When there is an ICE in the tests, the output is unreadable

[RalfJung]

This can be easily reproduced by making some shim ICE and running ./miri test. It leads to output like

pass test got exit status: 101, but expected 0

A bug in `ui_test` occurred: test panicked: stderr:
thread 'rustc' panicked at src/shims/panic.rs:132:9:
not yet implemented
stack backtrace:
   0:     0x7f367a563dec - std::backtrace_rs::backtrace::libunwind::trace::h4b664a9a7853e75c
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
   1:     0x7f367a563dec - std::backtrace_rs::backtrace::trace_unsynchronized::h93aa5c3a7318d076
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f367a563dec - std::sys_common::backtrace::_print_fmt::h2f8987280a2d968f
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/library/std/src/sys_common/backtrace.rs:67:5
   3:     0x7f367a563dec - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h105ce4d686fff802
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x7f367a5ca05c - core::fmt::rt::Argument::fmt::hb779957f0b55f469
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/library/core/src/fmt/rt.rs:138:9
   5:     0x7f367a5ca05c - core::fmt::write::hbaebfa7aeff4d564
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/library/core/src/fmt/mod.rs:1094:21
   6:     0x7f367a5568fe - std::io::Write::write_fmt::h1aac7745b5ca625f
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/library/std/src/io/mod.rs:1714:15
   7:     0x7f367a563bd4 - std::sys_common::backtrace::_print::h1b05691ed6dfdd5d
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/library/std/src/sys_common/backtrace.rs:47:5
   8:     0x7f367a563bd4 - std::sys_common::backtrace::print::h59d8584ac40b66e8
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/library/std/src/sys_common/backtrace.rs:34:9
   9:     0x7f367a566cea - std::panicking::panic_hook_with_disk_dump::{{closure}}::h3d9014002f8cd732
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/library/std/src/panicking.rs:280:22
  10:     0x7f367a5669e5 - std::panicking::panic_hook_with_disk_dump::ha9bd9f0c11eb0ef4
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/library/std/src/panicking.rs:314:9
  11:     0x7f367d751de9 - rustc_driver_impl[d85fae848861c4cc]::install_ice_hook::{closure#0}
  12:     0x7f367a5675a3 - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::h9b6c3254e69f7b38
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/library/alloc/src/boxed.rs:2021:9
  13:     0x7f367a5675a3 - std::panicking::rust_panic_with_hook::hb1a71452160738b5
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/library/std/src/panicking.rs:757:13
  14:     0x7f367a5672d6 - std::panicking::begin_panic_handler::{{closure}}::h61afee132e3dfffd
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/library/std/src/panicking.rs:623:13
  15:     0x7f367a564316 - std::sys_common::backtrace::__rust_end_short_backtrace::h444631489abc9ff7
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/library/std/src/sys_common/backtrace.rs:170:18
  16:     0x7f367a567062 - rust_begin_unwind
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/library/std/src/panicking.rs:619:5
  17:     0x7f367a5c6405 - core::panicking::panic_fmt::h6ebb53beffd55382
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/library/core/src/panicking.rs:72:14
  18:     0x7f367a5c64a3 - core::panicking::panic::h77aa768aea1111af
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/library/core/src/panicking.rs:127:5
  19:     0x55bdf313d280 - miri::shims::panic::EvalContextExt::handle_stack_pop_unwind::h8816ea6b4ffbf1ab
                               at /home/r/src/rust/miri/src/shims/panic.rs:132:9
  20:     0x55bdf313d280 - <miri::machine::MiriMachine as rustc_const_eval::interpret::machine::Machine>::after_stack_pop::h254e95757ad775ba
                               at /home/r/src/rust/miri/src/machine.rs:1405:19
  21:     0x55bdf313d280 - rustc_const_eval::interpret::eval_context::InterpCx<M>::pop_stack_frame::h88cf71fb86a95642
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/compiler/rustc_const_eval/src/interpret/eval_context.rs:868:12
  22:     0x55bdf316ae56 - rustc_const_eval::interpret::terminator::<impl rustc_const_eval::interpret::eval_context::InterpCx<M>>::eval_terminator::hb5ab54be79b5d5fc
  23:     0x55bdf316ae56 - rustc_const_eval::interpret::step::<impl rustc_const_eval::interpret::eval_context::InterpCx<M>>::terminator::h352b0ad1d5d06d97
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/compiler/rustc_const_eval/src/interpret/step.rs:317:9
  24:     0x55bdf316ae56 - rustc_const_eval::interpret::step::<impl rustc_const_eval::interpret::eval_context::InterpCx<M>>::step::h4646f33e925f5fbd
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/compiler/rustc_const_eval/src/interpret/step.rs:48:9
  25:     0x55bdf316ae56 - miri::concurrency::thread::EvalContextExt::run_threads::hb9b0ec506dd885bf
                               at /home/r/src/rust/miri/src/concurrency/thread.rs:1043:25
  26:     0x55bdf30c3dac - miri::eval::eval_entry::{{closure}}::hb0729c385c251d06
                               at /home/r/src/rust/miri/src/eval.rs:446:49
  27:     0x55bdf30c3dac - core::ops::function::FnOnce::call_once::h30a5dfbc51033d29
