Getting internal error: entered unreachable code

[elichai]

Hi,
I tried to follow the Readme and I'm getting into an unreachable in the lib.
I drilled it down to just having:
let mut cfg = ctest::TestGenerator::new().generate("../secp256k1-sys/src/lib.rs", "all.rs");

Full backtrace:

--- stderr
thread 'main' panicked at 'internal error: entered unreachable code', /home/elichai2/.cargo/registry/src/github.jparrowsec.cn-1ecc6299db9ec823/syntex_syntax2-0.0.2/src/ext/expand.rs:314:21
stack backtrace:
   0:     0x5653ecfbfac4 - backtrace::backtrace::libunwind::trace::h90669f559fb267f0
                               at /cargo/registry/src/github.jparrowsec.cn-1ecc6299db9ec823/backtrace-0.3.40/src/backtrace/libunwind.rs:88
   1:     0x5653ecfbfac4 - backtrace::backtrace::trace_unsynchronized::hffde4e353d8f2f9a
                               at /cargo/registry/src/github.jparrowsec.cn-1ecc6299db9ec823/backtrace-0.3.40/src/backtrace/mod.rs:66
   2:     0x5653ecfbfac4 - std::sys_common::backtrace::_print_fmt::heaf44068b7eaaa6a
                               at src/libstd/sys_common/backtrace.rs:77
   3:     0x5653ecfbfac4 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h88671019cf081de2
                               at src/libstd/sys_common/backtrace.rs:59
   4:     0x5653ecfdf16c - core::fmt::write::h4e6a29ee6319c9fd
                               at src/libcore/fmt/mod.rs:1052
   5:     0x5653ecfbbc87 - std::io::Write::write_fmt::hf06b1c86d898d7d6
                               at src/libstd/io/mod.rs:1426
   6:     0x5653ecfc1de5 - std::sys_common::backtrace::_print::h404ff5f2b50cae09
                               at src/libstd/sys_common/backtrace.rs:62
   7:     0x5653ecfc1de5 - std::sys_common::backtrace::print::hcc4377f1f882322e
                               at src/libstd/sys_common/backtrace.rs:49
   8:     0x5653ecfc1de5 - std::panicking::default_hook::{{closure}}::hc172eff6f35b7f39
                               at src/libstd/panicking.rs:204
   9:     0x5653ecfc1ad1 - std::panicking::default_hook::h7a68887d113f8029
                               at src/libstd/panicking.rs:224
  10:     0x5653ecfc244a - std::panicking::rust_panic_with_hook::hb7ad5693188bdb00
                               at src/libstd/panicking.rs:472
  11:     0x5653ece3dbeb - std::panicking::begin_panic::h5895e03812433dcb
                               at /rustc/b8cedc00407a4c56a3bda1ed605c6fc166655447/src/libstd/panicking.rs:399
  12:     0x5653ece0b222 - syntex_syntax2::ext::expand::MacroExpander::expand::h18253f4574feeea7
                               at /home/elichai2/.cargo/registry/src/github.jparrowsec.cn-1ecc6299db9ec823/syntex_syntax2-0.0.2/src/ext/expand.rs:314
  13:     0x5653ece0a0f3 - syntex_syntax2::ext::expand::MacroExpander::expand_crate::h38981502652bb841
                               at /home/elichai2/.cargo/registry/src/github.jparrowsec.cn-1ecc6299db9ec823/syntex_syntax2-0.0.2/src/ext/expand.rs:219
  14:     0x5653ec92af37 - ctest::TestGenerator::_generate_files::h25ce2f5aaed48e73
                               at /home/elichai2/.cargo/registry/src/github.jparrowsec.cn-1ecc6299db9ec823/ctest-0.2.22/src/lib.rs:921
  15:     0x5653ec92a094 - ctest::TestGenerator::generate_files::h7c4c182d6f8b89a1
                               at /home/elichai2/.cargo/registry/src/github.jparrowsec.cn-1ecc6299db9ec823/ctest-0.2.22/src/lib.rs:870
  16:     0x5653ec929315 - ctest::TestGenerator::_generate::hd941ddc8a4908095
                               at /home/elichai2/.cargo/registry/src/github.jparrowsec.cn-1ecc6299db9ec823/ctest-0.2.22/src/lib.rs:806
  17:     0x5653ec925a42 - ctest::TestGenerator::generate::he1740da48b9120d1
                               at /home/elichai2/.cargo/registry/src/github.jparrowsec.cn-1ecc6299db9ec823/ctest-0.2.22/src/lib.rs:802
  18:     0x5653ec9258d6 - build_script_build::main::h8987232324dcabc9
                               at /home/elichai2/gits/rust-secp256k1/systest/build.rs:4
  19:     0x5653ec9259b0 - std::rt::lang_start::{{closure}}::h377f2547084926bb
                               at /rustc/b8cedc00407a4c56a3bda1ed605c6fc166655447/src/libstd/rt.rs:67
  20:     0x5653ecfc1f13 - std::rt::lang_start_internal::{{closure}}::hb26e39676675046f
                               at src/libstd/rt.rs:52
  21:     0x5653ecfc1f13 - std::panicking::try::do_call::he4701ab6e48d80c0
                               at src/libstd/panicking.rs:305
  22:     0x5653ecfca357 - __rust_maybe_catch_panic
                               at src/libpanic_unwind/lib.rs:86
  23:     0x5653ecfc28f0 - std::panicking::try::hd3de25f3cb7024b8
                               at src/libstd/panicking.rs:281
  24:     0x5653ecfc28f0 - std::panic::catch_unwind::h86c02743a24e3d92
                               at src/libstd/panic.rs:394
  25:     0x5653ecfc28f0 - std::rt::lang_start_internal::h9cf8802361ad86c2
                               at src/libstd/rt.rs:51
  26:     0x5653ec925989 - std::rt::lang_start::h54f9b0f6e32ccd40
                               at /rustc/b8cedc00407a4c56a3bda1ed605c6fc166655447/src/libstd/rt.rs:67
  27:     0x5653ec92593a - main
  28:     0x7fc919a65023 - __libc_start_main
  29:     0x5653ec92517e - _start
  30:                0x0 - <unknown>