ICE when implementing Drop for a struct with a lifetime, without #[unsafe_destructor].

[sebcrozet]

The following compiles:

#![feature(unsafe_destructor)]

struct A;

struct B<'a> {
    a: &'a mut A
}

#[unsafe_destructor]
impl<'a> Drop for B<'a> {
    fn drop(&mut self) {
    }
}

fn main() {
} 

Removing the unsafe_destructor gives an ICE:

struct A;

struct B<'a> {
    a: &'a mut A
}

impl<'a> Drop for B<'a> {
    fn drop(&mut self) {
    }
}

fn main() {
}

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 0 but the index is 0', /home/rustbuild/src/rust-buildbot/slave/nightly-linux/build/src/librustc/lib.rs:1

stack backtrace:
   1:     0x7fe7c0b40710 - rt::backtrace::imp::write::h70be4bfca778d3deKGp::v0.11.0.pre
   2:     0x7fe7c0b47e40 - failure::on_fail::h04d04700f5348da7Z1p::v0.11.0.pre
   3:     0x7fe7c2c79940 - unwind::begin_unwind_inner::h97af3d04f923ce77QRd::v0.11.0.pre
   4:     0x7fe7c2c793d0 - unwind::begin_unwind_fmt::he34766b08c9c3bffjPd::v0.11.0.pre
   5:     0x7fe7c2c79390 - rust_begin_unwind
   6:     0x7fe7c2cc2120 - failure::begin_unwind::he173e4b304989dc8k2v::v0.11.0.pre
   7:     0x7fe7c2cc5f10 - failure::fail_bounds_check::h5d25220010d9234cw0v::v0.11.0.pre
   8:     0x7fe7c35cd370 - middle::subst::SubstFolder<'a>.TypeFolder::fold_region::h87f3a88e034f0808awU::v0.11.0.pre
   9:     0x7fe7c3573d00 - middle::subst::SubstFolder<'a>.TypeFolder::fold_ty::hfe8a92cc8f6786e4JwU::v0.11.0.pre
  10:     0x7fe7c3573c10 - middle::subst::T.Subst::subst_spanned::h7311720506834529690::v0.11.0.pre
  11:     0x7fe7c36fb0b0 - middle::ty::lookup_field_type::hddf6e164c6d23ce9XbS::v0.11.0.pre
  12:     0x7fe7c35b3cc0 - middle::ty::struct_fields::hc733bb5e62aec902ekS::v0.11.0.pre
  13:     0x7fe7c372ab20 - middle::ty::type_contents::tc_ty::hb4fb865b8c9b3a21YrP::v0.11.0.pre
  14:     0x7fe7c36c1b70 - middle::ty::type_contents::ha9a882bed7271f1dUqP::v0.11.0.pre
  15:     0x7fe7c3ac5160 - middle::kind::check_item::h32f6a93801c8fc8cN5V::v0.11.0.pre
  16:     0x7fe7c3ac8050 - middle::kind::check_crate::h633ef117cb58f864cWV::v0.11.0.pre
  17:     0x7fe7c3ebbcb0 - driver::driver::phase_3_run_analysis_passes::hc133de981f2c567e91v::v0.11.0.pre
  18:     0x7fe7c3eb4210 - driver::driver::compile_input::hf9ab49f375606457oQv::v0.11.0.pre
  19:     0x7fe7c3f82e30 - driver::run_compiler::h943691fce94537a0jAy::v0.11.0.pre
  20:     0x7fe7c3f82d40 - driver::main_args::closure.99055
  21:     0x7fe7c3f98790 - task::TaskBuilder<S>::try_future::closure.100185
  22:     0x7fe7c3f983b0 - task::TaskBuilder<S>::spawn_internal::closure.100162
  23:     0x7fe7c2fd5880 - task::spawn_opts::closure.7220
  24:     0x7fe7c2c76510 - task::Task::run::closure.5243
  25:     0x7fe7c2cdb9a0 - rust_try
  26:     0x7fe7c2c78f60 - unwind::try::h0c05741f8b8835e1fGd::v0.11.0.pre
  27:     0x7fe7c2c76390 - task::Task::run::h88fa45777ee68cfeVVc::v0.11.0.pre
  28:     0x7fe7c2fd5620 - task::spawn_opts::closure.7185
  29:     0x7fe7c2c78520 - thread::thread_start::hd6e04bc6ce5c8296kdd::v0.11.0.pre
  30:     0x7fe7c05b2fe0 - start_thread
  31:     0x7fe7c2942ce9 - clone
  32:                0x0 - <unknown>

Note that ommiting the unsafe_destructor and not storing the pointer to A does compile too:

struct A;

struct B<'a>;

impl<'a> Drop for B<'a> {
    fn drop(&mut self) {
    }
}

fn main() {
}

[alexcrichton]

Closing as a dupe of #14889