ICE: TypeParameterDef lookup failure in tc_ty

[kmcallister]

Extracted from an issue I encountered upgrading html5ever to Rust master.

foo.rs:

#![crate_type="lib"]

pub trait TokenSink {
    fn process_token(&self, token: ());
}

pub struct TreeBuilder<Handle> {
    pub open_elems: Vec<Handle>,
}

impl<Handle> TokenSink for TreeBuilder<Handle> {
    fn process_token(&self, token: ()) {
        match token {
            _ => for x in self.open_elems.iter() { },
        }
    }
}

bar.rs:

extern crate foo;

use foo::{TreeBuilder, TokenSink};

fn main() {
    let tb: TreeBuilder<uint> = TreeBuilder {
        open_elems: vec!(),
    };
    tb.process_token(());
}

It seems like more or less every part of this code is necessary to hit the bug. Here's the result:

$ rustc -v
rustc 0.12.0-pre (e11cb5bba 2014-08-20 16:25:53 +0000)

$ rustc foo.rs

$ RUST_BACKTRACE=1 rustc -L. bar.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 'TypeParameterDef lookup failed for ParamTy { space: TypeSpace, idx: 0, def_id: DefId { krate: 0, node: 598 } }', /home/keegan/rust/src/librustc/middle/ty.rs:2294

