compiler error

[arturoc]

just updated rust to latest master and while trying to compile a program that was working before i'm getting:

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 'assertion failed: `(left == right) && (right == left)` (left: `12`, right: `0`)', /home/arturo/Code/rust/src/librustc/middle/ty.rs:2481

the code is rather large, i have tried to reproduce the error in a smaller example but can't find exactly where's the problem, it seems to be related with doing a borrow_mut() on a RefCell but as i said it doesn't happen on a smaller test

this is the backtrace:

stack backtrace:
   1:     0x2b92ca1e5630 - rt::backtrace::imp::write::h8e9eb4c0a425b5a5c0q
   2:     0x2b92ca1e8820 - failure::on_fail::h4325ba604d2e06acTlr
   3:     0x2b92c5d5c980 - unwind::begin_unwind_inner::h58dc61866064edc9Zie
   4:     0x2b92c5d5c620 - unwind::begin_unwind_fmt::hd2c2fac189295ad0pge
   5:     0x2b92c4ca3dd0 - middle::ty::type_contents::tc_ty::h25a65baa252c658f7yF
   6:     0x2b92c4ca3dd0 - middle::ty::type_contents::tc_ty::h25a65baa252c658f7yF
   7:     0x2b92c49f44d0 - middle::ty::type_contents::h9b457050afb365782xF
   8:     0x2b92c4c331b0 - middle::expr_use_visitor::ExprUseVisitor<'d, 't, TYPER>::delegate_consume::h8962338896925635098
   9:     0x2b92c4c33810 - middle::expr_use_visitor::ExprUseVisitor<'d, 't, TYPER>::consume_expr::h8571352652834906512
  10:     0x2b92c4c2d4a0 - middle::expr_use_visitor::ExprUseVisitor<'d, 't, TYPER>::walk_expr::h4231890686328975281
  11:     0x2b92c4c33810 - middle::expr_use_visitor::ExprUseVisitor<'d, 't, TYPER>::consume_expr::h8571352652834906512
  12:     0x2b92c4c339e0 - middle::expr_use_visitor::ExprUseVisitor<'d, 't, TYPER>::walk_block::h4782883345545531812
  13:     0x2b92c4c2d4a0 - middle::expr_use_visitor::ExprUseVisitor<'d, 't, TYPER>::walk_expr::h4231890686328975281
  14:     0x2b92c4c37f50 - middle::trans::_match::create_bindings_map::h7016d3b670778ad74Th
  15:     0x2b92c4baf510 - middle::trans::_match::trans_match::hb6674054b0332fc8IPh
  16:     0x2b92c4b9a810 - middle::trans::expr::trans_rvalue_dps_unadjusted::h4885403a65bbadd16Q3
  17:     0x2b92c4b54980 - middle::trans::expr::trans_into::h5fa2aa27ba5f38abIs2
  18:     0x2b92c4b54f20 - middle::trans::controlflow::trans_block::hcf633bc09a595155wmY
  19:     0x2b92c4c0a8e0 - middle::trans::base::trans_closure::h6af85961afc5e10fvye
  20:     0x2b92c4b45950 - middle::trans::base::trans_fn::ha71ddc353381e3f5iKe
  21:     0x2b92c4b45fa0 - middle::trans::monomorphize::monomorphic_fn::hdc6c7b4578f922f8uJX
  22:     0x2b92c4b80bf0 - middle::trans::callee::trans_fn_ref_with_vtables::h98854ce341dfbb4ald1
  23:     0x2b92c4b7e2c0 - middle::trans::callee::trans_fn_ref::h1ee105fae6943b76tZ0
  24:     0x2b92c4ba38a0 - middle::trans::expr::trans_def::hdd427d1cdf1a3c95vH3
  25:     0x2b92c4b998b0 - middle::trans::expr::trans_unadjusted::h0e3e3a0f0810cd7eFh3
  26:     0x2b92c4b56150 - middle::trans::expr::trans::hb5d2106e56480123Ew2
  27:     0x2b92c4b91c60 - middle::trans::callee::trans_args::h64bca7f588848043aZ1
  28:     0x2b92c4b5e170 - middle::trans::callee::trans_call_inner::hde6eb414bb58985daE1
  29:     0x2b92c4b8c5f0 - middle::trans::callee::trans_method_call::h7e39c5fba92b93feoz1
  30:     0x2b92c4b9a810 - middle::trans::expr::trans_rvalue_dps_unadjusted::h4885403a65bbadd16Q3
  31:     0x2b92c4b54980 - middle::trans::expr::trans_into::h5fa2aa27ba5f38abIs2
  32:     0x2b92c4b53e30 - middle::trans::controlflow::trans_stmt_semi::h1da7aaaee12528e9ClY
  33:     0x2b92c4b53500 - middle::trans::controlflow::trans_stmt::he615239a63278692lhY
  34:     0x2b92c4b54f20 - middle::trans::controlflow::trans_block::hcf633bc09a595155wmY
  35:     0x2b92c4c0a8e0 - middle::trans::base::trans_closure::h6af85961afc5e10fvye
  36:     0x2b92c4b45950 - middle::trans::base::trans_fn::ha71ddc353381e3f5iKe
  37:     0x2b92c4b45fa0 - middle::trans::monomorphize::monomorphic_fn::hdc6c7b4578f922f8uJX
  38:     0x2b92c4b80bf0 - middle::trans::callee::trans_fn_ref_with_vtables::h98854ce341dfbb4ald1
  39:     0x2b92c4b7e2c0 - middle::trans::callee::trans_fn_ref::h1ee105fae6943b76tZ0
  40:     0x2b92c4b8bc50 - middle::trans::callee::trans_call::closure.115680
  41:     0x2b92c4b5e170 - middle::trans::callee::trans_call_inner::hde6eb414bb58985daE1
  42:     0x2b92c4b8b9e0 - middle::trans::callee::trans_call::h0243a778d0717798fy1
  43:     0x2b92c4b9a810 - middle::trans::expr::trans_rvalue_dps_unadjusted::h4885403a65bbadd16Q3
  44:     0x2b92c4b998b0 - middle::trans::expr::trans_unadjusted::h0e3e3a0f0810cd7eFh3
  45:     0x2b92c4b56150 - middle::trans::expr::trans::hb5d2106e56480123Ew2
  46:     0x2b92c4b91c60 - middle::trans::callee::trans_args::h64bca7f588848043aZ1
  47:     0x2b92c4b5e170 - middle::trans::callee::trans_call_inner::hde6eb414bb58985daE1
  48:     0x2b92c4b8c5f0 - middle::trans::callee::trans_method_call::h7e39c5fba92b93feoz1
  49:     0x2b92c4b9a810 - middle::trans::expr::trans_rvalue_dps_unadjusted::h4885403a65bbadd16Q3
  50:     0x2b92c4b54980 - middle::trans::expr::trans_into::h5fa2aa27ba5f38abIs2
  51:     0x2b92c4b53e30 - middle::trans::controlflow::trans_stmt_semi::h1da7aaaee12528e9ClY
  52:     0x2b92c4b53500 - middle::trans::controlflow::trans_stmt::he615239a63278692lhY
  53:     0x2b92c4b54f20 - middle::trans::controlflow::trans_block::hcf633bc09a595155wmY
  54:     0x2b92c4b55250 - middle::trans::controlflow::trans_if::h456ce55c98d730614oY
  55:     0x2b92c4b9a810 - middle::trans::expr::trans_rvalue_dps_unadjusted::h4885403a65bbadd16Q3
  56:     0x2b92c4b54980 - middle::trans::expr::trans_into::h5fa2aa27ba5f38abIs2
  57:     0x2b92c4b53e30 - middle::trans::controlflow::trans_stmt_semi::h1da7aaaee12528e9ClY
  58:     0x2b92c4b53500 - middle::trans::controlflow::trans_stmt::he615239a63278692lhY
  59:     0x2b92c4b54f20 - middle::trans::controlflow::trans_block::hcf633bc09a595155wmY
  60:     0x2b92c4c0a8e0 - middle::trans::base::trans_closure::h6af85961afc5e10fvye
  61:     0x2b92c4b45950 - middle::trans::base::trans_fn::ha71ddc353381e3f5iKe
  62:     0x2b92c4b40c90 - middle::trans::base::trans_item::hd7d78d670c61d953i2e
  63:     0x2b92c4c155b0 - middle::trans::base::trans_crate::hecf431b91ee08b4bJWf
  64:     0x2b92c4fe6eb0 - driver::driver::phase_4_translate_to_llvm::hcdd287bb9dda01e3pzy
  65:     0x2b92c4fde860 - driver::driver::compile_input::h48de06e93da98f07Qby
  66:     0x2b92c5070680 - driver::run_compiler::h8615fa3184fda61cJIB
  67:     0x2b92c5070590 - driver::main_args::closure.138206
  68:     0x2b92c5082820 - task::TaskBuilder<S>::try_future::closure.139324
  69:     0x2b92c5082620 - task::TaskBuilder<S>::spawn_internal::closure.139301
  70:     0x2b92c5abc660 - task::spawn_opts::closure.8369
  71:     0x2b92c5db57c0 - rust_try_inner
  72:     0x2b92c5db57b0 - rust_try
  73:     0x2b92c5d59fb0 - unwind::try::h188e044e161bf4e2f7d
  74:     0x2b92c5d59d70 - task::Task::run::hcf0d8d6cf4337bfazdd
  75:     0x2b92c5abc3c0 - task::spawn_opts::closure.8315
  76:     0x2b92c5d5bb70 - thread::thread_start::h0fac7ed375094744lCd
  77:     0x2b92caf8d0c0 - start_thread
  78:     0x2b92c6177359 - __clone
  79:                0x0 - <unknown>

