Calling FnMut on immutable reference causes: internal compiler error: impossible case reached

[JakkuSakura]

Code

Change &self.snapshot to &mut self.snapshot would make it work.

struct SnapshotMetadata {
    builder: Box<dyn FnMut() -> String>,
}

pub struct SnapshotCollector {
    snapshot: Vec<SnapshotMetadata>,
}

impl SnapshotCollector {
    pub fn collect_snapshots(&mut self) {
        for meta in &self.snapshot {
            (meta.builder)();
        }
    }
}

fn main() {
    println!("Hello, world!");
}

Meta

rustc --version --verbose:

rustc 1.52.0-nightly (e9920ef77 2021-02-11)
binary: rustc
commit-hash: e9920ef7749d11fc71cc32ca4ba055bcfeaab945
commit-date: 2021-02-11
host: x86_64-unknown-linux-gnu
release: 1.52.0-nightly
LLVM version: 11.0.1

Error output

/usr/bin/cargo build --color=always --message-format=json-diagnostic-rendered-ansi --package rust_test --bin rust_test
   Compiling rust_test v0.1.0 (/home/jack/Dev/rust_test)
error: internal compiler error: compiler/rustc_middle/src/hir/map/mod.rs:306:18: impossible case reached

thread 'rustc' panicked at 'Box<Any>', /rustc/e9920ef7749d11fc71cc32ca4ba055bcfeaab945/library/std/src/panic.rs:59:5
stack backtrace:
   0: std::panicking::begin_panic
   1: std::panic::panic_any
   2: rustc_errors::HandlerInner::bug
   3: rustc_errors::Handler::bug
   4: rustc_middle::ty::context::tls::with_opt
   5: rustc_middle::util::bug::opt_span_bug_fmt
   6: rustc_middle::util::bug::bug_fmt
   7: rustc_middle::hir::map::Map::item
   8: rustc_mir::borrow_check::diagnostics::mutability_errors::<impl rustc_mir::borrow_check::MirBorrowckCtxt>::report_mutability_error
   9: rustc_mir::borrow_check::MirBorrowckCtxt::access_place
  10: <rustc_mir::borrow_check::MirBorrowckCtxt as rustc_mir::dataflow::framework::visitor::ResultsVisitor>::visit_statement_before_primary_effect
  11: <rustc_mir::dataflow::framework::direction::Forward as rustc_mir::dataflow::framework::direction::Direction>::visit_results_in_block
  12: rustc_mir::dataflow::framework::visitor::visit_results
  13: rustc_mir::borrow_check::do_mir_borrowck
  14: rustc_infer::infer::InferCtxtBuilder::enter
  15: rustc_mir::borrow_check::mir_borrowck
  16: 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
  17: rustc_middle::dep_graph::<impl rustc_query_system::dep_graph::DepKind for rustc_middle::dep_graph::dep_node::DepKind>::with_deps
  18: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  19: rustc_data_structures::stack::ensure_sufficient_stack
  20: rustc_query_system::query::plumbing::force_query_with_job
  21: rustc_query_system::query::plumbing::get_query_impl
  22: rustc_query_system::query::plumbing::ensure_query_impl
  23: rustc_interface::passes::analysis
  24: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::analysis>::compute
  25: rustc_middle::dep_graph::<impl rustc_query_system::dep_graph::DepKind for rustc_middle::dep_graph::dep_node::DepKind>::with_deps
  26: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  27: rustc_data_structures::stack::ensure_sufficient_stack
  28: rustc_query_system::query::plumbing::force_query_with_job
  29: rustc_query_system::query::plumbing::get_query_impl
  30: rustc_interface::passes::QueryContext::enter
  31: rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter
  32: rustc_span::with_source_map
  33: rustc_interface::interface::create_compiler_and_run
  34: scoped_tls::ScopedKey<T>::set
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/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md
note: rustc 1.52.0-nightly (e9920ef77 2021-02-11) running on x86_64-unknown-linux-gnu
note: compiler flags: -C embed-bitcode=no -C debuginfo=2 -C incremental --crate-type bin
note: some of the compiler flags provided by cargo are hidden
query stack during panic:
#0 [mir_borrowck] borrow-checking `SnapshotCollector::collect_snapshots`
#1 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to previous error

error: could not compile `rust_test`
To learn more, run the command again with --verbose.
Process finished with exit code 101

