ICE with Unreachable patterns and Incremental compilation

[Julian-Wollersberger]

Minimized Code

fn main() {
    const BOO: &[u8; 0] = &[];
    match &[] {
        [] => (),
        BOO => (), // unreachable pattern
        b"" => (), // unreachable pattern
    }
}

Summary

I got this ICE when compiling one of the UI test files ( slice-pattern-const.rs ) as a normal cargo project.
How can that be? Well, compiler flags are different than in the test suit. The culprit turns out to be incremental compilation.

The following ICEs:

• rustc main.rs -C incremental=true
• cargo check

The following works as expected:

• rustc main.rs
• cargo build --release

.

There is a fun bonus bug in here:

• cargo clean ; cargo check
• delete the line b"" => (),
• run cargo check
• add that line again.
• Now cargo check doesn't ICE anymore, on the original code.

Affected versions

The bug report is made with rustc 1.63.0-nightly (1fede1753 2022-05-28), but this ICE seems to be very old.

Output of cargo bisect-rustc --preserve --prompt --end=2021-09-11 --start=2020-01-01:

[...]
searched toolchains nightly-2020-01-01 through nightly-2021-09-11


********************************************************************************
Regression in nightly-2020-10-26
********************************************************************************

fetching https://static.rust-lang.org/dist/2020-10-25/channel-rust-nightly-git-commit-hash.txt
nightly manifest 2020-10-25: 40 B / 40 B [=======================================================] 100.00 % 57.27 KB/s converted 2020-10-25 to ffa2e7ae8fbf9badc035740db949b9dae271c29f
fetching https://static.rust-lang.org/dist/2020-10-26/channel-rust-nightly-git-commit-hash.txt
nightly manifest 2020-10-26: 40 B / 40 B [=======================================================] 100.00 % 81.40 KB/s converted 2020-10-26 to 4760b8fb886a3702ae11bfa7868d495b2675b5ed
looking for regression commit between 2020-10-25 and 2020-10-26
cloning rust repository
fetching (via local git) commits from ffa2e7ae8fbf9badc035740db949b9dae271c29f to 4760b8fb886a3702ae11bfa7868d495b2675b5ed
opening existing repository at "rust.git"
Found origin remote under name `origin`
refreshing repository at "rust.git"
looking up first commit
looking up second commit
checking that commits are by bors and thus have ci artifacts...
finding bors merge commits
found 11 bors merge commits in the specified range
  commit[0] 2020-10-24UTC: Auto merge of #77255 - Aaron1011:feature/collect-attr-tokens, r=petrochenkov
  commit[1] 2020-10-24UTC: Auto merge of #78334 - jonas-schievink:rollup-z0gzbmm, r=jonas-schievink
  commit[2] 2020-10-25UTC: Auto merge of #78310 - ebroto:clippyup, r=Manishearth
  commit[3] 2020-10-25UTC: Auto merge of #77526 - RalfJung:dont-promote-unions, r=lcnr
  commit[4] 2020-10-25UTC: Auto merge of #77398 - wesleywiser:measureme_0_8, r=Mark-Simulacrum
  commit[5] 2020-10-25UTC: Auto merge of #77546 - lcnr:impl-trait-closure, r=eddyb
  commit[6] 2020-10-25UTC: Auto merge of #77476 - tgnottingham:buffered_siphasher128, r=nnethercote
  commit[7] 2020-10-25UTC: Auto merge of #78350 - JohnTitor:rollup-vbbm5wf, r=JohnTitor
  commit[8] 2020-10-25UTC: Auto merge of #78253 - Aaron1011:bump-llvm-deadarg, r=cuviper
  commit[9] 2020-10-25UTC: Auto merge of #77901 - jonas-schievink:unignore-test-36710, r=Mark-Simulacrum
  commit[10] 2020-10-25UTC: Auto merge of #78179 - RalfJung:miri-comments, r=oli-obk
ERROR: no CI builds available between ffa2e7ae8fbf9badc035740db949b9dae271c29f and 4760b8fb886a3702ae11bfa7868d495b2675b5ed within last 167 days

