$ cargo new repro
$ cd repro
$ echo "😀" > Cargo.toml
$ cargo check
thread 'main' panicked at /rust/deps/annotate-snippets-0.11.1/src/renderer/display_list.rs:914:45:
byte index 1 is not a char boundary; it is inside '😀' (bytes 0..4) of `😀`
stack backtrace:
   0:     0x556fa0dd2ad5 - std::backtrace_rs::backtrace::libunwind::trace::hc79cced6f418596d
                               at /rustc/9d5cdf75aa42faaf0b58ba21a510117e8d0051a3/library/std/src/../../backtrace/src/backtrace/libunwind.rs:105:5
   1:     0x556fa0dd2ad5 - std::backtrace_rs::backtrace::trace_unsynchronized::h06f3eef6c8a22cf0
                               at /rustc/9d5cdf75aa42faaf0b58ba21a510117e8d0051a3/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x556fa0dd2ad5 - std::sys_common::backtrace::_print_fmt::hba273d0c77fc3421
                               at /rustc/9d5cdf75aa42faaf0b58ba21a510117e8d0051a3/library/std/src/sys_common/backtrace.rs:68:5
   3:     0x556fa0dd2ad5 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h409f1e3c1e32650e
                               at /rustc/9d5cdf75aa42faaf0b58ba21a510117e8d0051a3/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x556fa0e05d6b - core::fmt::rt::Argument::fmt::h8811fe3c91cda7b3
                               at /rustc/9d5cdf75aa42faaf0b58ba21a510117e8d0051a3/library/core/src/fmt/rt.rs:142:9
   5:     0x556fa0e05d6b - core::fmt::write::h7a8f70a9b146d9ee
                               at /rustc/9d5cdf75aa42faaf0b58ba21a510117e8d0051a3/library/core/src/fmt/mod.rs:1153:17
   6:     0x556fa0dccabf - std::io::Write::write_fmt::h32fb818656611c58
                               at /rustc/9d5cdf75aa42faaf0b58ba21a510117e8d0051a3/library/std/src/io/mod.rs:1843:15
   7:     0x556fa0dd28ae - std::sys_common::backtrace::_print::h0dc0bbf9b429a58b
                               at /rustc/9d5cdf75aa42faaf0b58ba21a510117e8d0051a3/library/std/src/sys_common/backtrace.rs:47:5
   8:     0x556fa0dd28ae - std::sys_common::backtrace::print::hf60182bd4aee207d
                               at /rustc/9d5cdf75aa42faaf0b58ba21a510117e8d0051a3/library/std/src/sys_common/backtrace.rs:34:9
   9:     0x556fa0dd46b9 - std::panicking::default_hook::{{closure}}::hd90db44a41f772dc
  10:     0x556fa0dd43d5 - std::panicking::default_hook::hd86be16b87521210
                               at /rustc/9d5cdf75aa42faaf0b58ba21a510117e8d0051a3/library/std/src/panicking.rs:291:9
  11:     0x556fa0dd4bc4 - std::panicking::rust_panic_with_hook::ha4f8caa112a16574
                               at /rustc/9d5cdf75aa42faaf0b58ba21a510117e8d0051a3/library/std/src/panicking.rs:788:13
  12:     0x556fa0dd4aa6 - std::panicking::begin_panic_handler::{{closure}}::hc879855deab44ed0
                               at /rustc/9d5cdf75aa42faaf0b58ba21a510117e8d0051a3/library/std/src/panicking.rs:657:13
  13:     0x556fa0dd2f99 - std::sys_common::backtrace::__rust_end_short_backtrace::h85e59f289fdfff6c
                               at /rustc/9d5cdf75aa42faaf0b58ba21a510117e8d0051a3/library/std/src/sys_common/backtrace.rs:171:18
  14:     0x556fa0dd47d7 - rust_begin_unwind
                               at /rustc/9d5cdf75aa42faaf0b58ba21a510117e8d0051a3/library/std/src/panicking.rs:645:5
  15:     0x556fa0e02ee6 - core::panicking::panic_fmt::h0baef2c59e253f8d
                               at /rustc/9d5cdf75aa42faaf0b58ba21a510117e8d0051a3/library/core/src/panicking.rs:72:14
