook::{{closure}}::ha6c807149ce20f8f
                               at src/libstd/panicking.rs:198
   9:     0x7f129fb6a7f2 - std::panicking::default_hook::he49a9c12e358cc45
                               at src/libstd/panicking.rs:218
  10:     0x7f12a0107923 - rustc_driver::report_ice::h303988fb5b9997d4
  11:     0x7f129fb6b235 - std::panicking::rust_panic_with_hook::h93f74f5ef2f71f31
                               at src/libstd/panicking.rs:515
  12:     0x7f12a28f125e - std::panicking::begin_panic::hc68bee93462232be
  13:     0x7f12a292aa12 - <rustc_errors::HandlerInner as core::ops::drop::Drop>::drop::h1f879c4351fba67a
  14:     0x7f12a024c166 - core::ptr::drop_in_place::h4d80a69fc5b8b26d
  15:     0x7f12a0254536 - <alloc::rc::Rc<T> as core::ops::drop::Drop>::drop::h11773fcd49f47beb
  16:     0x7f12a027801d - core::ptr::drop_in_place::ha136f12949be28b0
  17:     0x7f12a025ea45 - rustc_interface::interface::run_compiler_in_existing_thread_pool::h1fe14dfeda5e7ff8
  18:     0x7f12a011152d - scoped_tls::ScopedKey<T>::set::h7ef5c845735c44d5
  19:     0x7f12a010e3d4 - rustc_ast::attr::with_globals::h80403999168944fb
  20:     0x7f12a0119a92 - std::sys_common::backtrace::__rust_begin_short_backtrace::h65e906f83ddca1d2
  21:     0x7f12a026140e - core::ops::function::FnOnce::call_once{{vtable.shim}}::h4a7aeea8942a4e2c
  22:     0x7f129fb7b2aa - <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once::hf207c3654ee300a0
                               at /rustc/c7087fe00d2ba919df1d813c040a5d47e43b0fe7/src/liballoc/boxed.rs:1008
  23:     0x7f129fb7b2aa - <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once::h66e0c6190e34816b
                               at /rustc/c7087fe00d2ba919df1d813c040a5d47e43b0fe7/src/liballoc/boxed.rs:1008
  24:     0x7f129fb7b2aa - std::sys::unix::thread::Thread::new::thread_start::h30687bc0b1c3cd55
                               at src/libstd/sys/unix/thread.rs:87
  25:     0x7f129fabb609 - start_thread
                               at /build/glibc-YYA7BZ/glibc-2.31/nptl/pthread_create.c:477
  26:     0x7f129f9cf103 - __clone
  27:                0x0 - <unknown>

error: internal compiler error: unexpected panic

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 1.44.1 (c7087fe00 2020-06-17) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type lib

thread panicked while panicking. aborting.
Illegal instruction (core dumped)

Backtrace

hread 'rustc' panicked at 'no entry found for key', src/librustc_mir_build/build/mod.rs:345:9
stack backtrace:
   0: backtrace::backtrace::libunwind::trace
             at /cargo/registry/src/gh.neting.cc-1ecc6299db9ec823/backtrace-0.3.46/src/backtrace/libunwind.rs:86
   1: backtrace::backtrace::trace_unsynchronized
             at /cargo/registry/src/gh.neting.cc-1ecc6299db9ec823/backtrace-0.3.46/src/backtrace/mod.rs:66
   2: std::sys_common::backtrace::_print_fmt
             at src/libstd/sys_common/backtrace.rs:78
   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:1069
   5: std::io::Write::write_fmt
             at src/libstd/io/mod.rs:1504
   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:198
   9: std::panicking::default_hook
             at src/libstd/panicking.rs:218
  10: rustc_driver::report_ice
  11: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:515
  12: rust_begin_unwind
             at src/libstd/panicking.rs:419
  13: core::panicking::panic_fmt
             at src/libcore/panicking.rs:111
  14: core::option::expect_failed
             at src/libcore/option.rs:1260
  15: rustc_mir_build::build::expr::as_place::<impl rustc_mir_build::build::Builder>::expr_as_place
  16: rustc_mir_build::build::expr::as_place::<impl rustc_mir_build::build::Builder>::as_place
  17: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
  18: rustc_mir_build::build::expr::as_temp::<impl rustc_mir_build::build::Builder>::expr_as_temp
  19: rustc_mir_build::build::expr::as_operand::<impl rustc_mir_build::build::Builder>::expr_as_operand
  20: rustc_mir_build::build::expr::as_operand::<impl rustc_mir_build::build::Builder>::as_call_operand
  21: rustc_mir_build::build::expr::as_operand::<impl rustc_mir_build::build::Builder>::as_call_operand
  22: <core::iter::adapters::Map<I,F> as core::iter::traits::iterator::Iterator>::fold
  23: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
  24: rustc_mir_build::build::expr::as_temp::<impl rustc_mir_build::build::Builder>::expr_as_temp
  25: rustc_mir_build::build::expr::as_operand::<impl rustc_mir_build::build::Builder>::expr_as_operand
  26: rustc_mir_build::build::expr::as_operand::<impl rustc_mir_build::build::Builder>::as_call_operand
  27: rustc_mir_build::build::expr::as_operand::<impl rustc_mir_build::build::Builder>::as_call_operand
  28: <core::iter::adapters::Map<I,F> as core::iter::traits::iterator::Iterator>::fold
  29: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
  30: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
  31: rustc_mir_build::build::scope::<impl rustc_mir_build::build::Builder>::break_scope
  32: rustc_mir_build::build::expr::stmt::<impl rustc_mir_build::build::Builder>::stmt_expr
  33: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
  34: rustc_mir_build::build::expr::as_temp::<impl rustc_mir_build::build::Builder>::expr_as_temp
  35: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
  36: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
  37: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
  38: rustc_mir_build::build::scope::<impl rustc_mir_build::build::Builder>::in_scope
  39: <core::iter::adapters::Map<I,F> as core::iter::traits::iterator::Iterator>::fold
  40: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
  41: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
  42: rustc_mir_build::build::block::<impl rustc_mir_build::build::Builder>::ast_block_stmts
  43: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
  44: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
  45: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
  46: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
  47: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
  48: rustc_mir_build::build::block::<impl rustc_mir_build::build::Builder>::ast_block_stmts
  49: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
  50: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
  51: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
  52: rustc_mir_build::build::construct_fn
  53: rustc_infer::infer::InferCtxtBuilder::enter
  54: rustc_mir_build::build::mir_built
  55: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::mir_built>::compute
  56: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  57: rustc_query_system::query::plumbing::get_query
  58: rustc_mir::transform::check_unsafety::unsafety_check_result
  59: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::unsafety_check_result>::compute
  60: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  61: rustc_query_system::query::plumbing::get_query
  62: <rustc_mir::transform::check_unsafety::UnsafetyChecker as rustc_middle::mir::visit::Visitor>::visit_rvalue
  63: <rustc_mir::transform::check_unsafety::UnsafetyChecker as rustc_middle::mir::visit::Visitor>::visit_statement
  64: rustc_mir::transform::check_unsafety::unsafety_check_result
  65: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::unsafety_check_result>::compute
  66: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  67: rustc_query_system::query::plumbing::get_query
  68: rustc_mir::transform::mir_const
  69: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::mir_const>::compute
  70: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  71: rustc_query_system::query::plumbing::get_query
  72: rustc_mir::transform::mir_validated
  73: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::mir_validated>::compute
  74: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  75: rustc_query_system::query::plumbing::get_query
  76: rustc_mir::borrow_check::mir_borrowck
  77: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::mir_borrowck>::compute
  78: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  79: rustc_query_system::query::plumbing::get_query
  80: rustc_typeck::collect::type_of::type_of
  81: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  82: rustc_query_system::query::plumbing::get_query
  83: rustc_middle::ty::util::<impl rustc_middle::ty::context::TyCtxt>::try_expand_impl_trait_type::OpaqueTypeExpander::expand_opaque_ty
  84: rustc_middle::ty::util::<impl rustc_middle::ty::context::TyCtxt>::try_expand_impl_trait_type
  85: rustc_typeck::check::check_item_type
  86: rustc_middle::hir::map::Map::visit_item_likes_in_module
  87: rustc_typeck::check::check_mod_item_types
  88: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::check_mod_item_types>::compute
  89: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  90: rustc_query_system::query::plumbing::get_query
  91: rustc_query_system::query::plumbing::ensure_query
  92: rustc_typeck::check_crate
  93: rustc_interface::passes::analysis
  94: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::analysis>::compute
  95: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  96: rustc_query_system::query::plumbing::get_query
  97: rustc_middle::ty::context::tls::enter_global
  98: rustc_interface::interface::run_compiler_in_existing_thread_pool
  99: scoped_tls::ScopedKey<T>::set
 100: rustc_ast::attr::with_globals
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

