ICE: 'trimmed_def_paths constructed but no error emitted' in THIR unsafety checker

[LeSeulArtichaut]

Code

In some external crate, say macro_foo:

#[macro_export]
macro_rules! foo {
    () => {
        unsafe fn __unsf() {}
        unsafe fn __foo() {
            __unsf();
        }
    };
}

Main crate:

#![deny(unsafe_op_in_unsafe_fn)]

macro_foo::foo!();

Meta

rustc --version --verbose:

rustc 1.68.0-nightly (af3e06f1b 2022-12-23)
binary: rustc
commit-hash: af3e06f1bf4ca49407562b1b84744e27905bea98
commit-date: 2022-12-23
host: x86_64-unknown-linux-gnu
release: 1.68.0-nightly
LLVM version: 15.0.6

Error output

With -Zthir-unsafeck, this gives the following ICE:

Backtrace

error: internal compiler error: no warnings or errors encountered even though `delayed_good_path_bugs` issued

error: internal compiler error: trimmed_def_paths constructed but no error emitted; use `DelayDm` for lints or `with_no_trimmed_paths` for debugging
  |
  = note: delayed at    0: <rustc_errors::Handler>::delay_good_path_bug::<&str>
             1: rustc_middle::ty::print::pretty::trimmed_def_paths
             2: <rustc_middle::dep_graph::dep_node::DepKind as rustc_query_system::dep_graph::DepKind>::with_deps::<<rustc_query_system::dep_graph::graph::DepGraph<rustc_middle::dep_graph::dep_node::DepKind>>::with_task_impl<rustc_middle::ty::context::TyCtxt, (), std::collections::hash::map::HashMap<rustc_span::def_id::DefId, rustc_span::symbol::Symbol, core::hash::BuildHasherDefault<rustc_hash::FxHasher>>>::{closure#0}, std::collections::hash::map::HashMap<rustc_span::def_id::DefId, rustc_span::symbol::Symbol, core::hash::BuildHasherDefault<rustc_hash::FxHasher>>>
             3: <rustc_query_system::dep_graph::graph::DepGraph<rustc_middle::dep_graph::dep_node::DepKind>>::with_task::<rustc_middle::ty::context::TyCtxt, (), std::collections::hash::map::HashMap<rustc_span::def_id::DefId, rustc_span::symbol::Symbol, core::hash::BuildHasherDefault<rustc_hash::FxHasher>>>
             4: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::plumbing::QueryCtxt, rustc_query_system::query::caches::ArenaCache<(), std::collections::hash::map::HashMap<rustc_span::def_id::DefId, rustc_span::symbol::Symbol, core::hash::BuildHasherDefault<rustc_hash::FxHasher>>>>
             5: rustc_query_system::query::plumbing::force_query::<rustc_query_impl::queries::trimmed_def_paths, rustc_query_impl::plumbing::QueryCtxt, rustc_middle::dep_graph::dep_node::DepKind>
             6: rustc_query_impl::plumbing::force_from_dep_node::<rustc_query_impl::queries::trimmed_def_paths>
             7: <rustc_query_system::dep_graph::graph::DepGraph<rustc_middle::dep_graph::dep_node::DepKind>>::try_mark_previous_green::<rustc_query_impl::plumbing::QueryCtxt>
             8: <rustc_query_system::dep_graph::graph::DepGraph<rustc_middle::dep_graph::dep_node::DepKind>>::try_mark_previous_green::<rustc_query_impl::plumbing::QueryCtxt>
             9: <rustc_query_system::dep_graph::graph::DepGraph<rustc_middle::dep_graph::dep_node::DepKind>>::try_mark_previous_green::<rustc_query_impl::plumbing::QueryCtxt>
            10: <rustc_query_system::dep_graph::graph::DepGraph<rustc_middle::dep_graph::dep_node::DepKind>>::try_mark_previous_green::<rustc_query_impl::plumbing::QueryCtxt>
            11: <rustc_query_system::dep_graph::graph::DepGraph<rustc_middle::dep_graph::dep_node::DepKind>>::try_mark_previous_green::<rustc_query_impl::plumbing::QueryCtxt>
            12: <rustc_query_system::dep_graph::graph::DepGraph<rustc_middle::dep_graph::dep_node::DepKind>>::try_mark_previous_green::<rustc_query_impl::plumbing::QueryCtxt>
            13: rustc_query_system::query::plumbing::ensure_must_run::<rustc_query_impl::plumbing::QueryCtxt, rustc_span::def_id::LocalDefId, bool>
            14: rustc_data_structures::sync::par_for_each_in::<&[rustc_span::def_id::LocalDefId], <rustc_middle::hir::map::Map>::par_body_owners<rustc_interface::passes::analysis::{closure#2}::{closure#0}>::{closure#0}>
            15: <rustc_session::session::Session>::time::<(), rustc_interface::passes::analysis::{closure#2}>
            16: rustc_interface::passes::analysis
            17: <rustc_query_system::dep_graph::graph::DepGraph<rustc_middle::dep_graph::dep_node::DepKind>>::with_task::<rustc_middle::ty::context::TyCtxt, (), core::result::Result<(), rustc_errors::ErrorGuaranteed>>
            18: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::plumbing::QueryCtxt, rustc_query_system::query::caches::DefaultCache<(), core::result::Result<(), rustc_errors::ErrorGuaranteed>>>
            19: rustc_query_system::query::plumbing::get_query::<rustc_query_impl::queries::analysis, rustc_query_impl::plumbing::QueryCtxt, rustc_middle::dep_graph::dep_node::DepKind>
            20: <rustc_interface::passes::QueryContext>::enter::<rustc_driver::run_compiler::{closure#1}::{closure#2}::{closure#2}, core::result::Result<(), rustc_errors::ErrorGuaranteed>>
            21: <rustc_interface::interface::Compiler>::enter::<rustc_driver::run_compiler::{closure#1}::{closure#2}, core::result::Result<core::option::Option<rustc_interface::queries::Linker>, rustc_errors::ErrorGuaranteed>>
            22: rustc_span::with_source_map::<core::result::Result<(), rustc_errors::ErrorGuaranteed>, rustc_interface::interface::run_compiler<core::result::Result<(), rustc_errors::ErrorGuaranteed>, rustc_driver::run_compiler::{closure#1}>::{closure#0}::{closure#0}>
            23: <scoped_tls::ScopedKey<rustc_span::SessionGlobals>>::set::<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>>
            24: std::sys_common::backtrace::__rust_begin_short_backtrace::<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>>
            25: <<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}
            26: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
                       at /rustc/af3e06f1bf4ca49407562b1b84744e27905bea98/library/alloc/src/boxed.rs:2000:9
            27: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
                       at /rustc/af3e06f1bf4ca49407562b1b84744e27905bea98/library/alloc/src/boxed.rs:2000:9
            28: std::sys::unix::thread::Thread::new::thread_start
                       at /rustc/af3e06f1bf4ca49407562b1b84744e27905bea98/library/std/src/sys/unix/thread.rs:108:17
            29: <unknown>
            30: <unknown>
          

