Proc-Macro-Diagnostics allow error subdiagnostics #145305
Description
Code
// Macro impl
#![feature(proc_macro_diagnostic)]
use proc_macro::{Diagnostic, Level, Span};
#[proc_macro_attribute]
pub fn proc_emit_err(
_: proc_macro::TokenStream,
input: proc_macro::TokenStream,
) -> proc_macro::TokenStream {
Diagnostic::new(Level::Error, "Parent message")
.span_error(Span::call_site(), "Child message")
.emit();
input
}
// Application code
#[proc_emit_err]
fn some_func() {}Meta
rustc --version --verbose:
rustc 1.91.0-nightly (1ebbd87a6 2025-08-11)
binary: rustc
commit-hash: 1ebbd87a62ce96a72b22da61b7c2c43893534842
commit-date: 2025-08-11
host: x86_64-unknown-linux-gnu
release: 1.91.0-nightly
LLVM version: 21.1.0
Error output
error: custom attribute panicked
--> poc/src/main.rs:3:1
|
3 | #[proc_emit_err]
| ^^^^^^^^^^^^^^^^
|
= help: message: assertion failed: child.level.can_be_subdiag()
error: could not compile `poc` (bin "poc") due to 1 previous error
Backtrace
thread 'rustc' panicked at compiler/rustc_errors/src/emitter.rs:2521:25:
assertion failed: child.level.can_be_subdiag()
stack backtrace:
0: 0x7feb129caf85 - std::backtrace::Backtrace::create::h797e71eb0947b9a8
1: 0x7feb129caed5 - std::backtrace::Backtrace::force_capture::h4488dd94f9a784fe
2: 0x7feb11a25418 - std[675541678c9ea455]::panicking::update_hook::<alloc[69732d6495b06f7e]::boxed::Box<rustc_driver_impl[5f59bbdcc6d5c2ab]::install_ice_hook::{closure#1}>>::{closure#0}
3: 0x7feb129e513e - std::panicking::panic_with_hook::h920938fbe8355f07
4: 0x7feb129e4e06 - std::panicking::panic_handler::{{closure}}::hd7501236e9cac696
5: 0x7feb129e1499 - std::sys::backtrace::__rust_end_short_backtrace::hd1de819b45b5e370
6: 0x7feb129e4b1d - __rustc[d4effb916b19455c]::rust_begin_unwind
7: 0x7feb0f0d1710 - core::panicking::panic_fmt::h7f4d53d811596956
8: 0x7feb0f1692cc - core::panicking::panic::he98e298768f51c7f
9: 0x7feb146e178e - <rustc_errors[92139785c6308770]::emitter::HumanEmitter as rustc_errors[92139785c6308770]::emitter::Emitter>::emit_diagnostic
10: 0x7feb146e6559 - <rustc_errors[92139785c6308770]::json::Diagnostic>::from_errors_diagnostic
11: 0x7feb146e5c60 - <rustc_errors[92139785c6308770]::json::JsonEmitter as rustc_errors[92139785c6308770]::emitter::Emitter>::emit_diagnostic
12: 0x7feb146ef897 - <rustc_errors[92139785c6308770]::DiagCtxtInner>::emit_diagnostic::{closure#3}
13: 0x7feb146ed014 - rustc_interface[fd75cb43796b9d5f]::callbacks::track_diagnostic::<core[f81d9d17b2423934]::option::Option<rustc_span[e8c7b9f398dc1a0]::ErrorGuaranteed>>
14: 0x7feb146ec036 - <rustc_errors[92139785c6308770]::DiagCtxtInner>::emit_diagnostic
15: 0x7feb146ebeff - <rustc_errors[92139785c6308770]::DiagCtxtHandle>::emit_diagnostic
16: 0x7feb146ebd95 - <() as rustc_errors[92139785c6308770]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
17: 0x7feb11ad67a7 - <rustc_expand[9d5d7e814236ccf7]::proc_macro_server::Rustc as rustc_proc_macro[5300c59e89c06793]::bridge::server::FreeFunctions>::emit_diagnostic
18: 0x7feb14187b33 - <rustc_proc_macro[5300c59e89c06793]::bridge::server::Dispatcher<rustc_proc_macro[5300c59e89c06793]::bridge::server::MarkedTypes<rustc_expand[9d5d7e814236ccf7]::proc_macro_server::Rustc>> as rustc_proc_macro[5300c59e89c06793]::bridge::server::DispatcherTrait>::dispatch
19: 0x7feb14181cf0 - <rustc_proc_macro[5300c59e89c06793]::bridge::closure::Closure<_, _> as core[f81d9d17b2423934]::convert::From<&mut _>>::from::call::<rustc_proc_macro[5300c59e89c06793]::bridge::buffer::Buffer, rustc_proc_macro[5300c59e89c06793]::bridge::buffer::Buffer, <rustc_proc_macro[5300c59e89c06793]::bridge::server::SameThread as rustc_proc_macro[5300c59e89c06793]::bridge::server::ExecutionStrategy>::run_bridge_and_client<rustc_proc_macro[5300c59e89c06793]::bridge::server::Dispatcher<rustc_proc_macro[5300c59e89c06793]::bridge::server::MarkedTypes<rustc_expand[9d5d7e814236ccf7]::proc_macro_server::Rustc>>>::{closure#0}>
