Collect and emit proper backtraces for delay_span_bugs

[compiler-errors]

This is a follow-up to #106317, which addresses this comment (#106267 (comment)) which notes that delay_span_bugs' backtraces are nonsense.

Captures and emits the backtrace of the delayed span bug when it's created, rather than using the backtrace of the place where delayed bugs are flushed.

---

To test, I delayed a span bug during HIR typeck, specifically in typeck_with_fallback...

Before, note flush_delayed on frame 18. This is at the end of the compilation session, far from where the bug is being delayed.

error: internal compiler error: test
 --> /home/ubuntu/test.rs:1:1
  |
1 | fn main() {}
  | ^^^^^^^^^
  |
  = note: delayed at compiler/rustc_hir_typeck/src/lib.rs:196:14

thread 'rustc' panicked at 'Box<dyn Any>', compiler/rustc_errors/src/lib.rs:1634:13
stack backtrace:
   0:     0x7f9c3ec69dd1 - std::backtrace_rs::backtrace::libunwind::trace::h26056f81198c6594
                               at /home/ubuntu/rust2/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
   1:     0x7f9c3ec69dd1 - std::backtrace_rs::backtrace::trace_unsynchronized::hacfb345a0c6d5bb1
                               at /home/ubuntu/rust2/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f9c3ec69dd1 - std::sys_common::backtrace::_print_fmt::h18ea6016ac8030f3
                               at /home/ubuntu/rust2/library/std/src/sys_common/backtrace.rs:65:5
   3:     0x7f9c3ec69dd1 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::he35dde201d0c2d09
                               at /home/ubuntu/rust2/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x7f9c3ecee308 - core::fmt::write::h094ad263467a053c
                               at /home/ubuntu/rust2/library/core/src/fmt/mod.rs:1208:17
   5:     0x7f9c3ec8aaf1 - std::io::Write::write_fmt::hd47b4e2324b4d9b7
                               at /home/ubuntu/rust2/library/std/src/io/mod.rs:1682:15
   6:     0x7f9c3ec69bfa - std::sys_common::backtrace::_print::h43044162653a17fc
                               at /home/ubuntu/rust2/library/std/src/sys_common/backtrace.rs:47:5
   7:     0x7f9c3ec69bfa - std::sys_common::backtrace::print::hc8605da258fa5aeb
                               at /home/ubuntu/rust2/library/std/src/sys_common/backtrace.rs:34:9
   8:     0x7f9c3ec4db87 - std::panicking::default_hook::{{closure}}::h9e37f23f75122a15
   9:     0x7f9c3ec4d97b - std::panicking::default_hook::h602873a063f84da2
                               at /home/ubuntu/rust2/library/std/src/panicking.rs:286:9
  10:     0x7f9c3f6672b2 - <alloc[48d7b30605060536]::boxed::Box<dyn for<'a, 'b> core[672e3947e150d6c6]::ops::function::Fn<(&'a core[672e3947e150d6c6]::panic::panic_info::PanicInfo<'b>,), Output = ()> + core[672e3947e150d6c6]::marker::Send + core[672e3947e150d6c6]::marker::Sync> as core[672e3947e150d6c6]::ops::function::Fn<(&core[672e3947e150d6c6]::panic::panic_info::PanicInfo,)>>::call
                               at /home/ubuntu/rust2/library/alloc/src/boxed.rs:2002:9
  11:     0x7f9c3f6672b2 - rustc_driver[f5b6d32d8905ecdd]::DEFAULT_HOOK::{closure#0}::{closure#0}
                               at /home/ubuntu/rust2/compiler/rustc_driver/src/lib.rs:1204:17
  12:     0x7f9c3ec4e0d3 - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::hfd13333ca953ae8e
                               at /home/ubuntu/rust2/library/alloc/src/boxed.rs:2002:9
  13:     0x7f9c3ec4e0d3 - std::panicking::rust_panic_with_hook::h45753e10264ebe7e
                               at /home/ubuntu/rust2/library/std/src/panicking.rs:692:13
  14:     0x7f9c422a1aa3 - std[3330b4673efabfce]::panicking::begin_panic::<rustc_errors[1b15f4e7e49d1fd5]::ExplicitBug>::{closure#0}
                               at /home/ubuntu/rust2/library/std/src/panicking.rs:608:9
  15:     0x7f9c422a1a46 - std[3330b4673efabfce]::sys_common::backtrace::__rust_end_short_backtrace::<std[3330b4673efabfce]::panicking::begin_panic<rustc_errors[1b15f4e7e49d1fd5]::ExplicitBug>::{closure#0}, !>
                               at /home/ubuntu/rust2/library/std/src/sys_common/backtrace.rs:137:18
  16:     0x7f9c3f63a996 - std[3330b4673efabfce]::panicking::begin_panic::<rustc_errors[1b15f4e7e49d1fd5]::ExplicitBug>
                               at /home/ubuntu/rust2/library/std/src/panicking.rs:607:12
  17:     0x7f9c4227a496 - std[3330b4673efabfce]::panic::panic_any::<rustc_errors[1b15f4e7e49d1fd5]::ExplicitBug>
                               at /home/ubuntu/rust2/library/std/src/panic.rs:61:5
  18:     0x7f9c4227cdf7 - <rustc_errors[1b15f4e7e49d1fd5]::HandlerInner>::flush_delayed::<alloc[48d7b30605060536]::vec::Vec<rustc_errors[1b15f4e7e49d1fd5]::diagnostic::Diagnostic>, &str, rustc_errors[1b15f4e7e49d1fd5]::ExplicitBug>
                               at /home/ubuntu/rust2/compiler/rustc_errors/src/lib.rs:1634:13
  19:     0x7f9c422498cf - <rustc_errors[1b15f4e7e49d1fd5]::Handler>::flush_delayed
                               at /home/ubuntu/rust2/compiler/rustc_errors/src/lib.rs:1225:9
 