note: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: https://github.com/rust-lang/rust/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: rustc 1.68.0-nightly (af3e06f1b 2022-12-23) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type bin -C embed-bitcode=no -C debuginfo=2 -C incremental=[REDACTED] -Z thir-unsafeck

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
end of query stack

This is because the unsafe_op_in_unsafe_fn lint calls def_path_str to insert the name in the diagnostic message (this delays a good path bug), then the lint gets cancelled because it's in an external macro, which means we don't emit any diagnostic which triggers the good path bug.

This ICE is currently preventing rustc from building std with -Zthir-unsafeck enabled.

I see several ways to fix this:

1. Just don't print the function name. It arguably carries little value, with the span already pointing to the offending function call, and brings THIR unsafeck in line with MIR unsafeck (cc Fix incremental perf regression unsafety checking #96425).
2. Don't trim the path. This might lead to longer messages but other lints already do this so it is probably acceptable?
3. Don't create the lint if we're in an external macro and we know the lint will be cancelled anyway. It's a little hacky and breaks down if changes are made to lint emission.
4. Change the lint emission API to allow lint messages to be lazily evaluated.

@rustbot label +A-diagnostics +requires-nightly
@rusbot claim

[rustbot]

Error: Label thir-unsafeck can only be set by Rust team members

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[lqd]

Would not trimming the path also be acceptable ? (via https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/ty/print/macro.with_no_trimmed_paths.html)

[LeSeulArtichaut]

It looks like some lints are already not trimming paths so this is probably acceptable? I can do that if that's the preferred option.

[LeSeulArtichaut]

@rustbot claim