ICE: "resolving bounds outside of type inference": -Zmir-opt-level=3 --emit=mir

[matthiaskrgr]

Code

// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

// run-pass

// Check that tautalogically false bounds are accepted, and are used
// in type inference.
#![feature(trivial_bounds)]
#![allow(unused)]

pub trait Foo {
    fn test(&self);
}

fn generic_function<X: Foo>(x: X) {}

enum E where i32: Foo { V }

struct S where i32: Foo;

trait T where i32: Foo {}

union U where i32: Foo { f: i32 }

type Y where i32: Foo = ();

impl Foo for () where i32: Foo {
    fn test(&self) {
        3i32.test();
        Foo::test(&4i32);
        generic_function(5i32);
    }
}

fn f() where i32: Foo {
    let s = S;
    3i32.test();
    Foo::test(&4i32);
    generic_function(5i32);
}

fn g() where &'static str: Foo {
    "Foo".test();
    Foo::test(&"Foo");
    generic_function("Foo");
}

trait A {}

impl A for i32 {}

struct Dst<X: ?Sized> {
    x: X,
}

struct TwoStrs(str, str) where str: Sized;

fn unsized_local() where for<'a> Dst<A + 'a>: Sized {
    let x: Dst<A> = *(Box::new(Dst { x: 1 }) as Box<Dst<A>>);
}

fn return_str() -> str where str: Sized {
    *"Sized".to_string().into_boxed_str()
}

fn use_op(s: String) -> String where String: ::std::ops::Neg<Output=String> {
    -s
}

fn use_for() where i32: Iterator {
    for _ in 2i32 {}
}

fn main() {}

Meta

rustc --version --verbose:

rustc 1.62.0-nightly (878c7833f 2022-04-16)
binary: rustc
commit-hash: 878c7833f6c1ff10e2fd89074e5bd4ef5ff15936
commit-date: 2022-04-16
host: x86_64-unknown-linux-gnu
release: 1.62.0-nightly
LLVM version: 14.0.0

Error output

warning: trait objects without an explicit `dyn` are deprecated
  --> ./2c8b873b8c9462db590283b28bf0778bd62ac0e4.rs:65:38
   |
65 | fn unsized_local() where for<'a> Dst<A + 'a>: Sized {
   |                                      ^^^^^^
   |
   = note: `#[warn(bare_trait_objects)]` on by default
   = warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
   = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>
help: use `dyn`
   |
65 - fn unsized_local() where for<'a> Dst<A + 'a>: Sized {
65 + fn unsized_local() where for<'a> Dst<dyn A + 'a>: Sized {
   |

warning: trait objects without an explicit `dyn` are deprecated
  --> ./2c8b873b8c9462db590283b28bf0778bd62ac0e4.rs:66:16
   |
66 |     let x: Dst<A> = *(Box::new(Dst { x: 1 }) as Box<Dst<A>>);
   |                ^
   |
   = warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
   = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>
help: use `dyn`
   |
66 -     let x: Dst<A> = *(Box::new(Dst { x: 1 }) as Box<Dst<A>>);
66 +     let x: Dst<dyn A> = *(Box::new(Dst { x: 1 }) as Box<Dst<A>>);
   |

warning: trait objects without an explicit `dyn` are deprecated
  --> ./2c8b873b8c9462db590283b28bf0778bd62ac0e4.rs:66:57
   |
66 |     let x: Dst<A> = *(Box::new(Dst { x: 1 }) as Box<Dst<A>>);
   |                                                         ^
   |
   = warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
   = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>
help: use `dyn`
   |
66 -     let x: Dst<A> = *(Box::new(Dst { x: 1 }) as Box<Dst<A>>);
66 +     let x: Dst<A> = *(Box::new(Dst { x: 1 }) as Box<Dst<dyn A>>);
   |

warning: trait bound i32: Foo does not depend on any type or lifetime parameters
  --> ./2c8b873b8c9462db590283b28bf0778bd62ac0e4.rs:24:19
   |
24 | enum E where i32: Foo { V }
   |                   ^^^
   |
   = note: `#[warn(trivial_bounds)]` on by default

warning: trait bound i32: Foo does not depend on any type or lifetime parameters
  --> ./2c8b873b8c9462db590283b28bf0778bd62ac0e4.rs:26:21
   |
26 | struct S where i32: Foo;
   |                     ^^^

warning: trait bound i32: Foo does not depend on any type or lifetime parameters
  --> ./2c8b873b8c9462db590283b28bf0778bd62ac0e4.rs:28:20
   |
28 | trait T where i32: Foo {}
   |                    ^^^

warning: trait bound i32: Foo does not depend on any type or lifetime parameters
  --> ./2c8b873b8c9462db590283b28bf0778bd62ac0e4.rs:30:20
   |
30 | union U where i32: Foo { f: i32 }
   |                    ^^^