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/library/core/src/ops/function.rs:250:5
  28:     0x55bdf30c3dac - <core::panic::unwind_safe::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once::hded092bd1920cfd0
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/library/core/src/panic/unwind_safe.rs:271:9
  29:     0x55bdf30c3dac - std::panicking::try::do_call::ha267ef4f3a8e9753
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/library/std/src/panicking.rs:526:40
  30:     0x55bdf30c3dac - std::panicking::try::he6d5145c92826396
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/library/std/src/panicking.rs:490:19
  31:     0x55bdf30c3dac - std::panic::catch_unwind::h0ba7bc5a12cf3d0a
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/library/std/src/panic.rs:142:14
  32:     0x55bdf30c3dac - miri::eval::eval_entry::h6a4a2c6bb6f993f6
                               at /home/r/src/rust/miri/src/eval.rs:446:9
  33:     0x55bdf302b14c - <miri::MiriCompilerCalls as rustc_driver_impl::Callbacks>::after_analysis::{{closure}}::h14dcc27ccfd19476
                               at /home/r/src/rust/miri/src/bin/miri.rs:106:40
  34:     0x55bdf302b14c - rustc_middle::ty::context::GlobalCtxt::enter::{{closure}}::hefa188aa9cce1a8c
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/compiler/rustc_middle/src/ty/context.rs:593:37
  35:     0x55bdf302b14c - rustc_middle::ty::context::tls::enter_context::{{closure}}::h38294d9618d19063
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/compiler/rustc_middle/src/ty/context/tls.rs:82:9
  36:     0x55bdf302b14c - std::thread::local::LocalKey<T>::try_with::h3ad36c6fce68b6c9
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/library/std/src/thread/local.rs:270:16
  37:     0x55bdf302b14c - std::thread::local::LocalKey<T>::with::hc489a096e9f1fb25
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/library/std/src/thread/local.rs:246:9
  38:     0x55bdf302b14c - rustc_middle::ty::context::tls::enter_context::hf678fdc99c5bc317
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/compiler/rustc_middle/src/ty/context/tls.rs:79:9
  39:     0x55bdf302b14c - rustc_middle::ty::context::GlobalCtxt::enter::h05b8b7ae207f80a4
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/compiler/rustc_middle/src/ty/context.rs:593:9
  40:     0x55bdf302796d - rustc_interface::queries::QueryResult<&rustc_middle::ty::context::GlobalCtxt>::enter::h4bc4565053936a1b
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/compiler/rustc_interface/src/queries.rs:69:9
  41:     0x55bdf302796d - <miri::MiriCompilerCalls as rustc_driver_impl::Callbacks>::after_analysis::h7ae9bc11b35dfea7
                               at /home/r/src/rust/miri/src/bin/miri.rs:66:9
  42:     0x7f367c9b291c - <rustc_interface[8a6f8ad1c34a5f70]::interface::Compiler>::enter::<rustc_driver_impl[d85fae848861c4cc]::run_compiler::{closure#1}::{closure#2}, core[d800f448664a514]::result::Result<core[d800f448664a514]::option::Option<rustc_interface[8a6f8ad1c34a5f70]::queries::Linker>, rustc_span[5837f1b58b81b15d]::ErrorGuaranteed>>
  43:     0x7f367c9aa0f8 - std[b009c5d90180bac5]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[8a6f8ad1c34a5f70]::util::run_in_thread_with_globals<rustc_interface[8a6f8ad1c34a5f70]::interface::run_compiler<core[d800f448664a514]::result::Result<(), rustc_span[5837f1b58b81b15d]::ErrorGuaranteed>, rustc_driver_impl[d85fae848861c4cc]::run_compiler::{closure#1}>::{closure#0}, core[d800f448664a514]::result::Result<(), rustc_span[5837f1b58b81b15d]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[d800f448664a514]::result::Result<(), rustc_span[5837f1b58b81b15d]::ErrorGuaranteed>>
  44:     0x7f367c9a986e - <<std[b009c5d90180bac5]::thread::Builder>::spawn_unchecked_<rustc_interface[8a6f8ad1c34a5f70]::util::run_in_thread_with_globals<rustc_interface[8a6f8ad1c34a5f70]::interface::run_compiler<core[d800f448664a514]::result::Result<(), rustc_span[5837f1b58b81b15d]::ErrorGuaranteed>, rustc_driver_impl[d85fae848861c4cc]::run_compiler::{closure#1}>::{closure#0}, core[d800f448664a514]::result::Result<(), rustc_span[5837f1b58b81b15d]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[d800f448664a514]::result::Result<(), rustc_span[5837f1b58b81b15d]::ErrorGuaranteed>>::{closure#1} as core[d800f448664a514]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  45:     0x7f367a572015 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h7d9536b59d7c2183
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/library/alloc/src/boxed.rs:2007:9
  46:     0x7f367a572015 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::hdfad988db41bfee4
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/library/alloc/src/boxed.rs:2007:9
  47:     0x7f367a572015 - std::sys::unix::thread::Thread::new::thread_start::hb811e169405d44af
                               at /rustc/a989e25f1b87949a886eab3da10324d14189fe95/library/std/src/sys/unix/thread.rs:108:17
  48:     0x7f367a30c3ec - start_thread
                               at ./nptl/pthread_create.c:444:8
  49:     0x7f367a38ca1c - __GI___clone3
                               at ./misc/../sysdeps/unix/sysv/linux/x86_64/clone3.S:81
  50:                0x0 - <unknown>

