thread 'rustc' panicked at 'no label after fn', compiler/rustc_span/src/source_map.rs:958:18

[Badel2]

I'm seeing an internal compiler error on the following input, found by fuzz-rustc:

Code

fn�a<e>(){fn�p(){e}}

Error output

   Compiling playground v0.0.1 (/playground)
error: unknown start of token: \u{fffd}
 --> src/lib.rs:1:3
  |
1 | fn�a<e>(){fn�p(){e}}
  |   ^

error: unknown start of token: \u{fffd}
 --> src/lib.rs:1:13
  |
1 | fn�a<e>(){fn�p(){e}}
  |             ^

thread 'rustc' panicked at 'no label after fn', compiler/rustc_span/src/source_map.rs:958:18

The ICE happens after correctly reporting the error "unknown start of token", so low priority. I guess that one part of the code treats � as whitespace, while another part of the code treats it as not whitespace, causing a logic error with this input. Affected versions: nightly 2022-02-26 and beta 1.60.0-beta1 are affected, but stable 1.59.0 does not ICE.

Backtrace

   Compiling playground v0.0.1 (/playground)
error: unknown start of token: \u{fffd}
 --> src/lib.rs:1:3
  |
1 | fn�a<e>(){fn�p(){e}}
  |   ^

error: unknown start of token: \u{fffd}
 --> src/lib.rs:1:13
  |
1 | fn�a<e>(){fn�p(){e}}
  |             ^

