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internal compiler error: librustc/traits/structural_impls.rs:180: impossible case reached #53008

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malikolivier opened this issue Aug 2, 2018 · 3 comments
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internal compiler error: librustc/traits/structural_impls.rs:180: impossible case reached #53008

malikolivier opened this issue Aug 2, 2018 · 3 comments

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@malikolivier
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malikolivier commented Aug 2, 2018 •
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I get an internal compiler error. I met with this while randomly moving code around while working on a project. I tried to reduce it to a minimal reproducible example.

I tried this code:

extern crate reqwest; // <- If I remove this line, rustc does not crash
extern crate select;

use select::{
    document::Document, predicate::{Class, Name},
};

fn main() {
    let document = Document::from("");
    for node in document.find(Class("foo")) {
        let mut img_url = None;
        if let Some(img_link) = node.attr("src") {
            img_url = img_link.as_ref(); // <- If I remove this line, rustc does not crash
        }
    }
}

Full reproducible code is available here: https://github.com/malikolivier/rust-structural_impls-internal_compiler_error

I expected to see this happen: Something different from "internal compiler error". Probably this output:

error[E0308]: mismatched types
  --> src/main.rs:10:23
   |
10 |             img_url = img_link.as_ref();
   |                       ^^^^^^^^^^^^^^^^^
   |                       |
   |                       expected enum `std::option::Option`, found reference
   |                       help: try using a variant of the expected type: `Some(img_link.as_ref())`
   |
   = note: expected type `std::option::Option<_>`
              found type `&_`

Instead, this happened: internal compiler error: librustc/traits/structural_impls.rs:180: impossible case reached

Meta

rustc --version --verbose:

$ rustc --version --verbose
rustc 1.27.2 (58cc626de 2018-07-18)
binary: rustc
commit-hash: 58cc626de3301192d5d8c6dcbde43b5b44211ae2
commit-date: 2018-07-18
host: x86_64-unknown-linux-gnu
release: 1.27.2
LLVM version: 6.0

The same bug happens on rustc 1.29.0-nightly (97085f9fb 2018-08-01).

Backtrace:

