ICE: assertion failed (left == right) in astconv.rs

[Nashenas88]

The following code:

struct NotTrait { } // <--- Struct instead of trait

fn do_something() {
    let x: <NotImportant as NotTrait>::test = test;
    //                      ^ This and ^ this together are the problem
}

Produces the following error only on nightly. Stable and beta fail compilation without an ICE.

$ RUST_BACKTRACE=1 cargo build --verbose
   Compiling compiler_error v0.1.0 (file:///home/pfaria/compiler_error)
     Running `rustc --crate-name compiler_error src/lib.rs --crate-type lib -g -C metadata=8b5a0bdfc8a3f707 -C extra-filename=-8b5a0bdfc8a3f707 --out-dir /home/pfaria/compiler_error/target/debug/deps --emit=dep-info,link -L dependency=/home/pfaria/compiler_error/target/debug/deps`
error[E0404]: `NotTrait` is not a trait
 --> src/lib.rs:4:29
  |
4 |     let x: <NotImportant as NotTrait>::test = test;
  |                             ^^^^^^^^^^^^^^^ expected trait, found struct

error[E0412]: type name `NotImportant` is undefined or not in scope
 --> src/lib.rs:4:13
  |
4 |     let x: <NotImportant as NotTrait>::test = test;
  |             ^^^^^^^^^^^^ undefined or not in scope
  |
  = help: no candidates by the name of `NotImportant` found in your project; maybe you misspelled the name or forgot to import an external crate?

error[E0425]: unresolved name `test`
 --> src/lib.rs:4:47
  |
4 |     let x: <NotImportant as NotTrait>::test = test;
  |                                               ^^^^ unresolved name

