Non returning compilation on 1.48, 1.49, 1.50-beta and nightly-2021-01-13

[krtab]

Hi!

The crate located here:
https://github.com/krtab/diff/releases/tag/infiloop at commit c7d13ab3473147785a7f35f97461d828e9421fd2
Makes cargo/rustc go to an infinite loop. (I tried for 4 hours, it went up to 80GB of RAM).

git clone 'https://github.com/krtab/diff.git'
cd diff
git checkout c7d13ab3473147785a7f35f97461d828e9421fd2
cargo check

Given the amount of type-level black-magic, I'd wager there is some cycle/infinite recursion when trying to type-check.

Meta

rustc --version --verbose:

rustc 1.49.0 (e1884a8e3 2020-12-29)
binary: rustc
commit-hash: e1884a8e3c3e813aada8254edfa120e85bf5ffca
commit-date: 2020-12-29
host: x86_64-unknown-linux-gnu
release: 1.49.0

I have also tried 1.50-beta and today's nightly, and ask someone to test 1.48, to no avail.

Given that it doesn't finish, there is no backtrace.

Let me know how I can help!

[tesuji]

@rustbot label E-needs-bisection I-hang T-compiler regression-from-stable-to-stable

I tested on 1.47 x86_64-linux-gnu, the compiler still hangs but there are errors displayed about trait bound not satisfied.
Memory always goes up in the hanged process.
Given that this is a regression about errors -> hang, maybe we could tag this issue with P-medium.

The backtrace of hanged rustc attached through pid `gdb --pid `:

#0  0x00007f9c4cce2add in rustc_data_structures::obligation_forest::ObligationForest<O>::register_obligation_at () from /home/lzutao/.rustup/toolchains/1.47-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-ff4ec557f69b94a7.so
#1  0x00007f9c4cce16b4 in rustc_data_structures::obligation_forest::ObligationForest<O>::process_obligations () from /home/lzutao/.rustup/toolchains/1.47-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-ff4ec557f69b94a7.so
#2  0x00007f9c4cc32af6 in <rustc_trait_selection::traits::fulfill::FulfillmentContext as rustc_infer::traits::engine::TraitEngine>::select_where_possible () from /home/lzutao/.rustup/toolchains/1.47-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-ff4ec557f69b94a7.so
#3  0x00007f9c4cc328bb in <rustc_trait_selection::traits::fulfill::FulfillmentContext as rustc_infer::traits::engine::TraitEngine>::select_all_or_error () from /home/lzutao/.rustup/toolchains/1.47-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-ff4ec557f69b94a7.so
#4  0x00007f9c4b37dde4 in rustc_typeck::check::FnCtxt::select_all_obligations_or_error () from /home/lzutao/.rustup/toolchains/1.47-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-ff4ec557f69b94a7.so
#5  0x00007f9c4b5fbb64 in rustc_infer::infer::InferCtxtBuilder::enter () from /home/lzutao/.rustup/toolchains/1.47-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-ff4ec557f69b94a7.so
#6  0x00007f9c4b504952 in rustc_typeck::check::wfcheck::check_associated_item () from /home/lzutao/.rustup/toolchains/1.47-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-ff4ec557f69b94a7.so
#7  0x00007f9c4b3672d7 in rustc_typeck::check::check_impl_item_well_formed () from /home/lzutao/.rustup/toolchains/1.47-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-ff4ec557f69b94a7.so
#8  0x00007f9c4b4c1a9e in rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::check_impl_item_well_formed>::compute () from /home/lzutao/.rustup/toolchains/1.47-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-ff4ec557f69b94a7.so
#9  0x00007f9c4b4c63b1 in rustc_middle::dep_graph::<impl rustc_query_system::dep_graph::DepKind for rustc_middle::dep_graph::dep_node::DepKind>::with_deps () from /home/lzutao/.rustup/toolchains/1.47-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-ff4ec557f69b94a7.so
#10 0x00007f9c4b540ab7 in rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl () from /home/lzutao/.rustup/toolchains/1.47-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-ff4ec557f69b94a7.so
#11 0x00007f9c4b554b93 in rustc_data_structures::stack::ensure_sufficient_stack () from /home/lzutao/.rustup/toolchains/1.47-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-ff4ec557f69b94a7.so