$ RUST_BACKTRACE=1 cargo run --verbose
       Fresh version_check v0.1.4
       Fresh nodrop v0.1.12
       Fresh libc v0.2.42
       Fresh cfg-if v0.1.4
       Fresh byteorder v1.2.4
       Fresh lazy_static v1.0.2
       Fresh memoffset v0.2.1
       Fresh siphasher v0.2.3
       Fresh unicode-xid v0.1.0
       Fresh scopeguard v0.3.3
       Fresh pkg-config v0.3.12
       Fresh cc v1.0.18
       Fresh lazycell v0.6.0
       Fresh futures v0.1.23
       Fresh slab v0.4.0
       Fresh void v1.0.2
       Fresh string_cache_shared v0.3.0
       Fresh unicode-xid v0.0.4
       Fresh foreign-types-shared v0.1.1
       Fresh build_const v0.2.1
       Fresh rustc-serialize v0.3.24
       Fresh bitflags v0.9.1
       Fresh mac v0.1.1
       Fresh quote v0.3.15
       Fresh matches v0.1.7
       Fresh try-lock v0.1.0
       Fresh utf-8 v0.7.4
       Fresh safemem v0.2.0
       Fresh unicode-normalization v0.1.7
       Fresh scoped-tls v0.1.2
       Fresh precomputed-hash v0.1.1
       Fresh lazy_static v0.2.11
       Fresh language-tags v0.2.2
       Fresh percent-encoding v1.0.1
       Fresh adler32 v1.0.3
       Fresh dtoa v0.4.3
       Fresh bit-vec v0.4.4
       Fresh itoa v0.4.2
       Fresh arrayvec v0.4.7
       Fresh iovec v0.1.2
       Fresh rand v0.4.2
       Fresh num_cpus v1.8.0
       Fresh time v0.1.40
       Fresh crossbeam-utils v0.3.2
       Fresh log v0.4.3
       Fresh net2 v0.2.33
       Fresh encoding_rs v0.7.2
       Fresh proc-macro2 v0.3.8
       Fresh tokio-executor v0.1.2
       Fresh tokio-service v0.1.0
       Fresh relay v0.1.1
       Fresh unreachable v1.0.0
       Fresh unreachable v0.1.1
       Fresh synom v0.11.3
       Fresh foreign-types v0.3.2
       Fresh unicode-bidi v0.3.4
       Fresh base64 v0.9.2
       Fresh bit-set v0.4.0
       Fresh bytes v0.4.9
       Fresh uuid v0.6.5
       Fresh futures-cpupool v0.1.8
       Fresh crossbeam-epoch v0.4.3
       Fresh want v0.0.4
       Fresh log v0.3.9
       Fresh mio v0.6.15
       Fresh quote v0.5.2
       Fresh tokio-timer v0.2.4
       Fresh new_debug_unreachable v1.0.1
       Fresh debug_unreachable v0.1.1
       Fresh syn v0.11.11
       Fresh serde v1.0.70
       Fresh httparse v1.3.2
       Fresh idna v0.1.5
       Fresh unicase v1.4.2
       Fresh unicase v2.1.0
       Fresh tokio-io v0.1.7
       Fresh crossbeam-deque v0.3.1
       Fresh openssl-sys v0.9.33
       Fresh futf v0.1.4
       Fresh serde_json v1.0.24
       Fresh crc v1.8.1
       Fresh url v1.7.1
       Fresh phf_shared v0.7.22
       Fresh mime v0.3.8
       Fresh tokio-reactor v0.1.2
       Fresh tokio-codec v0.1.0
       Fresh tokio-threadpool v0.1.5
       Fresh openssl v0.9.24
       Fresh tendril v0.3.1
       Fresh libflate v0.1.16
       Fresh serde_urlencoded v0.5.2
       Fresh phf_generator v0.7.22
       Fresh phf v0.7.22
       Fresh tokio-tcp v0.1.0
       Fresh tokio-udp v0.1.1
       Fresh tokio-fs v0.1.2
       Fresh native-tls v0.1.5
       Fresh string_cache_codegen v0.4.1
       Fresh phf_codegen v0.7.22
       Fresh tokio v0.1.7
       Fresh tokio-core v0.1.17
       Fresh hyper v0.11.27
       Fresh tokio-tls v0.1.4
       Fresh string_cache v0.6.2
       Fresh mime_guess v2.0.0-alpha.6
       Fresh hyper-tls v0.1.4
       Fresh markup5ever v0.3.2
       Fresh reqwest v0.8.7
       Fresh html5ever v0.18.0
       Fresh select v0.4.2
   Compiling select-test v0.1.0 (file:///home/malik/workspace/veille/mercari-scrap)
     Running `rustc --crate-name select_test src/main.rs --crate-type bin --emit=dep-info,link -C debuginfo=2 -C metadata=822bd59bde9136c9 -C extra-filename=-822bd59bde9136c9 --out-dir /home/malik/workspace/veille/mercari-scrap/target/debug/deps -C incremental=/home/malik/workspace/veille/mercari-scrap/target/debug/incremental -L dependency=/home/malik/workspace/veille/mercari-scrap/target/debug/deps --extern select=/home/malik/workspace/veille/mercari-scrap/target/debug/deps/libselect-5ca4f723d69fde13.rlib --extern reqwest=/home/malik/workspace/veille/mercari-scrap/target/debug/deps/libreqwest-c3068e3d2875fc5b.rlib`
error: internal compiler error: librustc/traits/structural_impls.rs:180: impossible case reached

