Complier Crash: internal compiler error: cannot relate bound region

[sbwtw]

I'm using Rocket to build my website, and got a complier error, here is a minimum demo to reproduce:

Cargo.toml:

[package]
name = "demo"
version = "0.1.0"
authors = ["石博文 <sbw@sbw.so>"]

[dependencies]
rocket = "*"
rocket_codegen = "*"
mysql = "*"

[dependencies.rocket_contrib]
version = "*"
default-features = false

main.rs:

#![feature(conservative_impl_trait)]
#![feature(plugin, custom_derive)]
#![plugin(rocket_codegen)]

extern crate rocket;
extern crate rocket_contrib;

use rocket::response::*;
use rocket::http::*;

#[get("/<hash>")]
fn index_with_hash(hash: &RawStr) -> impl Responder {

    if hash.len() != 0 {
        let url = vec![];

        return Some(Redirect::to(std::str::from_utf8(&url).unwrap()));
    }

    return None;
}

fn main() {
    rocket::ignite()
        .mount("/", routes![index_with_hash])
        .launch();
}

here is output after execute cargo build --verbose

       Fresh yansi v0.3.4
       Fresh language-tags v0.2.2
       Fresh lazy_static v0.2.8
       Fresh ordermap v0.2.12
       Fresh dtoa v0.4.2
       Fresh version_check v0.1.3
       Fresh libc v0.2.31
       Fresh httparse v1.2.3
       Fresh cfg-if v0.1.2
       Fresh log v0.3.8
       Fresh scopeguard v0.3.2
       Fresh regex-syntax v0.4.1
       Fresh bufstream v0.1.3
       Fresh utf8-ranges v1.0.0
       Fresh bit-vec v0.4.4
       Fresh num-traits v0.1.40
       Fresh safemem v0.2.0
       Fresh void v1.0.2
       Fresh futures v0.1.16
       Fresh untrusted v0.5.1
       Fresh gcc v0.3.54
       Fresh traitobject v0.1.0
       Fresh fnv v1.0.5
       Fresh smallvec v0.4.3
       Fresh pear_codegen v0.0.10
       Fresh unicode-normalization v0.1.5
       Fresh pear v0.0.10
       Fresh byteorder v1.1.0
       Fresh matches v0.1.6
       Fresh state v0.3.2
       Fresh uuid v0.5.1
       Fresh serde v1.0.15
       Fresh bitflags v0.9.1
       Fresh percent-encoding v1.0.0
       Fresh typeable v0.1.2
       Fresh either v1.1.0
       Fresh itoa v0.3.4
       Fresh isatty v0.1.3
       Fresh time v0.1.38
       Fresh num_cpus v1.6.2
       Fresh memchr v1.0.1
       Fresh rand v0.3.16
       Fresh net2 v0.2.31
       Fresh mime v0.2.6
       Fresh atoi v0.2.2
       Fresh num-integer v0.1.35
       Fresh unreachable v1.0.0
       Fresh base64 v0.6.0
       Fresh unicode-bidi v0.3.4
       Fresh toml v0.4.5
       Fresh nix v0.9.0
       Fresh coco v0.1.1
       Fresh serde_json v1.0.3
       Fresh aho-corasick v0.6.3
       Fresh twox-hash v1.1.0
       Fresh num-iter v0.1.34
       Fresh thread_local v0.3.4
       Fresh idna v0.1.4
       Fresh rayon-core v1.2.1
       Fresh unicase v1.4.2
       Fresh num v0.1.40
       Fresh regex v0.2.2
       Fresh url v1.5.1
       Fresh rayon v0.7.1
       Fresh chrono v0.4.0
       Fresh hyper v0.10.13
       Fresh mysql_common v0.2.0
       Fresh mysql v12.0.3
       Fresh ring v0.11.0
       Fresh cookie v0.9.1
       Fresh rocket v0.3.2
       Fresh rocket_contrib v0.3.2
       Fresh rocket_codegen v0.3.2
   Compiling demo v0.1.0 (file:///home/Projects/demo)
     Running `rustc --crate-name demo src/main.rs --crate-type bin --emit=dep-info,link -C debuginfo=2 -C metadata=921caa19a954fe24 -C extra-filename=-921caa19a954fe24 --out-dir /home/.cache/rust-build/debug/deps -L dependency=/home/.cache/rust-build/debug/deps --extern rocket_contrib=/home/.cache/rust-build/debug/deps/librocket_contrib-deae706dc6aff940.rlib --extern mysql=/home/.cache/rust-build/debug/deps/libmysql-eb615418c3bc2492.rlib --extern rocket_codegen=/home/.cache/rust-build/debug/deps/librocket_codegen-d88168fd88807be8.so --extern rocket=/home/.cache/rust-build/debug/deps/librocket-09121367ccb45b19.rlib -L native=/home/.cache/rust-build/debug/build/ring-a774c3003c43ee5b/out`
error: internal compiler error: /checkout/src/librustc/infer/region_inference/mod.rs:706: cannot relate bound region: ReLateBound(DebruijnIndex { depth: 2 }, BrAnon(0)) <= '_#114r
  --> src/main.rs:12:1
   |
12 | #[get("/<hash>")]
   | ^^^^^^^^^^^^^^^^^

