internal compiler error: Explicit index of non-index type `[u8]`

[nwin]

The following code

struct Wrapper<'a> {
    slice: &'a [u8]
}

fn main() {
    let foo = Some(b"Hello World!");
    let bar: Option<Wrapper<'static>> = foo.map(|&x| Wrapper { slice: x });

}

triggers a compiler bug:

$ RUST_BACKTRACE=1 rustc test.rs 
test.rs:7:71: 7:72 error: internal compiler error: Explicit index of non-index type `[u8]`
test.rs:7     let bar: Option<Wrapper<'static>> = foo.map(|&x| Wrapper { slice: x });
                                                                                ^
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 'Box<Any>', /Users/rustbuild/src/rust-buildbot/slave/nightly-mac/build/src/libsyntax/diagnostic.rs:107

stack backtrace:
   1:        0x10753a635 - rt::backtrace::imp::write::hbede6c694eb9f2cbIQp::v0.11.0.pre
   2:        0x107540bd7 - failure::on_fail::h30a7f46ec21fe35516p::v0.11.0.pre
   3:        0x1077eb249 - unwind::begin_unwind_inner::h6c751dc42f0f7f17IVd::v0.11.0.pre
   4:        0x106c51e25 - unwind::begin_unwind::h16840659320017284217::v0.11.0.pre
   5:        0x106c51dad - diagnostic::SpanHandler::span_bug::hb5a406cf5dd1450cWac::v0.11.0.pre
   6:        0x1045047e5 - driver::session::Session::span_bug::hc60df83bd7dbe984Trr::v0.11.0.pre
   7:        0x10478c506 - middle::mem_categorization::MemCategorizationContext<'t, TYPER>::cat_index::h11027325414672250850::v0.11.0.pre
   8:        0x10476be2b - middle::typeck::check::regionck::visit_expr::h8ad96e881d8c059afH8::v0.11.0.pre
   9:        0x104770542 - visit::walk_expr::h7092108895728945809::v0.11.0.pre
  10:        0x10476b2a0 - middle::typeck::check::regionck::visit_expr::h8ad96e881d8c059afH8::v0.11.0.pre
  11:        0x10476cf8e - visit::walk_block::h6655035168579021138::v0.11.0.pre
  12:        0x104770936 - visit::walk_fn::h7111590603532843168::v0.11.0.pre
  13:        0x10476b865 - middle::typeck::check::regionck::visit_expr::h8ad96e881d8c059afH8::v0.11.0.pre
  14:        0x104770113 - visit::walk_expr::h7092108895728945809::v0.11.0.pre
  15:        0x10476b2a0 - middle::typeck::check::regionck::visit_expr::h8ad96e881d8c059afH8::v0.11.0.pre
  16:        0x10476ce12 - middle::typeck::check::regionck::visit_local::ha0697ea4d5b15fbeUD8::v0.11.0.pre
  17:        0x10476cf6a - visit::walk_block::h6655035168579021138::v0.11.0.pre
  18:        0x1047afc0e - middle::typeck::check::check_bare_fn::hcd02e3ea22711cdcA2c::v0.11.0.pre
  19:        0x1047a98ce - middle::typeck::check::check_item::h066c89136b0abe5fOzd::v0.11.0.pre
  20:        0x1047af98d - middle::typeck::check::check_item_types::ha45c368daeab74efS1c::v0.11.0.pre
  21:        0x10492161e - middle::typeck::check_crate::hae37e3b7b5c6e1b3Q3C::v0.11.0.pre
  22:        0x104d75878 - driver::driver::phase_3_run_analysis_passes::hfbfa07100b0674bdFrq::v0.11.0.pre
  23:        0x104d708c5 - driver::driver::compile_input::hf1aa489ba45a9efcDeq::v0.11.0.pre
  24:        0x104e3709b - driver::run_compiler::h9c79a8fc68073767b0s::v0.11.0.pre
  25:        0x104e348b6 - driver::main_args::closure.117540
  26:        0x104e48f8b - task::TaskBuilder<S>::try_future::closure.118681
  27:        0x104e48e24 - task::TaskBuilder<S>::spawn_internal::closure.118658
  28:        0x10444395c - task::spawn_opts::closure.7563
  29:        0x107850dac - rust_try
  30:        0x1077e76ea - unwind::try::h7f3fc3b0329b49ea7Jd::v0.11.0.pre
  31:        0x1077e73ec - task::Task::run::h4a0e5408354628dfZVc::v0.11.0.pre
  32:        0x1044437eb - task::spawn_opts::closure.7508
  33:        0x1077e9f59 - thread::thread_start::h5aa600706e7c5c88xid::v0.11.0.pre
  34:     0x7fff973fd899 - _pthread_body
  35:     0x7fff973fd72a - _pthread_struct_init

[alexcrichton]

cc @nick29581, this seems to be triggering DST which I didn't think was enabled...

