`werk` regression

[compiler-errors]

Some type of recursive opaque + auto trait that results in infinite blowup:

https://crater-reports.s3.amazonaws.com/pr-133502-11/try%2328f13ad7c79d80decb5a3d54595a8b4105f397a3/gh/simonask.werk/log.txt

[INFO] [stdout] note: no errors encountered even though delayed bugs were created
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] note: those delayed bugs will now be shown as internal compiler errors
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] error: internal compiler error: errors selecting obligation during MIR typeck: [Ambiguity]
[INFO] [stdout]   |
[INFO] [stdout]   = note: delayed at /rustc/28f13ad7c79d80decb5a3d54595a8b4105f397a3/compiler/rustc_trait_selection/src/traits/query/type_op/custom.rs:95:18
[INFO] [stdout]              0: <rustc_errors::DiagCtxtInner>::emit_diagnostic
[INFO] [stdout]              1: <rustc_errors::DiagCtxtHandle>::emit_diagnostic
[INFO] [stdout]              2: <rustc_span::ErrorGuaranteed as rustc_errors::diagnostic::EmissionGuarantee>::emit_producing_guarantee
[INFO] [stdout]              3: <rustc_errors::DiagCtxtHandle>::delayed_bug::<alloc::string::String>
[INFO] [stdout]              4: <rustc_borrowck::type_check::TypeChecker>::fully_perform_op::<(), rustc_middle::ty::ParamEnvAnd<rustc_middle::traits::query::type_op::ProvePredicate>>
[INFO] [stdout]              5: <rustc_borrowck::type_check::TypeChecker>::normalize_and_prove_instantiated_predicates
[INFO] [stdout]              6: <rustc_borrowck::type_check::TypeChecker as rustc_middle::mir::visit::Visitor>::visit_const_operand
[INFO] [stdout]              7: <rustc_borrowck::type_check::TypeChecker as rustc_middle::mir::visit::Visitor>::visit_body
[INFO] [stdout]              8: rustc_borrowck::start_do_mir_borrowck
[INFO] [stdout]              9: <rustc_borrowck::type_check::TypeChecker>::prove_closure_bounds
[INFO] [stdout]             10: <rustc_borrowck::type_check::TypeChecker as rustc_middle::mir::visit::Visitor>::visit_rvalue
[INFO] [stdout]             11: <rustc_borrowck::type_check::TypeChecker as rustc_middle::mir::visit::Visitor>::visit_body
[INFO] [stdout]             12: rustc_borrowck::start_do_mir_borrowck
[INFO] [stdout]             13: <rustc_borrowck::root_cx::BorrowCheckRootCtxt>::borrowck_root
[INFO] [stdout]             14: rustc_borrowck::mir_borrowck
[INFO] [stdout]             15: 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]>>
[INFO] [stdout]             16: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_data_structures::vec_cache::VecCache<rustc_span::def_id::LocalDefId, rustc_middle::query::erase::Erased<[u8; 8]>, rustc_query_system::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
[INFO] [stdout]             17: rustc_query_impl::query_impl::mir_borrowck::get_query_non_incr::__rust_end_short_backtrace
[INFO] [stdout]             18: rustc_hir_analysis::collect::type_of::opaque::find_opaque_ty_constraints_for_rpit
[INFO] [stdout]             19: rustc_hir_analysis::collect::type_of::type_of_opaque
[INFO] [stdout]             20: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::type_of_opaque::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 8]>>
[INFO] [stdout]             21: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 8]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
[INFO] [stdout]             22: rustc_query_impl::query_impl::type_of_opaque::get_query_non_incr::__rust_end_short_backtrace
[INFO] [stdout]             23: rustc_hir_analysis::collect::type_of::type_of
[INFO] [stdout]             24: rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::type_of::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 8]>>
[INFO] [stdout]             25: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::DefIdCache<rustc_middle::query::erase::Erased<[u8; 8]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false>
[INFO] [stdout]             26: rustc_query_impl::query_impl::type_of::get_query_non_incr::__rust_end_short_backtrace
[INFO] [stdout]             27: rustc_hir_analysis::check::check::check_opaque
[INFO] [stdout]             28: rustc_hir_analysis::check::check::check_item_type
[INFO] [stdout]             29: rustc_hir_analysis::check::wfcheck::check_well_formed

[lqd]

I saw another ICE, so I kept that too just in case. godbolt for them both.

(werk is on edition 2024)

pub async fn run_task(t: &u32) {
    build_dependencies(t).await;
}

async fn build_dependencies(t: &u32) {
    Box::pin(run_task(t)).await;
    Box::pin(build_multiple(t)).await;
}

fn build_multiple(t: &u32) -> impl Future<Output = ()> + Send {
    async move {
        spawn(async move { run_task(t).await }); // MIR typeck Ambiguity
        // spawn(run_task(t)); // index out of bounds in ena
    }
}

fn spawn<T>(_: impl Future<Output = T> + Send) {}

[lcnr]

fn build_multiple<'a>() -> impl Future<Output = ()> {
    spawn(async { run_task().await });
    std::future::ready(())
}

async fn run_task() {
    build_dependencies().await;
}

async fn build_dependencies() {
    Box::pin(run_task()).await;
    Box::pin(build_multiple()).await;
}

fn spawn<F: Send>(_: F) {}

[lcnr]

fn build_multiple<'a>() -> impl Sized {
    spawn(async { build_dependencies().await });
}

fn build_dependencies() -> impl Future<Output = ()> /* + Send */ {
    async {
        Box::pin(build_dependencies()).await;
        async { build_multiple() }.await;
    }
}

fn spawn<F: Send>(_: F) {}

fn main() {}

[lcnr]

tracked in #209