Error output

    Checking tempdir v0.1.0 (D:\Dokumente\Rust\fuzzing-rustc\repos\Second ICE\tempdir)
thread 'rustc' panicked at 'forcing query with already existing `DepNode`
- query-key: ParamEnvAnd { param_env: ParamEnv { caller_bounds: [], reveal: UserFacing, constness: NotConst }, value: Val(Scalar(alloc5), &[u8; 0]) }
- dep-node: deref_mir_constant(f274d09d4d410170-67b2b755964a310a)', /rustc/1fede1753c33f4ce0660ad9b8edbd618d9733daf\compiler\rustc_query_system\src\dep_graph\graph.rs:300:9
stack backtrace:
   0:     0x7ff9cf899b4f - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h58508b3f8525c109
   1:     0x7ff9cf8d4e5a - core::fmt::write::h00a3e95c7c04103e
   2:     0x7ff9cf88c009 - <std::io::IoSlice as core::fmt::Debug>::fmt::h7884a9e95f1b1022
   3:     0x7ff9cf89d43b - std::panicking::default_hook::h3f8dbc57d7df9994
   4:     0x7ff9cf89d0bb - std::panicking::default_hook::h3f8dbc57d7df9994
   5:     0x7ff9b77ef2d6 - <rustc_metadata[b2f2848d139875d1]::rmeta::encoder::EncodeContext as rustc_serialize[979d5f7f20b036c4]::serialize::Encoder>::emit_raw_bytes
   6:     0x7ff9cf89dbe2 - std::panicking::rust_panic_with_hook::he403a961d6bd3e59
   7:     0x7ff9cf89d97d - <std::panicking::begin_panic_handler::StrPanicPayload as core::panic::BoxMeUp>::get::h9b9722e75b45b376
   8:     0x7ff9cf89a787 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h58508b3f8525c109
   9:     0x7ff9cf89d659 - rust_begin_unwind
  10:     0x7ff9cf908935 - core::panicking::panic_fmt::hcf4174d66c865fdf
  11:     0x7ff9bb0919f4 - <&[rustc_middle[c72282b761ffb2ca]::thir::abstract_const::Node] as rustc_serialize[979d5f7f20b036c4]::serialize::Decodable<rustc_query_impl[fcbe4ce9962e1e39]::on_disk_cache::CacheDecoder>>::decode
  12:     0x7ff9bb028c80 - <&[rustc_middle[c72282b761ffb2ca]::thir::abstract_const::Node] as rustc_serialize[979d5f7f20b036c4]::serialize::Decodable<rustc_query_impl[fcbe4ce9962e1e39]::on_disk_cache::CacheDecoder>>::decode
  13:     0x7ff9bacbdff6 - <rustc_query_impl[fcbe4ce9962e1e39]::Queries as rustc_middle[c72282b761ffb2ca]::ty::query::QueryEngine>::try_mark_green
  14:     0x7ff9ba74ce4b - <rustc_mir_build[6ed738a698dde9b0]::thir::pattern::PatternError as core[97cc336334fd47ab]::fmt::Debug>::fmt
  15:     0x7ff9ba742450 - <rustc_mir_build[6ed738a698dde9b0]::thir::pattern::PatternError as core[97cc336334fd47ab]::fmt::Debug>::fmt
  16:     0x7ff9ba7303be - <rustc_mir_build[6ed738a698dde9b0]::build::NeedsTemporary as core[97cc336334fd47ab]::fmt::Debug>::fmt
  17:     0x7ff9ba72c236 - <rustc_mir_build[6ed738a698dde9b0]::build::NeedsTemporary as core[97cc336334fd47ab]::fmt::Debug>::fmt
  18:     0x7ff9ba6d50bb - <rustc_mir_build[6ed738a698dde9b0]::thir::pattern::check_match::MatchVisitor as rustc_hir[58843d480a0d6ffd]::intravisit::Visitor>::visit_param
  19:     0x7ff9ba6dfc8c - <rustc_mir_build[6ed738a698dde9b0]::thir::pattern::check_match::LetSource as core[97cc336334fd47ab]::fmt::Debug>::fmt
  20:     0x7ff9ba6d2cff - <rustc_mir_build[6ed738a698dde9b0]::thir::pattern::check_match::MatchVisitor as rustc_hir[58843d480a0d6ffd]::intravisit::Visitor>::visit_expr
  21:     0x7ff9ba6d2991 - <rustc_mir_build[6ed738a698dde9b0]::thir::pattern::check_match::MatchVisitor as rustc_hir[58843d480a0d6ffd]::intravisit::Visitor>::visit_expr
  22:     0x7ff9ba6d2447 - <rustc_mir_build[6ed738a698dde9b0]::thir::pattern::deconstruct_pat::Fields as core[97cc336334fd47ab]::fmt::Debug>::fmt
  23:     0x7ff9bad84651 - <&[(rustc_middle[c72282b761ffb2ca]::middle::exported_symbols::ExportedSymbol, rustc_middle[c72282b761ffb2ca]::middle::exported_symbols::SymbolExportInfo)] as rustc_serialize[979d5f7f20b036c4]::serialize::Decodable<rustc_query_impl[fcbe4ce9962e1e39]::on_disk_cache::CacheDecoder>>::decode