  16:     0x556fa0e09b0b - core::str::slice_error_fail_rt::h0fde66b0a6d20273
  17:     0x556fa0e096ea - core::str::slice_error_fail::hbfd47a9ba2a36f47
                               at /rustc/9d5cdf75aa42faaf0b58ba21a510117e8d0051a3/library/core/src/str/mod.rs:89:5
  18:     0x556fa0427fc9 - annotate_snippets[e4e707aa9ab1739b]::renderer::display_list::format_message
  19:     0x556fa042a09e - <annotate_snippets[e4e707aa9ab1739b]::renderer::Renderer>::render
  20:     0x556fa0383380 - cargo[f8998d74d42138ce]::util::toml::emit_diagnostic
  21:     0x556fa03fa4c8 - cargo[f8998d74d42138ce]::util::toml::read_manifest
  22:     0x556fa01bda70 - <cargo[f8998d74d42138ce]::core::workspace::Packages>::load
  23:     0x556fa01ad9d2 - <cargo[f8998d74d42138ce]::core::workspace::Workspace>::find_root
  24:     0x556fa01a396b - <cargo[f8998d74d42138ce]::core::workspace::Workspace>::new
  25:     0x556f9fc2d552 - <clap_builder[332e728b3c5c62a0]::parser::matches::arg_matches::ArgMatches as cargo[f8998d74d42138ce]::util::command_prelude::ArgMatchesExt>::workspace
  26:     0x556f9fc4e397 - cargo[94ff50f027133d42]::commands::check::exec
  27:     0x556f9fc74ce1 - <cargo[94ff50f027133d42]::cli::Exec>::exec
  28:     0x556f9fc6b035 - cargo[94ff50f027133d42]::main
  29:     0x556f9fbe5fc3 - std[2c420855e262d42e]::sys_common::backtrace::__rust_begin_short_backtrace::<fn(), ()>
  30:     0x556f9fbf7229 - std[2c420855e262d42e]::rt::lang_start::<()>::{closure#0}
  31:     0x556fa0dc1526 - core::ops::function::impls::<impl core::ops::function::FnOnce<A> for &F>::call_once::hf3af2e81b57eee1a
                               at /rustc/9d5cdf75aa42faaf0b58ba21a510117e8d0051a3/library/core/src/ops/function.rs:284:13
  32:     0x556fa0dc1526 - std::panicking::try::do_call::hb3a235e132e17a7b
                               at /rustc/9d5cdf75aa42faaf0b58ba21a510117e8d0051a3/library/std/src/panicking.rs:552:40
  33:     0x556fa0dc1526 - std::panicking::try::h9a35e2fbb67ddfb8
                               at /rustc/9d5cdf75aa42faaf0b58ba21a510117e8d0051a3/library/std/src/panicking.rs:516:19
  34:     0x556fa0dc1526 - std::panic::catch_unwind::h70d81b8297945eb2
                               at /rustc/9d5cdf75aa42faaf0b58ba21a510117e8d0051a3/library/std/src/panic.rs:149:14
  35:     0x556fa0dc1526 - std::rt::lang_start_internal::{{closure}}::h27683abc3351933d
                               at /rustc/9d5cdf75aa42faaf0b58ba21a510117e8d0051a3/library/std/src/rt.rs:141:48
  36:     0x556fa0dc1526 - std::panicking::try::do_call::h2c3b862fb38ac0d1
                               at /rustc/9d5cdf75aa42faaf0b58ba21a510117e8d0051a3/library/std/src/panicking.rs:552:40
  37:     0x556fa0dc1526 - std::panicking::try::hf08b476bbfbd814f
                               at /rustc/9d5cdf75aa42faaf0b58ba21a510117e8d0051a3/library/std/src/panicking.rs:516:19
  38:     0x556fa0dc1526 - std::panic::catch_unwind::hd5ad4d488136ca1a
                               at /rustc/9d5cdf75aa42faaf0b58ba21a510117e8d0051a3/library/std/src/panic.rs:149:14
  39:     0x556fa0dc1526 - std::rt::lang_start_internal::heb1252f709ae92c2
                               at /rustc/9d5cdf75aa42faaf0b58ba21a510117e8d0051a3/library/std/src/rt.rs:141:20
  40:     0x556f9fc7b0b5 - main
  41:     0x7f037831acd0 - <unknown>
  42:     0x7f037831ad8a - __libc_start_main
  43:     0x556f9fbc4029 - <unknown>
  44:                0x0 - <unknown>