Unsupported proc macro punctuation character while rendering device from svd

[Alan-JH]

I've been trying to generate crates from svd for S32K3 processors, but svd2rust errors while rendering the device. Here is the command and output:

$ svd2rust -i S32K344_M7.svd
[INFO  svd2rust] Parsing device from SVD file
[INFO  svd2rust] Rendering device
thread 'main' panicked at /home/alan/.cargo/registry/src/index.crates.io-6f17d22bba15001f/proc-macro2-1.0.87/src/lib.rs:847:13:
unsupported proc macro punctuation character '{'
stack backtrace:
   0:     0x56d31bfb10f5 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::h1b9dad2a88e955ff
   1:     0x56d31bfd4efb - core::fmt::write::h4b5a1270214bc4a7
   2:     0x56d31bfaef4f - std::io::Write::write_fmt::hd04af345a50c312d
   3:     0x56d31bfb2241 - std::panicking::default_hook::{{closure}}::h96ab15e9936be7ed
   4:     0x56d31bfb1f1c - std::panicking::default_hook::h3cacb9c27561ad33
   5:     0x56d31bfb28a1 - std::panicking::rust_panic_with_hook::hfe205f6954b2c97b
   6:     0x56d31bfb2707 - std::panicking::begin_panic_handler::{{closure}}::h6cb44b3a50f28c44
   7:     0x56d31bfb15b9 - std::sys::backtrace::__rust_end_short_backtrace::hf1c1f2a92799bb0e
   8:     0x56d31bfb2394 - rust_begin_unwind
   9:     0x56d31bb33e23 - core::panicking::panic_fmt::h3d8fc78294164da7
  10:     0x56d31bf7aac7 - proc_macro2::Punct::new::ha98fcb302f38a7f8
  11:     0x56d31bcc1d53 - svd2rust::generate::register::render_register_mod::h984d025f9b4ff5bf
  12:     0x56d31bcbfc2d - svd2rust::generate::register::render::h50dd757fecc731d8
  13:     0x56d31bcf53fc - svd2rust::generate::peripheral::render_ercs::h49ca57539bc0198b
  14:     0x56d31bce63fe - svd2rust::generate::peripheral::render::hf621df3c5ab9d684
  15:     0x56d31bc2fa0d - svd2rust::generate::device::render::h7ad2eee6726a060c
  16:     0x56d31bb48caa - svd2rust::run::ha72c8b7caa53a83f
  17:     0x56d31bb4b56d - svd2rust::main::h707855b15b260831
  18:     0x56d31bb61f33 - std::sys::backtrace::__rust_begin_short_backtrace::h1766bca47e196873
  19:     0x56d31bb5e299 - std::rt::lang_start::{{closure}}::hdc4d91e205a6d325
  20:     0x56d31bfa8dc0 - std::rt::lang_start_internal::h5e7c81cecd7f0954
  21:     0x56d31bb4b695 - main
  22:     0x72d777029d90 - __libc_start_call_main
                               at ./csu/../sysdeps/nptl/libc_start_call_main.h:58:16
  23:     0x72d777029e40 - __libc_start_main_impl
                               at ./csu/../csu/libc-start.c:392:3
  24:     0x56d31bb34635 - _start
  25:                0x0 - <unknown>

I'm new to rust, so I don't have much of an idea of how to troubleshoot, but I also tried a couple other SVD files and had the same error output:
S32K144.svd from s32k-rust/s32k144.rs (which was generated using svd2rust)
stm32f411.svd from tinygo-org/stm32-svd

svd2rust was installed using cargo and is version 0.33.4

[burrbull]

Looks like issue with new proc-macro.
Try to install with:

cargo install svd2rust --locked

[Alan-JH]

That solved it, thanks!

[jannic]

While --locked helped to work around this issue for now, I think this is actually a bug in svd2rust.

The change in proc-macro2 that triggered this issue was https://github.com/dtolnay/proc-macro2/pull/471.
One might argue that this is a breaking change and should therefore not be in a bugfix release of proc-macro2. But the way svd2rust uses Punct was actually forbidden by the documentation before:

The ch argument must be a valid punctuation character permitted by the language, otherwise the function will panic.

      let open: Punct = Punct::new(ch: '{', Spacing::Alone);
      let close: Punct = Punct::new(ch: '}', Spacing::Alone);

These braces are clearly not punctuation characters but delimiters:
https://doc.rust-lang.org/reference/tokens.html#punctuation
https://doc.rust-lang.org/reference/tokens.html#delimiters

So svd2rust should probably use proc_macro2::Group(Delimiter::Brace, ...) instead. Unfortunately, that requires restructuring the code in render_register_mod_debug: https://github.com/rust-embedded/svd2rust/blob/master/src/generate/register.rs#L476