#12 0x00007f9c4b41a7e0 in rustc_query_system::query::plumbing::get_query_impl () from /home/lzutao/.rustup/toolchains/1.47-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-ff4ec557f69b94a7.so
#13 0x00007f9c4b46c71e in rustc_query_system::query::plumbing::ensure_query_impl () from /home/lzutao/.rustup/toolchains/1.47-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-ff4ec557f69b94a7.so
#14 0x00007f9c4b66faf7 in rustc_data_structures::sync::par_for_each_in () from /home/lzutao/.rustup/toolchains/1.47-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-ff4ec557f69b94a7.so
#15 0x00007f9c4b3b27db in rustc_hir::hir::Crate::par_visit_all_item_likes () from /home/lzutao/.rustup/toolchains/1.47-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-ff4ec557f69b94a7.so
#16 0x00007f9c4b4a0fb8 in rustc_session::session::Session::track_errors () from /home/lzutao/.rustup/toolchains/1.47-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-ff4ec557f69b94a7.so
#17 0x00007f9c4b5a5915 in rustc_typeck::check_crate () from /home/lzutao/.rustup/toolchains/1.47-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-ff4ec557f69b94a7.so
#18 0x00007f9c48b0c83f in rustc_interface::passes::analysis () from /home/lzutao/.rustup/toolchains/1.47-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-ff4ec557f69b94a7.so
#19 0x00007f9c487d0c2b in rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::analysis>::compute () from /home/lzutao/.rustup/toolchains/1.47-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-ff4ec557f69b94a7.so
#20 0x00007f9c487339b8 in rustc_middle::dep_graph::<impl rustc_query_system::dep_graph::DepKind for rustc_middle::dep_graph::dep_node::DepKind>::with_deps () from /home/lzutao/.rustup/toolchains/1.47-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-ff4ec557f69b94a7.so
#21 0x00007f9c487b4747 in rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl () from /home/lzutao/.rustup/toolchains/1.47-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-ff4ec557f69b94a7.so
#22 0x00007f9c487c50d3 in rustc_data_structures::stack::ensure_sufficient_stack () from /home/lzutao/.rustup/toolchains/1.47-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-ff4ec557f69b94a7.so
#23 0x00007f9c4875be33 in rustc_query_system::query::plumbing::get_query_impl () from /home/lzutao/.rustup/toolchains/1.47-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-ff4ec557f69b94a7.so
#24 0x00007f9c487d1ffa in rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter () from /home/lzutao/.rustup/toolchains/1.47-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-ff4ec557f69b94a7.so
#25 0x00007f9c48765f27 in rustc_span::with_source_map () from /home/lzutao/.rustup/toolchains/1.47-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-ff4ec557f69b94a7.so
#26 0x00007f9c487d3513 in rustc_interface::interface::create_compiler_and_run () from /home/lzutao/.rustup/toolchains/1.47-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-ff4ec557f69b94a7.so
#27 0x00007f9c487b19fa in scoped_tls::ScopedKey<T>::set () from /home/lzutao/.rustup/toolchains/1.47-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-ff4ec557f69b94a7.so
#28 0x00007f9c487c6957 in std::sys_common::backtrace::__rust_begin_short_backtrace () from /home/lzutao/.rustup/toolchains/1.47-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-ff4ec557f69b94a7.so
#29 0x00007f9c4874fdae in core::ops::function::FnOnce::call_once{{vtable-shim}} () from /home/lzutao/.rustup/toolchains/1.47-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-ff4ec557f69b94a7.so
#30 0x00007f9c47b5df5a in <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once () at /rustc/18bf6b4f01a6feaf7259ba7cdae58031af1b7b39/library/alloc/src/boxed.rs:1042
#31 <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once () at /rustc/18bf6b4f01a6feaf7259ba7cdae58031af1b7b39/library/alloc/src/boxed.rs:1042
#32 std::sys::unix::thread::Thread::new::thread_start () at library/std/src/sys/unix/thread.rs:87
#33 0x00007f9c474954a4 in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
#34 0x00007f9c471d7d0f in clone () from /lib/x86_64-linux-gnu/libc.so.6