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: rustc 1.22.0-nightly (325ba23d5 2017-09-19) running on x86_64-unknown-linux-gnu

thread 'rustc' panicked at 'Box<Any>', /checkout/src/librustc_errors/lib.rs:439:8
note: Run with `RUST_BACKTRACE=1` for a backtrace.

error: Could not compile `demo`.

Caused by:
  process didn't exit successfully: `rustc --crate-name demo src/main.rs --crate-type bin --emit=dep-info,link -C debuginfo=2 -C metadata=921caa19a954fe24 -C extra-filename=-921caa19a954fe24 --out-dir /home/.cache/rust-build/debug/deps -L dependency=/home/.cache/rust-build/debug/deps --extern rocket_contrib=/home/.cache/rust-build/debug/deps/librocket_contrib-deae706dc6aff940.rlib --extern mysql=/home/.cache/rust-build/debug/deps/libmysql-eb615418c3bc2492.rlib --extern rocket_codegen=/home/.cache/rust-build/debug/deps/librocket_codegen-d88168fd88807be8.so --extern rocket=/home/.cache/rust-build/debug/deps/librocket-09121367ccb45b19.rlib -L native=/home/.cache/rust-build/debug/build/ring-a774c3003c43ee5b/out` (exit code: 101)

cc @SergioBenitez

[hashedone]

Exactly same error here. My code can be found here: hashedone/rpgtool@022e181. I found, that the problem is with "impl Trait", everything compiles when I change main.rs:17:

fn index(ctx: State<ViewContext>) -> impl Responder {

to:

fn index(ctx: State<ViewContext>) -> maud::Markup {

rustc version:

➜  rpgtool git:(master) ✗ rustc --version --verbose
rustc 1.22.0-nightly (5dfc84cfa 2017-09-14)
binary: rustc
commit-hash: 5dfc84cfa72b405c194228b53c4de3f6474204ec
commit-date: 2017-09-14
host: x86_64-unknown-linux-gnu
release: 1.22.0-nightly
LLVM version: 4.0

Full backtrace:

