ICE in subst.rs (task 'rustc' failed at 'index out of bounds: the len is 1 but the index is 1', /home/rustbuild/src/rust-buildbot/slave/nightly-linux/build/src/librustc/middle/subst.rs:420

[pythonesque]

Edited with a (reasonably) minimal testcase below. Reproducible with rustc 0.12.0-pre-nightly (f15d6d2 2014-07-20 22:46:29 +0000) on ArchLinux on a Macbook Pro on https://github.com/pythonesque/mud.rs/blob/cee7a78e449a507f3faacf4de16232fed7df5d29/src/main.rs

#![feature(unsafe_destructor)]

fn main() {
    trait Trait<T> {}
    struct Struct<S>(S);

    #[unsafe_destructor]
    impl<S, T: Trait<S>> Drop for Struct<T> {
        fn drop(&mut self) {}
    }
    Struct(());
}

---

% RUST_BACKTRACE=1 cargo build          
   Compiling mud v0.1.0 (file:/home/$HOME/dev/personal/mud.rs)
error: internal compiler error: unexpected failure
note: the compiler hit an unexpected failure path. 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' failed at 'index out of bounds: the len is 1 but the index is 1', /home/rustbuild/src/rust-buildbot/slave/nightly-linux/build/src/librustc/middle/subst.rs:420

stack backtrace:
   1:     0x7fc6f7010d80 - rt::backtrace::imp::write::h86f9dc98984aaec9A7p
   2:     0x7fc6f7014220 - failure::on_fail::h03e0e71824a692d7Psq
   3:     0x7fc6fb06b5d0 - unwind::begin_unwind_inner::h9ad6a00aad1794b670d
   4:     0x7fc6fb06b230 - unwind::begin_unwind_fmt::ha76f7ed4dc0c1e80AYd
   5:     0x7fc6fb06b1f0 - rust_begin_unwind
   6:     0x7fc6fb0aecf0 - failure::begin_unwind::hb5438e30e14a068bKsj
   7:     0x7fc6fb0b25a0 - failure::fail_bounds_check::hc18c7c2fe9e6f28aWqj
   8:     0x7fc6fbc49ad0 - middle::typeck::check::vtable::lookup_vtables::h23a9c732dd2dfb40HZI
   9:     0x7fc6fbb58ae0 - middle::typeck::check::vtable::trans_resolve_method::h924e60b00e7cb248zFK
  10:     0x7fc6fbac4d40 - middle::trans::base::get_res_dtor::h148cab4191686935MYa
  11:     0x7fc6fbac4650 - middle::trans::glue::trans_struct_drop::h6344c728b401d014seY
  12:     0x7fc6fbac45e0 - middle::trans::glue::trans_struct_drop_flag::closure.$x22closure$x22$LP$115800$RP$
  13:     0x7fc6fbac4290 - middle::trans::base::with_cond::hf7e5084ee7d2350c9Rb
  14:     0x7fc6fbabe570 - middle::trans::glue::make_drop_glue::as_closure.$x22as_closure$x22$LP$115766$RP$
  15:     0x7fc6fbabda10 - middle::trans::glue::make_generic_glue::he9f27f4c0d1a742eIHY
  16:     0x7fc6fbab9aa0 - middle::trans::glue::get_drop_glue::h54121c91b866dd1dL4X
  17:     0x7fc6fbab9930 - middle::trans::glue::drop_ty::h21df00a92156d02dr2X
  18:     0x7fc6fbbec520 - middle::trans::cleanup::DropValue.Cleanup::trans::h2dd9d2d61ef253daEJv
  19:     0x7fc6fbaae220 - middle::trans::cleanup::FunctionContext<'a>.CleanupMethods<'a>::pop_and_trans_ast_cleanup_scope::h8ca861c1072d0b147ou
  20:     0x7fc6fbaad280 - middle::trans::controlflow::trans_stmt::h378fa113b41a1fa4jqX
  21:     0x7fc6fbaaee80 - middle::trans::controlflow::trans_block::h10c5d442d00e4096zvX
  22:     0x7fc6fbb62290 - middle::trans::base::trans_closure::h7e6f5cbf01f38b24Fwc
  23:     0x7fc6fbaa2310 - middle::trans::base::trans_fn::hac67266cb4b6c569lJc
  24:     0x7fc6fba9d2d0 - middle::trans::base::trans_item::h1d4f0e354901b9f6H1c
  25:     0x7fc6fbb72200 - middle::trans::base::trans_crate::h59305eb6a53411cbAUd
  26:     0x7fc6fbf934d0 - driver::driver::phase_4_translate_to_llvm::h163f2ef73368e89dbxw
  27:     0x7fc6fbf8a1d0 - driver::driver::compile_input::h2714688c818fc93cD9v
  28:     0x7fc6fc035640 - driver::run_compiler::hdc3f7737fe0af6fbDiz
  29:     0x7fc6fc035550 - driver::main_args::closure.$x22closure$x22$LP$138065$RP$
  30:     0x7fc6fc048bf0 - task::TaskBuilder<S>::try_future::closure.$x22closure$x22$LP$139209$RP$
  31:     0x7fc6fc0489b0 - task::TaskBuilder<S>::spawn_internal::closure.$x22closure$x22$LP$139186$RP$
  32:     0x7fc6fb3cc210 - task::spawn_opts::closure.$x22closure$x22$LP$8165$RP$
  33:     0x7fc6fb0c2ab0 - rust_try
  34:     0x7fc6fb068680 - unwind::try::h0fa4943ea00a482ewPd
  35:     0x7fc6fb0683e0 - task::Task::run::hf8555f915ed22c94S0c
  36:     0x7fc6fb3cc000 - task::spawn_opts::closure.$x22closure$x22$LP$8111$RP$
  37:     0x7fc6fb06a660 - thread::thread_start::he6fee52c0ee35cbcqnd
  38:     0x7fc6f6378060 - start_thread
  39:     0x7fc6fad33489 - __clone
  40:                0x0 - <unknown>

