ICE with borrow checker in nightly

[kdar]

ICE with the borrow checker on nightly. Tried on stable/beta and it correctly errors with

tx.send(Event::Rpc(response(resp.id))).unwrap();
   |                                             ^^^^^^^ cannot move out of borrowed content

in nightly, I get

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 1.37.0-nightly (8aa42ed7c 2019-06-24) running on x86_64-unknown-linux-gnu

note: compiler flags: -C debuginfo=2 -C incremental -C linker=clang -C link-arg=-fuse-ld=lld --crate-type bin

note: some of the compiler flags provided by cargo are hidden

Code

use std::sync::mpsc;

pub enum Event {
    Rpc(JsonRpc),
}

pub enum Id {
    Str(String),
}

pub fn response<I: Into<Id>>(id: I) -> JsonRpc {
    JsonRpc::Response(Response {
        id: id.into(),
        method: "request".into(),
    })
}

struct Response {
    id: Id,
    method: String,
}

pub enum JsonRpc {
    Response(Response),
}

fn main() {
    let (tx, rx) = mpsc::channel();
    for evt in rx {
        match evt {
            Event::Rpc(JsonRpc::Response(ref resp)) if resp.method == "shutdown" => {}
            Event::Rpc(JsonRpc::Response(ref resp)) if resp.method == "request" => {
                tx.send(Event::Rpc(response(resp.id))).unwrap();
            }
            _ => (),
        };
    }
}

https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=45bda3f34fa2a19e826f1e1be88711a7

Meta

rustc --version --verbose:

rustc 1.37.0-nightly (8aa42ed7c 2019-06-24)
binary: rustc
commit-hash: 8aa42ed7c2adb9f37faa6eb905f890f6199e1db9
commit-date: 2019-06-24
host: x86_64-unknown-linux-gnu
release: 1.37.0-nightly
LLVM version: 8.0

Backtrace:

