<p dir="auto">Hi,</p>
<p dir="auto">As described in this <a href="https://github.com/denoland/deno_std/issues/543#issuecomment-541817552" data-hovercard-type="issue" data-hovercard-url="/denoland/deno_std/issues/543/hovercard">issue</a>, when I run <code class="notranslate">cargo test</code> I receive this output:</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="FAILED (errors=1)
', cli/tests/util/mod.rs:34:5
stack backtrace:
   0: backtrace::backtrace::libunwind::trace
             at /Users/vsts/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.34/src/backtrace/libunwind.rs:88
   1: backtrace::backtrace::trace_unsynchronized
             at /Users/vsts/.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:211
   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: std::thread::local::fast::Key&lt;T&gt;::try_initialize
   9: integration_tests::util::run_python_script
             at cli/tests/util/mod.rs:34
  10: integration_tests::fmt_test
             at cli/tests/integration_tests.rs:32
  11: integration_tests::fmt_test::{{closure}}
             at cli/tests/integration_tests.rs:30
  12: core::ops::function::FnOnce::call_once
             at /rustc/625451e376bb2e5283fc4741caa0a3e8a2ca4d54/src/libcore/ops/function.rs:235
  13: &lt;alloc::boxed::Box&lt;F&gt; as core::ops::function::FnOnce&lt;A&gt;&gt;::call_once
             at /rustc/625451e376bb2e5283fc4741caa0a3e8a2ca4d54/src/liballoc/boxed.rs:787
  14: __rust_maybe_catch_panic
             at src/libpanic_unwind/lib.rs:80
  15: std::panicking::try
             at /rustc/625451e376bb2e5283fc4741caa0a3e8a2ca4d54/src/libstd/panicking.rs:275
  16: std::panic::catch_unwind
             at /rustc/625451e376bb2e5283fc4741caa0a3e8a2ca4d54/src/libstd/panic.rs:394
  17: test::run_test::run_test_inner::{{closure}}
             at src/libtest/lib.rs:1408
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

---- js_unit_tests stdout ----
thread 'js_unit_tests' panicked at 'called `Result::unwrap()` on an `Err` value: &quot;PoisonError { inner: .. }&quot;', src/libcore/result.rs:1084:5
stack backtrace:
   0: backtrace::backtrace::libunwind::trace
             at /Users/vsts/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.34/src/backtrace/libunwind.rs:88
   1: backtrace::backtrace::trace_unsynchronized
             at /Users/vsts/.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:211
   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: std::panicking::begin_panic
  10: std::panicking::begin_panic
  11: core::result::Result&lt;T,E&gt;::unwrap
             at /rustc/625451e376bb2e5283fc4741caa0a3e8a2ca4d54/src/libcore/result.rs:852
  12: deno_cli::test_util::http_server
             at cli/test_util.rs:62
  13: integration_tests::js_unit_tests
             at cli/tests/integration_tests.rs:38
  14: integration_tests::js_unit_tests::{{closure}}
             at cli/tests/integration_tests.rs:37
  15: core::ops::function::FnOnce::call_once
             at /rustc/625451e376bb2e5283fc4741caa0a3e8a2ca4d54/src/libcore/ops/function.rs:235
  16: &lt;alloc::boxed::Box&lt;F&gt; as core::ops::function::FnOnce&lt;A&gt;&gt;::call_once
             at /rustc/625451e376bb2e5283fc4741caa0a3e8a2ca4d54/src/liballoc/boxed.rs:787
  17: __rust_maybe_catch_panic
             at src/libpanic_unwind/lib.rs:80
  18: std::panicking::try
             at /rustc/625451e376bb2e5283fc4741caa0a3e8a2ca4d54/src/libstd/panicking.rs:275
  19: std::panic::catch_unwind
             at /rustc/625451e376bb2e5283fc4741caa0a3e8a2ca4d54/src/libstd/panic.rs:394
  20: test::run_test::run_test_inner::{{closure}}
             at src/libtest/lib.rs:1408
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace."><pre class="notranslate"><code class="notranslate">FAILED (errors=1)
', cli/tests/util/mod.rs:34:5
stack backtrace:
   0: backtrace::backtrace::libunwind::trace
             at /Users/vsts/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.34/src/backtrace/libunwind.rs:88
   1: backtrace::backtrace::trace_unsynchronized
             at /Users/vsts/.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:211
   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: std::thread::local::fast::Key&lt;T&gt;::try_initialize
   9: integration_tests::util::run_python_script
             at cli/tests/util/mod.rs:34
  10: integration_tests::fmt_test
             at cli/tests/integration_tests.rs:32
