Repository navigation
ICE resolving non-existent PartialEq::Eq from match of const #65466
Description
Activity
Answer: under PR #67088, this produces:
error: to use a constant of type `B` in a pattern, `B` must be annotated with `#[derive(PartialEq, Eq)]` --> issue-65466.rs:16:9 | 16 | C => (), | ^ error: aborting due to previous error(which is what we want).
Note to self, matching on
&O<B>is enough to trigger the ICE. A slice is not necessary.Still crashing (obviously on nightly, beta and stable by now...).
warning: variant is never constructed: `Some` --> src/main.rs:5:5 | 5 | Some(*const T), // Can also use PhantomData<T> | ^^^^^^^^^^^^^^ | = note: `#[warn(dead_code)]` on by default warning: Error finalizing incremental compilation session directory `/tmp/a/target/debug/incremental/a-3ibewktm5f4s7/s-frdnn34p4t-5wozmt-working`: No such file or directory (os error 2) warning: 2 warnings emitted error: internal compiler error: broken MIR in DefId(0:6 ~ a[e6bb]::foo[0]) (NoSolution): could not prove TraitPredicate(<[O<B>] as std::cmp::PartialEq>) | = note: delayed at compiler/rustc_mir/src/borrow_check/type_check/mod.rs:258:27 thread 'rustc' panicked at 'no errors encountered even though `delay_span_bug` issued', compiler/rustc_errors/src/lib.rs:961:13 stack backtrace: 0: 0x7fb253922b30 - std::backtrace_rs::backtrace::libunwind::trace::he85dfb3ae4206056 at /rustc/f68e08933d8f519a9655934fedebbc509661b219/library/std/src/../../backtrace/src/backtrace/libunwind.rs:96 1: 0x7fb253922b30 - std::backtrace_rs::backtrace::trace_unsynchronized::h1ad28094d7b00c21 at /rustc/f68e08933d8f519a9655934fedebbc509661b219/library/std/src/../../backtrace/src/backtrace/mod.rs:66 2: 0x7fb253922b30 - std::sys_common::backtrace::_print_fmt::h901b54610713cd21 at /rustc/f68e08933d8f519a9655934fedebbc509661b219/library/std/src/sys_common/backtrace.rs:79 3: 0x7fb253922b30 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::hb0ad78ee1571f7e0 at /rustc/f68e08933d8f519a9655934fedebbc509661b219/library/std/src/sys_common/backtrace.rs:58 4: 0x7fb253990e7c - core::fmt::write::h1857a60b204f1b6a at /rustc/f68e08933d8f519a9655934fedebbc509661b219/library/core/src/fmt/mod.rs:1080 5: 0x7fb253914f07 - std::io::Write::write_fmt::hf7b7d7b243f84a36 at /rustc/f68e08933d8f519a9655934fedebbc509661b219/library/std/src/io/mod.rs:1517 6: 0x7fb253927880 - std::sys_common::backtrace::_print::hd093978a5287b8ff at /rustc/f68e08933d8f519a9655934fedebbc509661b219/library/std/src/sys_common/backtrace.rs:61 7: 0x7fb253927880 - std::sys_common::backtrace::print::h20f46787581d56d7 at /rustc/f68e08933d8f519a9655934fedebbc509661b219/library/std/src/sys_common/backtrace.rs:48 8: 0x7fb253927880 - std::panicking::default_hook::{{closure}}::h486cbb4b82ffc357 at /rustc/f68e08933d8f519a9655934fedebbc509661b219/library/std/src/panicking.rs:208 9: 0x7fb253927538 - std::panicking::default_hook::h4190c9e3edd4d591 at /rustc/f68e08933d8f519a9655934fedebbc509661b219/library/std/src/panicking.rs:227 10: 0x7fb2541bb8d4 - rustc_driver::report_ice::h0baa69c9fa359ad1 11: 0x7fb2539280b6 - std::panicking::rust_panic_with_hook::h72e78719cdda225c at /rustc/f68e08933d8f519a9655934fedebbc509661b219/library/std/src/panicking.rs:581 12: 0x7fb253927c39 - std::panicking::begin_panic_handler::{{closure}}::h8bd07dbd34150a96 at /rustc/f68e08933d8f519a9655934fedebbc509661b219/library/std/src/panicking.rs:484 13: 0x7fb253922fbc - std::sys_common::backtrace::__rust_end_short_backtrace::hdb6b3066ad29028a at /rustc/f68e08933d8f519a9655934fedebbc509661b219/library/std/src/sys_common/backtrace.rs:153 