thread 'rustc' panicked at 'assertion failed: self.bccx.region_scope_tree.scopes_intersect(old_loan.kill_scope,
                                             new_loan.kill_scope)', src/librustc_borrowck/borrowck/check_loans.rs:493:9
stack backtrace:
   0:     0x7f51a0b3b14b - backtrace::backtrace::libunwind::trace::h9099c158484abe51
                               at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.29/src/backtrace/libunwind.rs:88
   1:     0x7f51a0b3b14b - backtrace::backtrace::trace_unsynchronized::he4479cf789916be1
                               at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.29/src/backtrace/mod.rs:66
   2:     0x7f51a0b3b14b - std::sys_common::backtrace::_print::hfd97ddfcd581ce47
                               at src/libstd/sys_common/backtrace.rs:47
   3:     0x7f51a0b3b14b - std::sys_common::backtrace::print::h72fe9b1ac0779f0b
                               at src/libstd/sys_common/backtrace.rs:36
   4:     0x7f51a0b3b14b - std::panicking::default_hook::{{closure}}::hb2410098a9792a61
                               at src/libstd/panicking.rs:198
   5:     0x7f51a0b3ae27 - std::panicking::default_hook::he3b875f8eb532cbe
                               at src/libstd/panicking.rs:212
   6:     0x7f519e8248e1 - rustc::util::common::panic_hook::h4c77d6782bc64924
   7:     0x7f51a0b3b9a9 - std::panicking::rust_panic_with_hook::hb2c131403b9ff330
                               at src/libstd/panicking.rs:479
   8:     0x7f51a025ff45 - std::panicking::begin_panic::h48a8c740da159997
   9:     0x7f51a022f65d - rustc_borrowck::borrowck::check_loans::CheckLoanCtxt::report_error_if_loans_conflict::hbcb4607cfdf861b8
  10:     0x7f51a020f1be - rustc_borrowck::dataflow::DataFlowContext<O>::each_bit_on_entry::h1d18ec17e0a321d3
  11:     0x7f51a022ea40 - <rustc_borrowck::borrowck::check_loans::CheckLoanCtxt as rustc::middle::expr_use_visitor::Delegate>::borrow::h8dfd8b989effcd98
  12:     0x7f519e7f4c1a - rustc::middle::expr_use_visitor::ExprUseVisitor::borrow_expr::hed798c4f337e2b4a
  13:     0x7f519e7f6172 - rustc::middle::expr_use_visitor::ExprUseVisitor::walk_expr::h478289325f1f661d
  14:     0x7f519e7f4a5d - rustc::middle::expr_use_visitor::ExprUseVisitor::consume_expr::h7283293f253a7027
  15:     0x7f519e7f651d - rustc::middle::expr_use_visitor::ExprUseVisitor::walk_expr::h478289325f1f661d
  16:     0x7f519e7f4c2a - rustc::middle::expr_use_visitor::ExprUseVisitor::borrow_expr::hed798c4f337e2b4a
  17:     0x7f519e7f5e06 - rustc::middle::expr_use_visitor::ExprUseVisitor::walk_expr::h478289325f1f661d
  18:     0x7f519e7f4a5d - rustc::middle::expr_use_visitor::ExprUseVisitor::consume_expr::h7283293f253a7027
  19:     0x7f519e7f5579 - rustc::middle::expr_use_visitor::ExprUseVisitor::walk_expr::h478289325f1f661d
  20:     0x7f519e7f4a5d - rustc::middle::expr_use_visitor::ExprUseVisitor::consume_expr::h7283293f253a7027
  21:     0x7f519e7f5fd3 - rustc::middle::expr_use_visitor::ExprUseVisitor::walk_expr::h478289325f1f661d
  22:     0x7f519e7f4a5d - rustc::middle::expr_use_visitor::ExprUseVisitor::consume_expr::h7283293f253a7027
  23:     0x7f519e7f62f3 - rustc::middle::expr_use_visitor::ExprUseVisitor::walk_expr::h478289325f1f661d
  24:     0x7f519e7f4a5d - rustc::middle::expr_use_visitor::ExprUseVisitor::consume_expr::h7283293f253a7027
  25:     0x7f519e7f62f3 - rustc::middle::expr_use_visitor::ExprUseVisitor::walk_expr::h478289325f1f661d
  26:     0x7f519e7f4a5d - rustc::middle::expr_use_visitor::ExprUseVisitor::consume_expr::h7283293f253a7027
  27:     0x7f51a022f342 - rustc_borrowck::borrowck::check_loans::check_loans::h70d160e6225c3793
  28:     0x7f51a02364d2 - rustc_borrowck::borrowck::borrowck::hc11e557e6bcb2700
  29:     0x7f519fab0bd0 - rustc::ty::query::__query_compute::borrowck::hb326ee1e01ea2f5f
  30:     0x7f519fe2abed - rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::borrowck>::compute::h4dfd3020c39922c3
  31:     0x7f519fb62c9f - rustc::dep_graph::graph::DepGraph::with_task_impl::hf9138b4ba4a263ec
  32:     0x7f519feab41d - rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query::he7a81b2f25a24351
  33:     0x7f519fb7d72a - rustc_mir::borrow_check::do_mir_borrowck::h041182468ca0f2be
  34:     0x7f519feb685d - rustc::ty::context::GlobalCtxt::enter_local::hdb6c427c7c20906e
  35:     0x7f519fb7a60a - rustc_mir::borrow_check::mir_borrowck::h15870aaa4fd0f5e5
  36:     0x7f51a05b9c87 - rustc::ty::query::__query_compute::mir_borrowck::hab3ac695671a6c49
  37:     0x7f51a0579b05 - rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::mir_borrowck>::compute::h308bdadc41948ba3
  38:     0x7f51a05ac550 - rustc::dep_graph::graph::DepGraph::with_task_impl::hb82856897b911bf1
  39:     0x7f51a058469f - rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query::h4b21f0bb085eb07f
  40:     0x7f51a0579983 - rustc::ty::<impl rustc::ty::context::TyCtxt>::par_body_owners::hbc77efbf68d01392
  41:     0x7f51a054cdfe - rustc::util::common::time::h448867c0d110e11e
  42:     0x7f51a04fa742 - rustc_interface::passes::analysis::hffd7ed50e2787ccd
  43:     0x7f51a0e8fca6 - rustc::ty::query::__query_compute::analysis::h4f745f8b753a54a0
  44:     0x7f51a0ea165c - rustc::dep_graph::graph::DepGraph::with_task_impl::hae3d1d8b68983bb5
  45:     0x7f51a0e9c0ad - rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query::h849c974350419d2a
  46:     0x7f51a0e01256 - rustc::ty::context::tls::enter_global::h8e6320204fd477f6
  47:     0x7f51a0e229c7 - rustc_interface::passes::BoxedGlobalCtxt::access::{{closure}}::hd42b09eb1e70ba2e
  48:     0x7f51a05559fa - rustc_interface::passes::create_global_ctxt::{{closure}}::h57368add3655177a
  49:     0x7f51a0e23c28 - rustc_interface::interface::run_compiler_in_existing_thread_pool::h49a948c9a09e4fd5
  50:     0x7f51a0e3da22 - std::thread::local::LocalKey<T>::with::h56185318caee7c8e
  51:     0x7f51a0e2cca1 - scoped_tls::ScopedKey<T>::set::h0795a1620a3ca850
  52:     0x7f51a0e61e04 - syntax::with_globals::h226a9e65871d3e23
  53:     0x7f51a0e809dd - std::sys_common::backtrace::__rust_begin_short_backtrace::h65635ba31aa34691
  54:     0x7f51a0b4c40a - __rust_maybe_catch_panic
                               at src/libpanic_unwind/lib.rs:82
  55:     0x7f51a0e0a2e9 - core::ops::function::FnOnce::call_once{{vtable.shim}}::hd6ecffcd44130a12
  56:     0x7f51a0b1edff - <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once::h8d7c6883fcf13717
                               at /rustc/8aa42ed7c2adb9f37faa6eb905f890f6199e1db9/src/liballoc/boxed.rs:746
  57:     0x7f51a0b4b0f0 - <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once::h2cb8e7ed98d76ce7
                               at /rustc/8aa42ed7c2adb9f37faa6eb905f890f6199e1db9/src/liballoc/boxed.rs:746
  58:     0x7f51a0b4b0f0 - std::sys_common::thread::start_thread::h657d20c664378d90
                               at src/libstd/sys_common/thread.rs:13
  59:     0x7f51a0b4b0f0 - std::sys::unix::thread::Thread::new::thread_start::hf4dea44ba5680dfb
                               at src/libstd/sys/unix/thread.rs:79
  60:     0x7f51a0a6d57f - start_thread
  61:     0x7f51a098cf13 - __clone
  62:                0x0 - <unknown>
query stack during panic:
#0 [borrowck] processing `main`
#1 [mir_borrowck] processing `main`
#2 [analysis] running analysis passes on this crate
end of query stack

[Centril]

Reduced:

struct Id {}
struct E { id: Id }
struct A {}

fn response(id: Id) -> E { E { id } }

fn send<'a>(_: &'a A, _: E) {}

fn foo() {
    let evt = E { id: Id {} };
    match evt {
        ref resp if true => {}
        ref resp if true => {
            let tx = A {};
            send(&tx, response(resp.id));
        }
        _ => (),
    }
}

cc @pnkfelix

[lqd]

Bisected this one to nightly-2019-05-24 and 85334c5, that is, PR #60174. cc @matthewjasper