thread 'rustc' panicked at 'no label after fn', compiler/rustc_span/src/source_map.rs:958:18
stack backtrace:
   0:     0x7fd3804f4c1c - std::backtrace_rs::backtrace::libunwind::trace::h7c3070cb81dd0024
                               at /rustc/10cc7a6d031fd607f594f4c7af113bfaa9a879e9/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
   1:     0x7fd3804f4c1c - std::backtrace_rs::backtrace::trace_unsynchronized::h129f364a0750ab76
                               at /rustc/10cc7a6d031fd607f594f4c7af113bfaa9a879e9/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7fd3804f4c1c - std::sys_common::backtrace::_print_fmt::h3c104a8a0383955d
                               at /rustc/10cc7a6d031fd607f594f4c7af113bfaa9a879e9/library/std/src/sys_common/backtrace.rs:66:5
   3:     0x7fd3804f4c1c - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h940a7f8f5de484d7
                               at /rustc/10cc7a6d031fd607f594f4c7af113bfaa9a879e9/library/std/src/sys_common/backtrace.rs:45:22
   4:     0x7fd38055483c - core::fmt::write::h27ac5c2512a100f3
                               at /rustc/10cc7a6d031fd607f594f4c7af113bfaa9a879e9/library/core/src/fmt/mod.rs:1190:17
   5:     0x7fd3804e4d48 - std::io::Write::write_fmt::hd4b8be36d77e5a08
                               at /rustc/10cc7a6d031fd607f594f4c7af113bfaa9a879e9/library/std/src/io/mod.rs:1657:15
   6:     0x7fd3804f8bf7 - std::sys_common::backtrace::_print::h65e4e62ae12d787f
                               at /rustc/10cc7a6d031fd607f594f4c7af113bfaa9a879e9/library/std/src/sys_common/backtrace.rs:48:5
   7:     0x7fd3804f8bf7 - std::sys_common::backtrace::print::he64debcdf0537427
                               at /rustc/10cc7a6d031fd607f594f4c7af113bfaa9a879e9/library/std/src/sys_common/backtrace.rs:35:9
   8:     0x7fd3804f8bf7 - std::panicking::default_hook::{{closure}}::hcd202f51b1ab7d9b
                               at /rustc/10cc7a6d031fd607f594f4c7af113bfaa9a879e9/library/std/src/panicking.rs:295:22
   9:     0x7fd3804f88af - std::panicking::default_hook::hce3c74efe341dfb8
                               at /rustc/10cc7a6d031fd607f594f4c7af113bfaa9a879e9/library/std/src/panicking.rs:314:9
  10:     0x7fd380c90f91 - rustc_driver[27fdb45c6d63455f]::DEFAULT_HOOK::{closure#0}::{closure#0}
  11:     0x7fd3804f94c6 - std::panicking::rust_panic_with_hook::ha0edfd54e80bef59
                               at /rustc/10cc7a6d031fd607f594f4c7af113bfaa9a879e9/library/std/src/panicking.rs:702:17
  12:     0x7fd3804f9177 - std::panicking::begin_panic_handler::{{closure}}::h968f7b19f1564476
                               at /rustc/10cc7a6d031fd607f594f4c7af113bfaa9a879e9/library/std/src/panicking.rs:588:13
  13:     0x7fd3804f50e4 - std::sys_common::backtrace::__rust_end_short_backtrace::h4b69be26095274cc
                               at /rustc/10cc7a6d031fd607f594f4c7af113bfaa9a879e9/library/std/src/sys_common/backtrace.rs:138:18
  14:     0x7fd3804f8e89 - rust_begin_unwind
                               at /rustc/10cc7a6d031fd607f594f4c7af113bfaa9a879e9/library/std/src/panicking.rs:584:5
  15:     0x7fd3804c1913 - core::panicking::panic_fmt::h74e85b388cc5eea2
                               at /rustc/10cc7a6d031fd607f594f4c7af113bfaa9a879e9/library/core/src/panicking.rs:143:14
  16:     0x7fd380551641 - core::panicking::panic_display::hd8c5c6145f7843ad
                               at /rustc/10cc7a6d031fd607f594f4c7af113bfaa9a879e9/library/core/src/panicking.rs:72:5
  17:     0x7fd3805515eb - core::panicking::panic_str::h5b28b81c4c9b2d81
                               at /rustc/10cc7a6d031fd607f594f4c7af113bfaa9a879e9/library/core/src/panicking.rs:56:5
  18:     0x7fd3804c1786 - core::option::expect_failed::h8786578558ede675
                               at /rustc/10cc7a6d031fd607f594f4c7af113bfaa9a879e9/library/core/src/option.rs:1852:5
  19:     0x7fd381df657d - <rustc_span[559d849e8363120e]::source_map::SourceMap>::generate_fn_name_span
  20:     0x7fd3810b5d75 - <rustc_resolve[d438b2f733e802ab]::Resolver>::into_struct_error
  21:     0x7fd3810b2f0c - <rustc_resolve[d438b2f733e802ab]::Resolver>::report_error
  22:     0x7fd38218110a - <rustc_resolve[d438b2f733e802ab]::Resolver>::resolve_path_with_ribs
  23:     0x7fd38219c4b1 - <rustc_resolve[d438b2f733e802ab]::late::LateResolutionVisitor>::smart_resolve_path_fragment
  24:     0x7fd38219ea1a - <rustc_resolve[d438b2f733e802ab]::late::LateResolutionVisitor>::resolve_expr
  25:     0x7fd382191cbc - <rustc_resolve[d438b2f733e802ab]::late::LateResolutionVisitor as rustc_ast[503e33a30ca156de]::visit::Visitor>::visit_block
  26:     0x7fd382192d6f - <rustc_resolve[d438b2f733e802ab]::late::LateResolutionVisitor as rustc_ast[503e33a30ca156de]::visit::Visitor>::visit_fn
  27:     0x7fd38214898e - rustc_ast[503e33a30ca156de]::visit::walk_item::<rustc_resolve[d438b2f733e802ab]::late::LateResolutionVisitor>
