ICE in mir_drops_elaborated_and_const_checked

[veluca93]

Code

pub type UserId<Backend> = <<Backend as AuthnBackend>::User as AuthUser>::Id;

pub trait AuthUser {
    type Id;
}

pub trait AuthnBackend {
    type User: AuthUser;
}

pub struct AuthSession<Backend: AuthnBackend> {
    user: Option<Backend::User>,
    data: Option<UserId<Backend>>,
}

pub trait Authz: Sized {
    type AuthnBackend: AuthnBackend<User = Self>;
}

pub trait Query<User: Authz> {
    type Output;
    async fn run(&self) -> Result<Self::Output, ()>;
}

pub async fn run_query<User: Authz, Q: Query<User> + 'static>(
    auth: AuthSession<User::AuthnBackend>,
    query: Q,
) -> Result<Q::Output, ()> {
    let user = auth.user;
    query.run().await
}

(this is my best attempt at minimizing -- it includes some modified pieces from axum_login)

Meta

rustc --version --verbose:

rustc 1.83.0 (90b35a623 2024-11-26)
binary: rustc
commit-hash: 90b35a6239c3d8bdabc530a6a0816f7ff89a0aaf
commit-date: 2024-11-26
host: x86_64-unknown-linux-gnu
release: 1.83.0
LLVM version: 19.1.1

The error appears to persist in the latest nightly (2025-01-01)

Error output

error: internal compiler error: compiler/rustc_middle/src/ty/normalize_erasing_regions.rs:169:90: Failed to normalize std::option::Option<Alias(Projection, AliasTy { args: [Alias(Projection, AliasTy { args: [Alias(Projection, AliasTy { args: [User/#0], def_id: DefId(0:14 ~ lib[8f96]::Authz::AuthnBackend), .. })], def_id: DefId(0:8 ~ lib[8f96]::AuthnBackend::User), .. })], def_id: DefId(0:6 ~ lib[8f96]::AuthUser::Id), .. })>, maybe try to call `try_normalize_erasing_regions` instead

thread 'rustc' panicked at compiler/rustc_middle/src/ty/normalize_erasing_regions.rs:169:90:
Box<dyn Any>