14: 0x7fb253927bf9 - rust_begin_unwind at /rustc/f68e08933d8f519a9655934fedebbc509661b219/library/std/src/panicking.rs:483 15: 0x7fb253927bab - std::panicking::begin_panic_fmt::hc19e75fd2b7bc39b at /rustc/f68e08933d8f519a9655934fedebbc509661b219/library/std/src/panicking.rs:437 16: 0x7fb2572fd471 - rustc_errors::HandlerInner::flush_delayed::hc01570dc9a0301e8 17: 0x7fb2572f9dd1 - <rustc_errors::HandlerInner as core::ops::drop::Drop>::drop::h2fa2449267c97abc 18: 0x7fb2541df306 - core::ptr::drop_in_place::h3ccf454d686c35e3 19: 0x7fb2541e9d36 - <alloc::rc::Rc<T> as core::ops::drop::Drop>::drop::h9871ec79020d3d08 20: 0x7fb2541cdb4d - core::ptr::drop_in_place::h37be4f3688653901 21: 0x7fb2541bfd31 - rustc_span::with_source_map::he9a81669cd160b82 22: 0x7fb2541eebd8 - rustc_interface::interface::create_compiler_and_run::h06c2389085f2a79e 23: 0x7fb2541c02aa - rustc_span::with_session_globals::h3a06e50e1db00721 24: 0x7fb2541f148d - std::sys_common::backtrace::__rust_begin_short_backtrace::h6f73648415d0d9ce 25: 0x7fb2541621ce - core::ops::function::FnOnce::call_once{{vtable.shim}}::h213be4bbd07cfb62 26: 0x7fb25393796a - <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once::h1080dfe0ef616bdf at /rustc/f68e08933d8f519a9655934fedebbc509661b219/library/alloc/src/boxed.rs:1042 27: 0x7fb25393796a - <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once::hd2747e1f2d5cec32 at /rustc/f68e08933d8f519a9655934fedebbc509661b219/library/alloc/src/boxed.rs:1042 28: 0x7fb25393796a - std::sys::unix::thread::Thread::new::thread_start::hd0f336b4ef6808a7 at /rustc/f68e08933d8f519a9655934fedebbc509661b219/library/std/src/sys/unix/thread.rs:87 29: 0x7fb2538343e9 - start_thread 30: 0x7fb253751293 - __GI___clone 31: 0x0 - <unknown> error: internal compiler error: unexpected panic 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 1.48.0-nightly (f68e08933 2020-09-19) 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: end of query stack error: could not compile `a` ```
(Spawned off of #61188 (comment) )
Sometimes the code-generation for pattern-matching a
constwill generate a invocation ofPartialEq::eq(rather than unfolding the structure of that constant inline, which is the usual compilation strategy used in rustc currently...)The difference between unfolding inline and invoking
PartialEq::eqis not meant to be observable, because of RFC 1445 (c.f. #31434): "Restrict constants in patterns"However, there are cases where rustc's static analysis of the pattern itself was not thorough enough, and it would let patterns through that do end up invoking
PartialEq::eqon constants that do not even implementPartialEqin the first place.We had been relying on the structural-match checking to catch such cases, where we would first run the structural match check, and if we found an ADT that was a non-structural-match, then we would then check if the
constin question even implementsPartialEq.But that strategy, of a delayed check for
PartialEq, does not suffice in every case. Here is an example, taken from @matthewjasper 's comment linked above:I had been tagging the above test case as being part of #61188, but at this point I think it is confusing matters, because the code/comments/commit messages say things like "this does not yet fix #61188" and it is ambgious whether that message refers to the original bug described by #61188, or the subsequent issue pointed out by @matthewjasper linked above.
So I am allocating a fresh issue to track the matter here.