  24:     0x7ff9bb0b35a7 - <&[rustc_middle[c72282b761ffb2ca]::thir::abstract_const::Node] as rustc_serialize[979d5f7f20b036c4]::serialize::Decodable<rustc_query_impl[fcbe4ce9962e1e39]::on_disk_cache::CacheDecoder>>::decode
  25:     0x7ff9baf6f3d7 - <&[rustc_middle[c72282b761ffb2ca]::thir::abstract_const::Node] as rustc_serialize[979d5f7f20b036c4]::serialize::Decodable<rustc_query_impl[fcbe4ce9962e1e39]::on_disk_cache::CacheDecoder>>::decode
  26:     0x7ff9bb010a9b - <&[rustc_middle[c72282b761ffb2ca]::thir::abstract_const::Node] as rustc_serialize[979d5f7f20b036c4]::serialize::Decodable<rustc_query_impl[fcbe4ce9962e1e39]::on_disk_cache::CacheDecoder>>::decode
  27:     0x7ff9b794ca29 - <rustc_interface[dd9c94d8fc04b103]::passes::boxed_resolver::BoxedResolver>::to_resolver_outputs
  28:     0x7ff9b78fc4d3 - <rustc_interface[dd9c94d8fc04b103]::queries::Linker>::link
  29:     0x7ff9b78ff64b - <rustc_interface[dd9c94d8fc04b103]::queries::Linker>::link
  30:     0x7ff9b78e8a20 - rustc_interface[dd9c94d8fc04b103]::passes::analysis
  31:     0x7ff9bad852de - <&[(rustc_middle[c72282b761ffb2ca]::middle::exported_symbols::ExportedSymbol, rustc_middle[c72282b761ffb2ca]::middle::exported_symbols::SymbolExportInfo)] as rustc_serialize[979d5f7f20b036c4]::serialize::Decodable<rustc_query_impl[fcbe4ce9962e1e39]::on_disk_cache::CacheDecoder>>::decode
  32:     0x7ff9bb0c45bf - <&[rustc_middle[c72282b761ffb2ca]::thir::abstract_const::Node] as rustc_serialize[979d5f7f20b036c4]::serialize::Decodable<rustc_query_impl[fcbe4ce9962e1e39]::on_disk_cache::CacheDecoder>>::decode
  33:     0x7ff9baf9f924 - <&[rustc_middle[c72282b761ffb2ca]::thir::abstract_const::Node] as rustc_serialize[979d5f7f20b036c4]::serialize::Decodable<rustc_query_impl[fcbe4ce9962e1e39]::on_disk_cache::CacheDecoder>>::decode
  34:     0x7ff9bb061c06 - <&[rustc_middle[c72282b761ffb2ca]::thir::abstract_const::Node] as rustc_serialize[979d5f7f20b036c4]::serialize::Decodable<rustc_query_impl[fcbe4ce9962e1e39]::on_disk_cache::CacheDecoder>>::decode
  35:     0x7ff9b77a96cf - <rustc_driver[2389871ec3bd2ddd]::args::Error as core[97cc336334fd47ab]::fmt::Debug>::fmt
  36:     0x7ff9b77853a9 - <rustc_mir_dataflow[3acb063bbaa902c6]::impls::liveness::MaybeLiveLocals as rustc_mir_dataflow[3acb063bbaa902c6]::framework::AnalysisDomain>::initialize_start_block
  37:     0x7ff9b77fbf75 - <rustc_driver[2389871ec3bd2ddd]::Compilation as core[97cc336334fd47ab]::fmt::Debug>::fmt
  38:     0x7ff9b77a5b70 - <rustc_mir_dataflow[3acb063bbaa902c6]::impls::liveness::MaybeLiveLocals as rustc_mir_dataflow[3acb063bbaa902c6]::framework::AnalysisDomain>::initialize_start_block
  39:     0x7ff9b777d8a7 - <rustc_mir_dataflow[3acb063bbaa902c6]::impls::liveness::MaybeLiveLocals as rustc_mir_dataflow[3acb063bbaa902c6]::framework::AnalysisDomain>::initialize_start_block
  40:     0x7ff9b77ebc16 - <rustc_metadata[b2f2848d139875d1]::rmeta::encoder::EncodeContext as rustc_serialize[979d5f7f20b036c4]::serialize::Encoder>::emit_raw_bytes
  41:     0x7ff9b77ae7f8 - <rustc_driver[2389871ec3bd2ddd]::args::Error as core[97cc336334fd47ab]::fmt::Debug>::fmt
  42:     0x7ff9cf8aee2c - std::sys::windows::thread::Thread::new::h811e7c4461002a6b
  43:     0x7ffa33f754e0 - BaseThreadInitThunk
  44:     0x7ffa350e485b - RtlUserThreadStart

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/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: rustc 1.63.0-nightly (1fede1753 2022-05-28) running on x86_64-pc-windows-msvc

note: compiler flags: --crate-type bin -C embed-bitcode=no -C debuginfo=2 -C incremental

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

query stack during panic:
#0 [deref_mir_constant] deref constant
#1 [check_match] match-checking `main`
#2 [analysis] running analysis passes on this crate
end of query stack
error: could not compile `tempdir`

[matthiaskrgr]

duplicate of #83085 ?

[Julian-Wollersberger]

Yes, seems to be a duplicate.