Possible regression of the language server resulting in a panic

[vrurg]

rust-analyzer version: rust-analyzer version: 0.3.2089-standalone (0f7f68d 2024-08-27)

rustc version: rustc 1.82.0-nightly (6de928dce 2024-08-18), though the error is there with stable too

editor or extension: VSCode

repository link (if public, optional): vrurg/fieldx

code snippet to reproduce: https://github.com/vrurg/fieldx

Straight to the output of the language server:

thread 'enum_dispatch' panicked at crates/proc-macro-srv/src/server_impl/rust_analyzer_span.rs:145:58:
cannot parse string: "lexing error"
stack backtrace:
   0: _rust_begin_unwind
   1: core::panicking::panic_fmt
   2: core::result::unwrap_failed
   3: std::panicking::try::do_call::<core::panic::unwind_safe::AssertUnwindSafe<<proc_macro::bridge::server::Dispatcher<proc_macro::bridge::server::MarkedTypes<proc_macro_srv::server_impl::rust_analyzer_span::RaSpanServer>> as proc_macro::bridge::server::DispatcherTrait>::dispatch::{closure#10}>, proc_macro::bridge::Marked<proc_macro_srv::server_impl::token_stream::TokenStream<span::SpanData<span::hygiene::SyntaxContextId>>, proc_macro::bridge::client::TokenStream>>
   4: <proc_macro::bridge::server::Dispatcher<proc_macro::bridge::server::MarkedTypes<proc_macro_srv::server_impl::rust_analyzer_span::RaSpanServer>> as proc_macro::bridge::server::DispatcherTrait>::dispatch
   5: <proc_macro::bridge::closure::Closure<_, _> as core::convert::From<&mut _>>::from::call::<proc_macro::bridge::buffer::Buffer, proc_macro::bridge::buffer::Buffer, <proc_macro::bridge::server::SameThread as proc_macro::bridge::server::ExecutionStrategy>::run_bridge_and_client<proc_macro::bridge::server::Dispatcher<proc_macro::bridge::server::MarkedTypes<proc_macro_srv::server_impl::rust_analyzer_span::RaSpanServer>>>::{closure#0}>
   6: proc_macro::bridge::closure::Closure<A,R>::call
             at /rustc/6de928dce9472b864f4e5d590dd7aa2075cb7551/library/proc_macro/src/bridge/closure.rs:30:18
   7: proc_macro::bridge::client::TokenStream::from_str::{{closure}}
             at /rustc/6de928dce9472b864f4e5d590dd7aa2075cb7551/library/proc_macro/src/bridge/client.rs:162:43
   8: proc_macro::bridge::client::Bridge::with::{{closure}}
             at /rustc/6de928dce9472b864f4e5d590dd7aa2075cb7551/library/proc_macro/src/bridge/client.rs:240:13
   9: proc_macro::bridge::client::state::with
             at /rustc/6de928dce9472b864f4e5d590dd7aa2075cb7551/library/proc_macro/src/bridge/client.rs:229:9
  10: proc_macro::bridge::client::Bridge::with
             at /rustc/6de928dce9472b864f4e5d590dd7aa2075cb7551/library/proc_macro/src/bridge/client.rs:235:9
  11: proc_macro::bridge::client::TokenStream::from_str
             at /rustc/6de928dce9472b864f4e5d590dd7aa2075cb7551/library/proc_macro/src/bridge/client.rs:155:17
  12: <proc_macro::TokenStream as core::str::traits::FromStr>::from_str
             at /rustc/6de928dce9472b864f4e5d590dd7aa2075cb7551/library/proc_macro/src/lib.rs:183:29
  13: core::str::<impl str>::parse
  14: enum_dispatch::cache::fulfilled_by_enum::{{closure}}::{{closure}}
  15: core::option::Option<T>::map
  16: enum_dispatch::cache::fulfilled_by_enum::{{closure}}
  17: core::ops::function::impls::<impl core::ops::function::FnMut<A> for &mut F>::call_mut
  18: <core::slice::iter::Iter<T> as core::iter::traits::iterator::Iterator>::find_map
  19: <core::iter::adapters::filter_map::FilterMap<I,F> as core::iter::traits::iterator::Iterator>::next
  20: <alloc::vec::Vec<T> as alloc::vec::spec_from_iter_nested::SpecFromIterNested<T,I>>::from_iter
  21: <alloc::vec::Vec<T> as alloc::vec::spec_from_iter::SpecFromIter<T,I>>::from_iter
  22: <alloc::vec::Vec<T> as core::iter::traits::collect::FromIterator<T>>::from_iter
  23: core::iter::traits::iterator::Iterator::collect
  24: enum_dispatch::cache::fulfilled_by_enum
  25: enum_dispatch::enum_dispatch2
  26: enum_dispatch::enum_dispatch
  27: core::ops::function::Fn::call
  28: proc_macro::bridge::client::Client<(proc_macro::TokenStream,proc_macro::TokenStream),proc_macro::TokenStream>::expand2::{{closure}}::{{closure}}
  29: proc_macro::bridge::client::run_client::{{closure}}::{{closure}}
  30: proc_macro::bridge::client::state::set
  31: proc_macro::bridge::client::run_client::{{closure}}
  32: <core::panic::unwind_safe::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once
  33: std::panicking::try::do_call
  34: ___rust_try
  35: proc_macro::bridge::client::run_client
  36: proc_macro::bridge::client::Client<(proc_macro::TokenStream,proc_macro::TokenStream),proc_macro::TokenStream>::expand2::{{closure}}
  37: proc_macro::bridge::selfless_reify::reify_to_extern_c_fn_hrt_bridge::wrapper
  38: proc_macro::bridge::server::run_server::<proc_macro_srv::server_impl::rust_analyzer_span::RaSpanServer, (proc_macro::bridge::Marked<proc_macro_srv::server_impl::token_stream::TokenStream<span::SpanData<span::hygiene::SyntaxContextId>>, proc_macro::bridge::client::TokenStream>, proc_macro::bridge::Marked<proc_macro_srv::server_impl::token_stream::TokenStream<span::SpanData<span::hygiene::SyntaxContextId>>, proc_macro::bridge::client::TokenStream>), core::option::Option<proc_macro::bridge::Marked<proc_macro_srv::server_impl::token_stream::TokenStream<span::SpanData<span::hygiene::SyntaxContextId>>, proc_macro::bridge::client::TokenStream>>, proc_macro::bridge::server::SameThread>
  39: <proc_macro_srv::proc_macros::ProcMacros>::expand::<span::SpanData<span::hygiene::SyntaxContextId>>
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

The problem pops up when the enum_dispatch crate is used in a proc_macro crate. For example, the entire trait is permanently marked as erroneous.

The problem looks like a regression to me as it hadn't been observed until some moment in time a month or two ago.

[Veykril]

Oh no, this is panicking within the proc-macro server (might be time for us to try backporting a fix to beta for the first time 🎉)

[Veykril]

That macro invocation is for some reason creating format ! (Field name is required for generating '{}' helper. , helper_kind . to_string ())) in its output which has an invalid character literal in it (we shouldnt panic either way, but something else is going wrong in there)

[Veykril]

We seem to be losing the quotation marks