ICE: `delay_span_bug`: `error performing ParamEnvAnd`

[eric-seppanen]

Code

use std::collections::HashMap;
use std::marker::PhantomData;
use std::sync::Arc;

trait DataTypePrimitive {
    type DataTypeHolder;
}

trait LayerT {
    type DataType: DataTypePrimitive;
}

struct Pooled<B> {
    _buffer: PhantomData<B>,
}

struct NdBufferView<B, T: DataTypePrimitive> {
    buffer: B,
    data_type_h: T::DataTypeHolder,
}

type NdBuffer<T> = NdBufferView<(), T>;

type PooledNdBuffer<T> = Pooled<NdBuffer<T>>;

struct LayerPage<L: LayerT> {
    // NOTE! ICE if this is PooledNdBuffer
    buffer: Arc<PooledNdBuffer<L::DataType>>,
    // These work fine:
    //buffer: Arc<Pooled<Vec<L::DataType>>>,
    //buffer: Arc<Vec<L::DataType>>,
}

type Layer<L> = HashMap<u32, LayerPage<L>>;

// This function triggers the ICE.
fn layer_from_proto<T, L: LayerT<DataType = T>>(
    _layer: &'static L,
) -> Result<Layer<L>, ()> {
    todo!()
}

Meta

rustc --version --verbose:

rustc 1.64.0 (a55dd71d5 2022-09-19)
binary: rustc
commit-hash: a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52
commit-date: 2022-09-19
host: x86_64-unknown-linux-gnu
release: 1.64.0
LLVM version: 14.0.6

Also happens on:

rustc 1.67.0-nightly (11ebe6512 2022-11-01)
rustc 1.66.0-beta.1 (e080cc5a6 2022-11-01)