20: 0x7feb01dbb242 - proc_macro::bridge::closure::Closure<A,R>::call::h9abe641c5d4c7980
at /rustc/1ebbd87a62ce96a72b22da61b7c2c43893534842/library/proc_macro/src/bridge/closure.rs:30:18
21: 0x7feb01dbb242 - proc_macro::bridge::client::FreeFunctions::emit_diagnostic::{{closure}}::h8a4b9d0caf66a842
at /rustc/1ebbd87a62ce96a72b22da61b7c2c43893534842/library/proc_macro/src/bridge/client.rs:149:43
22: 0x7feb01dbb242 - proc_macro::bridge::client::Bridge::with::{{closure}}::h12d48eda306488e9
at /rustc/1ebbd87a62ce96a72b22da61b7c2c43893534842/library/proc_macro/src/bridge/client.rs:227:13
23: 0x7feb01dbb242 - proc_macro::bridge::client::state::with::h63edf330697cee2e
at /rustc/1ebbd87a62ce96a72b22da61b7c2c43893534842/library/proc_macro/src/bridge/client.rs:216:9
24: 0x7feb01dbb242 - proc_macro::bridge::client::Bridge::with::h7fbff87cc01ce86c
at /rustc/1ebbd87a62ce96a72b22da61b7c2c43893534842/library/proc_macro/src/bridge/client.rs:222:9
25: 0x7feb01dbb242 - proc_macro::bridge::client::FreeFunctions::emit_diagnostic::hc42ef8d6f72ea9a4
at /rustc/1ebbd87a62ce96a72b22da61b7c2c43893534842/library/proc_macro/src/bridge/client.rs:142:17
26: 0x7feb01dbb242 - proc_macro::diagnostic::Diagnostic::emit::ha8d39ee2381b2405
at /rustc/1ebbd87a62ce96a72b22da61b7c2c43893534842/library/proc_macro/src/diagnostic.rs:173:9
27: 0x7feb01db8bdf - proc_repro::proc_emit_err::hde8a2cd045407e13
at ~/proc-macro-diagnostic/proc_repro/src/lib.rs:13:10
28: 0x7feb01db585e - core::ops::function::Fn::call::h2b91dd43179b7a1f
at ~/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ops/function.rs:80:5
29: 0x7feb01db6ead - proc_macro::bridge::client::Client<(proc_macro::TokenStream,proc_macro::TokenStream),proc_macro::TokenStream>::expand2::{{closure}}::{{closure}}::h4f3ce69c7940cd67
at ~/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/proc_macro/src/bridge/client.rs:351:21
30: 0x7feb01db6e52 - proc_macro::bridge::client::run_client::{{closure}}::{{closure}}::h675371de5293ecd3
at ~/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/proc_macro/src/bridge/client.rs:302:44
31: 0x7feb01db950e - proc_macro::bridge::client::state::set::h06602bf8e8fb3182
at ~/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/proc_macro/src/bridge/client.rs:201:9
32: 0x7feb01db6c66 - proc_macro::bridge::client::run_client::{{closure}}::h6bb7c7332db97092
at ~/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/proc_macro/src/bridge/client.rs:302:22
33: 0x7feb01db7470 - <core::panic::unwind_safe::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once::h2f102f5494eb2abf
at ~/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/panic/unwind_safe.rs:272:9
34: 0x7feb01db706b - std::panicking::catch_unwind::do_call::h3c79b37c9aed3507
at ~/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:590:40
35: 0x7feb01db6f6b - __rust_try
36: 0x7feb01db67db - std::panicking::catch_unwind::h4f4f83267e3b7eb1
at ~/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:553:19
37: 0x7feb01db67db - std::panic::catch_unwind::h9dd35db126f39070
at ~/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panic.rs:357:14
38: 0x7feb01db67db - proc_macro::bridge::client::run_client::hbb8fa7e37ab22308
at ~/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/proc_macro/src/bridge/client.rs:290:5
39: 0x7feb01db6e81 - proc_macro::bridge::client::Client<(proc_macro::TokenStream,proc_macro::TokenStream),proc_macro::TokenStream>::expand2::{{closure}}::h6017f2c767b896f3
at ~/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/proc_macro/src/bridge/client.rs:350:17
40: 0x7feb01db9724 - proc_macro::bridge::selfless_reify::reify_to_extern_c_fn_hrt_bridge::wrapper::h0bec6f105583baae
at ~/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/proc_macro/src/bridge/selfless_reify.rs:64:17