Backtrace

error: internal compiler error: compiler/rustc_middle/src/hir/map/mod.rs:306:18: impossible case reached

thread 'rustc' panicked at 'Box<Any>', /rustc/e9920ef7749d11fc71cc32ca4ba055bcfeaab945/library/std/src/panic.rs:59:5
stack backtrace:
   0:     0x7f45775a3fa0 - std::backtrace_rs::backtrace::libunwind::trace::hb4de9797f80b7b8c
                               at /rustc/e9920ef7749d11fc71cc32ca4ba055bcfeaab945/library/std/src/../../backtrace/src/backtrace/libunwind.rs:90:5
   1:     0x7f45775a3fa0 - std::backtrace_rs::backtrace::trace_unsynchronized::h59566d0bd20efff7
                               at /rustc/e9920ef7749d11fc71cc32ca4ba055bcfeaab945/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f45775a3fa0 - std::sys_common::backtrace::_print_fmt::hcfa5ce6be50275d4
                               at /rustc/e9920ef7749d11fc71cc32ca4ba055bcfeaab945/library/std/src/sys_common/backtrace.rs:67:5
   3:     0x7f45775a3fa0 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::hd8c307a38b9bab04
                               at /rustc/e9920ef7749d11fc71cc32ca4ba055bcfeaab945/library/std/src/sys_common/backtrace.rs:46:22
   4:     0x7f4577614ebc - core::fmt::write::h3868db8542c90941
                               at /rustc/e9920ef7749d11fc71cc32ca4ba055bcfeaab945/library/core/src/fmt/mod.rs:1096:17
   5:     0x7f4577596ea2 - std::io::Write::write_fmt::hab90295d5a0f197d
                               at /rustc/e9920ef7749d11fc71cc32ca4ba055bcfeaab945/library/std/src/io/mod.rs:1568:15
   6:     0x7f45775a7e85 - std::sys_common::backtrace::_print::h19224910b8700cf1
                               at /rustc/e9920ef7749d11fc71cc32ca4ba055bcfeaab945/library/std/src/sys_common/backtrace.rs:49:5
   7:     0x7f45775a7e85 - std::sys_common::backtrace::print::h25dedfa68c5fb84a
                               at /rustc/e9920ef7749d11fc71cc32ca4ba055bcfeaab945/library/std/src/sys_common/backtrace.rs:36:9
   8:     0x7f45775a7e85 - std::panicking::default_hook::{{closure}}::h12c5765653a72a42
                               at /rustc/e9920ef7749d11fc71cc32ca4ba055bcfeaab945/library/std/src/panicking.rs:208:50
   9:     0x7f45775a79e3 - std::panicking::default_hook::he65cee71c4209f0c
                               at /rustc/e9920ef7749d11fc71cc32ca4ba055bcfeaab945/library/std/src/panicking.rs:225:9
  10:     0x7f4577e09d6b - rustc_driver::report_ice::h9bfcf5769c15fbf2
  11:     0x7f45775a8786 - std::panicking::rust_panic_with_hook::h01a674d863fe0d8a
                               at /rustc/e9920ef7749d11fc71cc32ca4ba055bcfeaab945/library/std/src/panicking.rs:595:17
  12:     0x7f45795f318e - std::panicking::begin_panic::{{closure}}::h04d9d59beaf7438f
  13:     0x7f45795f2ff9 - std::sys_common::backtrace::__rust_end_short_backtrace::h91912ecacddbde4e
  14:     0x7f45795f3132 - std::panicking::begin_panic::h3001af3848957078
  15:     0x7f45795d4ed0 - std::panic::panic_any::h4f4426de976e6adf
  16:     0x7f45795d82da - rustc_errors::HandlerInner::bug::hdf11185f92e2a22a
  17:     0x7f45795d7db3 - rustc_errors::Handler::bug::h2dfda4f443e5c9b7
  18:     0x7f45792df51a - rustc_middle::ty::context::tls::with_opt::h931a04da690f236d
  19:     0x7f457abf0e00 - rustc_middle::util::bug::opt_span_bug_fmt::h550b33bd70d0f311
  20:     0x7f45792e1d86 - rustc_middle::util::bug::bug_fmt::h36f36510cd9d6fb0
  21:     0x7f457a059ef3 - rustc_middle::hir::map::Map::item::h38779ea831b29407
  22:     0x7f457895fdb5 - rustc_mir::borrow_check::diagnostics::mutability_errors::<impl rustc_mir::borrow_check::MirBorrowckCtxt>::report_mutability_error::h9f31953fdeab2a41
  23:     0x7f4579cb4de7 - rustc_mir::borrow_check::MirBorrowckCtxt::access_place::h7d6f5b9d65ba8ac9
  24:     0x7f4579cb2735 - <rustc_mir::borrow_check::MirBorrowckCtxt as rustc_mir::dataflow::framework::visitor::ResultsVisitor>::visit_statement_before_primary_effect::hfed3a82644adb2d8
  25:     0x7f4579bce408 - <rustc_mir::dataflow::framework::direction::Forward as rustc_mir::dataflow::framework::direction::Direction>::visit_results_in_block::hadc8c1a5509312c0
