Compiler panic when manually indexing vectors

[urschrei]

I'm manually indexing some vectors using a usize field from a struct. This is causing a compiler panic.

Code: commit c624f56 at https://github.com/urschrei/rust-geo/tree/polygon_distance.

Rustc version:
nightly-x86_64-apple-darwin
rustc 1.18.0-nightly (91ae22a01 2017-04-05)

Full Backtrace (under dropdown):

error: internal compiler error: src/librustc_typeck/check/coercion.rs:718: expr already has an adjustment on it!

thread 'rustc' panicked at 'Box<Any>', src/librustc_errors/lib.rs:416
stack backtrace:
 0:        0x10ad96953 - std::sys::imp::backtrace::tracing::imp::unwind_backtrace::hbdeac7eba2f064c6
 1:        0x10ada36ed - std::panicking::default_hook::{{closure}}::h9e0a6ca9bb64b479
 2:        0x10ada3234 - std::panicking::default_hook::h9043ae80af471c9f
 3:        0x10ada5e57 - std::panicking::rust_panic_with_hook::h05996066754c6be9
 4:        0x10833994a - std::panicking::begin_panic::hf47fe75ea38aa60c
 5:        0x108351194 - rustc_errors::Handler::bug::h5c4d3c22f7d6cf5f
 6:        0x10754f46c - rustc::session::opt_span_bug_fmt::{{closure}}::hc30486983bf7baa5
 7:        0x10754f270 - rustc::session::opt_span_bug_fmt::hbb1ce5f815a221d0
 8:        0x10754edfa - rustc::session::bug_fmt::h603b74c583ab5af8
 9:        0x106634f2d - rustc_typeck::check::coercion::<impl rustc_typeck::check::FnCtxt<'a, 'gcx, 'tcx>>::try_coerce::hf1afc4fb1f0fd049
10:        0x1066463c7 - rustc_typeck::check::demand::<impl rustc_typeck::check::FnCtxt<'a, 'gcx, 'tcx>>::demand_coerce::h5e0424652dca67df
11:        0x106698e9a - rustc_typeck::check::FnCtxt::check_argument_types::h6c5ac67922ecc7f4
12:        0x10669816d - rustc_typeck::check::FnCtxt::check_method_argument_types::hdfcaa2508888d95b
13:        0x1066a34b8 - rustc_typeck::check::FnCtxt::check_expr_kind::h1135e8c4361f6473
14:        0x10669eb20 - rustc_typeck::check::FnCtxt::check_expr_with_expectation_and_lvalue_pref::h1bb7590703cfb153
15:        0x10669a2f6 - rustc_typeck::check::FnCtxt::check_expr_has_type::heef4496f4d358bdf
16:        0x1066a437d - rustc_typeck::check::FnCtxt::check_expr_kind::h1135e8c4361f6473
17:        0x10669eb20 - rustc_typeck::check::FnCtxt::check_expr_with_expectation_and_lvalue_pref::h1bb7590703cfb153
18:        0x1066a6fa7 - rustc_typeck::check::FnCtxt::check_decl_initializer::hb2018bec0565c8ca
19:        0x1066a708c - rustc_typeck::check::FnCtxt::check_decl_local::h42d2a6e470f71fbe
20:        0x1066a72e1 - rustc_typeck::check::FnCtxt::check_stmt::h10977bf77ab03006
21:        0x1066a7cee - rustc_typeck::check::FnCtxt::check_block_with_expected::{{closure}}::h4fc16531f0890bf6
22:        0x1066a7746 - rustc_typeck::check::FnCtxt::check_block_with_expected::ha99b44f2b0900127
23:        0x10669f9bc - rustc_typeck::check::FnCtxt::check_expr_kind::h1135e8c4361f6473
24:        0x10669eb20 - rustc_typeck::check::FnCtxt::check_expr_with_expectation_and_lvalue_pref::h1bb7590703cfb153
25:        0x10669b13d - rustc_typeck::check::FnCtxt::check_return_expr::h31d207f50840039d
26:        0x10668b93e - rustc_typeck::check::check_fn::ha1265f1a8a15cfc7
27:        0x10668a12b - rustc_typeck::check::typeck_tables::h8f56b5a1240db926
28:        0x10762ad01 - rustc::ty::maps::<impl rustc::ty::maps::queries::typeck_tables<'tcx>>::try_get::h48076491a959043c
29:        0x10762aeb3 - rustc::ty::maps::<impl rustc::ty::maps::queries::typeck_tables<'tcx>>::get::hac6c722e7d137c6c
30:        0x1075df12c - rustc::ty::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::item_tables::h0cc43c4a7e140596
31:        0x106689062 - rustc_typeck::check::typeck_item_bodies::h023401d8604ce9d6
32:        0x107629fcd - rustc::ty::maps::<impl rustc::ty::maps::queries::typeck_item_bodies<'tcx>>::try_get::ha8f2587920e8897e
33:        0x10762a1d2 - rustc::ty::maps::<impl rustc::ty::maps::queries::typeck_item_bodies<'tcx>>::get::h355bebb502605440
34:        0x1066e16ef - rustc_typeck::check_crate::hbd024fa93952a70d
35:        0x10628e710 - rustc_driver::driver::phase_3_run_analysis_passes::{{closure}}::h268f1787328becc3
36:        0x1061dc844 - rustc::ty::context::TyCtxt::create_and_enter::h6fdf5bf007c6624c
37:        0x10628bc34 - rustc_driver::driver::phase_3_run_analysis_passes::he1ec91c87e760611
38:        0x10625cbad - rustc_driver::driver::compile_input::h2d34c130b0e09b8d
39:        0x1062b85cb - rustc_driver::run_compiler::hc1973c7a7c291533
40:        0x10618c928 - std::panicking::try::do_call::hc2d47b7090d8b7b0
41:        0x10ada8c6a - __rust_maybe_catch_panic
42:        0x1061d2a6f - <F as alloc::boxed::FnBox<A>>::call_box::h39cb667f07a35289
43:        0x10ada26d4 - std::sys::imp::thread::Thread::new::thread_start::h4008e1859fbd98b8
44:     0x7fffd89bbaaa - _pthread_body
45:     0x7fffd89bb9f6 - _pthread_start

[est31]

@urschrei its rejecting invalid code. &Polygon can't be indexed. Still, an ICE is a bug.

Minimized example:

struct Bar();

impl Bar {
    fn nv(&self, _: &()) -> usize { 42 }
}

fn foo(p: &Bar) {
    let _ = p[p.nv(&())];
}

fn main() {}

[eddyb]

Closing as duplicate of #40861.