error: internal compiler error: unexpected panic

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 1.44.1 (c7087fe00 2020-06-17) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type lib

query stack during panic:
#0 [mir_built] building MIR for
#1 [unsafety_check_result] unsafety-checking `MyStream::connect::{{closure}}#0`
#2 [unsafety_check_result] unsafety-checking `MyStream::connect`
#3 [mir_const] processing `MyStream::connect`
#4 [mir_validated] processing `MyStream::connect`
#5 [mir_borrowck] borrow-checking `MyStream::connect`
#6 [type_of] processing `MyStream::connect::{{opaque}}#0`
#7 [check_mod_item_types] checking item types in top-level module
#8 [analysis] running analysis passes on this crate
end of query stack
error: internal compiler error: cat_expr Errd
  --> src/lib.rs:12:32
   |
12 |         let stream: MyStream = socket.into_unix_stream().try_into()?;
   |                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: internal compiler error: cat_expr Errd
  --> src/lib.rs:12:32
   |
12 |         let stream: MyStream = socket.into_unix_stream().try_into()?;
   |                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: internal compiler error: cat_expr Errd
  --> src/lib.rs:12:68
   |
12 |         let stream: MyStream = socket.into_unix_stream().try_into()?;
   |                                                                    ^

thread 'rustc' panicked at 'no errors encountered even though `delay_span_bug` issued', src/librustc_errors/lib.rs:366:17
stack backtrace:
   0:     0x7f2c1885cab4 - backtrace::backtrace::libunwind::trace::h812748238d609e46
                               at /cargo/registry/src/gh.neting.cc-1ecc6299db9ec823/backtrace-0.3.46/src/backtrace/libunwind.rs:86
   1:     0x7f2c1885cab4 - backtrace::backtrace::trace_unsynchronized::h7c97e818aebf09c8
                               at /cargo/registry/src/gh.neting.cc-1ecc6299db9ec823/backtrace-0.3.46/src/backtrace/mod.rs:66
   2:     0x7f2c1885cab4 - std::sys_common::backtrace::_print_fmt::h60d914263b0ccd71
                               at src/libstd/sys_common/backtrace.rs:78
   3:     0x7f2c1885cab4 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::hf78227137afc7565
                               at src/libstd/sys_common/backtrace.rs:59
   4:     0x7f2c1889abac - core::fmt::write::h543cdf60775f89bf
                               at src/libcore/fmt/mod.rs:1069
   5:     0x7f2c1884e4d3 - std::io::Write::write_fmt::h0c7f3ce24c679426
                               at src/libstd/io/mod.rs:1504
   6:     0x7f2c18861ab5 - std::sys_common::backtrace::_print::h80e55e24be231368
                               at src/libstd/sys_common/backtrace.rs:62
   7:     0x7f2c18861ab5 - std::sys_common::backtrace::print::h3b197b9c1261c865
                               at src/libstd/sys_common/backtrace.rs:49
   8:     0x7f2c18861ab5 - std::panicking::default_hook::{{closure}}::ha6c807149ce20f8f
                               at src/libstd/panicking.rs:198
   9:     0x7f2c188617f2 - std::panicking::default_hook::he49a9c12e358cc45
                               at src/libstd/panicking.rs:218
  10:     0x7f2c18dfe923 - rustc_driver::report_ice::h303988fb5b9997d4
  11:     0x7f2c18862235 - std::panicking::rust_panic_with_hook::h93f74f5ef2f71f31
                               at src/libstd/panicking.rs:515
  12:     0x7f2c1b5e825e - std::panicking::begin_panic::hc68bee93462232be
  13:     0x7f2c1b621a12 - <rustc_errors::HandlerInner as core::ops::drop::Drop>::drop::h1f879c4351fba67a
  14:     0x7f2c18f43166 - core::ptr::drop_in_place::h4d80a69fc5b8b26d
  15:     0x7f2c18f4b536 - <alloc::rc::Rc<T> as core::ops::drop::Drop>::drop::h11773fcd49f47beb
  16:     0x7f2c18f6f01d - core::ptr::drop_in_place::ha136f12949be28b0
  17:     0x7f2c18f55a45 - rustc_interface::interface::run_compiler_in_existing_thread_pool::h1fe14dfeda5e7ff8
  18:     0x7f2c18e0852d - scoped_tls::ScopedKey<T>::set::h7ef5c845735c44d5
  19:     0x7f2c18e053d4 - rustc_ast::attr::with_globals::h80403999168944fb
  20:     0x7f2c18e10a92 - std::sys_common::backtrace::__rust_begin_short_backtrace::h65e906f83ddca1d2
  21:     0x7f2c18f5840e - core::ops::function::FnOnce::call_once{{vtable.shim}}::h4a7aeea8942a4e2c
  22:     0x7f2c188722aa - <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once::hf207c3654ee300a0
                               at /rustc/c7087fe00d2ba919df1d813c040a5d47e43b0fe7/src/liballoc/boxed.rs:1008
  23:     0x7f2c188722aa - <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once::h66e0c6190e34816b
                               at /rustc/c7087fe00d2ba919df1d813c040a5d47e43b0fe7/src/liballoc/boxed.rs:1008
  24:     0x7f2c188722aa - std::sys::unix::thread::Thread::new::thread_start::h30687bc0b1c3cd55
                               at src/libstd/sys/unix/thread.rs:87
  25:     0x7f2c187b2609 - start_thread
                               at /build/glibc-YYA7BZ/glibc-2.31/nptl/pthread_create.c:477
  26:     0x7f2c186c6103 - __clone
  27:                0x0 - <unknown>

