thread 'rustc' panicked at 'assertion failed: !value.has_escaping_bound_vars()'

[dario23]

encountered this one while debugging.

to reproduce, run e.g. PATH=${PWD}/target/debug:$PATH RUST_BACKTRACE=full cargo run --bin cargo-semver -- -S trust-dns-proto:0.21.0 -C trust-dns-proto:0.21.1.

this leads to the following backtrace

backtrace: thread 'rustc' panicked at 'assertion failed: !value.has_escaping_bound_vars()', /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/compiler/rustc_middle/src/ty/sty.rs:1098:9

thread 'rustc' panicked at 'assertion failed: !value.has_escaping_bound_vars()', /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/compiler/rustc_middle/src/ty/sty.rs:1098:9
stack backtrace:
   0:     0x7f5fb984d85d - std::backtrace_rs::backtrace::libunwind::trace::hd79e9b51bb0b02a3
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
   1:     0x7f5fb984d85d - std::backtrace_rs::backtrace::trace_unsynchronized::hc4b2624d11f57391
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f5fb984d85d - std::sys_common::backtrace::_print_fmt::h5b920b6df28041d5
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/library/std/src/sys_common/backtrace.rs:66:5
   3:     0x7f5fb984d85d - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h01f2db48eea34166
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/library/std/src/sys_common/backtrace.rs:45:22
   4:     0x7f5fb98a8efc - core::fmt::write::h743b8fce003c331c
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/library/core/src/fmt/mod.rs:1194:17
   5:     0x7f5fb983f041 - std::io::Write::write_fmt::h55edc38b905db9b5
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/library/std/src/io/mod.rs:1655:15
   6:     0x7f5fb9850575 - std::sys_common::backtrace::_print::h72c54a6b7a86b7bf
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/library/std/src/sys_common/backtrace.rs:48:5
   7:     0x7f5fb9850575 - std::sys_common::backtrace::print::h8b541992f5fa33c9
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/library/std/src/sys_common/backtrace.rs:35:9
   8:     0x7f5fb9850575 - std::panicking::default_hook::{{closure}}::h47e8a61e5844dea4
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/library/std/src/panicking.rs:295:22
   9:     0x7f5fb98501e9 - std::panicking::default_hook::h65ae1796882c178c
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/library/std/src/panicking.rs:314:9
  10:     0x7f5fb9850c98 - std::panicking::rust_panic_with_hook::h1c3eee211b989bad
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/library/std/src/panicking.rs:698:17
  11:     0x7f5fb9850b09 - std::panicking::begin_panic_handler::{{closure}}::h653627205f5b2cdc
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/library/std/src/panicking.rs:586:13
  12:     0x7f5fb984dd14 - std::sys_common::backtrace::__rust_end_short_backtrace::h36d845a914b6aae7
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/library/std/src/sys_common/backtrace.rs:138:18
  13:     0x7f5fb9850879 - rust_begin_unwind
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/library/std/src/panicking.rs:584:5
  14:     0x7f5fb9815bd3 - core::panicking::panic_fmt::hb6389d787a80a806
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/library/core/src/panicking.rs:142:14
  15:     0x7f5fb9815a9d - core::panicking::panic::hac9e097b59d15ac2
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/library/core/src/panicking.rs:48:5
  16:     0x562bc1c93eac - rustc_middle::ty::sty::Binder<T>::dummy::hc35695d3676baff3
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/compiler/rustc_middle/src/ty/sty.rs:1098:9
  17:     0x562bc1c09366 - semverver::translate::TranslationContext::translate::{{closure}}::{{closure}}::{{closure}}::hc6a8f1bf659feeee
                               at /home/dario/git/rust-semverver/src/translate.rs:217:61
  18:     0x562bc1c942ca - rustc_middle::ty::sty::Binder<T>::map_bound::heb9dd7ae3f8c9f15
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/compiler/rustc_middle/src/ty/sty.rs:1159:21
