Nightly compiler crash on Type substitution.

[oldwomanjosiah]

I am following along Philip Opperman blog and was on the [third post[(https://os.phil-opp.com/testing/) about testing. I was able to figure out that if I commented out the following test_case then it would no longer crash. The full code that I was using can be found here if that would help.

Code

Test that was causing the issue:

    #[test_case]
    fn print_to_screen() {
        let to_screen = "Prints to Screen";

        println!("{}", to_screen);

        let buffer = WRITER.lock();

        for (i, c) in to_screen.chars().enumerate() {
            assert_eq!(
                    char::from((buffer.chars[BUFFER_HEIGHT - 2][i]).read().ascii_char),
                    c
                );
        }
    }

Version of test harness where core::any::type_name was called:

#[cfg(test)]
fn test_runner(tests: &[&dyn Testable]) {
    println_serial!("[      ]: Running {} Tests", tests.len());

    for test in tests {
        println_serial!();
        test.run();
    }

    println_serial!("\n[      ]: All Tests passed");

    exit_qemu(QemuExitCode::Success);
}

pub trait Testable {
    fn run(&self) -> ();
}

impl<T> Testable for T where T: Fn() -> () {
    fn run(&self) -> () {
        println_serial!("[ TEST ]: {}", core::any::type_name::<T>());
        self();
        println_serial!("[  OK  ]");
    }
}

Meta

rustc --version --verbose:

rustc 1.51.0-nightly (368275062 2021-02-02)
binary: rustc
commit-hash: 368275062fb655c1f36e0398f88b15379a1f3c93
commit-date: 2021-02-02
host: x86_64-apple-darwin
release: 1.51.0-nightly
LLVM version: 11.0.1

Error output

Before backtrace:

error: internal compiler error: compiler/rustc_middle/src/ty/subst.rs:516:17: expected type for `T/#0` (T/0) but found Lifetime('_#77r) when substituting, substs=['_#77r, vga_buffer::Writer]

After Backtrace:

query stack during panic:
#0 [typeck] type-checking `vga_buffer::tests::print_to_screen`
#1 [typeck_item_bodies] type-checking all item bodies
#2 [analysis] running analysis passes on this crate
end of query stack

Backtrace

0: std::panicking::begin_panic
   1: rustc_errors::HandlerInner::span_bug
   2: rustc_errors::Handler::span_bug
   3: rustc_middle::util::bug::opt_span_bug_fmt::{{closure}}
   4: rustc_middle::ty::context::tls::with_opt
   5: rustc_middle::util::bug::opt_span_bug_fmt
   6: rustc_middle::util::bug::span_bug_fmt
   7: <rustc_middle::ty::subst::SubstFolder as rustc_middle::ty::fold::TypeFolder>::fold_ty
   8: rustc_middle::ty::FieldDef::ty
   9: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_for_nested_field
  10: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_for_nested_field
  11: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_for_nested_field
  12: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_field
  13: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_kind
  14: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation
  15: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_kind
  16: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation
  17: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_kind
  18: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation
  19: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_kind
  20: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation
  21: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_field
  22: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_kind
  23: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation
  24: rustc_typeck::check::fn_ctxt::checks::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_argument_types
  25: rustc_typeck::check::callee::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::confirm_builtin_call
  26: rustc_typeck::check::callee::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_call
  27: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_kind
  28: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation
  29: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_kind
  30: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation
  31: <smallvec::SmallVec<A> as core::iter::traits::collect::Extend<<A as smallvec::Array>::Item>>::extend
  32: <T as rustc_middle::ty::context::InternIteratorElement<T,R>>::intern_with
  33: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_kind
  34: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation
  35: rustc_typeck::check::_match::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::demand_scrutinee_type
  36: rustc_typeck::check::_match::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_match
  37: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_kind
  38: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation
  39: rustc_typeck::check::fn_ctxt::checks::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_block_with_expected
  40: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_kind
  41: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation
  42: rustc_typeck::check::fn_ctxt::checks::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_stmt
  43: rustc_typeck::check::fn_ctxt::checks::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_block_with_expected
  44: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_kind
  45: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation
  46: rustc_typeck::check::fn_ctxt::checks::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_stmt
  47: rustc_typeck::check::fn_ctxt::checks::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_block_with_expected
  48: rustc_typeck::check::fn_ctxt::checks::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_block_no_value
  49: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_kind
  50: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation
  51: rustc_typeck::check::_match::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_match
  52: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_kind
  53: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation
  54: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_kind
  55: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation
  56: rustc_typeck::check::fn_ctxt::checks::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_block_with_expected
  57: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_kind
  58: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_with_expectation
  59: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_return_expr
  60: rustc_typeck::check::check::check_fn
  61: rustc_infer::infer::InferCtxtBuilder::enter
  62: rustc_typeck::check::typeck
  63: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::typeck>::compute
  64: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  65: rustc_middle::ty::query::plumbing::<impl rustc_query_system::query::QueryContext for rustc_middle::ty::context::TyCtxt>::start_query::{{closure}}::{{closure}}::{{closure}}
  66: rustc_query_system::query::plumbing::force_query_with_job
  67: rustc_query_system::query::plumbing::get_query_impl
  68: rustc_query_system::query::plumbing::ensure_query_impl
  69: rustc_typeck::check::typeck_item_bodies
  70: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::typeck_item_bodies>::compute
  71: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  72: rustc_data_structures::stack::ensure_sufficient_stack
  73: rustc_query_system::query::plumbing::force_query_with_job
  74: rustc_query_system::query::plumbing::get_query_impl
  75: rustc_typeck::check_crate
  76: rustc_interface::passes::analysis
  77: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::analysis>::compute
  78: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  79: rustc_middle::ty::query::plumbing::<impl rustc_query_system::query::QueryContext for rustc_middle::ty::context::TyCtxt>::start_query::{{closure}}::{{closure}}::{{closure}}
  80: rustc_query_system::query::plumbing::force_query_with_job
  81: rustc_query_system::query::plumbing::get_query_impl
  82: rustc_interface::passes::QueryContext::enter
  83: rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter
  84: rustc_span::with_source_map
  85: rustc_interface::interface::create_compiler_and_run
  86: rustc_span::with_session_globals

[oldwomanjosiah]

Note: This specific instance of the bug did not reproduce on the latest nightly as of 2021-2-9

[Enselic]

I did a bisect and the ICE was fixed in nightly-2021-02-04, so probably #81716 which added a regression test. Closing.

cargo bisect-rustc --start 2021-02-03 --end 2021-02-09 --preserve --regress non-ice --with-src  -- test
...
********************************************************************************
Regression in nightly-2021-02-04
********************************************************************************
...
fetching (via local git) commits from 368275062fb655c1f36e0398f88b15379a1f3c93 to e708cbd91c9cae4426d69270248362b423324556