error: internal compiler error: unexpected panic

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 1.44.1 (c7087fe00 2020-06-17) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type lib

query stack during panic:
end of query stack
thread panicked while panicking. aborting.
Illegal instruction (core dumped)

[lcnr]

Thanks! Further minimized:

use std::convert::{TryFrom, TryInto};
use std::io;

pub struct MyStream;
pub struct OtherStream;

pub async fn connect() -> io::Result<MyStream> {
    let stream: MyStream = OtherStream.try_into()?;
    Ok(stream)
}

impl TryFrom<OtherStream> for MyStream {}

[JohnTitor]

Assigning P-high as discussed as part of the Prioritization Working Group process and removing I-prioritize.

[nikomatsakis]

Don't know the cause yet, but if you remove the async keyword or the ? operator, then you get this error:

error[E0046]: not all trait items implemented, missing: `Error`, `try_from`
  --> src/lib.rs:15:1
   |
15 | impl TryFrom<OtherStream> for MyStream {}
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ missing `Error`, `try_from` in implementation
   |
   = help: implement the missing item: `type Error = Type;`
   = help: implement the missing item: `fn try_from(_: T) -> std::result::Result<Self, <Self as std::convert::TryFrom<T>>::Error> { todo!() }`

My hunch is that somehow, lacking those items, the type of .try_from() is coming up with something that doesn't implement the expected traits -- I would bet that we are getting an error type, based on some of the output at the end. Perhaps some of the logic in MIR is failing as a result. The actual ICE location though isn't that illuminating:

rust/src/librustc_mir_build/build/mod.rs

Lines 344 to 346 in 51eeabf

	fn var_local_id(&self, id: hir::HirId, for_guard: ForGuard) -> Local {
	self.var_indices[&id].local_id(for_guard)
	}

[tmandry]

I did some digging here. The source of the panic is here, during HAIR construction:

rust/src/librustc_mir_build/hair/pattern/mod.rs

Lines 512 to 515 in 0820e54

	if let ty::Error(_) = ty.kind {
	// Avoid ICEs (e.g., #50577 and #50585).
	return Pat { span: pat.span, ty, kind: Box::new(PatKind::Wild) };
	}

In this case, the binding err below is of the error type (meaning type check for it failed). By replacing the binding with _ we prevent a local from being created for it, which means that when we try to generate code that reads the local we get a panic here.

pub async fn connect()
 ->
    /*impl Trait*/ ::std::future::from_generator(move |mut _task_context| {
        {
            let _t =
                {
                    let stream:
                            MyStream =
                        match ::std::ops::Try::into_result(OtherStream.try_into())
                            {
                            ::std::result::Result::Err(err) // `err` replaced with `_` here!
                            =>

                                #[allow(unreachable_code)]
                                return ::std::ops::Try::from_error(::std::convert::From::from(err)),
                            ::std::result::Result::Ok(val)
                            =>

                                #[allow(unreachable_code)]
                                val,
                        };
                    Ok(stream)
                };
            _t
        }
    })

I'm not sure what the correct fix is here. Replacing the binding with _ was done to prevent other ICEs, but we can't generate valid MIR without the local info.

More fundamentally: We're building MIR during typeck because this is an async fn. In the past we probably never would have gotten to this stage.

Backtrace:

thread 'rustc' panicked at 'no entry found for key', src/librustc_mir_build/build/mod.rs:354:9
stack backtrace:
   0: std::backtrace_rs::backtrace::libunwind::trace
             at ./src/libstd/../backtrace/src/backtrace/libunwind.rs:96
   1: std::backtrace_rs::backtrace::trace_unsynchronized
             at ./src/libstd/../backtrace/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:58
   4: core::fmt::write
             at ./src/libcore/fmt/mod.rs:1117
   5: std::io::Write::write_fmt
             at ./src/libstd/io/mod.rs:1508
   6: std::sys_common::backtrace::_print
             at ./src/libstd/sys_common/backtrace.rs:61
   7: std::sys_common::backtrace::print
             at ./src/libstd/sys_common/backtrace.rs:48
   8: std::panicking::default_hook::{{closure}}
             at ./src/libstd/panicking.rs:198
   9: std::panicking::default_hook
             at ./src/libstd/panicking.rs:217
  10: <alloc::boxed::Box<F> as core::ops::function::Fn<A>>::call
             at ./src/liballoc/boxed.rs:1095
  11: rustc_driver::report_ice
             at ./src/librustc_driver/lib.rs:1158
  12: std::panicking::rust_panic_with_hook
             at ./src/libstd/panicking.rs:530
  13: rust_begin_unwind
             at ./src/libstd/panicking.rs:437
  14: core::panicking::panic_fmt
             at ./src/libcore/panicking.rs:85
  15: core::option::expect_failed
             at ./src/libcore/option.rs:1265
  16: core::option::Option<T>::expect
             at ./src/libcore/option.rs:347
  17: <std::collections::hash::map::HashMap<K,V,S> as core::ops::index::Index<&Q>>::index
             at ./src/libstd/collections/hash/map.rs:1004
  18: rustc_mir_build::build::Builder::var_local_id
             at ./src/librustc_mir_build/build/mod.rs:354
  19: rustc_mir_build::build::expr::as_place::<impl rustc_mir_build::build::Builder>::expr_as_place
             at ./src/librustc_mir_build/build/expr/as_place.rs:169
  20: rustc_mir_build::build::expr::as_place::<impl rustc_mir_build::build::Builder>::as_place_builder
             at ./src/librustc_mir_build/build/expr/as_place.rs:84
  21: rustc_mir_build::build::expr::as_place::<impl rustc_mir_build::build::Builder>::as_place
             at ./src/librustc_mir_build/build/expr/as_place.rs:73
  22: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
             at ./src/librustc_mir_build/build/expr/into.rs:408
  23: <rustc_mir_build::hair::Expr as rustc_mir_build::build::into::EvalInto>::eval_into
             at ./src/librustc_mir_build/build/into.rs:53
  24: rustc_mir_build::build::into::<impl rustc_mir_build::build::Builder>::into
             at ./src/librustc_mir_build/build/into.rs:30
  25: rustc_mir_build::build::expr::as_temp::<impl rustc_mir_build::build::Builder>::expr_as_temp
             at ./src/librustc_mir_build/build/expr/as_temp.rs:112
  26: rustc_mir_build::build::expr::as_temp::<impl rustc_mir_build::build::Builder>::as_temp::{{closure}}
             at ./src/librustc_mir_build/build/expr/as_temp.rs:29
  27: stacker::maybe_grow
             at /usr/local/google/home/tmandry/.cargo/registry/src/gh.neting.cc-1ecc6299db9ec823/stacker-0.1.9/src/lib.rs:52
  28: rustc_data_structures::stack::ensure_sufficient_stack
             at ./src/librustc_data_structures/stack.rs:16
  29: rustc_mir_build::build::expr::as_temp::<impl rustc_mir_build::build::Builder>::as_temp
             at ./src/librustc_mir_build/build/expr/as_temp.rs:29
  30: rustc_mir_build::build::expr::as_operand::<impl rustc_mir_build::build::Builder>::expr_as_operand
             at ./src/librustc_mir_build/build/expr/as_operand.rs:143
  31: rustc_mir_build::build::expr::as_operand::<impl rustc_mir_build::build::Builder>::expr_as_call_operand
             at ./src/librustc_mir_build/build/expr/as_operand.rs:196
  32: rustc_mir_build::build::expr::as_operand::<impl rustc_mir_build::build::Builder>::as_call_operand
             at ./src/librustc_mir_build/build/expr/as_operand.rs:116
  33: rustc_mir_build::build::expr::as_operand::<impl rustc_mir_build::build::Builder>::expr_as_call_operand::{{closure}}
             at ./src/librustc_mir_build/build/expr/as_operand.rs:162
  34: rustc_mir_build::build::scope::<impl rustc_mir_build::build::Builder>::in_scope
             at ./src/librustc_mir_build/build/scope.rs:455
  35: rustc_mir_build::build::expr::as_operand::<impl rustc_mir_build::build::Builder>::expr_as_call_operand
             at ./src/librustc_mir_build/build/expr/as_operand.rs:161
  36: rustc_mir_build::build::expr::as_operand::<impl rustc_mir_build::build::Builder>::as_call_operand
             at ./src/librustc_mir_build/build/expr/as_operand.rs:116
  37: rustc_mir_build::build::expr::as_operand::<impl rustc_mir_build::build::Builder>::as_local_call_operand
             at ./src/librustc_mir_build/build/expr/as_operand.rs:82
  38: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr::{{closure}}
             at ./src/librustc_mir_build/build/expr/into.rs:200
  39: core::iter::adapters::map_fold::{{closure}}
             at ./src/libcore/iter/adapters/mod.rs:833
  40: core::iter::traits::iterator::Iterator::fold
             at ./src/libcore/iter/traits/iterator.rs:2003
  41: <core::iter::adapters::Map<I,F> as core::iter::traits::iterator::Iterator>::fold
             at ./src/libcore/iter/adapters/mod.rs:873
  42: core::iter::traits::iterator::Iterator::for_each
             at ./src/libcore/iter/traits/iterator.rs:649
  43: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T,I>>::spec_extend
             at ./src/liballoc/vec.rs:2140
  44: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T,I>>::from_iter
             at ./src/liballoc/vec.rs:2120
  45: <alloc::vec::Vec<T> as core::iter::traits::collect::FromIterator<T>>::from_iter
             at ./src/liballoc/vec.rs:1995
  46: core::iter::traits::iterator::Iterator::collect
             at ./src/libcore/iter/traits/iterator.rs:1652
  47: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
             at ./src/librustc_mir_build/build/expr/into.rs:198