Backtrace

stack backtrace:
   0:     0x79bade44012a - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::h5b6bd5631a6d1f6b
   1:     0x79badec218f8 - core::fmt::write::h7550c97b06c86515
   2:     0x79badfe58b91 - std::io::Write::write_fmt::h7b09c64fe0be9c84
   3:     0x79bade43ff82 - std::sys::backtrace::BacktraceLock::print::h2395ccd2c84ba3aa
   4:     0x79bade442456 - std::panicking::default_hook::{{closure}}::he19d4c7230e07961
   5:     0x79bade4422a0 - std::panicking::default_hook::hf614597d3c67bbdb
   6:     0x79badd504556 - std[c6eb78587944e35c]::panicking::update_hook::<alloc[148a978a4a62f5d]::boxed::Box<rustc_driver_impl[4c2d2ad79fb810ac]::install_ice_hook::{closure#0}>>::{closure#0}
   7:     0x79bade442b68 - std::panicking::rust_panic_with_hook::h8942133a8b252070
   8:     0x79badd53b371 - std[c6eb78587944e35c]::panicking::begin_panic::<rustc_errors[7f4c80274b6ccf5]::ExplicitBug>::{closure#0}
   9:     0x79badd52e976 - std[c6eb78587944e35c]::sys::backtrace::__rust_end_short_backtrace::<std[c6eb78587944e35c]::panicking::begin_panic<rustc_errors[7f4c80274b6ccf5]::ExplicitBug>::{closure#0}, !>
  10:     0x79badd52e933 - std[c6eb78587944e35c]::panicking::begin_panic::<rustc_errors[7f4c80274b6ccf5]::ExplicitBug>
  11:     0x79badd544a31 - <rustc_errors[7f4c80274b6ccf5]::diagnostic::BugAbort as rustc_errors[7f4c80274b6ccf5]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
  12:     0x79baddb6ee74 - rustc_middle[a886f61dbc61428a]::util::bug::opt_span_bug_fmt::<rustc_span[3e5cf3424d44936d]::span_encoding::Span>::{closure#0}
  13:     0x79baddb54f6a - rustc_middle[a886f61dbc61428a]::ty::context::tls::with_opt::<rustc_middle[a886f61dbc61428a]::util::bug::opt_span_bug_fmt<rustc_span[3e5cf3424d44936d]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  14:     0x79baddb54dfb - rustc_middle[a886f61dbc61428a]::ty::context::tls::with_context_opt::<rustc_middle[a886f61dbc61428a]::ty::context::tls::with_opt<rustc_middle[a886f61dbc61428a]::util::bug::opt_span_bug_fmt<rustc_span[3e5cf3424d44936d]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  15:     0x79badc4839a0 - rustc_middle[a886f61dbc61428a]::util::bug::bug_fmt
  16:     0x79badf2e7f70 - <rustc_middle[a886f61dbc61428a]::ty::normalize_erasing_regions::NormalizeAfterErasingRegionsFolder as rustc_type_ir[953d4871ec2d6eb6]::fold::TypeFolder<rustc_middle[a886f61dbc61428a]::ty::context::TyCtxt>>::fold_ty
  17:     0x79badf4fe25d - <rustc_mir_dataflow[9c27b51dffa9535c]::elaborate_drops::DropCtxt<rustc_mir_transform[b36c87ceb4bb9a8e]::elaborate_drops::ElaborateDropsCtxt>>::elaborate_drop
  18:     0x79badbc5ea22 - <rustc_mir_transform[b36c87ceb4bb9a8e]::elaborate_drops::ElaborateDrops as rustc_mir_transform[b36c87ceb4bb9a8e]::pass_manager::MirPass>::run_pass
  19:     0x79badec066b9 - rustc_mir_transform[b36c87ceb4bb9a8e]::run_analysis_to_runtime_passes
  20:     0x79badedf62de - rustc_mir_transform[b36c87ceb4bb9a8e]::mir_drops_elaborated_and_const_checked
  21:     0x79badedf5cfd - rustc_query_impl[db795c774d495014]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[db795c774d495014]::query_impl::mir_drops_elaborated_and_const_checked::dynamic_query::{closure#2}::{closure#0}, rustc_middle[a886f61dbc61428a]::query::erase::Erased<[u8; 8usize]>>
  22:     0x79badeef3e68 - rustc_query_system[b2bb6e43dd6b7fda]::query::plumbing::try_execute_query::<rustc_query_impl[db795c774d495014]::DynamicConfig<rustc_query_system[b2bb6e43dd6b7fda]::query::caches::VecCache<rustc_span[3e5cf3424d44936d]::def_id::LocalDefId, rustc_middle[a886f61dbc61428a]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[db795c774d495014]::plumbing::QueryCtxt, false>
  23:     0x79badeef36cd - rustc_query_impl[db795c774d495014]::query_impl::mir_drops_elaborated_and_const_checked::get_query_non_incr::__rust_end_short_backtrace
  24:     0x79badf10af19 - rustc_mir_transform[b36c87ceb4bb9a8e]::optimized_mir
  25:     0x79badf108369 - rustc_query_impl[db795c774d495014]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[db795c774d495014]::query_impl::optimized_mir::dynamic_query::{closure#2}::{closure#0}, rustc_middle[a886f61dbc61428a]::query::erase::Erased<[u8; 8usize]>>
  26:     0x79badec24b2d - rustc_query_system[b2bb6e43dd6b7fda]::query::plumbing::try_execute_query::<rustc_query_impl[db795c774d495014]::DynamicConfig<rustc_query_system[b2bb6e43dd6b7fda]::query::caches::DefIdCache<rustc_middle[a886f61dbc61428a]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[db795c774d495014]::plumbing::QueryCtxt, false>
  27:     0x79badec241b3 - rustc_query_impl[db795c774d495014]::query_impl::optimized_mir::get_query_non_incr::__rust_end_short_backtrace
  28:     0x79badf6ce39f - rustc_middle[a886f61dbc61428a]::query::plumbing::query_get_at::<rustc_query_system[b2bb6e43dd6b7fda]::query::caches::DefIdCache<rustc_middle[a886f61dbc61428a]::query::erase::Erased<[u8; 8usize]>>>
  29:     0x79baddb6e8b5 - <rustc_middle[a886f61dbc61428a]::ty::context::TyCtxt>::coroutine_layout