[zsparal]

The following code:

pub struct Matrix {
    data: [[int, ..2], ..2]
}

impl Index<uint, [int, ..2]> for Matrix {
    fn index<'a>(&'a self, index: &uint) -> &'a [int, ..2] {
        &self.data[*index]
    }
}

fn main() {
    let m = Matrix {data: [[1, 0], [0, 1]]};
    let e = m[0][0];    
}

Also triggers a similar compiler error:

rust_error.rs:13:13: 13:20 error: internal compiler error: Explicit index of non-index type `&Matrix`
rust_error.rs:13     let e = m[0][0];
                             ^~~~~~~
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 'Box<Any>', C:\bot\slave\nightly-win\build\src\libsyntax\diagnostic.rs:107

Unfortunately, I could not get the stack backtrace to print anything meaningful on Windows 8.1, if ran with RUST_BACKTRACE=1 the compiler outputs the following backtrace:

stack backtrace:
   1: 0x6a18242a
   2: 0x61f8893c
   3:   0x6e28da
   4:   0x6e2860
   5: 0x70f7255a
   6: 0x711eb8c5
   7: 0x711ea8fe
   8: 0x711d724b

Platform: Windows 8.1

$ rustc -v
rustc 0.11.0-nightly (1c711db551b9a5e56ba76e002e287dcfbb2cff3c 2014-07-09 00:36:40 +0000)

[flodiebold]

I've also encountered this error message, with the following (simplified) code:

pub struct It;

impl Iterator<[uint, ..3]> for It {
    fn next(&mut self) -> Option<[uint, ..3]> {
        None
    }
}

fn main() {
    for [x, y, z] in It {
    }
}

Resulting in:

~/Projekte$ RUST_BACKTRACE=1 rustc rust-bug.rs                                                              101 ↵ 
rust-bug.rs:10:9: 10:18 error: internal compiler error: Explicit index of non-index type `It`
rust-bug.rs:10     for [x, y, z] in It {
                       ^~~~~~~~~
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 'Box<Any>', /home/rustbuild/src/rust-buildbot/slave/nightly-linux/build/src/libsyntax/diagnostic.rs:113

stack backtrace:
   1:     0x7fc16f9208d0 - rt::backtrace::imp::write::h9a97349a494f89bePUq
   2:     0x7fc16f923a90 - failure::on_fail::hb11547504289a1ffhgr
   3:     0x7fc1700f22d0 - unwind::begin_unwind_inner::h5df2dc6f14b19f71MTd
   4:     0x7fc16e3b8620 - unwind::begin_unwind::h1365354703164647196
   5:     0x7fc16e3b85a0 - diagnostic::SpanHandler::span_bug::h810a8fac103d8c1cMhF
   6:     0x7fc170697460 - driver::session::Session::span_bug::h976022b1a0303ee7m8w
   7:     0x7fc170a13d20 - middle::mem_categorization::MemCategorizationContext<'t, TYPER>::cat_index::h6849561118867022794
   8:     0x7fc170a12100 - middle::mem_categorization::MemCategorizationContext<'t, TYPER>::cat_pattern::h3339052091073497715
   9:     0x7fc1709fa8e0 - middle::typeck::check::regionck::visit_expr::hd3c8b825c2773d621PM
  10:     0x7fc1709f7a80 - middle::typeck::check::regionck::Rcx<'a, 'tcx>::visit_fn_body::hc777c8ab8612eedbyqM
  11:     0x7fc1709f7990 - middle::typeck::check::regionck::regionck_fn::h83e3b6c2d3d53709tjM
  12:     0x7fc170a3a130 - middle::typeck::check::check_bare_fn::hfebc4617d948ec12E8R
  13:     0x7fc170a35ec0 - middle::typeck::check::check_item::h77a7f21c8a144855HAS
  14:     0x7fc170a39be0 - middle::typeck::check::check_item_types::h697321cef90212deO7R
  15:     0x7fc1704e85d0 - util::common::time::h18398786739644959194
  16:     0x7fc170ce1010 - middle::typeck::check_crate::h63bb01e16b1996cd4Uj
  17:     0x7fc170d4ab40 - driver::driver::phase_3_run_analysis_passes::h57b76357b4c15009Opw
  18:     0x7fc170d46290 - driver::driver::compile_input::hc03497de7e6c909eL6v
  19:     0x7fc170dc8360 - driver::run_compiler::h24a8daf18bbc3b70DWz
  20:     0x7fc170dc8240 - driver::main_args::closure.146005
  21:     0x7fc170501710 - task::TaskBuilder<S>::try_future::closure.101291
  22:     0x7fc170501500 - task::TaskBuilder<S>::spawn_internal::closure.101262
  23:     0x7fc1716d8650 - task::spawn_opts::closure.8491
  24:     0x7fc170148480 - rust_try_inner
  25:     0x7fc170148470 - rust_try
  26:     0x7fc1700ef910 - unwind::try::h8c8d3e6eb0ca16a6uId
  27:     0x7fc1700ef770 - task::Task::run::hfb873359c59e1424cYc
  28:     0x7fc1716d83c0 - task::spawn_opts::closure.8431
  29:     0x7fc1700f1360 - thread::thread_start::h2b0150e66287e12frid
  30:     0x7fc16f3e7e70 - start_thread
  31:     0x7fc16fdbac09 - clone
  32:                0x0 - <unknown>

Doing the destructuring inside the for loop avoids the error. This is on x86_64 Linux.