  48: <rustc_mir_build::hair::Expr as rustc_mir_build::build::into::EvalInto>::eval_into
             at ./src/librustc_mir_build/build/into.rs:53
  49: rustc_mir_build::build::into::<impl rustc_mir_build::build::Builder>::into
             at ./src/librustc_mir_build/build/into.rs:30
  50: rustc_mir_build::build::expr::as_temp::<impl rustc_mir_build::build::Builder>::expr_as_temp
             at ./src/librustc_mir_build/build/expr/as_temp.rs:112
  51: rustc_mir_build::build::expr::as_temp::<impl rustc_mir_build::build::Builder>::as_temp::{{closure}}
             at ./src/librustc_mir_build/build/expr/as_temp.rs:29
  52: stacker::maybe_grow
             at /usr/local/google/home/tmandry/.cargo/registry/src/gh.neting.cc-1ecc6299db9ec823/stacker-0.1.9/src/lib.rs:52
  53: rustc_data_structures::stack::ensure_sufficient_stack
             at ./src/librustc_data_structures/stack.rs:16
  54: rustc_mir_build::build::expr::as_temp::<impl rustc_mir_build::build::Builder>::as_temp
             at ./src/librustc_mir_build/build/expr/as_temp.rs:29
  55: rustc_mir_build::build::expr::as_operand::<impl rustc_mir_build::build::Builder>::expr_as_operand
             at ./src/librustc_mir_build/build/expr/as_operand.rs:143
  56: rustc_mir_build::build::expr::as_operand::<impl rustc_mir_build::build::Builder>::expr_as_call_operand
             at ./src/librustc_mir_build/build/expr/as_operand.rs:196
  57: rustc_mir_build::build::expr::as_operand::<impl rustc_mir_build::build::Builder>::as_call_operand
             at ./src/librustc_mir_build/build/expr/as_operand.rs:116
  58: rustc_mir_build::build::expr::as_operand::<impl rustc_mir_build::build::Builder>::expr_as_call_operand::{{closure}}
             at ./src/librustc_mir_build/build/expr/as_operand.rs:162
  59: rustc_mir_build::build::scope::<impl rustc_mir_build::build::Builder>::in_scope
             at ./src/librustc_mir_build/build/scope.rs:455
  60: rustc_mir_build::build::expr::as_operand::<impl rustc_mir_build::build::Builder>::expr_as_call_operand
             at ./src/librustc_mir_build/build/expr/as_operand.rs:161
  61: rustc_mir_build::build::expr::as_operand::<impl rustc_mir_build::build::Builder>::as_call_operand
             at ./src/librustc_mir_build/build/expr/as_operand.rs:116
  62: rustc_mir_build::build::expr::as_operand::<impl rustc_mir_build::build::Builder>::as_local_call_operand
             at ./src/librustc_mir_build/build/expr/as_operand.rs:82
  63: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr::{{closure}}
             at ./src/librustc_mir_build/build/expr/into.rs:200
  64: core::iter::adapters::map_fold::{{closure}}
             at ./src/libcore/iter/adapters/mod.rs:833
  65: core::iter::traits::iterator::Iterator::fold
             at ./src/libcore/iter/traits/iterator.rs:2003
  66: <core::iter::adapters::Map<I,F> as core::iter::traits::iterator::Iterator>::fold
             at ./src/libcore/iter/adapters/mod.rs:873
  67: core::iter::traits::iterator::Iterator::for_each
             at ./src/libcore/iter/traits/iterator.rs:649
  68: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T,I>>::spec_extend
             at ./src/liballoc/vec.rs:2140
  69: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T,I>>::from_iter
             at ./src/liballoc/vec.rs:2120
  70: <alloc::vec::Vec<T> as core::iter::traits::collect::FromIterator<T>>::from_iter
             at ./src/liballoc/vec.rs:1995
  71: core::iter::traits::iterator::Iterator::collect
             at ./src/libcore/iter/traits/iterator.rs:1652
  72: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
             at ./src/librustc_mir_build/build/expr/into.rs:198
  73: <rustc_mir_build::hair::ExprRef as rustc_mir_build::build::into::EvalInto>::eval_into
             at ./src/librustc_mir_build/build/into.rs:42
  74: rustc_mir_build::build::into::<impl rustc_mir_build::build::Builder>::into
             at ./src/librustc_mir_build/build/into.rs:30
  75: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr::{{closure}}
             at ./src/librustc_mir_build/build/expr/into.rs:46
  76: rustc_mir_build::build::scope::<impl rustc_mir_build::build::Builder>::in_scope
             at ./src/librustc_mir_build/build/scope.rs:455
  77: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
             at ./src/librustc_mir_build/build/expr/into.rs:46
  78: <rustc_mir_build::hair::ExprRef as rustc_mir_build::build::into::EvalInto>::eval_into
             at ./src/librustc_mir_build/build/into.rs:42
  79: rustc_mir_build::build::into::<impl rustc_mir_build::build::Builder>::into
             at ./src/librustc_mir_build/build/into.rs:30
  80: rustc_mir_build::build::scope::<impl rustc_mir_build::build::Builder>::break_scope
             at ./src/librustc_mir_build/build/scope.rs:523
  81: rustc_mir_build::build::expr::stmt::<impl rustc_mir_build::build::Builder>::stmt_expr
             at ./src/librustc_mir_build/build/expr/stmt.rs:97
  82: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
             at ./src/librustc_mir_build/build/expr/into.rs:396
  83: <rustc_mir_build::hair::Expr as rustc_mir_build::build::into::EvalInto>::eval_into
             at ./src/librustc_mir_build/build/into.rs:53
  84: rustc_mir_build::build::into::<impl rustc_mir_build::build::Builder>::into
             at ./src/librustc_mir_build/build/into.rs:30
  85: rustc_mir_build::build::expr::as_temp::<impl rustc_mir_build::build::Builder>::expr_as_temp
             at ./src/librustc_mir_build/build/expr/as_temp.rs:112
  86: rustc_mir_build::build::expr::as_temp::<impl rustc_mir_build::build::Builder>::as_temp::{{closure}}
             at ./src/librustc_mir_build/build/expr/as_temp.rs:29
  87: stacker::maybe_grow
             at /usr/local/google/home/tmandry/.cargo/registry/src/gh.neting.cc-1ecc6299db9ec823/stacker-0.1.9/src/lib.rs:52
  88: rustc_data_structures::stack::ensure_sufficient_stack
             at ./src/librustc_data_structures/stack.rs:16
  89: rustc_mir_build::build::expr::as_temp::<impl rustc_mir_build::build::Builder>::as_temp