  30:     0x79badf273c28 - rustc_ty_utils[45bf0f8bee683616]::layout::layout_of_uncached
  31:     0x79badf264a46 - rustc_ty_utils[45bf0f8bee683616]::layout::layout_of
  32:     0x79badf2649d1 - rustc_query_impl[db795c774d495014]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[db795c774d495014]::query_impl::layout_of::dynamic_query::{closure#2}::{closure#0}, rustc_middle[a886f61dbc61428a]::query::erase::Erased<[u8; 16usize]>>
  33:     0x79badf2640b2 - rustc_query_system[b2bb6e43dd6b7fda]::query::plumbing::try_execute_query::<rustc_query_impl[db795c774d495014]::DynamicConfig<rustc_query_system[b2bb6e43dd6b7fda]::query::caches::DefaultCache<rustc_middle[a886f61dbc61428a]::ty::ParamEnvAnd<rustc_middle[a886f61dbc61428a]::ty::Ty>, rustc_middle[a886f61dbc61428a]::query::erase::Erased<[u8; 16usize]>>, false, true, false>, rustc_query_impl[db795c774d495014]::plumbing::QueryCtxt, false>
  34:     0x79badf263da9 - rustc_query_impl[db795c774d495014]::query_impl::layout_of::get_query_non_incr::__rust_end_short_backtrace
  35:     0x79badc2130da - <rustc_mir_transform[b36c87ceb4bb9a8e]::known_panics_lint::KnownPanicsLint as rustc_mir_transform[b36c87ceb4bb9a8e]::pass_manager::MirLint>::run_lint
  36:     0x79badec066b9 - rustc_mir_transform[b36c87ceb4bb9a8e]::run_analysis_to_runtime_passes
  37:     0x79badedf62de - rustc_mir_transform[b36c87ceb4bb9a8e]::mir_drops_elaborated_and_const_checked
  38:     0x79badedf5cfd - rustc_query_impl[db795c774d495014]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[db795c774d495014]::query_impl::mir_drops_elaborated_and_const_checked::dynamic_query::{closure#2}::{closure#0}, rustc_middle[a886f61dbc61428a]::query::erase::Erased<[u8; 8usize]>>
  39:     0x79badeef3e68 - rustc_query_system[b2bb6e43dd6b7fda]::query::plumbing::try_execute_query::<rustc_query_impl[db795c774d495014]::DynamicConfig<rustc_query_system[b2bb6e43dd6b7fda]::query::caches::VecCache<rustc_span[3e5cf3424d44936d]::def_id::LocalDefId, rustc_middle[a886f61dbc61428a]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[db795c774d495014]::plumbing::QueryCtxt, false>
  40:     0x79badeef36cd - rustc_query_impl[db795c774d495014]::query_impl::mir_drops_elaborated_and_const_checked::get_query_non_incr::__rust_end_short_backtrace
  41:     0x79badf4f0705 - rustc_interface[88a02114bbdb2383]::passes::run_required_analyses
  42:     0x79badf4e72e5 - rustc_interface[88a02114bbdb2383]::passes::analysis
  43:     0x79badf4e72c9 - rustc_query_impl[db795c774d495014]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[db795c774d495014]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[a886f61dbc61428a]::query::erase::Erased<[u8; 1usize]>>
  44:     0x79badf9f2662 - rustc_query_system[b2bb6e43dd6b7fda]::query::plumbing::try_execute_query::<rustc_query_impl[db795c774d495014]::DynamicConfig<rustc_query_system[b2bb6e43dd6b7fda]::query::caches::SingleCache<rustc_middle[a886f61dbc61428a]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[db795c774d495014]::plumbing::QueryCtxt, false>
  45:     0x79badf9f238f - rustc_query_impl[db795c774d495014]::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
  46:     0x79badf9620bb - rustc_interface[88a02114bbdb2383]::interface::run_compiler::<core[c06ff78fa456ca03]::result::Result<(), rustc_span[3e5cf3424d44936d]::ErrorGuaranteed>, rustc_driver_impl[4c2d2ad79fb810ac]::run_compiler::{closure#0}>::{closure#1}
  47:     0x79badf9533d9 - std[c6eb78587944e35c]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[88a02114bbdb2383]::util::run_in_thread_with_globals<rustc_interface[88a02114bbdb2383]::interface::run_compiler<core[c06ff78fa456ca03]::result::Result<(), rustc_span[3e5cf3424d44936d]::ErrorGuaranteed>, rustc_driver_impl[4c2d2ad79fb810ac]::run_compiler::{closure#0}>::{closure#1}, core[c06ff78fa456ca03]::result::Result<(), rustc_span[3e5cf3424d44936d]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[c06ff78fa456ca03]::result::Result<(), rustc_span[3e5cf3424d44936d]::ErrorGuaranteed>>
  48:     0x79badfa22fac - <<std[c6eb78587944e35c]::thread::Builder>::spawn_unchecked_<rustc_interface[88a02114bbdb2383]::util::run_in_thread_with_globals<rustc_interface[88a02114bbdb2383]::interface::run_compiler<core[c06ff78fa456ca03]::result::Result<(), rustc_span[3e5cf3424d44936d]::ErrorGuaranteed>, rustc_driver_impl[4c2d2ad79fb810ac]::run_compiler::{closure#0}>::{closure#1}, core[c06ff78fa456ca03]::result::Result<(), rustc_span[3e5cf3424d44936d]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[c06ff78fa456ca03]::result::Result<(), rustc_span[3e5cf3424d44936d]::ErrorGuaranteed>>::{closure#1} as core[c06ff78fa456ca03]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  49:     0x79badfa23a6b - std::sys::pal::unix::thread::Thread::new::thread_start::hcc78f3943333fa94
  50:     0x79bad9ea339d - <unknown>
  51:     0x79bad9f2849c - <unknown>
  52:                0x0 - <unknown>