~/Projekte$ rustc -v                                                                                              
rustc 0.12.0-nightly (d64b4103d 2014-09-26 21:47:47 +0000)

[kubkon]

I've encountered a similar error as well. The code:

let values: Vec<u8> = vec![1,2,3,4,5,6,7,8];

for [x,y,z] in values.as_slice().chunks(3).filter(|&xs| xs.len() == 3) {
    println!("y={}", y);
}

The error message with the backtrace:

slice_match.rs:4:9: 4:16 error: internal compiler error: Explicit index of non-index type `core::iter::Filter<'_,&[u8],core::slice::Chunks<'_,u8>>`
slice_match.rs:4     for [x,y,z] in values.as_slice().chunks(3).filter(|&xs| xs.len() == 3) {
                         ^~~~~~~
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 'Box<Any>', /Users/rustbuild/src/rust-buildbot/slave/nightly-mac/build/src/libsyntax/diagnostic.rs:113

stack backtrace:
   1:        0x111c73269 - rt::backtrace::imp::write::he06af82d7d9ee38ecJq
   2:        0x111c765a1 - failure::on_fail::h9e3a39356479ba70QZq
   3:        0x111ef48e5 - unwind::begin_unwind_inner::h756181834df20b6dLud
   4:        0x1113e3b97 - unwind::begin_unwind::h18322048352354653950
   5:        0x1113e3b30 - unwind::begin_unwind::h18322048352354653950
   6:        0x10ea73b6d - driver::session::Session::span_bug::h2c0f6016b5fa651cwtx
   7:        0x10ede89fa - middle::mem_categorization::MemCategorizationContext<'t, TYPER>::cat_index::h13791422843569837526
   8:        0x10ede728d - middle::mem_categorization::MemCategorizationContext<'t, TYPER>::cat_pattern::h13679513847658926920
   9:        0x10edd10e8 - middle::typeck::check::regionck::visit_expr::h82e747716217ebf1GUM
  10:        0x10edcc884 - middle::typeck::check::regionck::Rcx<'a, 'tcx>::visit_fn_body::h3ac342a98dca80f6dvM
  11:        0x10edcbccd - middle::typeck::check::regionck::regionck_fn::h34dea5a76c44f2e38nM
  12:        0x10ee0f292 - middle::typeck::check::check_bare_fn::h6db665b3affe0759ZhS
  13:        0x10ee0b0b8 - middle::typeck::check::check_item::h82af91f6696c38872JS
  14:        0x10ee0f0df - middle::typeck::check::check_item_types::h55796e1a31aa1c3c9gS
  15:        0x10e8cc4b6 - util::common::time::h10131786875316863222
  16:        0x10f0bfb6e - middle::typeck::check_crate::h95db7480b8900497Edk
  17:        0x10f12967f - driver::driver::phase_3_run_analysis_passes::h8decd58d8d4c066eEKw
  18:        0x10f124558 - driver::driver::compile_input::heb0d35abb1543609qrw
  19:        0x10f1a3584 - driver::run_compiler::h420de67eacbe487cHhA
  20:        0x10f1a1726 - driver::run::closure.146515
  21:        0x10e8e4bfb - task::TaskBuilder<S>::try_future::closure.101324
  22:        0x10e8e4af3 - task::TaskBuilder<S>::spawn_internal::closure.101295
  23:        0x10e8616bd - task::spawn_opts::closure.8536
  24:        0x111f579ec - rust_try_inner
  25:        0x111f579d6 - rust_try
  26:        0x111ef2157 - unwind::try::h6df6339e56c18041tjd
  27:        0x111ef1fec - task::Task::run::hf7474df0e760efdfEzc
  28:        0x10e861512 - task::spawn_opts::closure.8475
  29:        0x111ef383a - thread::thread_start::h960eee62f4c643ffPTc
  30:     0x7fff8e93a899 - _pthread_body
  31:     0x7fff8e93a72a - _pthread_struct_init

I'm running OSX 10.9.5 with x86_64 architecture.

Rust version:

rustc 0.12.0-nightly (dc987adfc 2014-10-04 23:42:07 +0000)