             at ./src/librustc_mir_build/build/expr/as_temp.rs:29
  90: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
             at ./src/librustc_mir_build/build/expr/into.rs:63
  91: <rustc_mir_build::hair::ExprRef as rustc_mir_build::build::into::EvalInto>::eval_into
             at ./src/librustc_mir_build/build/into.rs:42
  92: rustc_mir_build::build::into::<impl rustc_mir_build::build::Builder>::into
             at ./src/librustc_mir_build/build/into.rs:30
  93: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr::{{closure}}
             at ./src/librustc_mir_build/build/expr/into.rs:46
  94: rustc_mir_build::build::scope::<impl rustc_mir_build::build::Builder>::in_scope
             at ./src/librustc_mir_build/build/scope.rs:455
  95: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
             at ./src/librustc_mir_build/build/expr/into.rs:46
  96: <rustc_mir_build::hair::ExprRef as rustc_mir_build::build::into::EvalInto>::eval_into
             at ./src/librustc_mir_build/build/into.rs:42
  97: rustc_mir_build::build::into::<impl rustc_mir_build::build::Builder>::into
             at ./src/librustc_mir_build/build/into.rs:30
  98: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr::{{closure}}
             at ./src/librustc_mir_build/build/expr/into.rs:46
  99: rustc_mir_build::build::scope::<impl rustc_mir_build::build::Builder>::in_scope
             at ./src/librustc_mir_build/build/scope.rs:455
 100: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
             at ./src/librustc_mir_build/build/expr/into.rs:46
 101: <rustc_mir_build::hair::Expr as rustc_mir_build::build::into::EvalInto>::eval_into
             at ./src/librustc_mir_build/build/into.rs:53
 102: rustc_mir_build::build::into::<impl rustc_mir_build::build::Builder>::into
             at ./src/librustc_mir_build/build/into.rs:30
 103: rustc_mir_build::build::matches::<impl rustc_mir_build::build::Builder>::lower_match_arms::{{closure}}::{{closure}}
             at ./src/librustc_mir_build/build/matches/mod.rs:260
 104: rustc_mir_build::build::scope::<impl rustc_mir_build::build::Builder>::in_scope
             at ./src/librustc_mir_build/build/scope.rs:455
 105: rustc_mir_build::build::matches::<impl rustc_mir_build::build::Builder>::lower_match_arms::{{closure}}
             at ./src/librustc_mir_build/build/matches/mod.rs:237
 106: core::iter::adapters::map_fold::{{closure}}
             at ./src/libcore/iter/adapters/mod.rs:833
 107: core::iter::traits::iterator::Iterator::fold
             at ./src/libcore/iter/traits/iterator.rs:2003
 108: <core::iter::adapters::Map<I,F> as core::iter::traits::iterator::Iterator>::fold
             at ./src/libcore/iter/adapters/mod.rs:873
 109: core::iter::traits::iterator::Iterator::for_each
             at ./src/libcore/iter/traits/iterator.rs:649
 110: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T,I>>::spec_extend
             at ./src/liballoc/vec.rs:2140
 111: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T,I>>::from_iter
             at ./src/liballoc/vec.rs:2120
 112: <alloc::vec::Vec<T> as core::iter::traits::collect::FromIterator<T>>::from_iter
             at ./src/liballoc/vec.rs:1995
 113: core::iter::traits::iterator::Iterator::collect
             at ./src/libcore/iter/traits/iterator.rs:1652
 114: rustc_mir_build::build::matches::<impl rustc_mir_build::build::Builder>::lower_match_arms
             at ./src/librustc_mir_build/build/matches/mod.rs:230
 115: rustc_mir_build::build::matches::<impl rustc_mir_build::build::Builder>::match_expr
             at ./src/librustc_mir_build/build/matches/mod.rs:105
 116: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
             at ./src/librustc_mir_build/build/expr/into.rs:52
 117: <rustc_mir_build::hair::ExprRef as rustc_mir_build::build::into::EvalInto>::eval_into
             at ./src/librustc_mir_build/build/into.rs:42
 118: rustc_mir_build::build::into::<impl rustc_mir_build::build::Builder>::into
             at ./src/librustc_mir_build/build/into.rs:30
 119: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr::{{closure}}
             at ./src/librustc_mir_build/build/expr/into.rs:46
 120: rustc_mir_build::build::scope::<impl rustc_mir_build::build::Builder>::in_scope
             at ./src/librustc_mir_build/build/scope.rs:455
 121: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
             at ./src/librustc_mir_build/build/expr/into.rs:46
 122: <rustc_mir_build::hair::ExprRef as rustc_mir_build::build::into::EvalInto>::eval_into
             at ./src/librustc_mir_build/build/into.rs:42
 123: rustc_mir_build::build::into::<impl rustc_mir_build::build::Builder>::into
             at ./src/librustc_mir_build/build/into.rs:30
 124: rustc_mir_build::build::matches::<impl rustc_mir_build::build::Builder>::expr_into_pattern
             at ./src/librustc_mir_build/build/matches/mod.rs:402
 125: rustc_mir_build::build::block::<impl rustc_mir_build::build::Builder>::ast_block_stmts::{{closure}}::{{closure}}
             at ./src/librustc_mir_build/build/block.rs:131
 126: rustc_mir_build::build::scope::<impl rustc_mir_build::build::Builder>::in_scope
             at ./src/librustc_mir_build/build/scope.rs:455
 127: rustc_mir_build::build::block::<impl rustc_mir_build::build::Builder>::ast_block_stmts::{{closure}}
             at ./src/librustc_mir_build/build/block.rs:123
 128: rustc_mir_build::build::scope::<impl rustc_mir_build::build::Builder>::in_opt_scope
             at ./src/librustc_mir_build/build/scope.rs:411
 129: rustc_mir_build::build::block::<impl rustc_mir_build::build::Builder>::ast_block_stmts
             at ./src/librustc_mir_build/build/block.rs:119
 130: rustc_mir_build::build::block::<impl rustc_mir_build::build::Builder>::ast_block::{{closure}}::{{closure}}
             at ./src/librustc_mir_build/build/block.rs:40
 131: rustc_mir_build::build::scope::<impl rustc_mir_build::build::Builder>::in_scope
             at ./src/librustc_mir_build/build/scope.rs:455