  11: integration_tests::fmt_test::{{closure}}
             at cli/tests/integration_tests.rs:30
  12: core::ops::function::FnOnce::call_once
             at /rustc/625451e376bb2e5283fc4741caa0a3e8a2ca4d54/src/libcore/ops/function.rs:235
  13: &lt;alloc::boxed::Box&lt;F&gt; as core::ops::function::FnOnce&lt;A&gt;&gt;::call_once
             at /rustc/625451e376bb2e5283fc4741caa0a3e8a2ca4d54/src/liballoc/boxed.rs:787
  14: __rust_maybe_catch_panic
             at src/libpanic_unwind/lib.rs:80
  15: std::panicking::try
             at /rustc/625451e376bb2e5283fc4741caa0a3e8a2ca4d54/src/libstd/panicking.rs:275
  16: std::panic::catch_unwind
             at /rustc/625451e376bb2e5283fc4741caa0a3e8a2ca4d54/src/libstd/panic.rs:394
  17: test::run_test::run_test_inner::{{closure}}
             at src/libtest/lib.rs:1408
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

---- js_unit_tests stdout ----
thread 'js_unit_tests' panicked at 'called `Result::unwrap()` on an `Err` value: "PoisonError { inner: .. }"', src/libcore/result.rs:1084:5
stack backtrace:
   0: backtrace::backtrace::libunwind::trace
             at /Users/vsts/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.34/src/backtrace/libunwind.rs:88
   1: backtrace::backtrace::trace_unsynchronized
             at /Users/vsts/.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:211
   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: std::panicking::begin_panic
  10: std::panicking::begin_panic
  11: core::result::Result&lt;T,E&gt;::unwrap
             at /rustc/625451e376bb2e5283fc4741caa0a3e8a2ca4d54/src/libcore/result.rs:852
  12: deno_cli::test_util::http_server
             at cli/test_util.rs:62
  13: integration_tests::js_unit_tests
             at cli/tests/integration_tests.rs:38
  14: integration_tests::js_unit_tests::{{closure}}
             at cli/tests/integration_tests.rs:37
  15: core::ops::function::FnOnce::call_once
             at /rustc/625451e376bb2e5283fc4741caa0a3e8a2ca4d54/src/libcore/ops/function.rs:235
  16: &lt;alloc::boxed::Box&lt;F&gt; as core::ops::function::FnOnce&lt;A&gt;&gt;::call_once
             at /rustc/625451e376bb2e5283fc4741caa0a3e8a2ca4d54/src/liballoc/boxed.rs:787
  17: __rust_maybe_catch_panic
             at src/libpanic_unwind/lib.rs:80
  18: std::panicking::try
             at /rustc/625451e376bb2e5283fc4741caa0a3e8a2ca4d54/src/libstd/panicking.rs:275
  19: std::panic::catch_unwind
             at /rustc/625451e376bb2e5283fc4741caa0a3e8a2ca4d54/src/libstd/panic.rs:394
  20: test::run_test::run_test_inner::{{closure}}
             at src/libtest/lib.rs:1408
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
</code></pre></div>
<p dir="auto">My <code class="notranslate">cargo --version</code> is <code class="notranslate">cargo 1.38.0 (23ef9a4ef 2019-08-20)</code> &amp; <code class="notranslate">rustc --version</code> is <code class="notranslate">rustc 1.38.0 (625451e37 2019-09-23)</code>.</p>
<p dir="auto">I also get this error earlier in the format test (<code class="notranslate">python2 tools/format.py</code> passes) and that is where the panic occurs:</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="Traceback (most recent call last):
  File &quot;tools/fmt_test.py&quot;, line 31, in test_fmt
    quiet=True)
  File &quot;/Users/usrname/Documents/deno/tools/util.py&quot;, line 99, in run_output
    sys.exit(retcode)
SystemExit: -4"><pre class="notranslate"><code class="notranslate">Traceback (most recent call last):
  File "tools/fmt_test.py", line 31, in test_fmt
    quiet=True)
  File "/Users/usrname/Documents/deno/tools/util.py", line 99, in run_output
    sys.exit(retcode)
SystemExit: -4
</code></pre></div>
<p dir="auto">I don't know enough about the logic of <code class="notranslate">util.py</code> to know why this is being thrown from L99 but it's in the <code class="notranslate">run_output</code> function.</p>
<p dir="auto"><g-emoji class="g-emoji" alias="slightly_frowning_face" fallback-src="https://github.githubassets.com/images/icons/emoji/unicode/1f641.png">🙁</g-emoji></p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="tmnk@buildDeno:~/deno$ ./target/debug/deno fmt badly_formatted.js 
Download https://deno.land/std@8c90bd9/prettier/vendor/standalone.js
Download https://deno.land/std@8c90bd9/prettier/vendor/parser_typescript.js
Download https://deno.land/std@8c90bd9/prettier/vendor/parser_markdown.js


