ICE using const raw pointer cast for array size

[murarth]

Code:

#![feature(const_fn)]

fn main() {
    let _ = [0; foo() as usize];
}

const fn foo() -> *const i32 {
    &0 as *const i32
}

Error with RUST_BACKTRACE=full:

error[E0018]: raw pointers cannot be cast to integers in constants
 --> foo.rs:4:17
  |
4 |     let _ = [0; foo() as usize];
  |                 ^^^^^^^^^^^^^^

error: internal compiler error: librustc/ty/relate.rs:506: arrays should not have Const { ty: usize, val: Value(Scalar(Ptr(Pointer { alloc_id: AllocId(6), offset: Size { raw: 0 } }))) } as length

thread 'main' panicked at 'Box<Any>', librustc_errors/lib.rs:554:9
stack backtrace:
   0:     0x7fdc61e260fe - std::sys::unix::backtrace::tracing::imp::unwind_backtrace::h50a634a60cb4e5f7
                               at libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1:     0x7fdc61dfd4b6 - std::sys_common::backtrace::print::hfdd27bb0425df770
                               at libstd/sys_common/backtrace.rs:71
                               at libstd/sys_common/backtrace.rs:59
   2:     0x7fdc61e2d34d - std::panicking::default_hook::{{closure}}::h027136eae47935d0
                               at libstd/panicking.rs:211
   3:     0x7fdc61e2d0c0 - std::panicking::default_hook::hed5917d304f00a1b
                               at libstd/panicking.rs:227
   4:     0x7fdc5e4ea3e5 - rustc::util::common::panic_hook::h9e9cb098ca9688d6
   5:     0x7fdc61e2dad3 - std::panicking::rust_panic_with_hook::hc482345e1eead25b
                               at libstd/panicking.rs:515
   6:     0x7fdc5d2b08ae - std::panicking::begin_panic::h91aef2ee5aa26450
   7:     0x7fdc5d2ac261 - rustc_errors::Handler::bug::h1be2d05f14de7d85
   8:     0x7fdc5e0ccbcc - rustc::session::opt_span_bug_fmt::{{closure}}::heb5c3a0ebc0b8cb9
   9:     0x7fdc5e186f29 - rustc::ty::context::tls::with_opt::{{closure}}::h6294c4a9102c2647
  10:     0x7fdc5e0cd95f - rustc::ty::context::tls::with_context_opt::ha499f455a0857cd3
  11:     0x7fdc5e1869a6 - rustc::ty::context::tls::with_opt::h50829cbea0b4a2b5
  12:     0x7fdc5e099284 - rustc::session::opt_span_bug_fmt::h909d74d76885e464
  13:     0x7fdc5e0991f6 - rustc::session::bug_fmt::h56d39c05f4237f0a
  14:     0x7fdc5e1f0def - rustc::ty::relate::super_relate_tys::{{closure}}::h0e5c5821e42893fb
  15:     0x7fdc5e1cba81 - <rustc::infer::combine::Generalizer<'cx, 'gcx, 'tcx> as rustc::ty::relate::TypeRelation<'cx, 'gcx, 'tcx>>::tys::h79391b27f99f3d90
  16:     0x7fdc5e1ca5b4 - rustc::infer::combine::CombineFields::instantiate::h1673388ad551389e
  17:     0x7fdc5e1cc818 - <rustc::infer::sub::Sub<'combine, 'infcx, 'gcx, 'tcx> as rustc::ty::relate::TypeRelation<'infcx, 'gcx, 'tcx>>::tys::h9857734987984713
  18:     0x7fdc60639706 - rustc::infer::InferCtxt::commit_if_ok::h2490ae759e0bddd1
  19:     0x7fdc606390d2 - rustc::infer::InferCtxt::commit_if_ok::h09c65af8556fc345
  20:     0x7fdc606e2fe5 - rustc_typeck::check::coercion::Coerce::coerce::h6c1101b044e206b7
  21:     0x7fdc606394ec - rustc::infer::InferCtxt::commit_if_ok::h1a6a85a1fca39f19
  22:     0x7fdc606410c8 - rustc::infer::InferCtxt::commit_if_ok::hafa1c534ca850ff9
  23:     0x7fdc605af22c - rustc_typeck::check::coercion::<impl rustc_typeck::check::FnCtxt<'a, 'gcx, 'tcx>>::try_coerce::h714c901dbb184ff3
  24:     0x7fdc605b49c7 - rustc_typeck::check::demand::<impl rustc_typeck::check::FnCtxt<'a, 'gcx, 'tcx>>::demand_coerce_diag::h0d3348845e18e33a
  25:     0x7fdc605b47e6 - rustc_typeck::check::demand::<impl rustc_typeck::check::FnCtxt<'a, 'gcx, 'tcx>>::demand_coerce::h605fe74462fe7c91
  26:     0x7fdc605e113f - rustc_typeck::check::FnCtxt::check_decl_local::h32f94738aaeb63bb
  27:     0x7fdc605e1694 - rustc_typeck::check::FnCtxt::check_block_with_expected::hee241f249d32fbd9
  28:     0x7fdc605d39d6 - rustc_typeck::check::FnCtxt::check_expr_kind::h319525d17a66c8df
  29:     0x7fdc605d3741 - rustc_typeck::check::FnCtxt::check_expr_with_expectation_and_needs::h07919108be9f5f44
  30:     0x7fdc605d2990 - rustc_typeck::check::FnCtxt::check_return_expr::h764e2e237ef673a8
  31:     0x7fdc605c6132 - rustc_typeck::check::check_fn::h5c7a30d85ca0d72e
  32:     0x7fdc60674dcd - rustc::ty::context::tls::with_related_context::h812eafb03d5e2a88
  33:     0x7fdc60637dc8 - rustc::infer::InferCtxtBuilder::enter::hfc232c248b49f6eb
  34:     0x7fdc605c4cca - rustc_typeck::check::typeck_tables_of::h7f50d10402e552d5
  35:     0x7fdc5e4f2832 - rustc::ty::query::__query_compute::typeck_tables_of::hd50fa71ff0e9f45e
