ICE: must_produce_diag: trimmed_def_paths called but no diagnostics emitted

[dtolnay]

Input:

// lib.rs

#[must_use]
fn f() {}

pub fn g() {
    f();
}

rustc lib.rs -Dunused_must_use -Awarnings --cap-lints=warn --crate-type=lib

thread 'rustc' panicked at compiler/rustc_errors/src/lib.rs:572:17:
must_produce_diag: trimmed_def_paths called but no diagnostics emitted; use `DelayDm` for lints or `with_no_trimmed_paths` for debugging
stack backtrace:
   0:     0x7f268108cdb6 - std::backtrace_rs::backtrace::libunwind::trace::h341f79bffd736d88
                               at /rustc/c475e2303b551d726307c646181e0677af1e0069/library/std/src/../../backtrace/src/backtrace/libunwind.rs:104:5
   1:     0x7f268108cdb6 - std::backtrace_rs::backtrace::trace_unsynchronized::h699175639bf0c53f
                               at /rustc/c475e2303b551d726307c646181e0677af1e0069/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f268108cdb6 - std::sys_common::backtrace::_print_fmt::he64554b6b8851325
                               at /rustc/c475e2303b551d726307c646181e0677af1e0069/library/std/src/sys_common/backtrace.rs:68:5
   3:     0x7f268108cdb6 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h6f1d81aff3ba783c
                               at /rustc/c475e2303b551d726307c646181e0677af1e0069/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x7f26810ddd3c - core::fmt::rt::Argument::fmt::ha094c70f8a774861
                               at /rustc/c475e2303b551d726307c646181e0677af1e0069/library/core/src/fmt/rt.rs:142:9
   5:     0x7f26810ddd3c - core::fmt::write::h7f13c4b287d5364f
                               at /rustc/c475e2303b551d726307c646181e0677af1e0069/library/core/src/fmt/mod.rs:1120:17
   6:     0x7f268108163f - std::io::Write::write_fmt::h33c62cb7f1d9ccd2
                               at /rustc/c475e2303b551d726307c646181e0677af1e0069/library/std/src/io/mod.rs:1846:15
   7:     0x7f268108cb64 - std::sys_common::backtrace::_print::h5a328173cecd6a17
                               at /rustc/c475e2303b551d726307c646181e0677af1e0069/library/std/src/sys_common/backtrace.rs:47:5
   8:     0x7f268108cb64 - std::sys_common::backtrace::print::h40f459d9b04f57e7
                               at /rustc/c475e2303b551d726307c646181e0677af1e0069/library/std/src/sys_common/backtrace.rs:34:9
   9:     0x7f268108f8ab - std::panicking::default_hook::{{closure}}::hd2a3df71af903bed
  10:     0x7f268108f5f9 - std::panicking::default_hook::ha092baec2054d09a
                               at /rustc/c475e2303b551d726307c646181e0677af1e0069/library/std/src/panicking.rs:292:9
  11:     0x7f267dc9bcbc - std[aeaa4a650f96ca4f]::panicking::update_hook::<alloc[4c4126b71025da3b]::boxed::Box<rustc_driver_impl[2ad8c6e0ef02d37]::install_ice_hook::{closure#0}>>::{closure#0}
  12:     0x7f2681090010 - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::he192bb5ab07c6e66
                               at /rustc/c475e2303b551d726307c646181e0677af1e0069/library/alloc/src/boxed.rs:2030:9
  13:     0x7f2681090010 - std::panicking::rust_panic_with_hook::h46c6fddd63cff830
                               at /rustc/c475e2303b551d726307c646181e0677af1e0069/library/std/src/panicking.rs:783:13
  14:     0x7f268108fd19 - std::panicking::begin_panic_handler::{{closure}}::h8abc72b89d98e75c
                               at /rustc/c475e2303b551d726307c646181e0677af1e0069/library/std/src/panicking.rs:649:13
  15:     0x7f268108d296 - std::sys_common::backtrace::__rust_end_short_backtrace::h1eafc870bd031abe
                               at /rustc/c475e2303b551d726307c646181e0677af1e0069/library/std/src/sys_common/backtrace.rs:171:18
  16:     0x7f268108fa84 - rust_begin_unwind
                               at /rustc/c475e2303b551d726307c646181e0677af1e0069/library/std/src/panicking.rs:645:5
  17:     0x7f26810da255 - core::panicking::panic_fmt::hd079a8afc216673e
                               at /rustc/c475e2303b551d726307c646181e0677af1e0069/library/core/src/panicking.rs:72:14
  18:     0x7f26805d5ea2 - <rustc_errors[8f2d5467e268fcd1]::DiagCtxtInner as core[ceaa87f59aeb8bba]::ops::drop::Drop>::drop.cold.0
  19:     0x7f267fb5719c - core[ceaa87f59aeb8bba]::ptr::drop_in_place::<rustc_errors[8f2d5467e268fcd1]::DiagCtxt>
