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ICE: Lifetime issue not detected for GAT #117489
Description
I encountered this while trying to understand the relatively new GAT feature in Rust.
Code
trait LendingIterator {
type Item<'a>
where
Self: 'a;
fn next(&mut self) -> Option<Self::Item<'_>>;
fn for_each(mut self, mut f: Box<dyn FnMut(Self::Item<'_>) + 'static>)
where
Self: Sized,
{
while let Some(next) = self.next() {
f(next);
}
}
}
struct Query<'q> {
inner: &'q [u32],
index: usize,
}
impl<'q> Query<'q> {
pub fn new(inner: &'q Vec<u32>) -> Self {
Self { index: 0, inner }
}
}
impl<'q> LendingIterator for Query<'q> {
type Item<'a> = &'a u32 where Self: 'a;
fn next(&mut self) -> Option<Self::Item<'_>> {
if let Some(value) = self.inner.get(self.index) {
self.index += 1;
return Some(value);
}
None
}
}
fn main() {
let mut data = vec![1, 2, 3];
LendingIterator::for_each(
Query::new(&data),
Box::new(|val| {
eprintln!("{}", val);
}),
);
// Picks up the 'static issue, doesn't compile/crash.
// Query::new(&data).for_each(Box::new(|val| {
// eprintln!("{}", val);
// }));
}Meta
rustc --version --verbose:
rustc 1.73.0 (cc66ad468 2023-10-03)
binary: rustc
commit-hash: cc66ad468955717ab92600c770da8c1601a4ff33
commit-date: 2023-10-03
host: aarch64-apple-darwin
release: 1.73.0
LLVM version: 17.0.2
rustc +nightly --version --verbose:
rustc 1.75.0-nightly (9d83ac217 2023-10-31)
binary: rustc
commit-hash: 9d83ac217957eece2189eccf4a7232caec7232ee
commit-date: 2023-10-31
host: aarch64-apple-darwin
release: 1.75.0-nightly
LLVM version: 17.0.3
Error output
error: internal compiler error: compiler/rustc_borrowck/src/universal_regions.rs:880:36: cannot convert `RePlaceholder(!1_BoundRegion { var: 0, kind: BrAnon(None) })` to a region vid
Backtrace
thread 'rustc' panicked at /rustc/cc66ad468955717ab92600c770da8c1601a4ff33/compiler/rustc_errors/src/lib.rs:1635:9:
Box<dyn Any>
stack backtrace:
0: std::panicking::begin_panic::<rustc_errors::ExplicitBug>
1: <rustc_errors::HandlerInner>::bug::<alloc::string::String>
2: <rustc_errors::Handler>::bug::<alloc::string::String>
3: rustc_middle::util::bug::opt_span_bug_fmt::<rustc_span::span_encoding::Span>::{closure#0}
4: rustc_middle::ty::context::tls::with_opt::<rustc_middle::util::bug::opt_span_bug_fmt<rustc_span::span_encoding::Span>::{closure#0}, !>::{closure#0}
5: rustc_middle::ty::context::tls::with_context_opt::<rustc_middle::ty::context::tls::with_opt<rustc_middle::util::bug::opt_span_bug_fmt<rustc_span::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
6: rustc_middle::util::bug::bug_fmt
7: <rustc_borrowck::universal_regions::UniversalRegionIndices>::to_region_vid
8: <rustc_borrowck::type_check::free_region_relations::UniversalRegionRelationsBuilder>::add_implied_bounds
9: rustc_borrowck::type_check::free_region_relations::create
10: rustc_borrowck::type_check::type_check
11: rustc_borrowck::nll::compute_regions
12: rustc_borrowck::do_mir_borrowck
13: rustc_borrowck::mir_borrowck
[... omitted 2 frames ...]
14: <rustc_borrowck::type_check::TypeChecker>::prove_closure_bounds
15: <rustc_borrowck::type_check::TypeChecker>::check_rvalue
16: <rustc_borrowck::type_check::TypeChecker>::typeck_mir
17: rustc_borrowck::type_check::type_check
18: rustc_borrowck::nll::compute_regions
19: rustc_borrowck::do_mir_borrowck
20: rustc_borrowck::mir_borrowck
[... omitted 2 frames ...]
21: <core::panic::unwind_safe::AssertUnwindSafe<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#1}::{closure#0}>::{closure#0}>::{closure#0}::{closure#0}> as core::ops::function::FnOnce<()>>::call_once
22: 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#1}::{closure#0}>::{closure#0}>
23: <rustc_session::session::Session>::time::<(), rustc_interface::passes::analysis::{closure#1}>
24: rustc_interface::passes::analysis
[... omitted 2 frames ...]
25: <rustc_middle::ty::context::GlobalCtxt>::enter::<rustc_driver_impl::run_compiler::{closure#1}::{closure#2}::{closure#6}, core::result::Result<(), rustc_span::ErrorGuaranteed>>
26: <rustc_interface::interface::Compiler>::enter::<rustc_driver_impl::run_compiler::{closure#1}::{closure#2}, core::result::Result<core::option::Option<rustc_interface::queries::Linker>, rustc_span::ErrorGuaranteed>>
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
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 1.73.0 (cc66ad468 2023-10-03) running on aarch64-apple-darwin
note: compiler flags: --crate-type bin -C embed-bitcode=no -C debuginfo=2 -C split-debuginfo=unpacked -C incremental=[REDACTED]
note: some of the compiler flags provided by cargo are hidden
query stack during panic:
#0 [mir_borrowck] borrow-checking `main::{closure#0}`
#1 [mir_borrowck] borrow-checking `main`
#2 [analysis] running analysis passes on this crate
end of query stack
error: could not compile `rust-playground` (bin "rust-playground")
Activity
[-]Crash when working with GATs[/-][+]ICE: Lifetime issue not detected for GAT[/+]lqd commentedon Nov 6, 2023
Reduced
Started ICEing in
nightly-2022-08-10, and the<rustc_borrowck::type_check::free_region_relations::UniversalRegionRelationsBuilder>::add_implied_boundsin the backtrace makes #99217 look pretty likely.lqd commentedon Nov 6, 2023
This may be more t-types than t-compiler per se.
matthiaskrgr commentedon Nov 6, 2023
Might be related to #112250 ?
lqd commentedon Nov 6, 2023
Yeah, implied bounds + placeholders so it seems to be around the same area indeed, and could likely be fixed by #112422 cc @aliemjay
aliemjay commentedon Nov 17, 2023
fixed by #112422.