stack backtrace:
   1:     0x7f12658b8a20 - rt::backtrace::imp::write::hd65c9804462fb8dcpxr
   2:     0x7f12658bb3e0 - failure::on_fail::hb34a0faf07b986176Sr
   3:     0x7f126a2ed030 - unwind::begin_unwind_inner::hfc98b793f314ea06pie
   4:     0x7f126a2ecb30 - unwind::begin_unwind_fmt::he2958ada65c1d41fPfe
   5:     0x7f126b53a670 - middle::ty::type_contents::tc_ty::h98abbbfc60a7d554waG
   6:     0x7f126b53a670 - middle::ty::type_contents::tc_ty::h98abbbfc60a7d554waG
   7:     0x7f126af18a50 - middle::ty::type_contents::h1b7aa404dfcb34d1r9F
   8:     0x7f126ae63e00 - middle::ty::type_moves_by_default::h8602de8843dbf54dcrG
   9:     0x7f126ada8ac0 - middle::expr_use_visitor::copy_or_move::h0d63d7bcb9e1b5295zv
  10:     0x7f126b417b50 - middle::expr_use_visitor::ExprUseVisitor<'d, 't, TYPER>::walk_pat::closure.118640
  11:     0x7f126b412d60 - middle::mem_categorization::MemCategorizationContext<'t, TYPER>::cat_pattern::h1612630838218560840
  12:     0x7f126b4127b0 - middle::expr_use_visitor::ExprUseVisitor<'d, 't, TYPER>::walk_pat::h17289765959183890288
  13:     0x7f126b4059c0 - middle::expr_use_visitor::ExprUseVisitor<'d, 't, TYPER>::walk_expr::h18108696973096423772
  14:     0x7f126b405430 - middle::trans::_match::is_discr_reassigned::ha03b6a6c6923b1b8MQh
  15:     0x7f126b41ab90 - middle::trans::_match::create_bindings_map::h5a49a20efb57c753jUh
  16:     0x7f126b4216e0 - middle::trans::_match::trans_match_inner::closure.118687
  17:     0x7f126b420630 - iter::Map<'a, A, B, T>::do_map::h4328457525798762931
  18:     0x7f126b4205c0 - iter::Map<'a, A, B, T>.Iterator<B>::next::h14044686831652860284
  19:     0x7f126b420570 - iter::ByRef<'a, T>.Iterator<A>::next::h7270709296560143036
  20:     0x7f126b420100 - vec::Vec<T>.FromIterator<T>::from_iter::h13079317938292968767
  21:     0x7f126b4200a0 - iter::Iterator::collect::h10157566076738839025
  22:     0x7f126b404a90 - middle::trans::_match::trans_match_inner::h3199dcbd82cb2abfAXh
  23:     0x7f126b2df4c0 - middle::trans::_match::trans_match::h1d773729c0952ac6XPh
  24:     0x7f126b2c5b40 - middle::trans::expr::trans_rvalue_dps_unadjusted::h68c42f27e53f341euG3
  25:     0x7f126b2610c0 - middle::trans::expr::trans_into::h02f395bc1df027d3QL2
  26:     0x7f126b2617e0 - middle::trans::controlflow::trans_block::h05731a7862534d438MY
  27:     0x7f126b3b30f0 - middle::trans::base::trans_closure::h761f159ac0f5b1d5Zve
  28:     0x7f126b24a4a0 - middle::trans::base::trans_fn::h7f652b8e491f5fceNIe
  29:     0x7f126b24ad10 - middle::trans::monomorphize::monomorphic_fn::h444eefff2433fcd158X
  30:     0x7f126b2a3ed0 - middle::trans::callee::trans_fn_ref_with_vtables::hbc4955abe0c5e25axp1
  31:     0x7f126b2a15b0 - middle::trans::callee::trans_fn_ref::h8cbdc53077e7d865za1
  32:     0x7f126b273f50 - middle::trans::meth::trans_method_callee::hd255bf18a4fec4edJhk
  33:     0x7f126b2b0d00 - middle::trans::callee::trans_method_call::closure.115194
  34:     0x7f126b271930 - middle::trans::callee::trans_call_inner::h3d3ba09198f29bc9nR1
  35:     0x7f126b2b05a0 - middle::trans::callee::trans_method_call::h20b5c2a1e6f706d1BM1
  36:     0x7f126b2c5b40 - middle::trans::expr::trans_rvalue_dps_unadjusted::h68c42f27e53f341euG3
  37:     0x7f126b2610c0 - middle::trans::expr::trans_into::h02f395bc1df027d3QL2
  38:     0x7f126b2601f0 - middle::trans::controlflow::trans_stmt_semi::h4399908e9bfb4a53eMY
  39:     0x7f126b25ee40 - middle::trans::controlflow::trans_stmt::h814b238e9dbd031fXHY
  40:     0x7f126b2617e0 - middle::trans::controlflow::trans_block::h05731a7862534d438MY
  41:     0x7f126b3b30f0 - middle::trans::base::trans_closure::h761f159ac0f5b1d5Zve
  42:     0x7f126b24a4a0 - middle::trans::base::trans_fn::h7f652b8e491f5fceNIe
  43:     0x7f126b246590 - middle::trans::base::trans_item::h9c3deb60b9a1469bO1e
  44:     0x7f126b3c0b10 - middle::trans::base::trans_mod::hdc94d62cb0c66b22X5e
  45:     0x7f126b3d3920 - middle::trans::base::trans_crate::h2bbe93d38696f05f2Wf
  46:     0x7f126bc77620 - driver::driver::phase_4_translate_to_llvm::closure.136750
  47:     0x7f126bc76fc0 - util::common::time::h4601779646530965728
  48:     0x7f126bbb8380 - driver::driver::phase_4_translate_to_llvm::hcbbe57487cf47912Y1z
  49:     0x7f126bbb2860 - driver::driver::compile_input::hd5ac6510c8591e16pEz
  50:     0x7f126bcbc170 - driver::run_compiler::hfb28193ee56e89e2jcD
  51:     0x7f126bcbc040 - driver::main_args::closure.137687
  52:     0x7f126bcee7f0 - task::TaskBuilder<S>::try_future::closure.138848
  53:     0x7f126bcee3a0 - task::TaskBuilder<S>::spawn_internal::closure.138825
  54:     0x7f126a715d90 - task::spawn_opts::closure.8331
  55:     0x7f126a2ec3a0 - unwind::try::try_fn::__rust_abi
  56:     0x7f126a2ebdd0 - unwind::try::try_fn::hd559f7a319afd50b38d
  57:     0x7f126a3a63d0 - rust_try_inner
  58:     0x7f126a3a63c0 - rust_try
  59:     0x7f126a2e6250 - unwind::try::ha1bfe3bb2c20efd2F6d
  60:     0x7f126a2e5d50 - task::Task::run::hd76056204f6bfc11Zcd
  61:     0x7f126a7159c0 - task::spawn_opts::closure.8277
  62:     0x7f126a2ea4f0 - thread::thread_start::__rust_abi
  63:     0x7f126a2ea4e0 - thread::thread_start::hc1291c833034ff64LBd
  64:     0x7f1264b53fe0 - start_thread
  65:     0x7f1269fa0019 - __clone
  66:                0x0 - <unknown>

(This has my modifications to give a marginally more useful error message.)

The failure happens when looking up a type parameter DefId when handling the ty_param case.

What I actually get building html5ever is a failure of the preceding assertion regarding crate IDs. I didn't find a small reproducer for that assertion failure, but this bug is likely to be related.

[huonw]

cc me

[huonw]

(Slightly) simpler example:

// euv_ice.rs
#![crate_type="lib"]

pub struct TreeBuilder<H>;

impl<H> Iterator<H> for TreeBuilder<H> {
    fn next(&mut self) -> Option<H> { None }
}

impl<H> TreeBuilder<H> {
    pub fn process_token(&mut self) {
        match self {
            _ => for _y in *self {},
        }
    }
}

extern crate euv_ice;

fn main() {
    euv_ice::TreeBuilder::<uint>.process_token();
}

This appears to be related to AST being inlined cross-crate, and the for internals (cc @pcwalton) since desugaring it to the equivalent loop { match self.next() { doesn't ICE. It also requires that process_token is a method, a freestanding function stops the ICE.

[kmcallister]

Cool, for now I'll go with the workaround of desugaring the for loop myself.