thread 'main' panicked at 'Box<Any>', librustc_errors/lib.rs:554:9
stack backtrace:
   0: std::sys::unix::backtrace::tracing::imp::unwind_backtrace
             at libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1: std::sys_common::backtrace::print
             at libstd/sys_common/backtrace.rs:71
             at libstd/sys_common/backtrace.rs:59
   2: std::panicking::default_hook::{{closure}}
             at libstd/panicking.rs:211
   3: std::panicking::default_hook
             at libstd/panicking.rs:227
   4: rustc::util::common::panic_hook
   5: std::panicking::rust_panic_with_hook
             at libstd/panicking.rs:467
   6: std::panicking::begin_panic
   7: rustc_errors::Handler::bug
   8: rustc::session::opt_span_bug_fmt::{{closure}}
   9: rustc::ty::context::tls::with_opt::{{closure}}
  10: rustc::ty::context::tls::with_context_opt
  11: rustc::ty::context::tls::with_opt
  12: rustc::session::opt_span_bug_fmt
  13: rustc::session::bug_fmt
  14: rustc::traits::structural_impls::<impl rustc::ty::context::Lift<'tcx> for rustc::traits::SelectionError<'a>>::lift_to_tcx
  15: rustc::traits::select::SelectionContext::candidate_from_obligation
  16: rustc::traits::select::SelectionContext::evaluate_stack
  17: rustc::ty::context::tls::with_context
  18: rustc::dep_graph::graph::DepGraph::with_anon_task
  19: rustc::traits::select::SelectionContext::evaluate_predicate_recursively
  20: rustc::traits::select::SelectionContext::evaluate_candidate
  21: <&'a mut I as core::iter::iterator::Iterator>::next
  22: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter
  23: rustc::traits::select::SelectionContext::candidate_from_obligation_no_cache
  24: rustc::ty::context::tls::with_context
  25: rustc::dep_graph::graph::DepGraph::with_anon_task
  26: rustc::traits::select::SelectionContext::candidate_from_obligation
  27: rustc::traits::select::SelectionContext::evaluate_stack
  28: rustc::ty::context::tls::with_context
  29: rustc::dep_graph::graph::DepGraph::with_anon_task
  30: rustc::traits::select::SelectionContext::evaluate_predicate_recursively
  31: rustc::traits::select::SelectionContext::evaluate_candidate
  32: <&'a mut I as core::iter::iterator::Iterator>::next
  33: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter
  34: rustc::traits::select::SelectionContext::candidate_from_obligation_no_cache
  35: rustc::ty::context::tls::with_context
  36: rustc::dep_graph::graph::DepGraph::with_anon_task
  37: rustc::traits::select::SelectionContext::candidate_from_obligation
  38: rustc::traits::select::SelectionContext::evaluate_stack
  39: rustc::ty::context::tls::with_context
  40: rustc::dep_graph::graph::DepGraph::with_anon_task
  41: rustc::traits::select::SelectionContext::evaluate_predicate_recursively
  42: rustc::traits::select::SelectionContext::evaluate_candidate
  43: <&'a mut I as core::iter::iterator::Iterator>::next
  44: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter
  45: rustc::traits::select::SelectionContext::candidate_from_obligation_no_cache
  46: rustc::ty::context::tls::with_context
  47: rustc::dep_graph::graph::DepGraph::with_anon_task
  48: rustc::traits::select::SelectionContext::candidate_from_obligation
  49: rustc::traits::select::SelectionContext::evaluate_stack
  50: rustc::ty::context::tls::with_context
  51: rustc::dep_graph::graph::DepGraph::with_anon_task
  52: rustc::traits::select::SelectionContext::evaluate_predicate_recursively
  53: rustc::traits::select::SelectionContext::evaluate_candidate
  54: <&'a mut I as core::iter::iterator::Iterator>::next
  55: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter
  56: rustc::traits::select::SelectionContext::candidate_from_obligation_no_cache
  57: rustc::ty::context::tls::with_context
  58: rustc::dep_graph::graph::DepGraph::with_anon_task
  59: rustc::traits::select::SelectionContext::candidate_from_obligation
  60: rustc::traits::select::SelectionContext::evaluate_stack
  61: rustc::ty::context::tls::with_context
  62: rustc::dep_graph::graph::DepGraph::with_anon_task
  63: rustc::traits::select::SelectionContext::evaluate_predicate_recursively
  64: rustc::traits::select::SelectionContext::evaluate_candidate
  65: <&'a mut I as core::iter::iterator::Iterator>::next
  66: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter
  67: rustc::traits::select::SelectionContext::candidate_from_obligation_no_cache
  68: rustc::ty::context::tls::with_context
  69: rustc::dep_graph::graph::DepGraph::with_anon_task
  70: rustc::traits::select::SelectionContext::candidate_from_obligation
  71: rustc::traits::select::SelectionContext::evaluate_stack
  72: rustc::ty::context::tls::with_context
  73: rustc::dep_graph::graph::DepGraph::with_anon_task
  74: rustc::traits::select::SelectionContext::evaluate_predicate_recursively
  75: rustc::traits::select::SelectionContext::evaluate_candidate
  76: <&'a mut I as core::iter::iterator::Iterator>::next
  77: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter
  78: rustc::traits::select::SelectionContext::candidate_from_obligation_no_cache
  79: rustc::ty::context::tls::with_context
  80: rustc::dep_graph::graph::DepGraph::with_anon_task
  81: rustc::traits::select::SelectionContext::candidate_from_obligation
  82: rustc::traits::select::SelectionContext::evaluate_stack
  83: rustc::ty::context::tls::with_context
  84: rustc::dep_graph::graph::DepGraph::with_anon_task
  85: rustc::traits::select::SelectionContext::evaluate_predicate_recursively
  86: rustc::traits::select::SelectionContext::evaluate_candidate
  87: <&'a mut I as core::iter::iterator::Iterator>::next
  88: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter
  89: rustc::traits::select::SelectionContext::candidate_from_obligation_no_cache
  90: rustc::ty::context::tls::with_context
  91: rustc::dep_graph::graph::DepGraph::with_anon_task
  92: rustc::traits::select::SelectionContext::candidate_from_obligation
  93: rustc::traits::select::SelectionContext::evaluate_stack
  94: rustc::ty::context::tls::with_context
  95: rustc::dep_graph::graph::DepGraph::with_anon_task
  96: rustc::traits::select::SelectionContext::evaluate_predicate_recursively
  97: rustc::traits::select::SelectionContext::evaluate_candidate
  98: <&'a mut I as core::iter::iterator::Iterator>::next
  99: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T, I>>::from_iter
query stack during panic:
#0 [evaluate_obligation] evaluating trait selection obligation `&'_ _: std::io::Read`
#1 [typeck_tables_of] processing `main`
#2 [typeck_item_bodies] type-checking all item bodies
end of query stack
error: aborting due to previous error