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

note: we would appreciate a bug report: https://github.com/rust-lang/miri/issues/new

note: rustc 1.74.0-nightly (a989e25f1 2023-09-03) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z ui-testing -Z miri-unique-is-unique -Z miri-tree-borrows

query stack during panic:
end of query stack

Miri caused an ICE during evaluation. Here's the interpreter backtrace at the time of the panic:
{"message":"the place in the program where the ICE was triggered","code":null,"level":"note","spans":[{"file_name":"/home/r/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/panicking.rs","byte_start":16646,"byte_end":16666,"line_start":477,"line_end":477,"column_start":30,"column_end":50,"is_primary":true,"text":[{"text":"    let mut data = Data { f: ManuallyDrop::new(f) };","highlight_start":30,"highlight_end":50}],"label":null,"suggested_replacement":null,"suggestion_applicability":null,"expansion":null}],"children":[{"message":"inside `std::panicking::r#try::<(), [closure@std::rt::lang_start_internal::{closure#1}]>` at /home/r/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/panicking.rs:477:30: 477:50","code":null,"level":"note","spans":[],"children":[],"rendered":null},{"message":"inside `std::panic::catch_unwind::<[closure@std::rt::lang_start_internal::{closure#1}], ()>` at /home/r/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/panic.rs:142:14: 142:33","code":null,"level":"note","spans":[],"children":[],"rendered":null},{"message":"inside `std::rt::lang_start_internal` at /home/r/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/rt.rs:147:5: 147:70","code":null,"level":"note","spans":[],"children":[],"rendered":null},{"message":"inside `std::rt::lang_start::<()>` at /home/r/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/rt.rs:165:17: 170:6","code":null,"level":"note","spans":[],"children":[],"rendered":null}],"rendered":"note: the place in the program where the ICE was triggered\n  --> /home/r/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/panicking.rs:477:30\n   |\nLL |     let mut data = Data { f: ManuallyDrop::new(f) };\n   |                              ^^^^^^^^^^^^^^^^^^^^\n   |\n   = note: inside `std::panicking::r#try::<(), [closure@std::rt::lang_start_internal::{closure#1}]>` at /home/r/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/panicking.rs:477:30: 477:50\n   = note: inside `std::panic::catch_unwind::<[closure@std::rt::lang_start_internal::{closure#1}], ()>` at /home/r/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/panic.rs:142:14: 142:33\n   = note: inside `std::rt::lang_start_internal` at /home/r/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/rt.rs:147:5: 147:70\n   = note: inside `std::rt::lang_start::<()>` at /home/r/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/rt.rs:165:17: 170:6\n\n"}

In particular note the unreadable junk of JSON at the end.

Seems to be some ui-test problem? Cc @oli-obk