[tesuji]

Backtrace of current nightly rustc:

#0  0x00007f8f3c98b769 in rustc_data_structures::obligation_forest::ObligationForest<O>::register_obligation_at () from /home/lzutao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-3c5369d6b996b200.so
#1  0x00007f8f3c98feeb in <rustc_trait_selection::traits::fulfill::FulfillmentContext as rustc_infer::traits::engine::TraitEngine>::select_where_possible () from /home/lzutao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-3c5369d6b996b200.so
#2  0x00007f8f3c98f800 in <rustc_trait_selection::traits::fulfill::FulfillmentContext as rustc_infer::traits::engine::TraitEngine>::select_all_or_error () from /home/lzutao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-3c5369d6b996b200.so
#3  0x00007f8f3c28966c in rustc_typeck::check::fn_ctxt::_impl::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::select_all_obligations_or_error () from /home/lzutao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-3c5369d6b996b200.so
#4  0x00007f8f3c377bd4 in rustc_infer::infer::InferCtxtBuilder::enter () from /home/lzutao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-3c5369d6b996b200.so
#5  0x00007f8f3c2f22c8 in rustc_typeck::check::wfcheck::check_associated_item () from /home/lzutao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-3c5369d6b996b200.so
#6  0x00007f8f3c2bc655 in rustc_typeck::check::check::check_impl_item_well_formed () from /home/lzutao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-3c5369d6b996b200.so
#7  0x00007f8f3c2e196c in rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::check_impl_item_well_formed>::compute () from /home/lzutao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-3c5369d6b996b200.so
#8  0x00007f8f3cee2ecc in rustc_middle::dep_graph::<impl rustc_query_system::dep_graph::DepKind for rustc_middle::dep_graph::dep_node::DepKind>::with_deps () from /home/lzutao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-3c5369d6b996b200.so
#9  0x00007f8f3c2aaeed in rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl () from /home/lzutao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-3c5369d6b996b200.so
#10 0x00007f8f3c2e3565 in rustc_data_structures::stack::ensure_sufficient_stack () from /home/lzutao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-3c5369d6b996b200.so
#11 0x00007f8f3c347dd5 in rustc_query_system::query::plumbing::force_query_with_job () from /home/lzutao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-3c5369d6b996b200.so
#12 0x00007f8f3c32722f in rustc_query_system::query::plumbing::get_query_impl () from /home/lzutao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-3c5369d6b996b200.so
#13 0x00007f8f3c345d57 in rustc_query_system::query::plumbing::ensure_query_impl () from /home/lzutao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-3c5369d6b996b200.so
#14 0x00007f8f3c2f496b in <rustc_typeck::check::wfcheck::CheckTypeWellFormedVisitor as rustc_hir::itemlikevisit::ParItemLikeVisitor>::visit_impl_item () from /home/lzutao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-3c5369d6b996b200.so
#15 0x00007f8f3c35532e in rustc_data_structures::sync::par_for_each_in () from /home/lzutao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-3c5369d6b996b200.so
#16 0x00007f8f3cf5715b in rustc_hir::hir::Crate::par_visit_all_item_likes () from /home/lzutao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-3c5369d6b996b200.so
#17 0x00007f8f3cf1c1a6 in rustc_session::session::Session::track_errors () from /home/lzutao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-3c5369d6b996b200.so
#18 0x00007f8f3cf586b9 in rustc_typeck::check_crate () from /home/lzutao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-3c5369d6b996b200.so
#19 0x00007f8f3cbf66aa in rustc_interface::passes::analysis () from /home/lzutao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-3c5369d6b996b200.so
#20 0x00007f8f3cb9f9a9 in rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::analysis>::compute () from /home/lzutao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-3c5369d6b996b200.so
#21 0x00007f8f3a83e5f3 in rustc_middle::dep_graph::<impl rustc_query_system::dep_graph::DepKind for rustc_middle::dep_graph::dep_node::DepKind>::with_deps () from /home/lzutao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-3c5369d6b996b200.so
#22 0x00007f8f3cb7c954 in rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl () from /home/lzutao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-3c5369d6b996b200.so
#23 0x00007f8f3cb9bd41 in rustc_data_structures::stack::ensure_sufficient_stack () from /home/lzutao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-3c5369d6b996b200.so
#24 0x00007f8f3cb7a0c6 in rustc_query_system::query::plumbing::force_query_with_job () from /home/lzutao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-3c5369d6b996b200.so
#25 0x00007f8f3cb79574 in rustc_query_system::query::plumbing::get_query_impl () from /home/lzutao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-3c5369d6b996b200.so
#26 0x00007f8f3cb9fd5d in rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter () from /home/lzutao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-3c5369d6b996b200.so
#27 0x00007f8f3cb95904 in rustc_span::with_source_map () from /home/lzutao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-3c5369d6b996b200.so
#28 0x00007f8f3cba0fea in rustc_interface::interface::create_compiler_and_run () from /home/lzutao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-3c5369d6b996b200.so
#29 0x00007f8f3cb96157 in std::sys_common::backtrace::__rust_begin_short_backtrace () from /home/lzutao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-3c5369d6b996b200.so
#30 0x00007f8f3cb7abaa in core::ops::function::FnOnce::call_once{{vtable-shim}} () from /home/lzutao/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/librustc_driver-3c5369d6b996b200.so
#31 0x00007f8f39fc52ba in <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once () at /rustc/a62a76047ea24aad7639f14eb3ce0e620b77bdb7/library/alloc/src/boxed.rs:1484
#32 <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once () at /rustc/a62a76047ea24aad7639f14eb3ce0e620b77bdb7/library/alloc/src/boxed.rs:1484
#33 std::sys::unix::thread::Thread::new::thread_start () at /rustc/a62a76047ea24aad7639f14eb3ce0e620b77bdb7//library/std/src/sys/unix/thread.rs:71
#34 0x00007f8f39cfb4a4 in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
#35 0x00007f8f39631d0f in clone () from /lib/x86_64-linux-gnu/libc.so.6

[SNCPlay42]

Reduced:

use std::ops::Mul;
pub trait Diff {
    type ValueType;
    type ForwardDiff;
}
pub struct Multiplication<L>
where
    L: Diff,
{
    left: L,
}
impl<L> Diff for Multiplication<L>
where
    L: Diff,
    L::ForwardDiff: Diff,
    Multiplication<L::ForwardDiff>: Diff<ValueType = ()>,
{
    type ValueType = ();
    type ForwardDiff = ();
}
impl<L: Diff> Mul for Multiplication<L> {
    type Output = Multiplication<Self>;
}

@rustbot label -E-needs-mcve

[hellow554]

There is no regression to find.
I tested it with the 01-06-2016 compiler (rustc 1.11.0) and even there it hangs, so it seems like it has been forever (01-01-2016 doesn't compile the code, but it doesn't hang (but IMHO that's not the same here))

@rustbot modify labels: -E-needs-bisection