#
# Fatal error in ../../core/libdeno/v8/src/parsing/preparser.h, line 1076
# Debug check failed: !parsing_module_.
#
#
#
#FailureMessage Object: 0x7eff75515cc0
==== C stack trace ===============================

    ./target/debug/deno(+0x286acb3) [0x55aadeed1cb3]
    ./target/debug/deno(+0x273e52b) [0x55aadeda552b]
    ./target/debug/deno(+0x1e6e648) [0x55aade4d5648]
    ./target/debug/deno(+0x1e6e375) [0x55aade4d5375]
    ./target/debug/deno(+0x1adf30f) [0x55aade14630f]
    ./target/debug/deno(+0x1a7927e) [0x55aade0e027e]
    ./target/debug/deno(+0x1a7b081) [0x55aade0e2081]
    ./target/debug/deno(+0x1a7abd0) [0x55aade0e1bd0]
    ./target/debug/deno(+0x1ad1346) [0x55aade138346]
    ./target/debug/deno(+0x1acf856) [0x55aade136856]
    ./target/debug/deno(+0x1ad6f14) [0x55aade13df14]
    ./target/debug/deno(+0x1ad68a6) [0x55aade13d8a6]
    ./target/debug/deno(+0x1ad4ee4) [0x55aade13bee4]
    ./target/debug/deno(+0x1ad63f0) [0x55aade13d3f0]
    ./target/debug/deno(+0x1ad4fea) [0x55aade13bfea]
    ./target/debug/deno(+0x1ad2753) [0x55aade139753]
    ./target/debug/deno(+0x1adf556) [0x55aade146556]
    ./target/debug/deno(+0x1addc1e) [0x55aade144c1e]
    ./target/debug/deno(+0x1a7927e) [0x55aade0e027e]
    ./target/debug/deno(+0x1a7b081) [0x55aade0e2081]
    ./target/debug/deno(+0x1a7abd0) [0x55aade0e1bd0]
    ./target/debug/deno(+0x1ad1346) [0x55aade138346]
    ./target/debug/deno(+0x1acf856) [0x55aade136856]
    ./target/debug/deno(+0x1ad6f14) [0x55aade13df14]
    ./target/debug/deno(+0x1ad68a6) [0x55aade13d8a6]
    ./target/debug/deno(+0x1ad4ee4) [0x55aade13bee4]
    ./target/debug/deno(+0x1ad45b4) [0x55aade13b5b4]
    ./target/debug/deno(+0x1aced95) [0x55aade135d95]
    ./target/debug/deno(+0x1ad6f78) [0x55aade13df78]
    ./target/debug/deno(+0x1ad68a6) [0x55aade13d8a6]
    ./target/debug/deno(+0x1ad4ee4) [0x55aade13bee4]
    ./target/debug/deno(+0x1ad63f0) [0x55aade13d3f0]
    ./target/debug/deno(+0x1adb37b) [0x55aade14237b]
    ./target/debug/deno(+0x1acc833) [0x55aade133833]
    ./target/debug/deno(+0x1a7927e) [0x55aade0e027e]
    ./target/debug/deno(+0x1a7b081) [0x55aade0e2081]
    ./target/debug/deno(+0x1a7abd0) [0x55aade0e1bd0]
    ./target/debug/deno(+0x1ad1346) [0x55aade138346]
    ./target/debug/deno(+0x1acf856) [0x55aade136856]
    ./target/debug/deno(+0x1ad6f14) [0x55aade13df14]
    ./target/debug/deno(+0x1ad68a6) [0x55aade13d8a6]
    ./target/debug/deno(+0x1ad4ee4) [0x55aade13bee4]
    ./target/debug/deno(+0x1ad45b4) [0x55aade13b5b4]
    ./target/debug/deno(+0x1aced95) [0x55aade135d95]
    ./target/debug/deno(+0x1ad6f78) [0x55aade13df78]
    ./target/debug/deno(+0x1ad68a6) [0x55aade13d8a6]
    ./target/debug/deno(+0x1ad4ee4) [0x55aade13bee4]
    ./target/debug/deno(+0x1ad63f0) [0x55aade13d3f0]