[ FRAMES INTENTIONALLY OMITTED ]

  44:     0x7f9c3f6f3584 - <std[3330b4673efabfce]::thread::Builder>::spawn_unchecked_::<rustc_interface[947706ead88047d0]::util::run_in_thread_pool_with_globals<rustc_interface[947706ead88047d0]::interface::run_compiler<core[672e3947e150d6c6]::result::Result<(), rustc_errors[1b15f4e7e49d1fd5]::ErrorGuaranteed>, rustc_driver[f5b6d32d8905ecdd]::run_compiler::{closure#1}>::{closure#0}, core[672e3947e150d6c6]::result::Result<(), rustc_errors[1b15f4e7e49d1fd5]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[672e3947e150d6c6]::result::Result<(), rustc_errors[1b15f4e7e49d1fd5]::ErrorGuaranteed>>::{closure#1}
                               at /home/ubuntu/rust2/library/std/src/thread/mod.rs:549:30
  45:     0x7f9c3f6f3584 - <<std[3330b4673efabfce]::thread::Builder>::spawn_unchecked_<rustc_interface[947706ead88047d0]::util::run_in_thread_pool_with_globals<rustc_interface[947706ead88047d0]::interface::run_compiler<core[672e3947e150d6c6]::result::Result<(), rustc_errors[1b15f4e7e49d1fd5]::ErrorGuaranteed>, rustc_driver[f5b6d32d8905ecdd]::run_compiler::{closure#1}>::{closure#0}, core[672e3947e150d6c6]::result::Result<(), rustc_errors[1b15f4e7e49d1fd5]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[672e3947e150d6c6]::result::Result<(), rustc_errors[1b15f4e7e49d1fd5]::ErrorGuaranteed>>::{closure#1} as core[672e3947e150d6c6]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
                               at /home/ubuntu/rust2/library/core/src/ops/function.rs:250:5
  46:     0x7f9c3ec81968 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::he8b26fc22c6f51ec
                               at /home/ubuntu/rust2/library/alloc/src/boxed.rs:1988:9
  47:     0x7f9c3ec81968 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h5cf9cbe75a8c3ddc
                               at /home/ubuntu/rust2/library/alloc/src/boxed.rs:1988:9
  48:     0x7f9c3ec5f99c - std::sys::unix::thread::Thread::new::thread_start::h2d6dd4455e97d031
                               at /home/ubuntu/rust2/library/std/src/sys/unix/thread.rs:108:17
  49:     0x7f9c37c69609 - start_thread
  50:     0x7f9c3ead0133 - clone
  51:                0x0 - <unknown>

