empty_array.rs test removed because it ICEs on CI

[Manishearth]

In #4606 I removed tests/ui/out_of_bounds_indexing/empty_array.rs because it was ICEing, but only on rustc CI (rust-lang/rust#64963 (comment))

We should restore the test when we figure out what's going on here. I've got a full rustc build ongoing in the background for now.

[mati865]

It's not usual ICE but a failed assertion. You need to enable rustc debug-assertions to reproduce it.

For the reference it fails here:
https://github.com/rust-lang/rust/blob/702b45e409495a41afcccbe87a251a692b0cefab/src/librustc_mir/interpret/place.rs#L736-L737

[Manishearth]

thread 'rustc' panicked at 'assertion failed: `(left == right)`
  left: `Size { raw: 0 }`,
 right: `Size { raw: 1 }`: Size mismatch when writing bits', src/librustc_mir/interpret/place.rs:736:21
stack backtrace:
   0: <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt
   1: core::fmt::write
   2: std::io::Write::write_fmt
   3: std::sys_common::backtrace::print
   4: std::panicking::default_hook::{{closure}}
   5: std::panicking::default_hook
   6: rustc_driver::report_ice
   7: std::panicking::rust_panic_with_hook
   8: std::panicking::continue_panic_fmt
   9: std::panicking::begin_panic_fmt
  10: rustc_mir::interpret::place::<impl rustc_mir::interpret::eval_context::InterpCx<M>>::write_immediate_no_validate
  11: rustc_mir::interpret::step::<impl rustc_mir::interpret::eval_context::InterpCx<M>>::eval_rvalue_into_place
  12: <rustc_mir::transform::const_prop::ConstPropagator as rustc::mir::visit::MutVisitor>::visit_statement
  13: <rustc_mir::transform::const_prop::ConstProp as rustc_mir::transform::MirPass>::run_pass
  14: rustc_mir::transform::run_passes
  15: rustc_mir::transform::run_optimization_passes
  16: rustc_mir::transform::optimized_mir
  17: rustc::ty::query::__query_compute::optimized_mir
  18: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::optimized_mir>::compute
  19: rustc::dep_graph::graph::DepGraph::with_task_impl
  20: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
  21: <clippy_lints::implicit_return::ImplicitReturn as rustc::lint::LateLintPass>::check_fn
  22: <rustc::lint::context::LateLintPassObjects as rustc::lint::LateLintPass>::check_fn
  23: rustc::hir::intravisit::walk_item
  24: rustc::hir::intravisit::Visitor::visit_nested_item
  25: rustc::hir::intravisit::walk_crate
  26: rustc::lint::context::late_lint_pass_crate
  27: rustc::lint::context::late_lint_crate
  28: rustc::util::common::time
  29: rustc::util::common::time
  30: std::panicking::try::do_call
  31: __rust_maybe_catch_panic
  32: std::panicking::try
  33: <std::panic::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once
  34: std::panicking::try::do_call
  35: __rust_maybe_catch_panic
  36: std::panicking::try
  37: rustc_interface::passes::analysis::{{closure}}
  38: rustc::util::common::time
  39: rustc_interface::passes::analysis
  40: rustc::ty::query::__query_compute::analysis
  41: rustc::dep_graph::graph::DepGraph::with_task_impl
  42: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
  43: rustc_interface::passes::BoxedGlobalCtxt::access::{{closure}}
  44: rustc_interface::passes::create_global_ctxt::{{closure}}
  45: rustc_interface::interface::run_compiler_in_existing_thread_pool
  46: std::thread::local::LocalKey<T>::with
  47: scoped_tls::ScopedKey<T>::set
  48: syntax::with_globals
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

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/blob/master/CONTRIBUTING.md#bug-reports

note: rustc 1.40.0-dev running on x86_64-unknown-linux-gnu

note: compiler flags: -Z ui-testing -C prefer-dynamic

query stack during panic:
#0 [optimized_mir] processing `main`
#1 [analysis] running analysis passes on this crate
end of query stack
{"message":"aborting due to previous error","code":null,"level":"error","spans":[],"children":[],"rendered":"error: aborting due to previous error\n\n"}

------------------------------------------



failures:
    [ui] ui/out_of_bounds_indexing/empty_array.rs

test result: FAILED. 6 passed; 1 failed; 0 ignored; 0 measured; 344 filtered out

test compile_test ... FAILED

failures:

---- compile_test stdout ----
thread 'compile_test' panicked at 'Some tests failed', /home/manishearth/.cargo/registry/src/github.com-1ecc6299db9ec823/compiletest_rs-0.3.23/src/lib.rs:102:22
stack backtrace:
   0: <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt
   1: core::fmt::write
   2: std::io::Write::write_fmt
   3: std::io::impls::<impl std::io::Write for alloc::boxed::Box<W>>::write_fmt
   4: std::sys_common::backtrace::print
   5: std::panicking::default_hook::{{closure}}
   6: std::panicking::default_hook
   7: std::panicking::rust_panic_with_hook
   8: std::panicking::begin_panic
   9: compiletest_rs::run_tests
  10: core::ops::function::FnOnce::call_once
  11: <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once
  12: std::panicking::try::do_call
  13: __rust_maybe_catch_panic
  14: std::panicking::try
  15: test::run_test_in_process

[Manishearth]

@oli-obk as far as I can tell the optimized_mir query (in implicit_return) is failing because we're calling it on code that doesn't consteval.

rust-clippy/clippy_lints/src/implicit_return.rs

Line 137 in b462905

let mir = cx.tcx.optimized_mir(def_id);

Is this a rustc bug? Is it our fault for calling it so early? Should we be doing something else here to allow for failed MIR?

[oli-obk]

This is const prop cc @wesleywiser

[oli-obk]

let's see if rust-lang/rust#64991 fixes this, too

[JohnTitor]

Triage: it still happens on recent rustc.