   0: std::sys::imp::backtrace::tracing::imp::unwind_backtrace
             at /checkout/src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1: std::sys_common::backtrace::_print
             at /checkout/src/libstd/sys_common/backtrace.rs:71
   2: std::panicking::default_hook::{{closure}}
             at /checkout/src/libstd/sys_common/backtrace.rs:60
             at /checkout/src/libstd/panicking.rs:381
   3: std::panicking::default_hook
             at /checkout/src/libstd/panicking.rs:391
   4: std::panicking::rust_panic_with_hook
             at /checkout/src/libstd/panicking.rs:577
   5: std::panicking::begin_panic
   6: rustc_errors::Handler::span_bug
   7: rustc::session::opt_span_bug_fmt::{{closure}}
   8: rustc::session::opt_span_bug_fmt
   9: rustc::session::span_bug_fmt
  10: rustc::infer::region_inference::RegionVarBindings::make_subregion
  11: rustc::infer::region_inference::RegionVarBindings::make_eqregion
  12: rustc::ty::relate::relate_substs::{{closure}}
  13: <core::result::Result<T, E> as rustc::ty::context::InternIteratorElement<T, R>>::intern_with
  14: rustc::infer::at::At::sub_exp
  15: rustc::traits::select::SelectionContext::match_projection
  16: rustc::traits::select::SelectionContext::match_projection_obligation_against_definition_bounds
  17: rustc::traits::select::SelectionContext::assemble_candidates
  18: rustc::traits::select::SelectionContext::candidate_from_obligation_no_cache
  19: rustc::dep_graph::graph::DepGraph::with_anon_task
  20: rustc::traits::select::SelectionContext::candidate_from_obligation
  21: rustc::traits::select::SelectionContext::select
  22: <rustc::traits::fulfill::FulfillProcessor<'a, 'b, 'gcx, 'tcx> as rustc_data_structures::obligation_forest::ObligationProcessor>::process_obligation
  23: rustc::traits::fulfill::FulfillmentContext::select
  24: rustc::traits::fulfill::FulfillmentContext::select_where_possible
  25: rustc_typeck::check::FnCtxt::select_obligations_where_possible
  26: rustc_typeck::check::FnCtxt::check_argument_types
  27: rustc_typeck::check::callee::<impl rustc_typeck::check::FnCtxt<'a, 'gcx, 'tcx>>::confirm_builtin_call
  28: rustc_typeck::check::FnCtxt::check_expr_kind
  29: rustc_typeck::check::FnCtxt::check_expr_with_expectation_and_lvalue_pref
  30: rustc_typeck::check::FnCtxt::check_block_with_expected::{{closure}}
  31: rustc_typeck::check::FnCtxt::check_block_with_expected
  32: rustc_typeck::check::FnCtxt::check_expr_kind
  33: rustc_typeck::check::FnCtxt::check_expr_with_expectation_and_lvalue_pref
  34: rustc_typeck::check::FnCtxt::check_return_expr
  35: rustc_typeck::check::check_fn
  36: rustc_typeck::check::typeck_tables_of::{{closure}}
  37: rustc_typeck::check::typeck_tables_of
  38: rustc::dep_graph::graph::DepGraph::with_task
  39: rustc::ty::maps::<impl rustc::ty::maps::queries::typeck_tables_of<'tcx>>::try_get
  40: rustc::ty::maps::TyCtxtAt::typeck_tables_of
  41: rustc::ty::maps::<impl rustc::ty::context::TyCtxt<'a, 'tcx, 'lcx>>::typeck_tables_of
  42: rustc_typeck::check::typeck_item_bodies
  43: rustc::dep_graph::graph::DepGraph::with_task
  44: rustc::ty::maps::<impl rustc::ty::maps::queries::typeck_item_bodies<'tcx>>::try_get
  45: rustc::ty::maps::TyCtxtAt::typeck_item_bodies
  46: rustc::ty::maps::<impl rustc::ty::context::TyCtxt<'a, 'tcx, 'lcx>>::typeck_item_bodies
  47: rustc_typeck::check_crate
  48: rustc::ty::context::TyCtxt::create_and_enter
  49: rustc_driver::driver::compile_input
  50: rustc_driver::run_compiler

[SergioBenitez]

This is almost certainly a dup of #43380, which itself is almost certainly a dup of #39872. The gist: Responder takes a lifetime parameter, but you're not supplying one. Supplying one should resolve the panic:

#[get("/")]
fn handler<'r>() -> impl Responder<'r> { ... }

[cramertj]

@sbwtw I believe this should be fixed now. Can you try on the latest nightly and confirm?

[pietroalbini]

Tested locally, this is fixed.