  19:     0x562bc1c07f27 - semverver::translate::TranslationContext::translate::{{closure}}::{{closure}}::h5ac5d64345af5ae7
                               at /home/dario/git/rust-semverver/src/translate.rs:214:33
  20:     0x562bc1be4ec0 - core::iter::adapters::map::map_fold::{{closure}}::h6b51feaca4e154b7
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/library/core/src/iter/adapters/map.rs:84:28
  21:     0x562bc1b7f74b - core::iter::adapters::copied::copy_fold::{{closure}}::hc714b4e8b394e4ff
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/library/core/src/iter/adapters/copied.rs:28:22
  22:     0x562bc1c0bb8a - core::iter::traits::iterator::Iterator::fold::h9f7486ecf315ae85
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/library/core/src/iter/traits/iterator.rs:2366:21
  23:     0x562bc1b7ba55 - <core::iter::adapters::copied::Copied<I> as core::iter::traits::iterator::Iterator>::fold::ha169f444cf8514c8
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/library/core/src/iter/adapters/copied.rs:64:9
  24:     0x562bc1be1e24 - <core::iter::adapters::map::Map<I,F> as core::iter::traits::iterator::Iterator>::fold::h25dc3993e2da7add
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/library/core/src/iter/adapters/map.rs:124:9
  25:     0x562bc1be378a - core::iter::traits::iterator::Iterator::for_each::hd45773299699416e
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/library/core/src/iter/traits/iterator.rs:783:9
  26:     0x562bc1c57d95 - <alloc::vec::Vec<T,A> as alloc::vec::spec_extend::SpecExtend<T,I>>::spec_extend::h783769f0e9efdddd
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/library/alloc/src/vec/spec_extend.rs:40:17
  27:     0x562bc1c4fee8 - <alloc::vec::Vec<T> as alloc::vec::spec_from_iter_nested::SpecFromIterNested<T,I>>::from_iter::h4ed792443346ed88
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/library/alloc/src/vec/spec_from_iter_nested.rs:62:9
  28:     0x562bc1c586ed - <alloc::vec::Vec<T> as alloc::vec::spec_from_iter::SpecFromIter<T,I>>::from_iter::h3f52b7a4f9b775a2
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/library/alloc/src/vec/spec_from_iter.rs:33:9
  29:     0x562bc1c578e0 - <alloc::vec::Vec<T> as core::iter::traits::collect::FromIterator<T>>::from_iter::hfda6628d337bb7e4
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/library/alloc/src/vec/mod.rs:2610:9
  30:     0x562bc1be32ad - core::iter::traits::iterator::Iterator::collect::h63cc56a05cda0be8
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/library/core/src/iter/traits/iterator.rs:1788:9
  31:     0x562bc1c0595d - semverver::translate::TranslationContext::translate::{{closure}}::h6c6c2a350a79e1de
                               at /home/dario/git/rust-semverver/src/translate.rs:211:43
  32:     0x562bc1c232dd - <rustc_middle::ty::fold::BottomUpFolder<F,G,H> as rustc_middle::ty::fold::TypeFolder>::fold_ty::hbcf3c3ccb88cc4ef
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/compiler/rustc_middle/src/ty/fold.rs:424:9
  33:     0x562bc1c23c44 - <F as rustc_middle::ty::fold::FallibleTypeFolder>::try_fold_ty::hf8ef379f4253fe23
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/compiler/rustc_middle/src/ty/fold.rs:337:12
  34:     0x562bc1b1ee71 - rustc_middle::ty::structural_impls::<impl rustc_middle::ty::fold::TypeFoldable for rustc_middle::ty::Ty>::try_fold_with::h4501b28e212430f0
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/compiler/rustc_middle/src/ty/structural_impls.rs:1020:9
  35:     0x562bc1ca0935 - <rustc_middle::ty::subst::GenericArg as rustc_middle::ty::fold::TypeFoldable>::try_super_fold_with::h54b6bf0441d718e5
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/compiler/rustc_middle/src/ty/subst.rs:205:41
  36:     0x562bc1c9f464 - rustc_middle::ty::fold::TypeFoldable::try_fold_with::hf2740bb3001e227e
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/compiler/rustc_middle/src/ty/fold.rs:79:9
  37:     0x562bc1c20d0a - rustc_middle::ty::subst::<impl rustc_middle::ty::fold::TypeFoldable for &rustc_middle::ty::list::List<rustc_middle::ty::subst::GenericArg>>::try_super_fold_with::hbc295fac082fe589
