Fuzzer bug test_syntax panic with push_str: ( with text

[lukewilliamboswell]

thread 'main' panicked at crates/compiler/fmt/src/def.rs:561:21:
push_str: `(` with text:
il3 \k -> # w#z
    CCCC # i
thread 'main' panicked at crates/compiler/fmt/src/def.rs:561:21:
push_str: `(` with text:
il3 \k -> # w#z
    CCC @C #
No more minimizations found
Final result:
il3\k->#w#z
 CCC@C(#i
t!K):i
 C

thread '<unnamed>' panicked at /Users/luke/Documents/GitHub/roc/crates/compiler/fmt/src/def.rs:561:21:
push_str: `(` with text:
il3 \k -> # w#z
    CCC @C # i
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
==5166== ERROR: libFuzzer: deadly signal
NOTE: libFuzzer has rudimentary signal handlers.
      Combine libFuzzer with AddressSanitizer or similar for better crash reports.
SUMMARY: libFuzzer: deadly signal
MS: 1 CopyPart-; base unit: 2f4c4c41219bde03ee299fdac010eb1afddf650b
0x69,0x6c,0x33,0x5c,0x6b,0x2d,0x3e,0x23,0x77,0x23,0x7a,0xa,0x20,0x20,0x43,0x43,0x43,0x40,0x43,0x28,0x23,0x69,0xa,0x20,0xa,0xa,0x74,0x61,0x31,0x21,0x4b,0x29,0x43,0x41,0x40,0x43,0x28,0xa,0xa,0x74,0x64,0x32,0x21,0x4b,0x29,0x3a,0x77,0x23,0x70,0x43,0x41,0x43,0x43,0x3a,0x77,0x23,0x69,0xa,0x20,0x43,
il3\\k->#w#z\012  CCC@C(#i\012 \012\012ta1!K)CA@C(\012\012td2!K):w#pCACC:w#i\012 C
artifact_prefix='/Users/luke/Documents/GitHub/roc/crates/compiler/test_syntax/fuzz/artifacts/fuzz_expr/'; Test unit written to /Users/luke/Documents/GitHub/roc/crates/compiler/test_syntax/fuzz/artifacts/fuzz_expr/crash-2a06e3de4562b36e52a38b13bd9aa929101b43b9
Base64: aWwzXGstPiN3I3oKICBDQ0NAQygjaQogCgp0YTEhSylDQUBDKAoKdGQyIUspOncjcENBQ0M6dyNpCiBD
stat::number_of_executed_units: 176245
stat::average_exec_per_sec:     17624
stat::new_units_added:          5580
stat::slowest_unit_time_sec:    0
stat::peak_rss_mb:              201
INFO: exiting: 19712 time: 81s