ICE: Compiling Commingle project

[aknuds1]

Code

git clone https://gitlab.com/commingle/commingle.git
git checkout 43b73938f4157bfb634bfeb175d1b02f5e6a4759
RUST_BACKTRACE=1 cargo run

Meta

rustc --version --verbose:

rustc 1.49.0-nightly (25c8c53dd 2020-10-03)
binary: rustc
commit-hash: 25c8c53dd994acb3f4f7c02fe6bb46076393f8b0
commit-date: 2020-10-03
host: x86_64-unknown-linux-gnu
release: 1.49.0-nightly
LLVM version: 11.0

Error output

Compiling commingle v0.0.2 (/home/arve/Projects/commingle)
error: internal compiler error: compiler/rustc_ty/src/instance.rs:136:21: AssocItem { def_id: DefId(168:66 ~ web[c7a2]::get_index::{closure#0}::Render::__maud_render_to), ident: __maud_render_to#10509, kind: Fn, vis: Restricted(DefId(168:0 ~ web[c7a2])), defaultness: Default { has_value: true }, container: TraitContainer(DefId(168:65 ~ web[c7a2]::get_index::{closure#0}::Render)), fn_has_self_parameter: true } not found in DefId(168:67 ~ web[c7a2]::get_index::{closure#0}::{impl#0})

Backtrace

stack backtrace:
   0: std::panicking::begin_panic
   1: rustc_errors::HandlerInner::bug
   2: rustc_errors::Handler::bug
   3: rustc_middle::util::bug::opt_span_bug_fmt::{{closure}}
   4: rustc_middle::ty::context::tls::with_opt::{{closure}}
   5: rustc_middle::ty::context::tls::with_opt
   6: rustc_middle::util::bug::opt_span_bug_fmt
   7: rustc_middle::util::bug::bug_fmt
   8: rustc_ty::instance::resolve_associated_item::{{closure}}
   9: rustc_ty::instance::inner_resolve_instance
  10: rustc_ty::instance::resolve_instance
  11: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::resolve_instance>::compute
  12: rustc_middle::dep_graph::<impl rustc_query_system::dep_graph::DepKind for rustc_middle::dep_graph::dep_node::DepKind>::with_deps
  13: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  14: rustc_data_structures::stack::ensure_sufficient_stack
  15: rustc_query_system::query::plumbing::get_query_impl
  16: rustc_middle::ty::instance::Instance::resolve_opt_const_arg
  17: rustc_middle::ty::instance::Instance::resolve
  18: <rustc_mir::monomorphize::collector::MirNeighborCollector as rustc_middle::mir::visit::Visitor>::visit_terminator
  19: rustc_mir::monomorphize::collector::collect_neighbours
  20: rustc_mir::monomorphize::collector::collect_items_rec
  21: rustc_mir::monomorphize::collector::collect_items_rec
  22: rustc_mir::monomorphize::collector::collect_items_rec
  23: rustc_mir::monomorphize::collector::collect_items_rec
  24: rustc_mir::monomorphize::collector::collect_items_rec
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note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

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 1.49.0-nightly (25c8c53dd 2020-10-03) running on x86_64-unknown-linux-gnu

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

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

query stack during panic:
#0 [resolve_instance] resolving instance `<web::svg::Svg as web::get_index::{closure#0}::Render>::__maud_render_to`
#1 [collect_and_partition_mono_items] collect_and_partition_mono_items
end of query stack
error: aborting due to previous error

[estebank]

I believe this might be related to higiene. It seems like we might be doing something wrong in TyTcx::higienic_eq because if I remove that filter in Node::item the code compiles.

CC @petrochenkov

[aknuds1]

Thanks @estebank, would be great to see this fixed.

[Aaron1011]

Minimized: https://github.com/Aaron1011/maud_bug

This issue seems to require the following setup:

1. A (nightly-only) proc macro emitting tokens using def-site hygiene
2. An async function that invokes said proc-macro
3. A separate crate which triggers monomorphization of the body of the async function (e.g. actually tries to poll it)

My guess is that this is a bug in hygiene serialization, since the issue doesn't occur if the async function and poller are in the same crate. I'll continue to investigate

[Aaron1011]

It looks like the issue occurs here:

rust/compiler/rustc_middle/src/ty/mod.rs

Lines 3023 to 3042 in f317a93

	/// Hygienically compares a use-site name (`use_name`) for a field or an associated item with
	/// its supposed definition name (`def_name`). The method also needs `DefId` of the supposed
	/// definition's parent/scope to perform comparison.
	pub fn hygienic_eq(self, use_name: Ident, def_name: Ident, def_parent_def_id: DefId) -> bool {
	// We could use `Ident::eq` here, but we deliberately don't. The name
	// comparison fails frequently, and we want to avoid the expensive
	// `normalize_to_macros_2_0()` calls required for the span comparison whenever possible.
	use_name.name == def_name.name
	&& use_name
	.span
	.ctxt()
	.hygienic_eq(def_name.span.ctxt(), self.expansion_that_defined(def_parent_def_id))
	}
	fn expansion_that_defined(self, scope: DefId) -> ExpnId {
	match scope.as_local() {
	Some(scope) => self.hir().definitions().expansion_that_defined(scope),
	None => ExpnId::root(),
	}
	}

With hygiene serialization, we may be comparing SyntaxContexts from a foreign crate. However, we don't serialize the expansion_that_defined data, so we'll always end up ExpnId::root() for foreign DefIds.

However, I don't really understand everything that's going on here ('adjusting' and 'normalizing' a SyntaxContext).