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 1.27.2 (58cc626de 2018-07-18) running on x86_64-unknown-linux-gnu

note: compiler flags: -C debuginfo=2 -C incremental --crate-type bin

note: some of the compiler flags provided by cargo are hidden

error: Could not compile `select-test`.

Caused by:
  process didn't exit successfully: `rustc --crate-name select_test src/main.rs --crate-type bin --emit=dep-info,link -C debuginfo=2 -C metadata=822bd59bde9136c9 -C extra-filename=-822bd59bde9136c9 --out-dir /home/malik/workspace/veille/mercari-scrap/target/debug/deps -C incremental=/home/malik/workspace/veille/mercari-scrap/target/debug/incremental -L dependency=/home/malik/workspace/veille/mercari-scrap/target/debug/deps --extern select=/home/malik/workspace/veille/mercari-scrap/target/debug/deps/libselect-5ca4f723d69fde13.rlib --extern reqwest=/home/malik/workspace/veille/mercari-scrap/target/debug/deps/libreqwest-c3068e3d2875fc5b.rlib` (exit code: 101)
@hellow554
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hellow554 commented Aug 3, 2018 •
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Occurs in 1.28.0, beta and nightly

error: internal compiler error: librustc/traits/structural_impls.rs:178: impossible case reached

@jamesray1 jamesray1 mentioned this issue Dec 7, 2018
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@jamesray1
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Should be a duplicate of #52873.

@estebank
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estebank commented Jan 8, 2019

ICE no longer repros.

@estebank estebank closed this as completed Jan 8, 2019
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4 participants
@hellow554 @estebank @malikolivier @jamesray1