  36:     0x7fdc5e187c1c - rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors<'tcx> for rustc::ty::query::queries::typeck_tables_of<'tcx>>::compute::h5ddfbde7628dd211
  37:     0x7fdc5df6200d - rustc::dep_graph::graph::DepGraph::with_task_impl::h2615ca8854025f24
  38:     0x7fdc5e1317f6 - rustc::ty::context::tls::with_related_context::h4513e1c17d844181
  39:     0x7fdc5e2e96ce - rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::force_query_with_job::h1f4db9eb8c0a364d
  40:     0x7fdc5e3beceb - rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::get_query::h9890a9d1dc40bd13
  41:     0x7fdc5e3131eb - rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::ensure_query::hf83b36f70243fa2a
  42:     0x7fdc6060a5cc - rustc::session::Session::track_errors::hba3da29fe1ce2480
  43:     0x7fdc605c485a - rustc_typeck::check::typeck_item_bodies::he6482650e87a8925
  44:     0x7fdc5e187bf8 - rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors<'tcx> for rustc::ty::query::queries::typeck_item_bodies<'tcx>>::compute::h14d44e448ca355cc
  45:     0x7fdc5df55356 - rustc::dep_graph::graph::DepGraph::with_task_impl::h0601e47024527472
  46:     0x7fdc5e157c56 - rustc::ty::context::tls::with_related_context::ha696a0c6c6ade91e
  47:     0x7fdc5e308f39 - rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::force_query_with_job::hf8ac4b981b9250dc
  48:     0x7fdc5e3e46d5 - rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::get_query::hbe60cc3f7a53633b
  49:     0x7fdc60609c14 - rustc::util::common::time::h62b55b79d8dc7e4e
  50:     0x7fdc607359e7 - rustc_typeck::check_crate::hc769360b74ff1fdc
  51:     0x7fdc6226c03a - rustc::ty::context::tls::enter_context::h91c9f96576851d36
  52:     0x7fdc62219aca - <std::thread::local::LocalKey<T>>::with::hc3b25e364245c00f
  53:     0x7fdc62184ec2 - rustc::ty::context::TyCtxt::create_and_enter::he17b49208d21e853
  54:     0x7fdc621c50ac - rustc_driver::driver::compile_input::h95eb8b7dd032d269
  55:     0x7fdc62250295 - rustc_driver::run_compiler_with_pool::h94fbd18de41dc2e2
  56:     0x7fdc621b497b - <scoped_tls::ScopedKey<T>>::set::h4c03440eebe30a1f
  57:     0x7fdc62189f2a - syntax::with_globals::h57af6031309babcc
  58:     0x7fdc6216a722 - <std::panic::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once::hb1f190602052e50b
  59:     0x7fdc61e3bc59 - __rust_maybe_catch_panic
                               at libpanic_unwind/lib.rs:105
  60:     0x7fdc6224d423 - rustc_driver::run::h7fa1696458a8f761
  61:     0x7fdc6225d26a - rustc_driver::main::he4d005c782d5073a
  62:     0x562dabfb7b52 - std::rt::lang_start::{{closure}}::h99d53d66d7fac3dd
  63:     0x7fdc61e2d512 - std::panicking::try::do_call::h7e0ed4dd1b773c21
                               at libstd/rt.rs:59
                               at libstd/panicking.rs:310
  64:     0x7fdc61e3bc59 - __rust_maybe_catch_panic
                               at libpanic_unwind/lib.rs:105
  65:     0x7fdc61df1d55 - std::rt::lang_start_internal::h7c38f1310577c409
                               at libstd/panicking.rs:289
                               at libstd/panic.rs:392
                               at libstd/rt.rs:58
  66:     0x562dabfb7bb3 - main
  67:     0x7fdc61a202e0 - __libc_start_main
  68:     0x562dabfb7a38 - <unknown>
query stack during panic:
#0 [typeck_tables_of] processing `main`
#1 [typeck_item_bodies] type-checking all item bodies
end of query stack
error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0018`.

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 1.28.0-nightly (e3bf634e0 2018-06-28) running on x86_64-unknown-linux-gnu

[estebank]

cc @varkor

[hellow554]

Even smaller and can be built on stable (not that it would matter, but you can rule out the const_fn feature

fn main() {
    let _ = [0; (&0 as *const i32) as usize];
}

[hellow554]

Actually, are those different errors? Nightly gives us

error: internal compiler error: librustc/ty/relate.rs:506: arrays should not have Const { ty: usize, val: Value(Scalar(Ptr(Pointer { alloc_id: AllocId(1), offset: Size { raw: 0 } }))) } as length

Stable:

Thread 'main' panicked at 'called Result::unwrap() on an Err value: EvalError { kind: a raw memory access tried to access part of a pointer value as raw bytes, backtrace: None }', libcore/result.rs:945:5

or as these just different error messages for the same error?

[oli-obk]

Yea these errors are resulting from the same issue, there were some recent changes that definitely would cause this change in the ICE.

Anyway, seems easy enough to fix. We just need to emit the E0080 error instead of panicking.