[veluca93]

A bit more investigation (with some help from @sarah-quinones) led me to this additional, possibly related ICE:

pub type UserId<Backend> = <<Backend as AuthnBackend>::User as AuthUser>::Id;           

pub trait AuthUser {
    type Id;
}

pub trait AuthnBackend {
    type User: AuthUser;
}

pub struct AuthSession<Backend: AuthnBackend> {                                         
    data: Option<UserId<Backend>>,                                                      
}

pub trait Authz: Sized {
    type AuthnBackend: AuthnBackend<User = Self>;
}

pub fn run_query<User: Authz>(auth: AuthSession<User::AuthnBackend>) {}

ICE + backtrace:

error: internal compiler error: error performing operation: fully_perform
  |
  = note: delayed at /rustc/90b35a6239c3d8bdabc530a6a0816f7ff89a0aaf/compiler/rustc_trait_selection/src/traits/query/type_op/custom.rs:87:25
             0: <rustc_errors::DiagCtxtInner>::emit_diagnostic
             1: <rustc_errors::DiagCtxtHandle>::emit_diagnostic
             2: <rustc_span::ErrorGuaranteed as rustc_errors::diagnostic::EmissionGuarantee>::emit_producing_guarantee
             3: <rustc_errors::DiagCtxtHandle>::span_delayed_bug::<rustc_span::span_encoding::Span, alloc::string::String>
             4: <rustc_middle::ty::ParamEnvAnd<rustc_trait_selection::traits::query::type_op::outlives::DropckOutlives> as rustc_trait_selection::traits::query::type_op::TypeOp>::fully_perform
             5: rustc_borrowck::type_check::liveness::trace::trace
             6: rustc_borrowck::type_check::type_check
             7: rustc_borrowck::nll::compute_regions
             8: rustc_borrowck::do_mir_borrowck
             9: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::mir_borrowck::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 8]>>
            10: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::Erased<[u8; 8]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
            11: rustc_query_impl::query_impl::mir_borrowck::get_query_non_incr::__rust_end_short_backtrace
            12: rustc_interface::passes::run_required_analyses
            13: rustc_interface::passes::analysis
            14: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 1]>>
            15: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::SingleCache<rustc_middle::query::erase::Erased<[u8; 1]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
            16: rustc_query_impl::query_impl::analysis::get_query_non_incr::__rust_end_short_backtrace
            17: rustc_interface::interface::run_compiler::<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}
            18: std::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface::util::run_in_thread_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>
            19: <<std::thread::Builder>::spawn_unchecked_<rustc_interface::util::run_in_thread_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#1}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#1} as core::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
            20: std::sys::pal::unix::thread::Thread::new::thread_start
            21: <unknown>
            22: <unknown>

Note that this example does not use async.

[compiler-errors]

Just noting that is not "minimized", since that second ICE is a totally different ICE from the first.

[veluca93]

Just noting that is not "minimized", since that second ICE is a totally different ICE from the first.

Good point, changed the wording (it might make sense to open a second issue, WDYT?)

[veluca93]

One more bit of information: the code is not supposed to compile (it is missing a Authz: AuthUser bound), which is something I missed when writing the code originally.

[lqd]

You don't need to change the code to get the two different ICEs, just cargo check the OP to get the second one.

[matthewjasper]

There's two causes to this problem:

• HIR typeck no longer runs dropck, so any normalization errors in dropck don't get noticed until borrowck/drop elaboration when we generally ICE on errors.
• Just because a generic struct type is well-formed doesn't mean that its field types are well formed: here we have that AuthSession<User::AuthnBackend> is fine because User::AuthnBackend: AuthnBackend from the bound in the trait definition. But Option<<<User::AuthnBackend as AuthnBackend>::User as AuthUser>::Id> is not because <<User::AuthnBackend as AuthnBackend>::User normalizes to User, which doesn't have an AuthUser bound.

I'll make a PR soon to fix this by addressing the first problem here since I don't think that there's anything that isn't breaking that would fix the second. But first, cc @rust-lang/types to see if they have any ideas.

[compiler-errors]

@matthewjasper: By "addressing the first problem here", are you suggesting running dropck in HIR? Or what?

[matthewjasper]

I mean reporting the errors in borrowck