Could not execute process rustc /home/$HOME/dev/personal/mud.rs/src/main.rs --crate-name mud --crate-type bin --out-dir /home/$HOME/dev/personal/mud.rs/target -L /home/$HOME/dev/personal/mud.rs/target -L /home/$HOME/dev/personal/mud.rs/target/deps (status=101)

[pythonesque]

Updated with a minimal testcase.

[seanmonstar]

I've gotten the same error, with different code, and slightly different backtrace.

#![feature(overloaded_calls)]
use std::fmt;
use std::ops::Fn;

pub struct Con<V> {
    data: V
}

pub static Three: Con<&'static [u8]> = Con {
    data: &[3]
};

impl<T: fmt::Show, V: Vector<u8>> Fn<(T,), ConText<T>> for Con<V> {
    #[rust_call_abi_hack]
    fn call(&self, (show,): (T,)) -> ConText<T> {
        ConText {
            data: Vec::from_slice(self.data.as_slice()),
            subject: show
        }
    }
}

pub struct ConText<T> {
    data: Vec<u8>,
    subject: T
}

#[test]
fn test() {
    let f = Three("foo");
}

task 'rustc' failed at 'index out of bounds: the len is 0 but the index is 1', /home/rustbuild/src/rust-buildbot/slave/nightly-linux/build/src/librustc/middle/subst.rs:420