  20:     0x7f267fdee217 - core[ceaa87f59aeb8bba]::ptr::drop_in_place::<rustc_session[6420a5b3483699f8]::parse::ParseSess>
  21:     0x7f267fdee7f1 - core[ceaa87f59aeb8bba]::ptr::drop_in_place::<rustc_interface[91b806f92bb77cda]::interface::Compiler>
  22:     0x7f267fd3e672 - rustc_interface[91b806f92bb77cda]::interface::run_compiler::<core[ceaa87f59aeb8bba]::result::Result<(), rustc_span[ac3b12a2af12cb0d]::ErrorGuaranteed>, rustc_driver_impl[2ad8c6e0ef02d37]::run_compiler::{closure#0}>::{closure#0}
  23:     0x7f267ffddd05 - std[aeaa4a650f96ca4f]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[91b806f92bb77cda]::util::run_in_thread_with_globals<rustc_interface[91b806f92bb77cda]::util::run_in_thread_pool_with_globals<rustc_interface[91b806f92bb77cda]::interface::run_compiler<core[ceaa87f59aeb8bba]::result::Result<(), rustc_span[ac3b12a2af12cb0d]::ErrorGuaranteed>, rustc_driver_impl[2ad8c6e0ef02d37]::run_compiler::{closure#0}>::{closure#0}, core[ceaa87f59aeb8bba]::result::Result<(), rustc_span[ac3b12a2af12cb0d]::ErrorGuaranteed>>::{closure#0}, core[ceaa87f59aeb8bba]::result::Result<(), rustc_span[ac3b12a2af12cb0d]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[ceaa87f59aeb8bba]::result::Result<(), rustc_span[ac3b12a2af12cb0d]::ErrorGuaranteed>>
  24:     0x7f267ffddb32 - <<std[aeaa4a650f96ca4f]::thread::Builder>::spawn_unchecked_<rustc_interface[91b806f92bb77cda]::util::run_in_thread_with_globals<rustc_interface[91b806f92bb77cda]::util::run_in_thread_pool_with_globals<rustc_interface[91b806f92bb77cda]::interface::run_compiler<core[ceaa87f59aeb8bba]::result::Result<(), rustc_span[ac3b12a2af12cb0d]::ErrorGuaranteed>, rustc_driver_impl[2ad8c6e0ef02d37]::run_compiler::{closure#0}>::{closure#0}, core[ceaa87f59aeb8bba]::result::Result<(), rustc_span[ac3b12a2af12cb0d]::ErrorGuaranteed>>::{closure#0}, core[ceaa87f59aeb8bba]::result::Result<(), rustc_span[ac3b12a2af12cb0d]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[ceaa87f59aeb8bba]::result::Result<(), rustc_span[ac3b12a2af12cb0d]::ErrorGuaranteed>>::{closure#1} as core[ceaa87f59aeb8bba]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  25:     0x7f26810999e5 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h4c4227d670230628
                               at /rustc/c475e2303b551d726307c646181e0677af1e0069/library/alloc/src/boxed.rs:2016:9
  26:     0x7f26810999e5 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h4bc52f0323c8ae82
                               at /rustc/c475e2303b551d726307c646181e0677af1e0069/library/alloc/src/boxed.rs:2016:9
  27:     0x7f26810999e5 - std::sys::pal::unix::thread::Thread::new::thread_start::hd34fbf5607308b31
                               at /rustc/c475e2303b551d726307c646181e0677af1e0069/library/std/src/sys/pal/unix/thread.rs:108:17
  28:     0x7f267aa94ac3 - start_thread
                               at ./nptl/pthread_create.c:442:8
  29:     0x7f267ab26850 - __GI___clone3
                               at ./misc/../sysdeps/unix/sysv/linux/x86_64/clone3.S:81
  30:                0x0 - <unknown>

$ rustc --version --verbose
rustc 1.78.0-nightly (c475e2303 2024-02-28)
binary: rustc
commit-hash: c475e2303b551d726307c646181e0677af1e0069
commit-date: 2024-02-28
host: x86_64-unknown-linux-gnu
release: 1.78.0-nightly
LLVM version: 18.1.0

[dtolnay]

Bisects to Rust 1.55.0, and nightly-2021-07-20. In older stable and nightly releases, this compiles successfully.

[apiraino]

WG-prioritization assigning priority (Zulip discussion).

@rustbot label -I-prioritize +P-medium

[apiraino]

bisection points to rollup 27f5d83

If I had to guess, I'd say that #93590 looks like the one. It's the only one in the rollup touching diagnostic code. Possibly my reasoning is off (pls correct me).

[dtolnay]

Something went wrong with your bisect, as 27f5d83 is from 2022-02-02, whereas this ICE is present in nightly-2021-07-20.

#86970 looks the most likely to me.

[Noratrieb]

Either way, this is probably easier to debug from scratch instead of digging around commits.
Previous issue with this ICE message should reveal information on how to fix these issues, which arise from eagerly formatting paths in lints instead of only when they're emitted.