  26:     0x7f4579b5fcd7 - rustc_mir::dataflow::framework::visitor::visit_results::hc22c9f4ceef08c61
  27:     0x7f4579cae17a - rustc_mir::borrow_check::do_mir_borrowck::h3413661263ce29f4
  28:     0x7f4579ba9cb3 - rustc_infer::infer::InferCtxtBuilder::enter::hb74fd86320ea36f1
  29:     0x7f4579cacf57 - rustc_mir::borrow_check::mir_borrowck::h57947c7876ea879f
  30:     0x7f4579740bac - 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::h626f7b9e9b78ef2d
  31:     0x7f457a18bfb7 - rustc_middle::dep_graph::<impl rustc_query_system::dep_graph::DepKind for rustc_middle::dep_graph::dep_node::DepKind>::with_deps::h2b9a3e2453557291
  32:     0x7f45797384d9 - rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl::h90db12b228ddedb6
  33:     0x7f4579735661 - rustc_data_structures::stack::ensure_sufficient_stack::h22af48d26d15ef1a
  34:     0x7f4579745b81 - rustc_query_system::query::plumbing::force_query_with_job::h5fa612051f70510d
  35:     0x7f45797432f8 - rustc_query_system::query::plumbing::get_query_impl::h6055f87cc26b791b
  36:     0x7f4579745997 - rustc_query_system::query::plumbing::ensure_query_impl::he177fc338b1f472c
  37:     0x7f4579757932 - rustc_interface::passes::analysis::heddb9cef62da4ab1
  38:     0x7f457a133d89 - rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::analysis>::compute::hc584fab50c0e9742
  39:     0x7f4577db689f - rustc_middle::dep_graph::<impl rustc_query_system::dep_graph::DepKind for rustc_middle::dep_graph::dep_node::DepKind>::with_deps::he189719f47fb03a4
  40:     0x7f457a145854 - rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl::h90cdb9d4b5390542
  41:     0x7f457a152835 - rustc_data_structures::stack::ensure_sufficient_stack::hc03964f1cadb8cd3
  42:     0x7f457a134ab1 - rustc_query_system::query::plumbing::force_query_with_job::h085fb2f93a800461
  43:     0x7f457a1340c1 - rustc_query_system::query::plumbing::get_query_impl::hc18a830d288c39e4
  44:     0x7f457a14c92a - rustc_interface::passes::QueryContext::enter::hf896adfd99e9040f
  45:     0x7f457a112c34 - rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter::h2ac7000621882a7f
  46:     0x7f457a14bf94 - rustc_span::with_source_map::h9c33ff8439fe9783
  47:     0x7f457a113d97 - rustc_interface::interface::create_compiler_and_run::h39c6799ffe196408
  48:     0x7f457a1525b8 - scoped_tls::ScopedKey<T>::set::h0eb8893a0191dbc1
  49:     0x7f457a152aa8 - std::sys_common::backtrace::__rust_begin_short_backtrace::hccc56e59b0e3233c
  50:     0x7f457a1339ba - core::ops::function::FnOnce::call_once{{vtable.shim}}::h09f6484b7e2514ef
  51:     0x7f45775b8daa - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h321523073ee11258
                               at /rustc/e9920ef7749d11fc71cc32ca4ba055bcfeaab945/library/alloc/src/boxed.rs:1548:9
  52:     0x7f45775b8daa - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::hf0e85e12c83b99b3
                               at /rustc/e9920ef7749d11fc71cc32ca4ba055bcfeaab945/library/alloc/src/boxed.rs:1548:9
  53:     0x7f45775b8daa - std::sys::unix::thread::Thread::new::thread_start::hba22c7961aa0e2f8
                               at /rustc/e9920ef7749d11fc71cc32ca4ba055bcfeaab945/library/std/src/sys/unix/thread.rs:71:17
  54:     0x7f45774bb299 - start_thread
  55:     0x7f45773d0153 - clone
  56:                0x0 - <unknown>

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 1.52.0-nightly (e9920ef77 2021-02-11) running on x86_64-unknown-linux-gnu

note: compiler flags: -C embed-bitcode=no -C debuginfo=2 -C incremental --crate-type bin

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

query stack during panic:
#0 [mir_borrowck] borrow-checking `SnapshotCollector::collect_snapshots`
#1 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to previous error

error: could not compile `rust_test`

[JohnTitor]

Duplicate of #82032, this should be fixed on the latest nightly.