After, note typeck_with_fallback on the 5th frame, that's where we actually need to be pointed to:

error: internal compiler error: no errors encountered even though `delay_span_bug` issued

error: internal compiler error: test
 --> /home/ubuntu/test.rs:1:1
  |
1 | fn main() {}
  | ^^^^^^^^^
  |
  = note: delayed at    0: <rustc_errors::HandlerInner>::emit_diagnostic
                       at ./compiler/rustc_errors/src/lib.rs:1279:29
             1: <rustc_errors::HandlerInner>::delay_span_bug::<rustc_span::span_encoding::Span, &str>
                       at ./compiler/rustc_errors/src/lib.rs:1553:9
             2: <rustc_errors::Handler>::delay_span_bug::<rustc_span::span_encoding::Span, &str>
                       at ./compiler/rustc_errors/src/lib.rs:995:9
             3: <rustc_session::session::Session>::delay_span_bug::<rustc_span::span_encoding::Span, &str>
                       at ./compiler/rustc_session/src/session.rs:600:9
             4: rustc_hir_typeck::typeck_with_fallback::<rustc_hir_typeck::typeck::{closure#0}>::{closure#0}
                       at ./compiler/rustc_hir_typeck/src/lib.rs:196:5
             5: rustc_hir_typeck::typeck_with_fallback::<rustc_hir_typeck::typeck::{closure#0}>
                       at ./compiler/rustc_hir_typeck/src/lib.rs:185:36
             6: rustc_hir_typeck::typeck
                       at ./compiler/rustc_hir_typeck/src/lib.rs:166:9

[ FRAMES INTENTIONALLY OMITTED ]

           108: std::panicking::try::<core::result::Result<(), rustc_errors::ErrorGuaranteed>, core::panic::unwind_safe::AssertUnwindSafe<<std::thread::Builder>::spawn_unchecked_<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_errors::ErrorGuaranteed>, rustc_driver::run_compiler::{closure#1}>::{closure#0}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>::{closure#1}::{closure#0}>>
                       at ./library/std/src/panicking.rs:447:19
           109: std::panic::catch_unwind::<core::panic::unwind_safe::AssertUnwindSafe<<std::thread::Builder>::spawn_unchecked_<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_errors::ErrorGuaranteed>, rustc_driver::run_compiler::{closure#1}>::{closure#0}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>::{closure#1}::{closure#0}>, core::result::Result<(), rustc_errors::ErrorGuaranteed>>
                       at ./library/std/src/panic.rs:140:14
           110: <std::thread::Builder>::spawn_unchecked_::<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_errors::ErrorGuaranteed>, rustc_driver::run_compiler::{closure#1}>::{closure#0}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>::{closure#1}
                       at ./library/std/src/thread/mod.rs:549:30
           111: <<std::thread::Builder>::spawn_unchecked_<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_errors::ErrorGuaranteed>, rustc_driver::run_compiler::{closure#1}>::{closure#0}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>::{closure#1} as core::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
                       at ./library/core/src/ops/function.rs:250:5
           112: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
                       at ./library/alloc/src/boxed.rs:1988:9
           113: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
                       at ./library/alloc/src/boxed.rs:1988:9
           114: std::sys::unix::thread::Thread::new::thread_start
                       at ./library/std/src/sys/unix/thread.rs:108:17
           115: start_thread
           116: clone

[rustbot]

r? @TaKO8Ki

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[Noratrieb]

r? Nilstrieb
@bors r+

I would like if we had a better way to test ICE messages in general (delayed bugs and also other kinds of ICEs), maybe some kind of -Z flag, but we can do that in a follow-up PR since we currently don't really have anything.

[bors]

📌 Commit 05c1ac0 has been approved by Nilstrieb

It is now in the queue for this repository.

[bors]

🌲 The tree is currently closed for pull requests below priority 50. This pull request will be tested once the tree is reopened.

[pnkfelix]

oddly, this appears to have injected a slight regression according to the timing results presented on rollup PR #106730.

it may well be noise, though.

[compiler-errors]

As @Nilstrieb said, I'm inclined to believe this is noise because this code is on the error path only. We never delay span bugs without fatally exiting.