    ./target/debug/deno(+0x1adb37b) [0x55aade14237b]
    ./target/debug/deno(+0x1acc833) [0x55aade133833]
    ./target/debug/deno(+0x1a7927e) [0x55aade0e027e]
    ./target/debug/deno(+0x1a7a423) [0x55aade0e1423]
    ./target/debug/deno(+0x1a798e0) [0x55aade0e08e0]
    ./target/debug/deno(+0x284c271) [0x55aadeeb3271]
    ./target/debug/deno(+0x284155b) [0x55aadeea855b]
    ./target/debug/deno(+0x2859c4d) [0x55aadeec0c4d]
    ./target/debug/deno(+0x2858284) [0x55aadeebf284]
    ./target/debug/deno(+0x2856a34) [0x55aadeebda34]
    ./target/debug/deno(+0x2855e46) [0x55aadeebce46]
    ./target/debug/deno(+0x28548e0) [0x55aadeebb8e0]
    ./target/debug/deno(+0x285bf35) [0x55aadeec2f35]
    ./target/debug/deno(+0x2857615) [0x55aadeebe615]
Illegal instruction (core dumped)"><pre class="notranslate"><code class="notranslate">tmnk@buildDeno:~/deno$ ./target/debug/deno fmt badly_formatted.js 
Download https://deno.land/std@8c90bd9/prettier/vendor/standalone.js
Download https://deno.land/std@8c90bd9/prettier/vendor/parser_typescript.js
Download https://deno.land/std@8c90bd9/prettier/vendor/parser_markdown.js


#
# Fatal error in ../../core/libdeno/v8/src/parsing/preparser.h, line 1076
# Debug check failed: !parsing_module_.
#
#
#
#FailureMessage Object: 0x7eff75515cc0
==== C stack trace ===============================

    ./target/debug/deno(+0x286acb3) [0x55aadeed1cb3]
    ./target/debug/deno(+0x273e52b) [0x55aadeda552b]
    ./target/debug/deno(+0x1e6e648) [0x55aade4d5648]
    ./target/debug/deno(+0x1e6e375) [0x55aade4d5375]
    ./target/debug/deno(+0x1adf30f) [0x55aade14630f]
    ./target/debug/deno(+0x1a7927e) [0x55aade0e027e]
    ./target/debug/deno(+0x1a7b081) [0x55aade0e2081]
    ./target/debug/deno(+0x1a7abd0) [0x55aade0e1bd0]
    ./target/debug/deno(+0x1ad1346) [0x55aade138346]
    ./target/debug/deno(+0x1acf856) [0x55aade136856]
    ./target/debug/deno(+0x1ad6f14) [0x55aade13df14]
    ./target/debug/deno(+0x1ad68a6) [0x55aade13d8a6]
    ./target/debug/deno(+0x1ad4ee4) [0x55aade13bee4]
    ./target/debug/deno(+0x1ad63f0) [0x55aade13d3f0]
    ./target/debug/deno(+0x1ad4fea) [0x55aade13bfea]
    ./target/debug/deno(+0x1ad2753) [0x55aade139753]
    ./target/debug/deno(+0x1adf556) [0x55aade146556]
    ./target/debug/deno(+0x1addc1e) [0x55aade144c1e]
    ./target/debug/deno(+0x1a7927e) [0x55aade0e027e]
    ./target/debug/deno(+0x1a7b081) [0x55aade0e2081]
    ./target/debug/deno(+0x1a7abd0) [0x55aade0e1bd0]
    ./target/debug/deno(+0x1ad1346) [0x55aade138346]
    ./target/debug/deno(+0x1acf856) [0x55aade136856]
    ./target/debug/deno(+0x1ad6f14) [0x55aade13df14]
    ./target/debug/deno(+0x1ad68a6) [0x55aade13d8a6]
    ./target/debug/deno(+0x1ad4ee4) [0x55aade13bee4]
    ./target/debug/deno(+0x1ad45b4) [0x55aade13b5b4]