Error output

thread 'rustc' panicked at 'called `Result::unwrap()` on an `Err` value: NoSolution', compiler/rustc_borrowck/src/type_check/liveness/trace.rs:574:88
stack backtrace:
   0:     0x7f755ad6619d - std::backtrace_rs::backtrace::libunwind::trace::h9135f25bc195152c
                               at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
   1:     0x7f755ad6619d - std::backtrace_rs::backtrace::trace_unsynchronized::h015ee85be510df51
                               at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f755ad6619d - std::sys_common::backtrace::_print_fmt::h5fad03caa9652a2c
                               at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/std/src/sys_common/backtrace.rs:66:5
   3:     0x7f755ad6619d - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h2b42ca28d244e5c7
                               at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/std/src/sys_common/backtrace.rs:45:22
   4:     0x7f755adc16ac - core::fmt::write::h401e827d053130ed
                               at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/core/src/fmt/mod.rs:1198:17
   5:     0x7f755ad574e1 - std::io::Write::write_fmt::hffec93268f5cde32
                               at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/std/src/io/mod.rs:1672:15
   6:     0x7f755ad68eb5 - std::sys_common::backtrace::_print::h180c4c706ee1d3fb
                               at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/std/src/sys_common/backtrace.rs:48:5
   7:     0x7f755ad68eb5 - std::sys_common::backtrace::print::hd0c35d18765761c9
                               at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/std/src/sys_common/backtrace.rs:35:9
   8:     0x7f755ad68eb5 - std::panicking::default_hook::{{closure}}::h1f023310983bc730
                               at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/std/src/panicking.rs:295:22
   9:     0x7f755ad68bd1 - std::panicking::default_hook::h188fec3334afd5be
                               at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/std/src/panicking.rs:314:9
  10:     0x7f755d63e484 - rustc_driver[4568cc0a685fd94d]::DEFAULT_HOOK::{closure#0}::{closure#0}
  11:     0x7f755ad695ea - std::panicking::rust_panic_with_hook::hf26e9d4f97b40096
                               at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/std/src/panicking.rs:702:17
  12:     0x7f755ad69427 - std::panicking::begin_panic_handler::{{closure}}::hfab912107608087a
                               at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/std/src/panicking.rs:588:13
  13:     0x7f755ad66694 - std::sys_common::backtrace::__rust_end_short_backtrace::h434b685ce8d9965b
                               at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/std/src/sys_common/backtrace.rs:138:18
  14:     0x7f755ad69159 - rust_begin_unwind
                               at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/std/src/panicking.rs:584:5
  15:     0x7f755adbe1c3 - core::panicking::panic_fmt::ha6dc7f2ab2479463
                               at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/core/src/panicking.rs:142:14
  16:     0x7f755adbe533 - core::result::unwrap_failed::h42ad8e915aa0a906
                               at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/core/src/result.rs:1814:5
  17:     0x7f755c3c800b - rustc_borrowck[9bf94ea6123d60bb]::type_check::liveness::trace::trace
  18:     0x7f755c3b66e2 - rustc_borrowck[9bf94ea6123d60bb]::type_check::liveness::generate
  19:     0x7f755c3aff96 - rustc_borrowck[9bf94ea6123d60bb]::type_check::type_check
  20:     0x7f755c38b2ce - rustc_borrowck[9bf94ea6123d60bb]::nll::compute_regions
  21:     0x7f755c375daf - rustc_borrowck[9bf94ea6123d60bb]::do_mir_borrowck
  22:     0x7f755d02094d - rustc_borrowck[9bf94ea6123d60bb]::mir_borrowck
  23:     0x7f755d01fe60 - <rustc_borrowck[9bf94ea6123d60bb]::provide::{closure#0} as core[6fcc70bcc91a5bf5]::ops::function::FnOnce<(rustc_middle[b6cf56a787d1e2a1]::ty::context::TyCtxt, rustc_span[721a57c036170ce]::def_id::LocalDefId)>>::call_once
  24:     0x7f755c93339f - <rustc_query_system[8caf4755e287670e]::dep_graph::graph::DepGraph<rustc_middle[b6cf56a787d1e2a1]::dep_graph::dep_node::DepKind>>::with_task::<rustc_middle[b6cf56a787d1e2a1]::ty::context::TyCtxt, rustc_span[721a57c036170ce]::def_id::LocalDefId, &rustc_middle[b6cf56a787d1e2a1]::mir::query::BorrowCheckResult>
  25:     0x7f755c93267d - rustc_query_system[8caf4755e287670e]::query::plumbing::try_execute_query::<rustc_query_impl[232efbc2900411f9]::plumbing::QueryCtxt, rustc_query_system[8caf4755e287670e]::query::caches::DefaultCache<rustc_span[721a57c036170ce]::def_id::LocalDefId, &rustc_middle[b6cf56a787d1e2a1]::mir::query::BorrowCheckResult>>
  26:     0x7f755d53c56a - <rustc_query_impl[232efbc2900411f9]::Queries as rustc_middle[b6cf56a787d1e2a1]::ty::query::QueryEngine>::mir_borrowck
