cargo fix panics thread 'main' panicked at 'byte index 22 is not a char boundary;

[matthiaskrgr]

Steps

git clone https://github.com/rust-lang/regex
cd regex
git checkout 06e26d070d1889062b96b138eb05117300ba0ec2
RUST_BACKTRACE=Full cargo fix -Z unstable-options --clippy 

I was not able to reproduce by just running "cargo clippy" so I assume this is a cargo fix bug.

Problem
Cargo fix panics:

thread 'main' panicked at 'byte index 22 is not a char boundary; it is inside '☃' (bytes 20..23) of `mat!(uni_literal, r"☃", "☃", Some((0, 3)));`', src/libcore/str/mod.rs:2046:5
stack backtrace:
   0: backtrace::backtrace::libunwind::trace
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.34/src/backtrace/libunwind.rs:88
   1: backtrace::backtrace::trace_unsynchronized
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.34/src/backtrace/mod.rs:66
   2: std::sys_common::backtrace::_print
             at src/libstd/sys_common/backtrace.rs:47
   3: std::sys_common::backtrace::print
             at src/libstd/sys_common/backtrace.rs:36
   4: std::panicking::default_hook::{{closure}}
             at src/libstd/panicking.rs:200
   5: std::panicking::default_hook
             at src/libstd/panicking.rs:214
   6: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:477
   7: std::panicking::continue_panic_fmt
             at src/libstd/panicking.rs:384
   8: rust_begin_unwind
             at src/libstd/panicking.rs:311
   9: core::panicking::panic_fmt
             at src/libcore/panicking.rs:85
  10: core::str::slice_error_fail
             at src/libcore/str/mod.rs:0
  11: core::str::traits::<impl core::slice::SliceIndex<str> for core::ops::range::Range<usize>>::index::{{closure}}
  12: rustfix::parse_snippet
  13: <core::iter::adapters::FilterMap<I,F> as core::iter::traits::iterator::Iterator>::next
  14: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T,I>>::from_iter
  15: rustfix::collect_suggestions
  16: cargo::ops::fix::rustfix_crate
  17: cargo::ops::fix::fix_maybe_exec_rustc
  18: cargo::main
  19: std::rt::lang_start::{{closure}}
  20: std::rt::lang_start_internal::{{closure}}
             at src/libstd/rt.rs:49
  21: std::panicking::try::do_call
             at src/libstd/panicking.rs:296
  22: __rust_maybe_catch_panic
             at src/libpanic_unwind/lib.rs:80
  23: std::panicking::try
             at src/libstd/panicking.rs:275
  24: std::panic::catch_unwind
             at src/libstd/panic.rs:394
  25: std::rt::lang_start_internal
             at src/libstd/rt.rs:48
  26: main
  27: __libc_start_main
  28: <unknown>

Possible Solution(s)
Don't panic ™

Notes

Output of cargo version:

cargo 1.38.0-nightly (d0f828419 2019-07-23)

rustc 1.38.0-nightly (8a58268b5 2019-07-31)
binary: rustc
commit-hash: 8a58268b5ad9c4a240be349a633069d48991eb0c
commit-date: 2019-07-31
host: x86_64-unknown-linux-gnu
release: 1.38.0-nightly
LLVM version: 9.0

clippy 0.0.212 (c3e9136 2019-07-30)

[ehuss]

Thanks! This has been fixed by rust-lang/rustfix#167, but the PR seems to be a little stuck.

[alexcrichton]

Ok I've published 0.4.6 of rustfix, @ehuss would you be up for pulling that into Cargo?