stack backtrace:
   1:     0x7ff0d4304350 - rt::backtrace::imp::write::ha4acd61ef18a62aeDUp
   2:     0x7ff0d4307640 - failure::on_fail::h147f48194e5619a2Afq
   3:     0x7ff0d83a4440 - unwind::begin_unwind_inner::h60a9644c6207f9d1iTd
   4:     0x7ff0d83a40e0 - unwind::begin_unwind_fmt::hbf6376b6994c2990rQd
   5:     0x7ff0d83a40a0 - rust_begin_unwind
   6:     0x7ff0d83e93f0 - failure::begin_unwind::h8aa4b293b7062f1bVWj
   7:     0x7ff0d83ecd70 - failure::fail_bounds_check::h7f693f45d174b9107Uj
   8:     0x7ff0d8e130b0 - middle::trans::common::find_vtable::hd49bb8bbb24cd20e223
   9:     0x7ff0d8db6d20 - middle::trans::meth::trans_method_callee::h13fac7d98a0aa817Hch
  10:     0x7ff0d8de0130 - middle::trans::callee::trans_method_call::closure.$x22closure$x22$LP$112159$RP$
  11:     0x7ff0d8db5090 - middle::trans::callee::trans_call_inner::ha2a49241f2d4197b6zZ
  12:     0x7ff0d8ddfa30 - middle::trans::callee::trans_method_call::h79aeb2e43c302a99mvZ
  13:     0x7ff0d8dee4b0 - middle::trans::expr::trans_rvalue_dps_unadjusted::h45f9ea70500363ffVm1
  14:     0x7ff0d8ded6c0 - middle::trans::expr::trans_unadjusted::h8e92248b02e688feVP0
  15:     0x7ff0d8dacc30 - middle::trans::expr::trans::h9131eec42a5ec2d5tw0
  16:     0x7ff0d8de6090 - middle::trans::callee::trans_args::h0beaffe0f9f6a5a97ZZ
  17:     0x7ff0d8db5090 - middle::trans::callee::trans_call_inner::ha2a49241f2d4197b6zZ
  18:     0x7ff0d8dded60 - middle::trans::callee::trans_call::h8f463c254e0698bdeuZ
  19:     0x7ff0d8dee4b0 - middle::trans::expr::trans_rvalue_dps_unadjusted::h45f9ea70500363ffVm1
  20:     0x7ff0d8dab3e0 - middle::trans::expr::trans_into::h0c47537ec0cfc708ys0
  21:     0x7ff0d8e020f0 - middle::trans::expr::trans_adt::h087e5bbda34e7217wX1
  22:     0x7ff0d8e05cd0 - middle::trans::expr::trans_rec_or_struct::closure.$x22closure$x22$LP$112427$RP$
  23:     0x7ff0d8dee4b0 - middle::trans::expr::trans_rvalue_dps_unadjusted::h45f9ea70500363ffVm1
  24:     0x7ff0d8dab3e0 - middle::trans::expr::trans_into::h0c47537ec0cfc708ys0
  25:     0x7ff0d8dab9e0 - middle::trans::controlflow::trans_block::h5bb191e037b70d18OBW
  26:     0x7ff0d8e5c430 - middle::trans::base::trans_closure::hc88ea69250b3efe49Gb
  27:     0x7ff0d8d9f820 - middle::trans::base::trans_fn::h80584f1466eb039bfTb
  28:     0x7ff0d8d9fe50 - middle::trans::monomorphize::monomorphic_fn::h61dcafaef40b50d8xZV
  29:     0x7ff0d8dd47f0 - middle::trans::callee::trans_fn_ref_with_vtables::h78751fb3aefc06f7R8Y
  30:     0x7ff0d8dd1e50 - middle::trans::callee::trans_fn_ref::h75cc428eb61c9be0wVY
  31:     0x7ff0d8db6d20 - middle::trans::meth::trans_method_callee::h13fac7d98a0aa817Hch
  32:     0x7ff0d8e0b2b0 - middle::trans::expr::trans_overloaded_call::closure.$x22closure$x22$LP$112492$RP$
  33:     0x7ff0d8db5090 - middle::trans::callee::trans_call_inner::ha2a49241f2d4197b6zZ
  34:     0x7ff0d8dee4b0 - middle::trans::expr::trans_rvalue_dps_unadjusted::h45f9ea70500363ffVm1
  35:     0x7ff0d8dab3e0 - middle::trans::expr::trans_into::h0c47537ec0cfc708ys0
  36:     0x7ff0d8e88460 - middle::trans::_match::store_local::closure.$x22closure$x22$LP$115578$RP$
  37:     0x7ff0d8e88100 - middle::trans::_match::mk_binding_alloca::h8111926511742816842
  38:     0x7ff0d8e567e0 - middle::trans::_match::store_local::hc16c4829486bf931D3e
  39:     0x7ff0d8daa930 - middle::trans::base::init_local::he0e6f8d8a560aba7hXa
  40:     0x7ff0d8da9f10 - middle::trans::controlflow::trans_stmt::h8c8ab5f00528c12dywW
  41:     0x7ff0d8dab9e0 - middle::trans::controlflow::trans_block::h5bb191e037b70d18OBW
  42:     0x7ff0d8e5c430 - middle::trans::base::trans_closure::hc88ea69250b3efe49Gb
  43:     0x7ff0d8d9f820 - middle::trans::base::trans_fn::h80584f1466eb039bfTb
  44:     0x7ff0d8d9a7f0 - middle::trans::base::trans_item::h1a8eb49262b769baKac
  45:     0x7ff0d8e6c010 - middle::trans::base::trans_crate::h6d9aacd380ee9d42H3c
  46:     0x7ff0d9299210 - driver::driver::phase_4_translate_to_llvm::h83f7bbcd209edddddiu
  47:     0x7ff0d928f950 - driver::driver::compile_input::h67e0103484fb9c9dTUt
  48:     0x7ff0d933e290 - driver::run_compiler::ha05dba9ca20aca52iZw
  49:     0x7ff0d933e1a0 - driver::main_args::closure.$x22closure$x22$LP$134272$RP$
  50:     0x7ff0d9351060 - task::TaskBuilder<S>::try_future::closure.$x22closure$x22$LP$135416$RP$
  51:     0x7ff0d9350e40 - task::TaskBuilder<S>::spawn_internal::closure.$x22closure$x22$LP$135393$RP$
  52:     0x7ff0d86f8590 - task::spawn_opts::closure.$x22closure$x22$LP$8187$RP$
  53:     0x7ff0d83fcc30 - rust_try
  54:     0x7ff0d83a1750 - unwind::try::h2d0dc9479d15367bnHd
  55:     0x7ff0d83a14b0 - task::Task::run::h854afb19e4abdac4dSc
  56:     0x7ff0d86f8380 - task::spawn_opts::closure.$x22closure$x22$LP$8133$RP$
  57:     0x7ff0d83a3510 - thread::thread_start::h2a1fd0502c67d799hfd
  58:     0x7ff0d36880c0 - start_thread
  59:     0x7ff0d80732d9 - __clone
  60:                0x0 - <unknown>

Seeing the last step in trace before unwind is 8, I turned on RUST_LOG=rustc::middle::trans::common=debug, and this is the last line before the failure.

DEBUG:rustc::middle::trans::common: find_vtable(n_param=middle::typeck::param_index{space: TypeSpace, index: 1u}, n_bound=0, ps=param_substs(Substs[types=[[&'static str, &'static [u8]];[];[]], regions=[[];[];[]]]))

[pythonesque]

I actually suspect that is a different error, since your code, error message (they are both "index out of bound" errors, but yours has length 0, not length 1), and stack trace are all different.

[seanmonstar]

True, they differ slightly, and if it completely unrelated I can open a second bug. But it seemed the cause is that vtables are somehow losing or not keeping some entries, and that may be causing both.

Dupe of #14695.