  28:     0x7fd382196468 - <rustc_resolve[d438b2f733e802ab]::late::LateResolutionVisitor>::resolve_item
  29:     0x7fd382191e48 - <rustc_resolve[d438b2f733e802ab]::late::LateResolutionVisitor as rustc_ast[503e33a30ca156de]::visit::Visitor>::visit_block
  30:     0x7fd382192d6f - <rustc_resolve[d438b2f733e802ab]::late::LateResolutionVisitor as rustc_ast[503e33a30ca156de]::visit::Visitor>::visit_fn
  31:     0x7fd38214898e - rustc_ast[503e33a30ca156de]::visit::walk_item::<rustc_resolve[d438b2f733e802ab]::late::LateResolutionVisitor>
  32:     0x7fd382196468 - <rustc_resolve[d438b2f733e802ab]::late::LateResolutionVisitor>::resolve_item
  33:     0x7fd382df80dc - <rustc_resolve[d438b2f733e802ab]::Resolver>::late_resolve_crate
  34:     0x7fd382de17bb - <rustc_session[a6da21e65b3d36fd]::session::Session>::time::<(), <rustc_resolve[d438b2f733e802ab]::Resolver>::resolve_crate::{closure#0}>
  35:     0x7fd382ad3c3e - rustc_interface[e15285c328f6dde8]::passes::configure_and_expand
  36:     0x7fd382ad8f31 - <rustc_interface[e15285c328f6dde8]::queries::Queries>::expansion
  37:     0x7fd382aac479 - <rustc_interface[e15285c328f6dde8]::interface::Compiler>::enter::<rustc_driver[27fdb45c6d63455f]::run_compiler::{closure#1}::{closure#2}, core[c2e0b789170cc5fa]::result::Result<core[c2e0b789170cc5fa]::option::Option<rustc_interface[e15285c328f6dde8]::queries::Linker>, rustc_errors[9da8cfde5692a04f]::ErrorReported>>
  38:     0x7fd382aae33c - rustc_span[559d849e8363120e]::with_source_map::<core[c2e0b789170cc5fa]::result::Result<(), rustc_errors[9da8cfde5692a04f]::ErrorReported>, rustc_interface[e15285c328f6dde8]::interface::create_compiler_and_run<core[c2e0b789170cc5fa]::result::Result<(), rustc_errors[9da8cfde5692a04f]::ErrorReported>, rustc_driver[27fdb45c6d63455f]::run_compiler::{closure#1}>::{closure#1}>
  39:     0x7fd382aabd77 - <scoped_tls[cb501334321ad8d4]::ScopedKey<rustc_span[559d849e8363120e]::SessionGlobals>>::set::<rustc_interface[e15285c328f6dde8]::interface::run_compiler<core[c2e0b789170cc5fa]::result::Result<(), rustc_errors[9da8cfde5692a04f]::ErrorReported>, rustc_driver[27fdb45c6d63455f]::run_compiler::{closure#1}>::{closure#0}, core[c2e0b789170cc5fa]::result::Result<(), rustc_errors[9da8cfde5692a04f]::ErrorReported>>
  40:     0x7fd382a9708d - std[b48f0f8e93cbe429]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[e15285c328f6dde8]::util::run_in_thread_pool_with_globals<rustc_interface[e15285c328f6dde8]::interface::run_compiler<core[c2e0b789170cc5fa]::result::Result<(), rustc_errors[9da8cfde5692a04f]::ErrorReported>, rustc_driver[27fdb45c6d63455f]::run_compiler::{closure#1}>::{closure#0}, core[c2e0b789170cc5fa]::result::Result<(), rustc_errors[9da8cfde5692a04f]::ErrorReported>>::{closure#0}, core[c2e0b789170cc5fa]::result::Result<(), rustc_errors[9da8cfde5692a04f]::ErrorReported>>
  41:     0x7fd382a95619 - <<std[b48f0f8e93cbe429]::thread::Builder>::spawn_unchecked_<rustc_interface[e15285c328f6dde8]::util::run_in_thread_pool_with_globals<rustc_interface[e15285c328f6dde8]::interface::run_compiler<core[c2e0b789170cc5fa]::result::Result<(), rustc_errors[9da8cfde5692a04f]::ErrorReported>, rustc_driver[27fdb45c6d63455f]::run_compiler::{closure#1}>::{closure#0}, core[c2e0b789170cc5fa]::result::Result<(), rustc_errors[9da8cfde5692a04f]::ErrorReported>>::{closure#0}, core[c2e0b789170cc5fa]::result::Result<(), rustc_errors[9da8cfde5692a04f]::ErrorReported>>::{closure#1} as core[c2e0b789170cc5fa]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  42:     0x7fd380505053 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::hd400eedbdf19ac5a
                               at /rustc/10cc7a6d031fd607f594f4c7af113bfaa9a879e9/library/alloc/src/boxed.rs:1854:9
  43:     0x7fd380505053 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::he262f0a88c6384ec
                               at /rustc/10cc7a6d031fd607f594f4c7af113bfaa9a879e9/library/alloc/src/boxed.rs:1854:9
  44:     0x7fd380505053 - std::sys::unix::thread::Thread::new::thread_start::haa0f92689c2258f1
                               at /rustc/10cc7a6d031fd607f594f4c7af113bfaa9a879e9/library/std/src/sys/unix/thread.rs:108:17
  45:     0x7fd380439609 - start_thread
  46:     0x7fd380353293 - clone
  47:                0x0 - <unknown>

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 1.61.0-nightly (10cc7a6d0 2022-02-26) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type lib -C embed-bitcode=no -C codegen-units=1 -C debuginfo=2

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

query stack during panic:
end of query stack
error: could not compile `playground` due to 2 previous errors

[chordtoll]

@rustbot claim

[Alexendoo]

Fixed by #98609, different enough to the added test that I'll mark as needs-test. But anybody feel free to close this if we don't generally add fuzzed inputs to tests