[huonw]

I believe this may possibly be related to #16643. What version of rustc do you have?

[arturoc]

rustc 0.12.0-pre (0d3bd77 2014-08-27 21:31:13 +0000)

[arturoc]

i've managed to reproduce this with a simple example:

test.rs:

extern crate lib;

use std::cell::RefCell;

struct App{
    i: int
}

impl lib::Update for App{
    fn update(&mut self){
        self.i += 1;
    }
}

fn main(){
    let app = App{i: 5};
    let window = lib::Window{data: RefCell::new(app)};
    window.update(1);
}

lib.rs

#![crate_type = "lib"]
#![crate_name = "lib"]

use std::cell::RefCell;

pub struct Window<Data>{
    pub data: RefCell<Data>
}

impl<Data:  Update> Window<Data>{
    pub fn update(&self, e: i32){

        match e{
            1 => self.data.borrow_mut().update(),
            _ => {}
        }
    }
}

pub trait Update{
    fn update(&mut self);
}

the error seems to happen only when accessing a RefCell from a library instanciated with a type coming from a program linking to that library and only if the borrow is inside a match!, it doesn't seem to matter if the borrow is mutable or not.

[arturoc]

here's the cargo files in case it helps to test:

[package]
name    = "test"
version = "0.1.0"
authors = []

[[bin]]
name = "test"
path = "test.rs"

[dependencies.lib]
path = "lib"

[package]
name    = "lib"
version = "0.1.0"
authors = []

[lib]
name = "lib"
path = "lib.rs"

[arturoc]

just git bissected this and seems like the buggy commit is one of:
5dca9fb
71df8e6