ICE on trying to impl Add for i32

[bugaevc]

Code

#![feature(no_core)]
#![feature(lang_items)]
#![no_core]
#![no_std]

#[lang = "sized"]
pub trait Sized {}

#[lang = "copy"]
pub trait Copy {}

#[lang = "add"]
pub trait Add<Rhs = Self> {
    type Output;
    fn add(self, rhs: Rhs) -> Self::Output;
}

impl Add for i32 {
    type Output = i32;
    fn add(self, rhs: i32) -> i32 {
        self + rhs
    }
}

Playground

Meta

rustc --version --verbose:

note: rustc 1.71.0-nightly (d0f204e4d 2023-04-16) running on x86_64-unknown-linux-gnu

Error output

error: internal compiler error: no errors encountered even though `delay_span_bug` issued

error: internal compiler error: broken MIR in DefId(0:9 ~ playground[7903]::{impl#0}::add) (NoSolution): could not prove Binder(TraitPredicate(<i32 as Copy>, polarity:Positive), [])
  |
  = note: delayed at    0: <rustc_errors::HandlerInner>::emit_diagnostic
             1: <rustc_errors::Handler>::delay_span_bug::<rustc_span::span_encoding::Span, &str>
             2: <rustc_borrowck::type_check::TypeVerifier as rustc_middle::mir::visit::Visitor>::visit_place
             3: <rustc_borrowck::type_check::TypeVerifier as rustc_middle::mir::visit::Visitor>::visit_body
             4: rustc_borrowck::nll::compute_regions
             5: rustc_borrowck::do_mir_borrowck
             6: rustc_borrowck::mir_borrowck
             7: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::queries::mir_borrowck, rustc_query_impl::plumbing::QueryCtxt>
             8: 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#2}::{closure#0}>::{closure#0}>
             9: <rustc_session::session::Session>::time::<(), rustc_interface::passes::analysis::{closure#2}>
            10: rustc_interface::passes::analysis
            11: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::queries::analysis, rustc_query_impl::plumbing::QueryCtxt>
            12: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::analysis
            13: <std::thread::local::LocalKey<core::cell::Cell<*const ()>>>::with::<rustc_middle::ty::context::tls::enter_context<<rustc_middle::ty::context::GlobalCtxt>::enter<rustc_driver_impl::run_compiler::{closure#1}::{closure#2}::{closure#4}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>
            14: <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>>
            15: rustc_span::set_source_map::<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#1}>::{closure#0}::{closure#0}>
            16: std::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#1}>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>
            17: <<std::thread::Builder>::spawn_unchecked_<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#1}>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#1} as core::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
            18: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
                       at /rustc/d0f204e4d750b62f9d6c2593405e828757126832/library/alloc/src/boxed.rs:1973:9
            19: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
                       at /rustc/d0f204e4d750b62f9d6c2593405e828757126832/library/alloc/src/boxed.rs:1973:9
            20: std::sys::unix::thread::Thread::new::thread_start
                       at /rustc/d0f204e4d750b62f9d6c2593405e828757126832/library/std/src/sys/unix/thread.rs:108:17
            21: start_thread
            22: clone

Tentatively adding some labels:
@rustbot modify labels: +A-diagnostics +requires-nightly

[asquared31415]

no_core and lang_items are not well supported and not intended to be used by consumers, so errors are often in the form of ICEs. Here the compiler expects the builtin type i32 to implement Copy but you don't have that impl.

[asquared31415]

@rustbot label +A-lang-item +F-no_core

[compiler-errors]

Yeah, I don't think this necessarily deserves to fix given that no_core is a perma-unstable feature.

[bugaevc]

Perma-unstable doesn't necessarily have to mean the compiler has to ICE in the most cryptic way, no? Could it at least ICE with something like "expected the built-in i32 type to implement the Copy trait"?

[compiler-errors]

Sure, My gut feeling is that it's not worth complicating the compiler in this case, sorry 😅

Writing a bug in a core implementation is akin to writing a bug in the compiler itself, as core can be viewed conceptually as an extension of the compiler, just outlining all of the "built-in type info" into a privileged crate.

And just like sometimes, but not always, a malformed function in the compiler itself causes an ICE, sometimes a malformed implementation of core will also cause an ICE.

[compiler-errors]

As for improving the ICE message itself, not sure. I guess we could do that, but I think it's actually typically more useful for compiler developers to have that (somewhat cryptic, but also more descriptive) error message that it has right now, for when they write real bugs in the compiler

[Noratrieb]

wontfix: rust-lang/compiler-team#620