  27:     0x7f755d0294d3 - rustc_data_structures[49e7163a34b889d1]::sync::par_for_each_in::<&[rustc_span[721a57c036170ce]::def_id::LocalDefId], <rustc_middle[b6cf56a787d1e2a1]::hir::map::Map>::par_body_owners<rustc_interface[f934826ba4c12dd9]::passes::analysis::{closure#2}::{closure#0}>::{closure#0}>
  28:     0x7f755d028c8b - <rustc_middle[b6cf56a787d1e2a1]::hir::map::Map>::par_body_owners::<rustc_interface[f934826ba4c12dd9]::passes::analysis::{closure#2}::{closure#0}>
  29:     0x7f755d028b63 - <rustc_session[98f7faf1d37bb5fb]::session::Session>::time::<(), rustc_interface[f934826ba4c12dd9]::passes::analysis::{closure#2}>
  30:     0x7f755d028955 - rustc_interface[f934826ba4c12dd9]::passes::analysis
  31:     0x7f755d3e32bc - <rustc_query_system[8caf4755e287670e]::dep_graph::graph::DepGraph<rustc_middle[b6cf56a787d1e2a1]::dep_graph::dep_node::DepKind>>::with_task::<rustc_middle[b6cf56a787d1e2a1]::ty::context::TyCtxt, (), core[6fcc70bcc91a5bf5]::result::Result<(), rustc_errors[5fcb1a1f56a762e6]::ErrorGuaranteed>>
  32:     0x7f755d3e2aab - rustc_query_system[8caf4755e287670e]::query::plumbing::try_execute_query::<rustc_query_impl[232efbc2900411f9]::plumbing::QueryCtxt, rustc_query_system[8caf4755e287670e]::query::caches::DefaultCache<(), core[6fcc70bcc91a5bf5]::result::Result<(), rustc_errors[5fcb1a1f56a762e6]::ErrorGuaranteed>>>
  33:     0x7f755d3e25fe - rustc_query_system[8caf4755e287670e]::query::plumbing::get_query::<rustc_query_impl[232efbc2900411f9]::queries::analysis, rustc_query_impl[232efbc2900411f9]::plumbing::QueryCtxt>
  34:     0x7f755cdbcd87 - <rustc_interface[f934826ba4c12dd9]::passes::QueryContext>::enter::<rustc_driver[4568cc0a685fd94d]::run_compiler::{closure#1}::{closure#2}::{closure#3}, core[6fcc70bcc91a5bf5]::result::Result<(), rustc_errors[5fcb1a1f56a762e6]::ErrorGuaranteed>>
  35:     0x7f755cdb597f - <rustc_interface[f934826ba4c12dd9]::interface::Compiler>::enter::<rustc_driver[4568cc0a685fd94d]::run_compiler::{closure#1}::{closure#2}, core[6fcc70bcc91a5bf5]::result::Result<core[6fcc70bcc91a5bf5]::option::Option<rustc_interface[f934826ba4c12dd9]::queries::Linker>, rustc_errors[5fcb1a1f56a762e6]::ErrorGuaranteed>>
  36:     0x7f755cdaa86a - rustc_span[721a57c036170ce]::with_source_map::<core[6fcc70bcc91a5bf5]::result::Result<(), rustc_errors[5fcb1a1f56a762e6]::ErrorGuaranteed>, rustc_interface[f934826ba4c12dd9]::interface::create_compiler_and_run<core[6fcc70bcc91a5bf5]::result::Result<(), rustc_errors[5fcb1a1f56a762e6]::ErrorGuaranteed>, rustc_driver[4568cc0a685fd94d]::run_compiler::{closure#1}>::{closure#1}>
  37:     0x7f755cdaa1a2 - <scoped_tls[80743de900a7f844]::ScopedKey<rustc_span[721a57c036170ce]::SessionGlobals>>::set::<rustc_interface[f934826ba4c12dd9]::interface::run_compiler<core[6fcc70bcc91a5bf5]::result::Result<(), rustc_errors[5fcb1a1f56a762e6]::ErrorGuaranteed>, rustc_driver[4568cc0a685fd94d]::run_compiler::{closure#1}>::{closure#0}, core[6fcc70bcc91a5bf5]::result::Result<(), rustc_errors[5fcb1a1f56a762e6]::ErrorGuaranteed>>
  38:     0x7f755cda85cf - std[306a94a967d8f5ee]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[f934826ba4c12dd9]::util::run_in_thread_pool_with_globals<rustc_interface[f934826ba4c12dd9]::interface::run_compiler<core[6fcc70bcc91a5bf5]::result::Result<(), rustc_errors[5fcb1a1f56a762e6]::ErrorGuaranteed>, rustc_driver[4568cc0a685fd94d]::run_compiler::{closure#1}>::{closure#0}, core[6fcc70bcc91a5bf5]::result::Result<(), rustc_errors[5fcb1a1f56a762e6]::ErrorGuaranteed>>::{closure#0}, core[6fcc70bcc91a5bf5]::result::Result<(), rustc_errors[5fcb1a1f56a762e6]::ErrorGuaranteed>>
  39:     0x7f755d4620b9 - <<std[306a94a967d8f5ee]::thread::Builder>::spawn_unchecked_<rustc_interface[f934826ba4c12dd9]::util::run_in_thread_pool_with_globals<rustc_interface[f934826ba4c12dd9]::interface::run_compiler<core[6fcc70bcc91a5bf5]::result::Result<(), rustc_errors[5fcb1a1f56a762e6]::ErrorGuaranteed>, rustc_driver[4568cc0a685fd94d]::run_compiler::{closure#1}>::{closure#0}, core[6fcc70bcc91a5bf5]::result::Result<(), rustc_errors[5fcb1a1f56a762e6]::ErrorGuaranteed>>::{closure#0}, core[6fcc70bcc91a5bf5]::result::Result<(), rustc_errors[5fcb1a1f56a762e6]::ErrorGuaranteed>>::{closure#1} as core[6fcc70bcc91a5bf5]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  40:     0x7f755ad73723 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h56d5fc072706762b
                               at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/alloc/src/boxed.rs:1935:9
  41:     0x7f755ad73723 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h41deef8e33b824bb
                               at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/alloc/src/boxed.rs:1935:9
  42:     0x7f755ad73723 - std::sys::unix::thread::Thread::new::thread_start::ha6436304a1170bba
                               at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/std/src/sys/unix/thread.rs:108:17
  43:     0x7f755aab7b43 - start_thread
                               at ./nptl/./nptl/pthread_create.c:442:8
  44:     0x7f755ab49a00 - clone3
                               at ./misc/../sysdeps/unix/sysv/linux/x86_64/clone3.S:81
  45:                0x0 - <unknown>

