ICE when combining wrong syntax with Unicode string literal

[eliasrg]

In syntactically erroneous inputs, non-ASCII string literals can cause a compiler panic.

Being a dilettante with fingers used to C++, I tried to initialize a struct without calling its new method, and it so happened that I was passing it a non-ASCII string. This gave me a compiler panic. Here's a small example:

struct X {}

fn f() {
    let x = X("ö");
}

Meta

I am using the Manjaro (Arch Linux) rustpackage, version 1:1.37.0-2.

rustc --version --verbose:

rustc 1.37.0
binary: rustc
commit-hash: unknown
commit-date: unknown
host: x86_64-unknown-linux-gnu
release: 1.37.0
LLVM version: 8.0

Backtrace:

thread 'rustc' panicked at 'byte index 38 is not a char boundary; it is inside 'ö' (bytes 37..39) of `struct X {}

fn f() {
    let x = X("ö");
}
`', src/libcore/str/mod.rs:2034:5
stack backtrace:
   0:     0x7f028b22db8b - <unknown>
   1:     0x7f028b22d867 - <unknown>
   2:     0x7f028a3914f1 - <unknown>
   3:     0x7f028b22e3e9 - std::panicking::rust_panic_with_hook::h4e663330759b90e1
   4:     0x7f028b22de82 - <unknown>
   5:     0x7f028b22dd66 - rust_begin_unwind
   6:     0x7f028b25812d - core::panicking::panic_fmt::ha8e419005b06d9fa
   7:     0x7f028b25a7a0 - core::str::slice_error_fail::h4de83ee694f497ba
   8:     0x7f0289a31332 - rust_metadata_syntax_1baa2f1ef67248f5354eb1ad9534ec0
   9:     0x7f0289a69c6a - syntax::source_map::SourceMap::span_to_snippet::h194946e102592953
  10:     0x7f028955c867 - <unknown>
  11:     0x7f028955a4fd - <unknown>
  12:     0x7f02895a9a1f - <unknown>
  13:     0x7f02895a96d2 - <unknown>
  14:     0x7f02895a87a5 - <unknown>
  15:     0x7f02895adc33 - <unknown>
  16:     0x7f02895adc48 - <unknown>
  17:     0x7f02895a3db2 - <unknown>
  18:     0x7f02895a78ba - <unknown>
  19:     0x7f02895898e4 - <rustc_resolve::Resolver as syntax::visit::Visitor>::visit_fn::h423a6899b245d8eb
  20:     0x7f028953f32c - rust_metadata_rustc_resolve_5579cc0878d821c85113ee4c903d2100
  21:     0x7f0289597a0c - <unknown>
  22:     0x7f028958f9cc - rustc_resolve::Resolver::resolve_crate::h7850549a32dca50e
  23:     0x7f028af65cc4 - <unknown>
  24:     0x7f028af73dcc - rustc_interface::queries::<impl rustc_interface::interface::Compiler>::expansion::hc3bebb558c007928
  25:     0x7f028af74bb4 - rustc_interface::queries::<impl rustc_interface::interface::Compiler>::lower_to_hir::h4f94678c772d58ae
  26:     0x7f028af751d2 - rustc_interface::queries::<impl rustc_interface::interface::Compiler>::prepare_outputs::h3c5b38fbb69a9154
  27:     0x7f028b2d8f39 - <unknown>
  28:     0x7f028b23f31a - __rust_maybe_catch_panic
  29:     0x7f028b2df729 - <unknown>
  30:     0x7f028b210d6f - rust_metadata_std_d72cd6cf31ff9bd7b7e3914e0cf9c8c9
  31:     0x7f028b23def0 - <unknown>
  32:     0x7f02897e257f - start_thread
  33:     0x7f028b0fd0e3 - __clone
  34:                0x0 - <unknown>
query stack during panic:
end of query stack

[Centril]

Reduced:

struct X {}
const Y: X = X("ö");

Backtrace:

   Compiling playground v0.0.1 (/playground)
thread 'rustc' panicked at 'byte index 30 is not a char boundary; it is inside 'ö' (bytes 29..31) of `struct X {}

const Y: X = X("ö");`', src/libcore/str/mod.rs:2034:5
stack backtrace:
   0: backtrace::backtrace::libunwind::trace
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.29/src/backtrace/libunwind.rs:88
   1: backtrace::backtrace::trace_unsynchronized
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.29/src/backtrace/mod.rs:66
   2: std::sys_common::backtrace::_print
             at src/libstd/sys_common/backtrace.rs:47
   3: std::sys_common::backtrace::print
             at src/libstd/sys_common/backtrace.rs:36
   4: std::panicking::default_hook::{{closure}}
             at src/libstd/panicking.rs:200
   5: std::panicking::default_hook
             at src/libstd/panicking.rs:214
   6: rustc::util::common::panic_hook
   7: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:481
   8: std::panicking::continue_panic_fmt
             at src/libstd/panicking.rs:384
   9: rust_begin_unwind
             at src/libstd/panicking.rs:311
  10: core::panicking::panic_fmt
             at src/libcore/panicking.rs:85
  11: core::str::slice_error_fail
             at src/libcore/str/mod.rs:0
  12: core::str::traits::<impl core::slice::SliceIndex<str> for core::ops::range::RangeFrom<usize>>::index::{{closure}}
  13: syntax::source_map::SourceMap::span_to_snippet
  14: rustc_resolve::diagnostics::<impl rustc_resolve::Resolver>::smart_resolve_context_dependent_help::{{closure}}
  15: rustc_resolve::diagnostics::<impl rustc_resolve::Resolver>::smart_resolve_report_errors
  16: rustc_resolve::Resolver::smart_resolve_path_fragment::{{closure}}
  17: rustc_resolve::Resolver::smart_resolve_path_fragment
  18: rustc_resolve::Resolver::smart_resolve_path
  19: rustc_resolve::Resolver::resolve_expr
  20: rustc_resolve::Resolver::resolve_expr
  21: rustc_resolve::Resolver::resolve_item
  22: rustc_resolve::Resolver::resolve_crate
  23: rustc::util::common::time
  24: rustc_interface::passes::configure_and_expand_inner
  25: rustc_interface::passes::configure_and_expand::{{closure}}
  26: rustc_data_structures::box_region::PinnedGenerator<I,A,R>::new
  27: rustc_interface::passes::configure_and_expand
  28: rustc_interface::queries::Query<T>::compute
  29: rustc_interface::queries::Query<T>::compute
  30: rustc_interface::queries::Query<T>::compute
  31: rustc_interface::queries::<impl rustc_interface::interface::Compiler>::prepare_outputs
  32: rustc_interface::interface::run_compiler_in_existing_thread_pool
  33: std::thread::local::LocalKey<T>::with
  34: scoped_tls::ScopedKey<T>::set
  35: syntax::with_globals
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
query stack during panic:
end of query stack

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/blob/master/CONTRIBUTING.md#bug-reports

note: rustc 1.37.0 (eae3437df 2019-08-13) running on x86_64-unknown-linux-gnu

note: compiler flags: -C codegen-units=1 -C debuginfo=2 --crate-type lib

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

error: Could not compile `playground`.

To learn more, run the command again with --verbose.

[Centril]

Cannot reproduce on beta or nightly (1.39.0 both).

[pnkfelix]

triage: P-medium. Would be good to identify point where it was fixed by bisection, and maybe add a test if one doesn't already exist. Removing nomination.

[goffrie]

Fixed by #63508, presumably (it bisected to a rollup).