 132: rustc_mir_build::build::block::<impl rustc_mir_build::build::Builder>::ast_block::{{closure}}
             at ./src/librustc_mir_build/build/block.rs:29
 133: rustc_mir_build::build::scope::<impl rustc_mir_build::build::Builder>::in_opt_scope
             at ./src/librustc_mir_build/build/scope.rs:411
 134: rustc_mir_build::build::block::<impl rustc_mir_build::build::Builder>::ast_block
             at ./src/librustc_mir_build/build/block.rs:28
 135: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
             at ./src/librustc_mir_build/build/expr/into.rs:49
 136: <rustc_mir_build::hair::ExprRef as rustc_mir_build::build::into::EvalInto>::eval_into
             at ./src/librustc_mir_build/build/into.rs:42
 137: rustc_mir_build::build::into::<impl rustc_mir_build::build::Builder>::into
             at ./src/librustc_mir_build/build/into.rs:30
 138: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr::{{closure}}
             at ./src/librustc_mir_build/build/expr/into.rs:46
 139: rustc_mir_build::build::scope::<impl rustc_mir_build::build::Builder>::in_scope
             at ./src/librustc_mir_build/build/scope.rs:455
 140: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
             at ./src/librustc_mir_build/build/expr/into.rs:46
 141: <rustc_mir_build::hair::ExprRef as rustc_mir_build::build::into::EvalInto>::eval_into
             at ./src/librustc_mir_build/build/into.rs:42
 142: rustc_mir_build::build::into::<impl rustc_mir_build::build::Builder>::into
             at ./src/librustc_mir_build/build/into.rs:30
 143: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr::{{closure}}
             at ./src/librustc_mir_build/build/expr/into.rs:46
 144: rustc_mir_build::build::scope::<impl rustc_mir_build::build::Builder>::in_scope
             at ./src/librustc_mir_build/build/scope.rs:455
 145: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
             at ./src/librustc_mir_build/build/expr/into.rs:46
 146: <rustc_mir_build::hair::ExprRef as rustc_mir_build::build::into::EvalInto>::eval_into
             at ./src/librustc_mir_build/build/into.rs:42
 147: rustc_mir_build::build::into::<impl rustc_mir_build::build::Builder>::into
             at ./src/librustc_mir_build/build/into.rs:30
 148: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
             at ./src/librustc_mir_build/build/expr/into.rs:232
 149: <rustc_mir_build::hair::ExprRef as rustc_mir_build::build::into::EvalInto>::eval_into
             at ./src/librustc_mir_build/build/into.rs:42
 150: rustc_mir_build::build::into::<impl rustc_mir_build::build::Builder>::into
             at ./src/librustc_mir_build/build/into.rs:30
 151: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr::{{closure}}
             at ./src/librustc_mir_build/build/expr/into.rs:46
 152: rustc_mir_build::build::scope::<impl rustc_mir_build::build::Builder>::in_scope
             at ./src/librustc_mir_build/build/scope.rs:455
 153: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
             at ./src/librustc_mir_build/build/expr/into.rs:46
 154: <rustc_mir_build::hair::ExprRef as rustc_mir_build::build::into::EvalInto>::eval_into
             at ./src/librustc_mir_build/build/into.rs:42
 155: rustc_mir_build::build::into::<impl rustc_mir_build::build::Builder>::into
             at ./src/librustc_mir_build/build/into.rs:30
 156: rustc_mir_build::build::block::<impl rustc_mir_build::build::Builder>::ast_block_stmts
             at ./src/librustc_mir_build/build/block.rs:184
 157: rustc_mir_build::build::block::<impl rustc_mir_build::build::Builder>::ast_block::{{closure}}::{{closure}}
             at ./src/librustc_mir_build/build/block.rs:40
 158: rustc_mir_build::build::scope::<impl rustc_mir_build::build::Builder>::in_scope
             at ./src/librustc_mir_build/build/scope.rs:455
 159: rustc_mir_build::build::block::<impl rustc_mir_build::build::Builder>::ast_block::{{closure}}
             at ./src/librustc_mir_build/build/block.rs:29
 160: rustc_mir_build::build::scope::<impl rustc_mir_build::build::Builder>::in_opt_scope
             at ./src/librustc_mir_build/build/scope.rs:411
 161: rustc_mir_build::build::block::<impl rustc_mir_build::build::Builder>::ast_block
             at ./src/librustc_mir_build/build/block.rs:28
 162: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
             at ./src/librustc_mir_build/build/expr/into.rs:49
 163: <rustc_mir_build::hair::ExprRef as rustc_mir_build::build::into::EvalInto>::eval_into
             at ./src/librustc_mir_build/build/into.rs:42
 164: rustc_mir_build::build::into::<impl rustc_mir_build::build::Builder>::into
             at ./src/librustc_mir_build/build/into.rs:30
 165: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr::{{closure}}
             at ./src/librustc_mir_build/build/expr/into.rs:46
 166: rustc_mir_build::build::scope::<impl rustc_mir_build::build::Builder>::in_scope
             at ./src/librustc_mir_build/build/scope.rs:455
 167: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
             at ./src/librustc_mir_build/build/expr/into.rs:46
 168: <rustc_mir_build::hair::ExprRef as rustc_mir_build::build::into::EvalInto>::eval_into
             at ./src/librustc_mir_build/build/into.rs:42
 169: rustc_mir_build::build::into::<impl rustc_mir_build::build::Builder>::into
             at ./src/librustc_mir_build/build/into.rs:30
 170: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr::{{closure}}
             at ./src/librustc_mir_build/build/expr/into.rs:46
 171: rustc_mir_build::build::scope::<impl rustc_mir_build::build::Builder>::in_scope
             at ./src/librustc_mir_build/build/scope.rs:455
 172: rustc_mir_build::build::expr::into::<impl rustc_mir_build::build::Builder>::into_expr
             at ./src/librustc_mir_build/build/expr/into.rs:46
 173: <rustc_mir_build::hair::Expr as rustc_mir_build::build::into::EvalInto>::eval_into
             at ./src/librustc_mir_build/build/into.rs:53
 174: rustc_mir_build::build::into::<impl rustc_mir_build::build::Builder>::into
             at ./src/librustc_mir_build/build/into.rs:30