    ./target/debug/deno(+0x1aced95) [0x55aade135d95]
    ./target/debug/deno(+0x1ad6f78) [0x55aade13df78]
    ./target/debug/deno(+0x1ad68a6) [0x55aade13d8a6]
    ./target/debug/deno(+0x1ad4ee4) [0x55aade13bee4]
    ./target/debug/deno(+0x1ad63f0) [0x55aade13d3f0]
    ./target/debug/deno(+0x1adb37b) [0x55aade14237b]
    ./target/debug/deno(+0x1acc833) [0x55aade133833]
    ./target/debug/deno(+0x1a7927e) [0x55aade0e027e]
    ./target/debug/deno(+0x1a7b081) [0x55aade0e2081]
    ./target/debug/deno(+0x1a7abd0) [0x55aade0e1bd0]
    ./target/debug/deno(+0x1ad1346) [0x55aade138346]
    ./target/debug/deno(+0x1acf856) [0x55aade136856]
    ./target/debug/deno(+0x1ad6f14) [0x55aade13df14]
    ./target/debug/deno(+0x1ad68a6) [0x55aade13d8a6]
    ./target/debug/deno(+0x1ad4ee4) [0x55aade13bee4]
    ./target/debug/deno(+0x1ad45b4) [0x55aade13b5b4]
    ./target/debug/deno(+0x1aced95) [0x55aade135d95]
    ./target/debug/deno(+0x1ad6f78) [0x55aade13df78]
    ./target/debug/deno(+0x1ad68a6) [0x55aade13d8a6]
    ./target/debug/deno(+0x1ad4ee4) [0x55aade13bee4]
    ./target/debug/deno(+0x1ad63f0) [0x55aade13d3f0]
    ./target/debug/deno(+0x1adb37b) [0x55aade14237b]
    ./target/debug/deno(+0x1acc833) [0x55aade133833]
    ./target/debug/deno(+0x1a7927e) [0x55aade0e027e]
    ./target/debug/deno(+0x1a7a423) [0x55aade0e1423]
    ./target/debug/deno(+0x1a798e0) [0x55aade0e08e0]
    ./target/debug/deno(+0x284c271) [0x55aadeeb3271]
    ./target/debug/deno(+0x284155b) [0x55aadeea855b]
    ./target/debug/deno(+0x2859c4d) [0x55aadeec0c4d]
    ./target/debug/deno(+0x2858284) [0x55aadeebf284]
    ./target/debug/deno(+0x2856a34) [0x55aadeebda34]
    ./target/debug/deno(+0x2855e46) [0x55aadeebce46]
    ./target/debug/deno(+0x28548e0) [0x55aadeebb8e0]
    ./target/debug/deno(+0x285bf35) [0x55aadeec2f35]
    ./target/debug/deno(+0x2857615) [0x55aadeebe615]
Illegal instruction (core dumped)
</code></pre></div>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="tmnk@buildDeno:~/deno$ cat badly_formatted.js 

console.log(
  &quot;Hello World&quot;
)"><pre class="notranslate"><code class="notranslate">tmnk@buildDeno:~/deno$ cat badly_formatted.js 

console.log(
  "Hello World"
)
</code></pre></div>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="tmnk@buildDeno:~/deno$ cat /proc/version
Linux version 5.0.0-1018-azure (buildd@lgw01-amd64-048) (gcc version 7.4.0 (Ubuntu 7.4.0-1ubuntu1~18.04.1)) #19~18.04.1-Ubuntu SMP Wed Aug 21 05:13:05 UTC 2019"><pre class="notranslate"><code class="notranslate">tmnk@buildDeno:~/deno$ cat /proc/version
Linux version 5.0.0-1018-azure (buildd@lgw01-amd64-048) (gcc version 7.4.0 (Ubuntu 7.4.0-1ubuntu1~18.04.1)) #19~18.04.1-Ubuntu SMP Wed Aug 21 05:13:05 UTC 2019
</code></pre></div>