ICE: const expr(8: &*"") of type &'static str has size 8 instead of 16

[rprichard]

Test case:

#[allow(dead_code)]
static X: &'static str = &*"";
fn main() {}

Output:

$ RUST_BACKTRACE=1 rustc test.rs  -O 
@ref8 = internal unnamed_addr constant %str_slice { i8* getelementptr inbounds ([0 x i8]* @str954, i32 0, i32 0), i64 0 }
{ i8*, i8* } undef
error: internal compiler error: const expr(8: &*"") of type &'static str has size 8 instead of 16
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: run with `RUST_BACKTRACE=1` for a backtrace
thread 'rustc' panicked at 'Box<Any>', /home/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libsyntax/diagnostic.rs:189

stack backtrace:
   1:         0x2c97f720 - sys::backtrace::write::h66f3f2784d0f6c5ddgA
   2:         0x2c9a7b80 - panicking::on_panic::h6fdde9e4e9166fe6jaJ
   3:         0x2c8e7c30 - rt::unwind::begin_unwind_inner::hba10c536ef2aae75MQI
   4:         0x29bf70c0 - rt::unwind::begin_unwind::h11287547919384241778
   5:         0x29bf7880 - diagnostic::Handler::bug::hcd811e06453c2215AHD
   6:         0x2a92f0e0 - session::Session::bug::h6899b8b34aff4289tjp
   7:         0x2b684c80 - trans::consts::const_expr::h035f67d1634baae2etn
   8:         0x2b5bdee0 - trans::base::get_item_val::h6996afac4f0d2cd8zdu
   9:         0x2b687ae0 - trans::consts::trans_static::h8a306b81be8d489c68n
  10:         0x2b5bbbf0 - trans::base::trans_item::h84b885e418e4a555QIt
  11:         0x2b6a49c0 - trans::base::trans_crate::h42b5704fc939dd15qEu
  12:         0x2d005970 - driver::phase_4_translate_to_llvm::h73df038fa8e4514eqNa
  13:         0x2cfdfec0 - driver::compile_input::h0de317319ab5c701Hba
  14:         0x2d0aae20 - run_compiler::hffa0c0711e361de8E5b
  15:         0x2d0a9720 - thunk::F.Invoke<A, R>::invoke::h12673221910893163557
  16:         0x2d0a8610 - rt::unwind::try::try_fn::h15130568597725528481
  17:         0x2ca13740 - rust_try_inner
  18:         0x2ca13730 - rust_try
  19:         0x2d0a8910 - thunk::F.Invoke<A, R>::invoke::h3924406537784056782
  20:         0x2c993990 - sys::thread::thread_start::h3734be2229bd3edegEE
  21:         0x268bb0c0 - start_thread
  22:         0x2c560449 - __clone
  23:                0x0 - <unknown>

Compiler version:

rustc 1.0.0-nightly (b47aebe3f 2015-02-26) (built 2015-02-27)
binary: rustc
commit-hash: b47aebe3fc2da06c760fd8ea19f84cbc41d34831
commit-date: 2015-02-26
build-date: 2015-02-27
host: x86_64-unknown-linux-gnu
release: 1.0.0-nightly

This issue has a similar error to that in #20074, but it's not clear to me that it's the same issue. The types involved are different, as are the mismatched size values. I'm also unable to reproduce that issue's failure -- maybe it's fixed already?

[dotdash]

@eddyb is that related to your recent changes?

[eddyb]

@dotdash dereferencing &Unsized in constants never worked, but I made it show up outside the functions as well (giving @gankro some trouble).
The solution would be to make dereferencing &Unsized and referencing Unsized noops.

[frewsxcv]

This is still an issue in Rust 1.0 beta2

~/Downloads $ rustc test.rs
@ref771 = internal unnamed_addr constant %str_slice { i8* getelementptr inbounds ([0 x i8]* @str770, i32 0, i32 0), i64 0 }
{ i8*, i8* } undef
error: internal compiler error: const expr(8: &*"") of type &'static str has size 8 instead of 16
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: run with `RUST_BACKTRACE=1` for a backtrace
thread 'rustc' panicked at 'Box<Any>', /Users/rustbuild/src/rust-buildbot/slave/beta-dist-rustc-mac/build/src/libsyntax/diagnostic.rs:209


~/Downloads $ rustc --version
rustc 1.0.0-beta.2 (e9080ec39 2015-04-16) (built 2015-04-16)

[bluss]

Still in nightly, same ICE

fn main() {
    (*"abc").len();
}

[kbknapp]

I ran into this today as well, so still an issue in rustc 1.7.0-nightly (2bd875d3d 2016-01-19)

if "a" == &*"" {()}

[steveklabnik]

This ICE seems to be fixed on

rustc 1.12.0-nightly (b30eff7ba 2016-08-05)

I have a hunch that this is due to MIR being turned on, though I'm not sure. Please let me know if this still ICEs for you, but closing for now 🎊