Closed
Description
The following code will result in an ICE in codegen MIR construction:
struct B(i32);
const A: &[B] = &[];
fn main() {
match &[][..] {
A => (),
_ => (),
}
}
Error and Backtrace
error: internal compiler error: src/librustc/traits/codegen/mod.rs:156: Encountered errors `[FulfillmentError(Obligation(predicate=Binder(TraitPredicate(<B as std::cmp::PartialEq>)),depth=2),Unimplemented)]` resolving bounds after type-checking
thread 'rustc' panicked at 'Box<Any>', src/librustc_errors/lib.rs:570:9
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
stack backtrace:
0: std::sys::unix::backtrace::tracing::imp::unwind_backtrace
at src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:39
1: std::sys_common::backtrace::_print
at src/libstd/sys_common/backtrace.rs:71
2: std::panicking::default_hook::{{closure}}
at src/libstd/sys_common/backtrace.rs:59
at src/libstd/panicking.rs:197
3: std::panicking::default_hook
at src/libstd/panicking.rs:211
4: rustc::util::common::panic_hook
5: std::panicking::rust_panic_with_hook
at src/libstd/panicking.rs:478
6: std::panicking::begin_panic
7: rustc_errors::Handler::span_bug
8: rustc::util::bug::opt_span_bug_fmt::{{closure}}
9: rustc::ty::context::tls::with_opt::{{closure}}
10: rustc::ty::context::tls::with_context_opt
11: rustc::ty::context::tls::with_opt
12: rustc::util::bug::opt_span_bug_fmt
13: rustc::util::bug::span_bug_fmt
14: rustc::traits::codegen::<impl rustc::infer::InferCtxt>::drain_fulfillment_cx_or_panic
15: rustc::ty::context::GlobalCtxt::enter_local
16: rustc::traits::codegen::codegen_fulfill_obligation
17: rustc::ty::query::__query_compute::codegen_fulfill_obligation
18: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::codegen_fulfill_obligation>::compute
19: rustc::dep_graph::graph::DepGraph::with_task_impl
20: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
21: rustc::ty::instance::Instance::resolve
22: rustc_mir::lints::check
23: rustc::ty::context::GlobalCtxt::enter_local
24: rustc_mir::build::mir_build
25: rustc_mir::transform::mir_built
26: rustc::ty::query::__query_compute::mir_built
27: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::mir_built>::compute
28: rustc::dep_graph::graph::DepGraph::with_task_impl
29: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
30: rustc_mir::transform::check_unsafety::unsafety_check_result
31: rustc::ty::query::__query_compute::unsafety_check_result
32: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::unsafety_check_result>::compute
33: rustc::dep_graph::graph::DepGraph::with_task_impl
34: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
35: rustc_mir::transform::mir_const
36: rustc::ty::query::__query_compute::mir_const
37: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::mir_const>::compute
38: rustc::dep_graph::graph::DepGraph::with_task_impl
39: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
40: rustc_mir::transform::mir_validated
41: rustc::ty::query::__query_compute::mir_validated
42: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::mir_validated>::compute
43: rustc::dep_graph::graph::DepGraph::with_task_impl
44: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
45: rustc_mir::borrow_check::mir_borrowck
46: rustc::ty::query::__query_compute::mir_borrowck
47: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::mir_borrowck>::compute
48: rustc::dep_graph::graph::DepGraph::with_task_impl
49: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
50: rustc::ty::<impl rustc::ty::context::TyCtxt>::par_body_owners
51: rustc::util::common::time
52: rustc_interface::passes::analysis
53: rustc::ty::query::__query_compute::analysis
54: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::analysis>::compute
55: rustc::dep_graph::graph::DepGraph::with_task_impl
56: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
57: rustc_interface::passes::BoxedGlobalCtxt::access::{{closure}}
58: rustc_interface::passes::create_global_ctxt::{{closure}}
59: rustc_interface::interface::run_compiler_in_existing_thread_pool
60: std::thread::local::LocalKey<T>::with
61: scoped_tls::ScopedKey<T>::set
62: syntax::with_globals
query stack during panic:
#0 [codegen_fulfill_obligation] checking if `std::cmp::PartialEq` fulfills its obligations
#1 [mir_built] processing `main`
#2 [unsafety_check_result] processing `main`
#3 [mir_const] processing `main`
#4 [mir_validated] processing `main`
#5 [mir_borrowck] processing `main`
#6 [analysis] running analysis passes on this crate
end of query stack
Activity
estebank commentedon May 25, 2019
CC #53708
pnkfelix commentedon Jun 6, 2019
As implied by @estebank above, this seems very likely to be a duplicate (or at least strongly related to) #53708 ...
Update: Not duplicate. Further investigation of #53708 shows that it is no longer an ICE, but "merely" an exhaustiveness checker bug. This bug, #61188, remains an ICE today.
pnkfelix commentedon Jun 6, 2019
Ah ha!
If you add
#[derive(PartialEq, Eq)]
to thestruct B(i32)
in the example above, then the code compiles successfully.Which may be something a user might infer from the message ...
... but probably not 🤣
pnkfelix commentedon Jun 6, 2019
triage: P-high; removing nomination. I want to know why we are not catching the failure to fulfill
B: PartialEq
earlier in the compilation. Is this perhaps a const-eval issue, based on the stack trace? (or a mir-borrowck one? I suppose the query-system is just making that appear on the stack, though it is not necessarily the root cause?)eddyb commentedon Jun 6, 2019
I suspect
rustc_typeck
is not enforcing it,and MIR borrowck, as I found recently, doesn't produce user errors from trait matching, but rather expects it to succeed, and only uses it to get lifetime obligations.EDIT: I should've read more carefully, looks like
Instance::resolve
is being used byrustc_mir::build
withoutrustc_typeck
having checked thatEq
is implemented for that type.pnkfelix commentedon Jun 6, 2019
assigning to self with intent to try to mentor.
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