error: internal compiler error: unexpected panic

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 1.64.0 (a55dd71d5 2022-09-19) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type lib -C embed-bitcode=no -C debuginfo=2 -C incremental

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

query stack during panic:
#0 [mir_borrowck] borrow-checking `layer_from_proto`
#1 [analysis] running analysis passes on this crate
end of query stack

Backtrace

thread 'rustc' panicked at 'called `Result::unwrap()` on an `Err` value: NoSolution', compiler/rustc_borrowck/src/type_check/liveness/trace.rs:574:88
stack backtrace:
   0: rust_begin_unwind
             at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/std/src/panicking.rs:584:5
   1: core::panicking::panic_fmt
             at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/core/src/panicking.rs:142:14
   2: core::result::unwrap_failed
             at /rustc/a55dd71d5fb0ec5a6a3a9e8c27b2127ba491ce52/library/core/src/result.rs:1814:5
   3: rustc_borrowck::type_check::liveness::trace::trace
   4: rustc_borrowck::type_check::liveness::generate
   5: rustc_borrowck::type_check::type_check
   6: rustc_borrowck::nll::compute_regions
   7: rustc_borrowck::do_mir_borrowck
   8: rustc_borrowck::mir_borrowck
   9: <rustc_borrowck::provide::{closure#0} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, rustc_span::def_id::LocalDefId)>>::call_once
  10: <rustc_query_system::dep_graph::graph::DepGraph<rustc_middle::dep_graph::dep_node::DepKind>>::with_task::<rustc_middle::ty::context::TyCtxt, rustc_span::def_id::LocalDefId, &rustc_middle::mir::query::BorrowCheckResult>
  11: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::plumbing::QueryCtxt, rustc_query_system::query::caches::DefaultCache<rustc_span::def_id::LocalDefId, &rustc_middle::mir::query::BorrowCheckResult>>
  12: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::mir_borrowck
  13: 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}>
  14: <rustc_middle::hir::map::Map>::par_body_owners::<rustc_interface::passes::analysis::{closure#2}::{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>
  20: <rustc_interface::passes::QueryContext>::enter::<rustc_driver::run_compiler::{closure#1}::{closure#2}::{closure#3}, 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::create_compiler_and_run<core::result::Result<(), rustc_errors::ErrorGuaranteed>, rustc_driver::run_compiler::{closure#1}>::{closure#1}>
  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>>
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

error: internal compiler error: unexpected panic

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 1.64.0 (a55dd71d5 2022-09-19) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type lib -C embed-bitcode=no -C debuginfo=2 -C incremental

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

query stack during panic:
#0 [mir_borrowck] borrow-checking `layer_from_proto`
#1 [analysis] running analysis passes on this crate
end of query stack

[Noratrieb]

Simplified it further

trait BaseWithAssoc {
    type Assoc;
}

trait WrapperWithAssoc {
    type BaseAssoc: BaseWithAssoc;
}

struct Wrapper<B> {
    inner: B,
}

struct ProjectToBase<T: BaseWithAssoc> {
    data_type_h: T::Assoc,
}

struct DoubleProject<L: WrapperWithAssoc> {
    buffer: Wrapper<ProjectToBase<L::BaseAssoc>>,
}

fn trigger<L: WrapperWithAssoc<BaseAssoc = ()>>() -> DoubleProject<L> {
    loop {}
}

fn main() {}

[Noratrieb]

@rustbot claim

[compiler-errors]

This issue basically hinges on the fact that this code is considered well-formed:

trait Foo {
    type Assoc: Bar;
}

trait Bar {}

fn test<T: Foo<Assoc = S>, S>() {}

Even though S doesn't satisfy the predicates of the associate type Assoc. This should only be a problem when we observe S through a projection, for example, in code like this:

trait Foo {
    type Assoc: Bar;
}

trait Bar {
    type Assoc2;
}

struct Wrapper<T: Foo> {
    inner: <<T as Foo>::Assoc as Bar>::Assoc2,
    _i: (),
}

fn test<T: Foo<Assoc = S>, S>(s: Wrapper<T>) {
    let _ = s.inner;
    //~^ ERROR the trait bound `S: Bar` is not satisfied
}

However, sometimes we don't observe this projection during HIR typeck, but only during drop elaboration... which is not designed to handle associated type normalization errors 😓 This is evident by commenting out that let _ = ... line, which manifests this ICE.

[Noratrieb]

That does sound like something that needs more discussion, so I'll @rustbot release-assignment