error: internal compiler error: unexpected panic

note: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#bug-reports

note: run with `RUST_BACKTRACE=1` for a backtrace

thread 'rustc' panicked at 'assertion failed: `(left == right)` (left: `Some([type error])`, right: `None`)', /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc_typeck/astconv.rs:1451
stack backtrace:
   1:     0x7f27b5bc038a - std::sys::imp::backtrace::tracing::imp::write::h0d1aacfb8fc693ac
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:42
   2:     0x7f27b5bce6ff - std::panicking::default_hook::{{closure}}::hff87359baf5754d0
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libstd/panicking.rs:349
   3:     0x7f27b5bce29d - std::panicking::default_hook::h936f17ca3b2b98dc
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libstd/panicking.rs:359
   4:     0x7f27b5bceba7 - std::panicking::rust_panic_with_hook::he9c830ab830c7944
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libstd/panicking.rs:553
   5:     0x7f27b5bcea34 - std::panicking::begin_panic::hbd10b7f500042f98
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libstd/panicking.rs:515
   6:     0x7f27b5bce959 - std::panicking::begin_panic_fmt::h49583ddd44614a0d
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libstd/panicking.rs:499
   7:     0x7f27b362edc2 - <rustc_typeck::astconv::AstConv<'gcx, 'tcx> + 'o>::def_to_ty::h103f6798e7cce8d2
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc_typeck/astconv.rs:1451
   8:     0x7f27b3630446 - <rustc_typeck::astconv::AstConv<'gcx, 'tcx> + 'o>::ast_ty_to_ty::h6713e7bc915e3b01
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc_typeck/astconv.rs:1661
   9:     0x7f27b362fcfe - <rustc_typeck::astconv::AstConv<'gcx, 'tcx> + 'o>::ast_ty_to_ty::h6713e7bc915e3b01
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc_typeck/astconv.rs:1665
  10:     0x7f27b35f0032 - <rustc_typeck::check::GatherLocalsVisitor<'a, 'gcx, 'tcx> as rustc::hir::intravisit::Visitor<'gcx>>::visit_local::h32caf495969107a5
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc_typeck/check/mod.rs:1871
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc_typeck/check/mod.rs:711
  11:     0x7f27b3568d85 - rustc::hir::intravisit::walk_expr::h46c69156dee86d5f
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc/hir/intravisit.rs:894
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc/hir/intravisit.rs:251
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc/hir/intravisit.rs:882
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc/hir/intravisit.rs:242
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/<walk_list macros>:2
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc_typeck/check/mod.rs:743
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc/hir/intravisit.rs:969
  12:     0x7f27b35f0c27 - rustc_typeck::check::check_fn::h21a5f04436a5bbc5
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc/hir/intravisit.rs:254
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc_typeck/check/mod.rs:821
  13:     0x7f27b35efa1b - rustc_typeck::check::check_bare_fn::h38d017b7cdf453a4
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc_typeck/check/mod.rs:661
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc_typeck/check/mod.rs:502
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc/infer/mod.rs:442
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc/ty/context.rs:1033
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libstd/thread/local.rs:245
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc/ty/context.rs:1030
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc/ty/context.rs:846
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc/infer/mod.rs:442
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc_typeck/check/mod.rs:502
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc_typeck/check/mod.rs:651
  14:     0x7f27b35f2783 - rustc_typeck::check::check_item_body::h93dbfca77b60ad10
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc_typeck/check/mod.rs:928
  15:     0x7f27b35ed2b0 - rustc_typeck::check::check_item_bodies::ha9191bbc667904b7
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc_typeck/check/mod.rs:565
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc/dep_graph/visit.rs:45
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc/hir/mod.rs:456
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc/dep_graph/visit.rs:67
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc/ty/mod.rs:2681
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc_typeck/check/mod.rs:591
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc/session/mod.rs:232
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc_typeck/check/mod.rs:589
  16:     0x7f27b3658f2f - rustc_typeck::check_crate::hd31dd2bc6ea91ceb
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc_typeck/lib.rs:347
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc/util/common.rs:34
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc_typeck/lib.rs:347
  17:     0x7f27b5f64d01 - rustc_driver::driver::phase_3_run_analysis_passes::{{closure}}::hd352d0090529a6be
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc_driver/driver.rs:895
  18:     0x7f27b5f51b88 - rustc_driver::driver::phase_3_run_analysis_passes::hf45ad5d717ac6301
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc/ty/context.rs:1033
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libstd/thread/local.rs:245
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc/ty/context.rs:1030
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc/ty/context.rs:1017
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libstd/thread/local.rs:245
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc/ty/context.rs:1014
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc/ty/context.rs:782
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc_driver/driver.rs:865
  19:     0x7f27b5f381d2 - rustc_driver::driver::compile_input::hc9da7de451d406ba
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc_driver/driver.rs:171
  20:     0x7f27b5f7db47 - rustc_driver::run_compiler::h408af14fa24a33a5
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc_driver/lib.rs:221
  21:     0x7f27b5e9b9e8 - std::panicking::try::do_call::h2c149962956958c1
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc_driver/lib.rs:1117
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc_driver/lib.rs:137
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/librustc_driver/lib.rs:1051
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libstd/panic.rs:295
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libstd/panicking.rs:458
  22:     0x7f27b5bd73ca - __rust_maybe_catch_panic
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libpanic_unwind/lib.rs:98
  23:     0x7f27b5ebd328 - <F as alloc::boxed::FnBox<A>>::call_box::hf839c55097f480b2
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libstd/panicking.rs:434
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libstd/panic.rs:351
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libstd/thread/mod.rs:287
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/liballoc/boxed.rs:605
  24:     0x7f27b5bcd564 - std::sys::imp::thread::Thread::new::thread_start::h1fa04983ba2271d0
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/liballoc/boxed.rs:615
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libstd/sys_common/thread.rs:21
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/libstd/sys/unix/thread.rs:84
  25:     0x7f27addd1709 - start_thread
  26:     0x7f27b588a82c - clone
  27:                0x0 - <unknown>

error: Could not compile `compiler_error`.

Caused by:
  process didn't exit successfully: `rustc --crate-name compiler_error src/lib.rs --crate-type lib -g -C metadata=8b5a0bdfc8a3f707 -C extra-filename=-8b5a0bdfc8a3f707 --out-dir /home/pfaria/compiler_error/target/debug/deps --emit=dep-info,link -L dependency=/home/pfaria/compiler_error/target/debug/deps` (exit code: 101)

[petrochenkov]

Duplicate of #38409, fixed in #38154