Add error messages instead of unwrap

I'm trying c2rust on an open source project https://github.com/berkeley-abc/abc I followed the instructions in README.md, installed c2rust from git (0.19.0), and generated compile_commands.json. c2rust panicked and I could not figure out which part of the C code caused the problem. Part of the command output of RUST_BACKTRACE=full c2rust transpile compile_commands.json

Transpiling abcDfs.c
thread 'main' panicked at c2rust-transpile/src/translator/mod.rs:233:47:
called `Option::unwrap()` on a `None` value

I read the code https://github.com/ChienKaiMa/c2rust/blob/9eaf8a15ede349a3ed9bff4af4638a80c88b8b65/c2rust-transpile/src/translator/mod.rs#L233

pub fn get_va_list_arg_name(&self) -> &str {
    return self.va_list_arg_name.as_ref().unwrap();
}

I assumed that it is abnormal that this unwrap would fail, but it just happened to me. My idea is to return a error message containing self.name so that users are able to identify which C function caused the panic. I'm fairly new to Rust, so I'm not sure if the program behavior is as intended, or it is an opportunity for me to work on a patch.

Full command output of RUST_BACKTRACE=full c2rust transpile compile_commands.json

warning: Skipping duplicate compilation cmd ...
warning: Skipping existing file ...
Transpiling abcDfs.c
thread 'main' panicked at c2rust-transpile/src/translator/mod.rs:233:47:
called `Option::unwrap()` on a `None` value
stack backtrace:
   0:     0x5af2f1943b95 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::h1b9dad2a88e955ff
   1:     0x5af2f1969bcb - core::fmt::write::h4b5a1270214bc4a7
   2:     0x5af2f1940e6f - std::io::Write::write_fmt::hd04af345a50c312d
   3:     0x5af2f1944ce1 - std::panicking::default_hook::{{closure}}::h96ab15e9936be7ed
   4:     0x5af2f19449bc - std::panicking::default_hook::h3cacb9c27561ad33
   5:     0x5af2f1945341 - std::panicking::rust_panic_with_hook::hfe205f6954b2c97b
   6:     0x5af2f1945173 - std::panicking::begin_panic_handler::{{closure}}::h6cb44b3a50f28c44
   7:     0x5af2f1944059 - std::sys::backtrace::__rust_end_short_backtrace::hf1c1f2a92799bb0e
   8:     0x5af2f1944e34 - rust_begin_unwind
   9:     0x5af2f13a91d3 - core::panicking::panic_fmt::h3d8fc78294164da7
  10:     0x5af2f13a925c - core::panicking::panic::hec978767ec2d35ff
  11:     0x5af2f13a9139 - core::option::unwrap_failed::hba6b08832f9ce30b
  12:     0x5af2f14d95dd - c2rust_transpile::translator::builtins::<impl c2rust_transpile::translator::Translation>::convert_builtin::hcc0514c63f59a6c3
  13:     0x5af2f1516fb1 - c2rust_transpile::translator::Translation::convert_expr::hd84ff785e5a3f9c2
  14:     0x5af2f14b07f9 - c2rust_transpile::cfg::CfgBuilder::convert_stmt_help::haa7683f6d52f5d2c
  15:     0x5af2f14ae0fc - c2rust_transpile::cfg::CfgBuilder::convert_stmts_help::hd439114e6c00fb51
  16:     0x5af2f151d989 - c2rust_transpile::translator::Translation::with_scope::h97ff826ad07da194
  17:     0x5af2f14a8f0c - c2rust_transpile::cfg::Cfg<c2rust_transpile::cfg::Label,c2rust_transpile::cfg::StmtOrDecl>::from_stmts::h3d700be0329c931c
  18:     0x5af2f150b9a7 - c2rust_transpile::translator::Translation::convert_function_body::hbec7894c1b727df1
  19:     0x5af2f150989e - c2rust_transpile::translator::Translation::convert_function::ha31b975ec6a38d75
  20:     0x5af2f1506d69 - c2rust_transpile::translator::Translation::convert_decl::hba428743f2f2181e
  21:     0x5af2f14f77b0 - c2rust_transpile::translator::translate::hf7235cc10c254ed3
  22:     0x5af2f13dfa7a - c2rust_transpile::transpile_single::hf06722b638c4d155
  23:     0x5af2f156da59 - <alloc::vec::Vec<T> as alloc::vec::spec_from_iter::SpecFromIter<T,I>>::from_iter::h39e510847d8c0a6b
  24:     0x5af2f13dc5bc - c2rust_transpile::transpile::h07c91dcbe877401c
  25:     0x5af2f13ae961 - c2rust_transpile::main::ha9f31e3816346ab2
  26:     0x5af2f13c03c3 - std::sys::backtrace::__rust_begin_short_backtrace::he2871ddce4c3574a
  27:     0x5af2f13c03b9 - std::rt::lang_start::{{closure}}::h29a6ce09ac4504ad
  28:     0x5af2f193bc00 - std::rt::lang_start_internal::h5e7c81cecd7f0954
  29:     0x5af2f13b99c5 - main
  30:     0x751cf0e29d90 - __libc_start_call_main
                               at ./csu/../sysdeps/nptl/libc_start_call_main.h:58:16
  31:     0x751cf0e29e40 - __libc_start_main_impl
                               at ./csu/../csu/libc-start.c:392:3
  32:     0x5af2f13a9ce5 - _start
  33:                0x0 - <unknown>

immunant / c2rust

Add error messages instead of unwrap #1123