41: 0x7feb13f4a3c1 - <rustc_proc_macro[5300c59e89c06793]::bridge::server::MaybeCrossThread<rustc_expand[9d5d7e814236ccf7]::proc_macro::MessagePipe<rustc_proc_macro[5300c59e89c06793]::bridge::buffer::Buffer>> as rustc_proc_macro[5300c59e89c06793]::bridge::server::ExecutionStrategy>::run_bridge_and_client::<rustc_proc_macro[5300c59e89c06793]::bridge::server::Dispatcher<rustc_proc_macro[5300c59e89c06793]::bridge::server::MarkedTypes<rustc_expand[9d5d7e814236ccf7]::proc_macro_server::Rustc>>>
42: 0x7feb13f499b0 - <rustc_expand[9d5d7e814236ccf7]::proc_macro::AttrProcMacro as rustc_expand[9d5d7e814236ccf7]::base::AttrProcMacro>::expand
43: 0x7feb147a864f - <rustc_expand[9d5d7e814236ccf7]::expand::MacroExpander>::fully_expand_fragment
44: 0x7feb14788be9 - <rustc_expand[9d5d7e814236ccf7]::expand::MacroExpander>::expand_crate
45: 0x7feb13d5b328 - rustc_interface[fd75cb43796b9d5f]::passes::configure_and_expand
46: 0x7feb143b76ed - rustc_interface[fd75cb43796b9d5f]::passes::resolver_for_lowering_raw
47: 0x7feb143b744d - rustc_query_impl[52ced257674aa24b]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[52ced257674aa24b]::query_impl::resolver_for_lowering_raw::dynamic_query::{closure#2}::{closure#0}, rustc_middle[c7deae55f4bd1b39]::query::erase::Erased<[u8; 16usize]>>
48: 0x7feb143b7427 - <rustc_query_impl[52ced257674aa24b]::query_impl::resolver_for_lowering_raw::dynamic_query::{closure#2} as core[f81d9d17b2423934]::ops::function::FnOnce<(rustc_middle[c7deae55f4bd1b39]::ty::context::TyCtxt, ())>>::call_once
49: 0x7feb1461f8f1 - rustc_query_system[8d730556a4fd7a7]::query::plumbing::try_execute_query::<rustc_query_impl[52ced257674aa24b]::DynamicConfig<rustc_query_system[8d730556a4fd7a7]::query::caches::SingleCache<rustc_middle[c7deae55f4bd1b39]::query::erase::Erased<[u8; 16usize]>>, false, false, false>, rustc_query_impl[52ced257674aa24b]::plumbing::QueryCtxt, true>
50: 0x7feb1461f301 - rustc_query_impl[52ced257674aa24b]::query_impl::resolver_for_lowering_raw::get_query_incr::__rust_end_short_backtrace
51: 0x7feb143e8636 - rustc_interface[fd75cb43796b9d5f]::passes::create_and_enter_global_ctxt::<core[f81d9d17b2423934]::option::Option<rustc_interface[fd75cb43796b9d5f]::queries::Linker>, rustc_driver_impl[5f59bbdcc6d5c2ab]::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0}
52: 0x7feb144e60e1 - rustc_interface[fd75cb43796b9d5f]::interface::run_compiler::<(), rustc_driver_impl[5f59bbdcc6d5c2ab]::run_compiler::{closure#0}>::{closure#1}
53: 0x7feb1433cd87 - std[675541678c9ea455]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[fd75cb43796b9d5f]::util::run_in_thread_with_globals<rustc_interface[fd75cb43796b9d5f]::util::run_in_thread_pool_with_globals<rustc_interface[fd75cb43796b9d5f]::interface::run_compiler<(), rustc_driver_impl[5f59bbdcc6d5c2ab]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
54: 0x7feb1433ca68 - <<std[675541678c9ea455]::thread::Builder>::spawn_unchecked_<rustc_interface[fd75cb43796b9d5f]::util::run_in_thread_with_globals<rustc_interface[fd75cb43796b9d5f]::util::run_in_thread_pool_with_globals<rustc_interface[fd75cb43796b9d5f]::interface::run_compiler<(), rustc_driver_impl[5f59bbdcc6d5c2ab]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[f81d9d17b2423934]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
55: 0x7feb1434230b - std::sys::pal::unix::thread::Thread::new::thread_start::had526f783dce54b0
56: 0x7feb0da969cb - <unknown>
57: 0x7feb0db1aa4c - <unknown>
58: 0x0 - <unknown>
rustc version: 1.91.0-nightly (1ebbd87a6 2025-08-11)
platform: x86_64-unknown-linux-gnu
query stack during panic:
#0 [resolver_for_lowering_raw] getting the resolver for lowering
end of query stack
Diagnostic functions for generating error subdiags are generated here:
rust/library/proc_macro/src/diagnostic.rs
Line 114 in a153133
can_be_subdiag disallows Error Level:
rust/compiler/rustc_errors/src/lib.rs
Line 1993 in a153133
Finally, breaks assertion when emitting:
rust/compiler/rustc_errors/src/emitter.rs
Line 2521 in a153133