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/compiler/rustc_middle/src/ty/subst.rs:444:30
  38:     0x562bc1c1c684 - rustc_middle::ty::fold::TypeFoldable::try_fold_with::hd13bd82c79325588
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/compiler/rustc_middle/src/ty/fold.rs:79:9
  39:     0x562bc1b227e5 - rustc_middle::ty::structural_impls::<impl rustc_middle::ty::fold::TypeFoldable for rustc_middle::ty::Ty>::try_super_fold_with::hea27a9e4a4f7dd5c
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/compiler/rustc_middle/src/ty/structural_impls.rs:983:50
  40:     0x562bc1b25494 - rustc_middle::ty::fold::TypeFoldable::super_fold_with::hfd4ab988bc211f81
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/compiler/rustc_middle/src/ty/fold.rs:102:9
  41:     0x562bc1c232b6 - <rustc_middle::ty::fold::BottomUpFolder<F,G,H> as rustc_middle::ty::fold::TypeFolder>::fold_ty::hbcf3c3ccb88cc4ef
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/compiler/rustc_middle/src/ty/fold.rs:423:17
  42:     0x562bc1c23c44 - <F as rustc_middle::ty::fold::FallibleTypeFolder>::try_fold_ty::hf8ef379f4253fe23
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/compiler/rustc_middle/src/ty/fold.rs:337:12
  43:     0x562bc1b1ee71 - rustc_middle::ty::structural_impls::<impl rustc_middle::ty::fold::TypeFoldable for rustc_middle::ty::Ty>::try_fold_with::h4501b28e212430f0
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/compiler/rustc_middle/src/ty/structural_impls.rs:1020:9
  44:     0x562bc1b255b4 - rustc_middle::ty::fold::TypeFoldable::fold_with::h5f951828bdeb9901
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/compiler/rustc_middle/src/ty/fold.rs:86:9
  45:     0x562bc1c04044 - semverver::translate::TranslationContext::translate::haf8700bb4f1b596e
                               at /home/dario/git/rust-semverver/src/translate.rs:169:9
  46:     0x562bc1b2fe08 - semverver::translate::TranslationContext::translate_item_type::h111fb72b8bf837fe
                               at /home/dario/git/rust-semverver/src/translate.rs:369:9
  47:     0x562bc1bc7c4e - semverver::traverse::cmp_types::{{closure}}::h88ca6b4075c5fa4c
                               at /home/dario/git/rust-semverver/src/traverse.rs:964:20
  48:     0x562bc1b1bd5d - rustc_infer::infer::InferCtxtBuilder::enter::ha6845fb8074b3475
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/compiler/rustc_infer/src/infer/mod.rs:628:9
  49:     0x562bc1b8fe1b - semverver::traverse::cmp_types::h3c31ea86b8ef4f28
                               at /home/dario/git/rust-semverver/src/traverse.rs:960:5
  50:     0x562bc1b8f5b8 - semverver::traverse::diff_types::h2b7470d2ca29cf09
                               at /home/dario/git/rust-semverver/src/traverse.rs:901:13
  51:     0x562bc1b806c9 - semverver::traverse::run_analysis::hb52283911fc549c3
                               at /home/dario/git/rust-semverver/src/traverse.rs:60:9
  52:     0x562bc194feeb - <rust_semverver::main::SemverCallbacks as rustc_driver::Callbacks>::after_analysis::{{closure}}::hf8bd7f68f1a32841
                               at /home/dario/git/rust-semverver/src/bin/rust-semverver.rs:77:43
  53:     0x562bc193f583 - rustc_interface::passes::QueryContext::enter::{{closure}}::hf945bd893778466f
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/compiler/rustc_interface/src/passes.rs:819:42
  54:     0x562bc1946e8b - rustc_middle::ty::context::tls::enter_context::{{closure}}::h27c39478cf020e88
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/compiler/rustc_middle/src/ty/context.rs:1818:50
  55:     0x562bc1946f61 - rustc_middle::ty::context::tls::set_tlv::h2b0f7ded1fd8fca8
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/compiler/rustc_middle/src/ty/context.rs:1802:9
  56:     0x562bc1946e49 - rustc_middle::ty::context::tls::enter_context::h207a64738ee9a859
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/compiler/rustc_middle/src/ty/context.rs:1818:9
  57:     0x562bc193f518 - rustc_interface::passes::QueryContext::enter::h498044fce823bc2f
