compiler bug: const expr(...) of type X has size 20 instead of 24

[conradkleinespel]

Hello every (reading this) 😃

I seem to have encountered a compiler bug. As explained in the bug report docs, I am reporting this here.

Here's my rustc version (on 64bits Linux Ubuntu 14.04):

rustc 0.13.0-nightly (193390d0e 2014-12-11 22:56:54 +0000)

I am compiling this through Cargo:

cargo 0.0.1-pre-nightly (0f6667c 2014-12-08 21:19:01 +0000)

Here's a backtrace of the error:

error: internal compiler error: const expr(81: Check::Chars('<', '\x00', '\x00', '\x00')) of type Check has size 20 instead of 24
note: the compiler unexpectedly panicked. this is a bug.
note: we would appreciate a bug report: http://doc.rust-lang.org/complement-bugreport.html
note: run with `RUST_BACKTRACE=1` for a backtrace
task 'rustc' panicked at 'Box<Any>', /home/rustbuild/src/rust-buildbot/slave/nightly-linux/build/src/libsyntax/diagnostic.rs:188

stack backtrace:
   1:     0x7fcec950a500 - rt::backtrace::imp::write::heed5901f9756dd23BOx
   2:     0x7fcec950d740 - failure::on_fail::ha44d264deefff4481fy
   3:     0x7fcec915ef30 - unwind::begin_unwind_inner::h8d953f2c1d079705CJc
   4:     0x7fcec6bad040 - unwind::begin_unwind::h6666496483973781562
   5:     0x7fcec6bad8f0 - diagnostic::Handler::bug::h3a50c284fdf4e0a0baF
   6:     0x7fcec7763c90 - session::Session::bug::h961d19b73812d5bclMz
   7:     0x7fcec81efd40 - trans::consts::const_expr::hfa0dfd22263a486eY9n
   8:     0x7fcec81f8d20 - trans::consts::const_expr_unadjusted::closure.43393
   9:     0x7fcec81f7b60 - trans::expr::with_field_tys::h14927854885479319893
  10:     0x7fcec81f2800 - trans::consts::const_expr_unadjusted::h8c6ef2cbf874918a5lo
  11:     0x7fcec81efd40 - trans::consts::const_expr::hfa0dfd22263a486eY9n
  12:     0x7fcec81f2800 - trans::consts::const_expr_unadjusted::h8c6ef2cbf874918a5lo
  13:     0x7fcec81efd40 - trans::consts::const_expr::hfa0dfd22263a486eY9n
  14:     0x7fcec81f2800 - trans::consts::const_expr_unadjusted::h8c6ef2cbf874918a5lo
  15:     0x7fcec81efd40 - trans::consts::const_expr::hfa0dfd22263a486eY9n
  16:     0x7fcec814f120 - trans::base::get_item_val::h5e961c6ea5c9b50aGhv
  17:     0x7fcec814c020 - trans::base::trans_item::h567773db3b83315aeMu
  18:     0x7fcec82135a0 - trans::base::trans_mod::hc21a44b9f586bc03JRu
  19:     0x7fcec8217430 - trans::base::trans_crate::h03fccece3ec7cb85oIv
  20:     0x7fcec9946540 - driver::phase_4_translate_to_llvm::hb8e7de445fc1ade7VCa
  21:     0x7fcec992b260 - driver::compile_input::hf96889ff0bafd855pba
  22:     0x7fcec99c8070 - run_compiler::h9db34658886d7891EYb
  23:     0x7fcec99c7f60 - run::closure.21438
  24:     0x7fcec99d9970 - task::TaskBuilder::try_future::closure.22892
  25:     0x7fcec94e2980 - task::TaskBuilder::spawn_internal::closure.30605
  26:     0x7fcec915cbd0 - task::Task::spawn::closure.5728
  27:     0x7fcec91ba250 - rust_try_inner
  28:     0x7fcec91ba240 - rust_try
  29:     0x7fcec915ccb0 - unwind::try::hf2f7fcf7ecc46c43Tyc
  30:     0x7fcec915ca70 - task::Task::run::h911f3b3bbb0c433efKb
  31:     0x7fcec915c660 - task::Task::spawn::closure.5704
  32:     0x7fcec915e0b0 - thread::thread_start::h051da3e5b33a422fw1b
  33:     0x7fcec40480c0 - start_thread
  34:     0x7fcec8e22ec9 - __clone
  35:                0x0 - <unknown>

Could not compile `parser`.

Just in case it could help, here's the code I am trying to compile (the start of a HTML lexer with a state transition table):

// Lookahead of 3 symbols, which allows to see "!--" for a comment.

enum State {
    General,
    TagName,
    TagAttributeName,
    TagAttributeValue,
    Text,
    Doctype,
    Comment
}

enum Check {
    Function(fn(c1: char, c2: char, c3: char, c4: char) -> bool),
    Chars(char, char, char, char)
}

struct Transition {
    from: State,
    to: State,
    lookahead: u8,
    through: Check,
    save_char: bool,
    save_previous_token: bool
}

static transition_table: &'static [Transition] = &[
    Transition {
        from: State::General,
        to: State::TagName,
        lookahead: 1,
        through: Check::Chars('<', '\0', '\0', '\0'),
        save_char: false,
        save_previous_token: false,
    }
];

fn main() {
    let mut stdin = std::io::stdio::stdin();

    for line_result in stdin.lock().lines() {
        match line_result {
            Ok(line) => {
                let slice = line.as_slice().slice_to(line.len() - 1);
                println!("{}", slice);
            },
            Err(err) => {
                println!("{}", err);
                return;
            }
        }
    }
}

Hopefully, this can help. Please feel free to ask for more information if you need :-)

[nodakai]

Seems like the enum tags are padded differently.

enum E {
    F(i64),
    C(i32, i32, i32, i32)
}

static T: &'static [E] = &[
    E::C(0,0,0,0)
];

fn main() { }

• http://is.gd/ksq8Ss [playpen]

{ i8, i32, i32, i32, i32, [0 x i8] } { i8 1, i32 0, i32 0, i32 0, i32 0, [0 x i8] undef }
{ i8, [7 x i8], [2 x i64] } undef
error: internal compiler error: const expr(31: E::C(0, 0, 0, 0)) of type E has size 20 instead of 24
note: the compiler unexpectedly panicked. this is a bug.

[dotdash]

Both examples compile fine with rustc 1.0.0-nightly (fed12499e 2015-03-03) (built 2015-03-04)