 175: rustc_mir_build::build::Builder::args_and_body
             at ./src/librustc_mir_build/build/mod.rs:959
 176: rustc_mir_build::build::construct_fn::{{closure}}::{{closure}}::{{closure}}
             at ./src/librustc_mir_build/build/mod.rs:621
 177: rustc_mir_build::build::scope::<impl rustc_mir_build::build::Builder>::in_scope
             at ./src/librustc_mir_build/build/scope.rs:455
 178: rustc_mir_build::build::construct_fn::{{closure}}::{{closure}}
             at ./src/librustc_mir_build/build/mod.rs:620
 179: rustc_mir_build::build::scope::<impl rustc_mir_build::build::Builder>::in_breakable_scope
             at ./src/librustc_mir_build/build/scope.rs:392
 180: rustc_mir_build::build::construct_fn::{{closure}}
             at ./src/librustc_mir_build/build/mod.rs:615
 181: rustc_mir_build::build::scope::<impl rustc_mir_build::build::Builder>::in_scope
             at ./src/librustc_mir_build/build/scope.rs:455
 182: rustc_mir_build::build::construct_fn
             at ./src/librustc_mir_build/build/mod.rs:606
 183: rustc_mir_build::build::mir_build::{{closure}}
             at ./src/librustc_mir_build/build/mod.rs:163
 184: rustc_infer::infer::InferCtxtBuilder::enter
             at ./src/librustc_infer/infer/mod.rs:621
 185: rustc_mir_build::build::mir_build
             at ./src/librustc_mir_build/build/mod.rs:72
 186: rustc_mir_build::build::mir_built
             at ./src/librustc_mir_build/build/mod.rs:34
 187: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::mir_built>::compute
             at ./src/librustc_middle/ty/query/plumbing.rs:381
 188: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
             at ./src/librustc_query_system/dep_graph/graph.rs:303
 189: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task
             at ./src/librustc_query_system/dep_graph/graph.rs:200
 190: rustc_query_system::query::plumbing::force_query_with_job::{{closure}}::{{closure}}
             at ./src/librustc_query_system/query/plumbing.rs:599
 191: rustc_middle::ty::query::plumbing::<impl rustc_query_system::query::QueryContext for rustc_middle::ty::context::TyCtxt>::start_query::{{closure}}::{{closure}}::{{closure}}
             at ./src/librustc_middle/ty/query/plumbing.rs:72
 192: stacker::maybe_grow
             at /usr/local/google/home/tmandry/.cargo/registry/src/gh.neting.cc-1ecc6299db9ec823/stacker-0.1.9/src/lib.rs:52
 193: rustc_data_structures::stack::ensure_sufficient_stack
             at ./src/librustc_data_structures/stack.rs:16
 194: rustc_middle::ty::query::plumbing::<impl rustc_query_system::query::QueryContext for rustc_middle::ty::context::TyCtxt>::start_query::{{closure}}::{{closure}}
             at ./src/librustc_middle/ty/query/plumbing.rs:72
 195: rustc_middle::ty::context::tls::enter_context::{{closure}}
             at ./src/librustc_middle/ty/context.rs:1721
 196: rustc_middle::ty::context::tls::set_tlv
             at ./src/librustc_middle/ty/context.rs:1705
 197: rustc_middle::ty::context::tls::enter_context
             at ./src/librustc_middle/ty/context.rs:1721
 198: rustc_middle::ty::query::plumbing::<impl rustc_query_system::query::QueryContext for rustc_middle::ty::context::TyCtxt>::start_query::{{closure}}
             at ./src/librustc_middle/ty/query/plumbing.rs:71
 199: rustc_middle::ty::context::tls::with_related_context::{{closure}}
             at ./src/librustc_middle/ty/context.rs:1809
 200: rustc_middle::ty::context::tls::with_context::{{closure}}
             at ./src/librustc_middle/ty/context.rs:1793
 201: rustc_middle::ty::context::tls::with_context_opt
             at ./src/librustc_middle/ty/context.rs:1782
 202: rustc_middle::ty::context::tls::with_context
             at ./src/librustc_middle/ty/context.rs:1793
 203: rustc_middle::ty::context::tls::with_related_context
             at ./src/librustc_middle/ty/context.rs:1806
 204: rustc_middle::ty::query::plumbing::<impl rustc_query_system::query::QueryContext for rustc_middle::ty::context::TyCtxt>::start_query
             at ./src/librustc_middle/ty/query/plumbing.rs:60
 205: rustc_query_system::query::plumbing::force_query_with_job::{{closure}}
             at ./src/librustc_query_system/query/plumbing.rs:589
 206: rustc_query_system::query::plumbing::with_diagnostics
             at ./src/librustc_query_system/query/plumbing.rs:296
 207: rustc_query_system::query::plumbing::force_query_with_job
             at ./src/librustc_query_system/query/plumbing.rs:588
 208: rustc_query_system::query::plumbing::try_execute_query
             at ./src/librustc_query_system/query/plumbing.rs:415
 209: rustc_query_system::query::plumbing::get_query_impl::{{closure}}
             at ./src/librustc_query_system/query/plumbing.rs:639
 210: <rustc_query_system::query::caches::DefaultCache<K,V> as rustc_query_system::query::caches::QueryCache>::lookup
             at ./src/librustc_query_system/query/caches.rs:111
 211: rustc_query_system::query::plumbing::try_get_cached
             at ./src/librustc_query_system/query/plumbing.rs:369
 212: rustc_query_system::query::plumbing::get_query_impl
             at ./src/librustc_query_system/query/plumbing.rs:631
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

error: internal compiler error: unexpected panic

note: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: https://github.com/rust-lang/rust/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: rustc 1.47.0-dev running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type lib

query stack during panic:
#0 [mir_built] building MIR for `connect::{{closure}}#0`
#1 [unsafety_check_result] unsafety-checking `connect::{{closure}}#0`
#2 [unsafety_check_result] unsafety-checking `connect`
#3 [mir_const] processing MIR for `connect`
#4 [mir_validated] processing `connect`
#5 [mir_borrowck] borrow-checking `connect`
#6 [type_of] computing type of `connect::{{opaque}}#0`
#7 [check_mod_item_types] checking item types in top-level module
#8 [analysis] running analysis passes on this crate
end of query stack