warning: where clauses are not enforced in type aliases
  --> ./2c8b873b8c9462db590283b28bf0778bd62ac0e4.rs:32:14
   |
32 | type Y where i32: Foo = ();
   |              ^^^^^^^^
   |
   = note: `#[warn(type_alias_bounds)]` on by default
help: the clause will not be checked when the type alias is used, and should be removed
   |
32 - type Y where i32: Foo = ();
32 + type Y  = ();
   |

warning: trait bound i32: Foo does not depend on any type or lifetime parameters
  --> ./2c8b873b8c9462db590283b28bf0778bd62ac0e4.rs:32:19
   |
32 | type Y where i32: Foo = ();
   |                   ^^^

warning: trait bound i32: Foo does not depend on any type or lifetime parameters
  --> ./2c8b873b8c9462db590283b28bf0778bd62ac0e4.rs:34:28
   |
34 | impl Foo for () where i32: Foo {
   |                            ^^^

warning: trait bound i32: Foo does not depend on any type or lifetime parameters
  --> ./2c8b873b8c9462db590283b28bf0778bd62ac0e4.rs:42:19
   |
42 | fn f() where i32: Foo {
   |                   ^^^

warning: trait bound &'static str: Foo does not depend on any type or lifetime parameters
  --> ./2c8b873b8c9462db590283b28bf0778bd62ac0e4.rs:49:28
   |
49 | fn g() where &'static str: Foo {
   |                            ^^^

warning: trait bound str: Sized does not depend on any type or lifetime parameters
  --> ./2c8b873b8c9462db590283b28bf0778bd62ac0e4.rs:63:37
   |
63 | struct TwoStrs(str, str) where str: Sized;
   |                                     ^^^^^

warning: trait bound for<'a> Dst<(dyn A + 'a)>: Sized does not depend on any type or lifetime parameters
  --> ./2c8b873b8c9462db590283b28bf0778bd62ac0e4.rs:65:47
   |
65 | fn unsized_local() where for<'a> Dst<A + 'a>: Sized {
   |                                               ^^^^^

warning: trait bound str: Sized does not depend on any type or lifetime parameters
  --> ./2c8b873b8c9462db590283b28bf0778bd62ac0e4.rs:69:35
   |
69 | fn return_str() -> str where str: Sized {
   |                                   ^^^^^

warning: trait bound String: Neg does not depend on any type or lifetime parameters
  --> ./2c8b873b8c9462db590283b28bf0778bd62ac0e4.rs:73:46
   |
73 | fn use_op(s: String) -> String where String: ::std::ops::Neg<Output=String> {
   |                                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

warning: trait bound i32: Iterator does not depend on any type or lifetime parameters
  --> ./2c8b873b8c9462db590283b28bf0778bd62ac0e4.rs:77:25
   |
77 | fn use_for() where i32: Iterator {
   |                         ^^^^^^^^

warning: 17 warnings emitted

error: internal compiler error: no errors encountered even though `delay_span_bug` issued

error: internal compiler error: Encountered error `Unimplemented` selecting `Binder(<i32 as Foo>, [])` during codegen
  |
  = note: delayed at compiler/rustc_trait_selection/src/traits/codegen.rs:65:43

error: internal compiler error: Encountered error `Unimplemented` selecting `Binder(<&str as Foo>, [])` during codegen
  |
  = note: delayed at compiler/rustc_trait_selection/src/traits/codegen.rs:65:43

error: internal compiler error: Encountered error `Unimplemented` selecting `Binder(<std::string::String as std::ops::Neg>, [])` during codegen
  |
  = note: delayed at compiler/rustc_trait_selection/src/traits/codegen.rs:65:43

error: internal compiler error: Encountered errors `[FulfillmentError(Obligation(predicate=Binder(TraitPredicate(<i32 as std::iter::Iterator>, polarity:Positive), []), depth=1),Unimplemented)]` resolving bounds outside of type inference
  |
  = note: delayed at compiler/rustc_trait_selection/src/traits/codegen.rs:125:24

error: internal compiler error: Encountered error `Unimplemented` selecting `Binder(<i32 as std::iter::Iterator>, [])` during codegen
  |
  = note: delayed at compiler/rustc_trait_selection/src/traits/codegen.rs:65:43

thread 'rustc' panicked at 'Box<dyn Any>', compiler/rustc_errors/src/lib.rs:1383:13
stack backtrace:

Backtrace

warning: 17 warnings emitted

error: internal compiler error: no errors encountered even though `delay_span_bug` issued

error: internal compiler error: Encountered error `Unimplemented` selecting `Binder(<i32 as Foo>, [])` during codegen
  |
  = note: delayed at compiler/rustc_trait_selection/src/traits/codegen.rs:65:43

error: internal compiler error: Encountered error `Unimplemented` selecting `Binder(<&str as Foo>, [])` during codegen
  |
  = note: delayed at compiler/rustc_trait_selection/src/traits/codegen.rs:65:43

error: internal compiler error: Encountered error `Unimplemented` selecting `Binder(<std::string::String as std::ops::Neg>, [])` during codegen
  |
  = note: delayed at compiler/rustc_trait_selection/src/traits/codegen.rs:65:43

error: internal compiler error: Encountered errors `[FulfillmentError(Obligation(predicate=Binder(TraitPredicate(<i32 as std::iter::Iterator>, polarity:Positive), []), depth=1),Unimplemented)]` resolving bounds outside of type inference
  |
  = note: delayed at compiler/rustc_trait_selection/src/traits/codegen.rs:125:24

error: internal compiler error: Encountered error `Unimplemented` selecting `Binder(<i32 as std::iter::Iterator>, [])` during codegen
  |
  = note: delayed at compiler/rustc_trait_selection/src/traits/codegen.rs:65:43