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/compiler/rustc_interface/src/passes.rs:819:9
  58:     0x562bc194a946 - <rust_semverver::main::SemverCallbacks as rustc_driver::Callbacks>::after_analysis::h78f00a7c2e50150b
                               at /home/dario/git/rust-semverver/src/bin/rust-semverver.rs:53:21
  59:     0x7f5fbc002ab5 - <rustc_interface[dacacaf3651fe347]::interface::Compiler>::enter::<rustc_driver[caca827775d68846]::run_compiler::{closure#1}::{closure#2}, core[864d7ae58f623181]::result::Result<core[864d7ae58f623181]::option::Option<rustc_interface[dacacaf3651fe347]::queries::Linker>, rustc_errors[14f27e81a88a2c7]::ErrorGuaranteed>>
  60:     0x7f5fbc02c3ff - rustc_span[ff646084812721ee]::with_source_map::<core[864d7ae58f623181]::result::Result<(), rustc_errors[14f27e81a88a2c7]::ErrorGuaranteed>, rustc_interface[dacacaf3651fe347]::interface::create_compiler_and_run<core[864d7ae58f623181]::result::Result<(), rustc_errors[14f27e81a88a2c7]::ErrorGuaranteed>, rustc_driver[caca827775d68846]::run_compiler::{closure#1}>::{closure#1}>
  61:     0x7f5fbc016d64 - rustc_interface[dacacaf3651fe347]::interface::create_compiler_and_run::<core[864d7ae58f623181]::result::Result<(), rustc_errors[14f27e81a88a2c7]::ErrorGuaranteed>, rustc_driver[caca827775d68846]::run_compiler::{closure#1}>
  62:     0x7f5fbbffffa1 - <scoped_tls[d6203f3b3010b98e]::ScopedKey<rustc_span[ff646084812721ee]::SessionGlobals>>::set::<rustc_interface[dacacaf3651fe347]::interface::run_compiler<core[864d7ae58f623181]::result::Result<(), rustc_errors[14f27e81a88a2c7]::ErrorGuaranteed>, rustc_driver[caca827775d68846]::run_compiler::{closure#1}>::{closure#0}, core[864d7ae58f623181]::result::Result<(), rustc_errors[14f27e81a88a2c7]::ErrorGuaranteed>>
  63:     0x7f5fbc01954f - std[fd2a1eaf3e081d4d]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[dacacaf3651fe347]::util::run_in_thread_pool_with_globals<rustc_interface[dacacaf3651fe347]::interface::run_compiler<core[864d7ae58f623181]::result::Result<(), rustc_errors[14f27e81a88a2c7]::ErrorGuaranteed>, rustc_driver[caca827775d68846]::run_compiler::{closure#1}>::{closure#0}, core[864d7ae58f623181]::result::Result<(), rustc_errors[14f27e81a88a2c7]::ErrorGuaranteed>>::{closure#0}, core[864d7ae58f623181]::result::Result<(), rustc_errors[14f27e81a88a2c7]::ErrorGuaranteed>>
  64:     0x7f5fbc019689 - <<std[fd2a1eaf3e081d4d]::thread::Builder>::spawn_unchecked_<rustc_interface[dacacaf3651fe347]::util::run_in_thread_pool_with_globals<rustc_interface[dacacaf3651fe347]::interface::run_compiler<core[864d7ae58f623181]::result::Result<(), rustc_errors[14f27e81a88a2c7]::ErrorGuaranteed>, rustc_driver[caca827775d68846]::run_compiler::{closure#1}>::{closure#0}, core[864d7ae58f623181]::result::Result<(), rustc_errors[14f27e81a88a2c7]::ErrorGuaranteed>>::{closure#0}, core[864d7ae58f623181]::result::Result<(), rustc_errors[14f27e81a88a2c7]::ErrorGuaranteed>>::{closure#1} as core[864d7ae58f623181]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  65:     0x7f5fb985abf3 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h211dae6d8dec3611
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/library/alloc/src/boxed.rs:1866:9
  66:     0x7f5fb985abf3 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::hb54334e8a7bb1f12
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/library/alloc/src/boxed.rs:1866:9
  67:     0x7f5fb985abf3 - std::sys::unix::thread::Thread::new::thread_start::hf8b57655f2f2e68e
                               at /rustc/4ca19e09d302a4cbde14f9cb1bc109179dc824cd/library/std/src/sys/unix/thread.rs:108:17
  68:     0x7f5fb9759d80 - start_thread
  69:     0x7f5fb967176f - clone
  70:                0x0 - <unknown>
error: rustc-semverver errored

the issue seems to be that we use Binder::dummy with something that does contain bound vars, so the call panic!s somewhere inside the rustc machinery.

note that there are a number of Binder::dummy calls in the codebase, and i guess we'd need to check this for any of them.