thread 'rustc' panicked at 'Box<dyn Any>', compiler/rustc_errors/src/lib.rs:1383:13
stack backtrace:
   0:     0x7f1344e9d7fd - std::backtrace_rs::backtrace::libunwind::trace::h533af29c806df9d1
                               at /rustc/878c7833f6c1ff10e2fd89074e5bd4ef5ff15936/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
   1:     0x7f1344e9d7fd - std::backtrace_rs::backtrace::trace_unsynchronized::hdb4c2ff88b52ef66
                               at /rustc/878c7833f6c1ff10e2fd89074e5bd4ef5ff15936/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f1344e9d7fd - std::sys_common::backtrace::_print_fmt::h68495a06222c4efb
                               at /rustc/878c7833f6c1ff10e2fd89074e5bd4ef5ff15936/library/std/src/sys_common/backtrace.rs:66:5
   3:     0x7f1344e9d7fd - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h91043f683408357d
                               at /rustc/878c7833f6c1ff10e2fd89074e5bd4ef5ff15936/library/std/src/sys_common/backtrace.rs:45:22
   4:     0x7f1344ef8eec - core::fmt::write::hcc15453d8963f001
                               at /rustc/878c7833f6c1ff10e2fd89074e5bd4ef5ff15936/library/core/src/fmt/mod.rs:1194:17
   5:     0x7f1344e8ef51 - std::io::Write::write_fmt::h5217846c280e1260
                               at /rustc/878c7833f6c1ff10e2fd89074e5bd4ef5ff15936/library/std/src/io/mod.rs:1655:15
   6:     0x7f1344ea0515 - std::sys_common::backtrace::_print::h88be4bfce1061450
                               at /rustc/878c7833f6c1ff10e2fd89074e5bd4ef5ff15936/library/std/src/sys_common/backtrace.rs:48:5
   7:     0x7f1344ea0515 - std::sys_common::backtrace::print::he017a6566e010988
                               at /rustc/878c7833f6c1ff10e2fd89074e5bd4ef5ff15936/library/std/src/sys_common/backtrace.rs:35:9
   8:     0x7f1344ea0515 - std::panicking::default_hook::{{closure}}::hb793c4d82607bce7
                               at /rustc/878c7833f6c1ff10e2fd89074e5bd4ef5ff15936/library/std/src/panicking.rs:295:22
   9:     0x7f1344ea0189 - std::panicking::default_hook::hc3c558385f484fdc
                               at /rustc/878c7833f6c1ff10e2fd89074e5bd4ef5ff15936/library/std/src/panicking.rs:314:9
  10:     0x7f13456d1421 - rustc_driver[19d608e2c8daf1f4]::DEFAULT_HOOK::{closure#0}::{closure#0}
  11:     0x7f1344ea0ce6 - std::panicking::rust_panic_with_hook::h28c3b2fc9e3a60cd
                               at /rustc/878c7833f6c1ff10e2fd89074e5bd4ef5ff15936/library/std/src/panicking.rs:702:17
  12:     0x7f134681af31 - std[cd658a55527ed977]::panicking::begin_panic::<rustc_errors[9417c7ccc58903d8]::ExplicitBug>::{closure#0}
  13:     0x7f1346819fe6 - std[cd658a55527ed977]::sys_common::backtrace::__rust_end_short_backtrace::<std[cd658a55527ed977]::panicking::begin_panic<rustc_errors[9417c7ccc58903d8]::ExplicitBug>::{closure#0}, !>
  14:     0x7f1346822fdf - std[cd658a55527ed977]::panicking::begin_panic::<rustc_errors[9417c7ccc58903d8]::ExplicitBug>
  15:     0x7f13468260f6 - std[cd658a55527ed977]::panic::panic_any::<rustc_errors[9417c7ccc58903d8]::ExplicitBug>
  16:     0x7f1347fde317 - <rustc_errors[9417c7ccc58903d8]::HandlerInner as core[9a854ec5d686c1fc]::ops::drop::Drop>::drop
  17:     0x7f13476ecea8 - core[9a854ec5d686c1fc]::ptr::drop_in_place::<rustc_session[52f1952c06c4e035]::parse::ParseSess>
  18:     0x7f13476ef4c3 - <alloc[c0e4610846cb0c5f]::rc::Rc<rustc_session[52f1952c06c4e035]::session::Session> as core[9a854ec5d686c1fc]::ops::drop::Drop>::drop
  19:     0x7f13477197ad - core[9a854ec5d686c1fc]::ptr::drop_in_place::<rustc_interface[c2767953942b9161]::interface::Compiler>
  20:     0x7f13477190a4 - rustc_span[ae9ba53627e4b7a2]::with_source_map::<core[9a854ec5d686c1fc]::result::Result<(), rustc_errors[9417c7ccc58903d8]::ErrorGuaranteed>, rustc_interface[c2767953942b9161]::interface::create_compiler_and_run<core[9a854ec5d686c1fc]::result::Result<(), rustc_errors[9417c7ccc58903d8]::ErrorGuaranteed>, rustc_driver[19d608e2c8daf1f4]::run_compiler::{closure#1}>::{closure#1}>
  21:     0x7f13476f0ee7 - <scoped_tls[673d87c3fad674a0]::ScopedKey<rustc_span[ae9ba53627e4b7a2]::SessionGlobals>>::set::<rustc_interface[c2767953942b9161]::interface::run_compiler<core[9a854ec5d686c1fc]::result::Result<(), rustc_errors[9417c7ccc58903d8]::ErrorGuaranteed>, rustc_driver[19d608e2c8daf1f4]::run_compiler::{closure#1}>::{closure#0}, core[9a854ec5d686c1fc]::result::Result<(), rustc_errors[9417c7ccc58903d8]::ErrorGuaranteed>>
  22:     0x7f13477062ff - std[cd658a55527ed977]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[c2767953942b9161]::util::run_in_thread_pool_with_globals<rustc_interface[c2767953942b9161]::interface::run_compiler<core[9a854ec5d686c1fc]::result::Result<(), rustc_errors[9417c7ccc58903d8]::ErrorGuaranteed>, rustc_driver[19d608e2c8daf1f4]::run_compiler::{closure#1}>::{closure#0}, core[9a854ec5d686c1fc]::result::Result<(), rustc_errors[9417c7ccc58903d8]::ErrorGuaranteed>>::{closure#0}, core[9a854ec5d686c1fc]::result::Result<(), rustc_errors[9417c7ccc58903d8]::ErrorGuaranteed>>
  23:     0x7f1347706439 - <<std[cd658a55527ed977]::thread::Builder>::spawn_unchecked_<rustc_interface[c2767953942b9161]::util::run_in_thread_pool_with_globals<rustc_interface[c2767953942b9161]::interface::run_compiler<core[9a854ec5d686c1fc]::result::Result<(), rustc_errors[9417c7ccc58903d8]::ErrorGuaranteed>, rustc_driver[19d608e2c8daf1f4]::run_compiler::{closure#1}>::{closure#0}, core[9a854ec5d686c1fc]::result::Result<(), rustc_errors[9417c7ccc58903d8]::ErrorGuaranteed>>::{closure#0}, core[9a854ec5d686c1fc]::result::Result<(), rustc_errors[9417c7ccc58903d8]::ErrorGuaranteed>>::{closure#1} as core[9a854ec5d686c1fc]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  24:     0x7f1344eaab93 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::ha55af26f35189599
                               at /rustc/878c7833f6c1ff10e2fd89074e5bd4ef5ff15936/library/alloc/src/boxed.rs:1866:9
  25:     0x7f1344eaab93 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h6a841b0f36efd076
                               at /rustc/878c7833f6c1ff10e2fd89074e5bd4ef5ff15936/library/alloc/src/boxed.rs:1866:9
  26:     0x7f1344eaab93 - std::sys::unix::thread::Thread::new::thread_start::h4d154f7a3783bf9b
                               at /rustc/878c7833f6c1ff10e2fd89074e5bd4ef5ff15936/library/std/src/sys/unix/thread.rs:108:17
  27:     0x7f1344c835c2 - start_thread
  28:     0x7f1344d08584 - __clone
  29:                0x0 - <unknown>

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

note: we would appreciate a bug report: https://github.com/rust-lang/rust/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: rustc 1.62.0-nightly (878c7833f 2022-04-16) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z mir-opt-level=3

query stack during panic:
end of query stack