Closed
Description
The original problem I tried to solve can be found here:
Referencing to a value with lifetime to pass it to a FnMut.
This code causes an ICE:
Code
#![feature(generic_associated_types)]
struct Foo<'a> {
foo: &'a mut usize,
}
trait Bar<'a> {
type FooRef<'b>
where
'a : 'b,
;
fn uwu (
foo: Foo<'a>,
f: impl for<'b> FnMut(Self::FooRef<'b>),
)
;
}
impl<'a> Bar<'a> for () {
type FooRef<'b>
=
&'b Foo<'a>
where
'a : 'b,
;
fn uwu (
foo: Foo<'a>,
mut f: impl for<'b> FnMut(&'b Foo<'a>), //relevant part
)
{
f(&foo);
}
}The behavior differs when I replace FnMut(&'b Foo<'a> with Self::FooRef<'b>. Then the compiling fails without an ICE:
Compiling playground v0.0.1 (/playground)
error[[E0478]](https://doc.rust-lang.org/nightly/error-index.html#E0478): lifetime bound not satisfied
--> src/lib.rs:26:8
|
26 | fn uwu (
| ^^^
|
note: lifetime parameter instantiated with the lifetime `'a` as defined here
--> src/lib.rs:18:6
|
18 | impl<'a> Bar<'a> for () {
| ^^
The compiling succeeds when all 'a : 'b are replaced with &'a () : 'b. Playground
Thanks Yandros for elaborating these details! (I don't know your github name)
Meta
rustc 1.65.0-nightly (86c6ebee8 2022-08-16) running on x86_64-unknown-linux-gnu
Error output
Compiling playground v0.0.1 (/playground)
warning: field `foo` is never read
--> src/lib.rs:4:5
|
3 | struct Foo<'a> {
| --- field in this struct
4 | foo: &'a mut usize,
| ^^^
|
= note: `#[warn(dead_code)]` on by default
error: internal compiler error: no errors encountered even though `delay_span_bug` issued
error: internal compiler error: failed region resolution while normalizing ParamEnv { caller_bounds: [Binder(ProjectionPredicate(ProjectionTy { substs: [impl for<'b> FnMut(&'b Foo<'a>), (<() as Bar<'a>>::FooRef<'b>,)], item_def_id: DefId(2:3527 ~ core[d628]::ops::function::FnOnce::Output) }, Ty(())), [Region(BrNamed(DefId(0:12 ~ playground[e047]::Bar::uwu::{opaque#0}::'b), 'b))]), Binder(TraitPredicate(<impl for<'b> FnMut(&'b Foo<'a>) as std::ops::FnMut<(<() as Bar<'a>>::FooRef<'b>,)>>, polarity:Positive), [Region(BrNamed(DefId(0:12 ~ playground[e047]::Bar::uwu::{opaque#0}::'b), 'b))]), Binder(TraitPredicate(<impl for<'b> FnMut(&'b Foo<'a>) as std::ops::FnOnce<(<() as Bar<'a>>::FooRef<'b>,)>>, polarity:Positive), [Region(BrNamed(DefId(0:12 ~ playground[e047]::Bar::uwu::{opaque#0}::'b), 'b))]), Binder(TraitPredicate(<impl for<'b> FnMut(&'b Foo<'a>) as std::marker::Sized>, polarity:Positive), [])], reveal: UserFacing, constness: NotConst }: [ConcreteFailure(RelateRegionParamBound(src/lib.rs:26:5: 29:6 (#0)), RePlaceholder(Placeholder { universe: U1, name: BrNamed(DefId(0:12 ~ playground[e047]::Bar::uwu::{opaque#0}::'b), 'b) }), ReEarlyBound(0, 'a)), ConcreteFailure(RelateRegionParamBound(src/lib.rs:26:5: 29:6 (#0)), RePlaceholder(Placeholder { universe: U2, name: BrNamed(DefId(0:12 ~ playground[e047]::Bar::uwu::{opaque#0}::'b), 'b) }), ReEarlyBound(0, 'a)), ConcreteFailure(RelateRegionParamBound(src/lib.rs:26:5: 29:6 (#0)), RePlaceholder(Placeholder { universe: U3, name: BrNamed(DefId(0:12 ~ playground[e047]::Bar::uwu::{opaque#0}::'b), 'b) }), ReEarlyBound(0, 'a))]
--> src/lib.rs:26:5
|
26 | / fn uwu (
27 | | foo: Foo<'a>,
28 | | mut f: impl for<'b> FnMut(&'b Foo<'a>),
29 | | )
| |_____^
|
= note: delayed at compiler/rustc_trait_selection/src/traits/mod.rs:246:22
thread 'rustc' panicked at 'Box<dyn Any>', compiler/rustc_errors/src/lib.rs:1426:13
Backtrace
0: 0x7f036805e6d0 - std::backtrace_rs::backtrace::libunwind::trace::h328903891f1ac962
at /rustc/86c6ebee8fa0a5ad1e18e375113b06bd2849b634/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
1: 0x7f036805e6d0 - std::backtrace_rs::backtrace::trace_unsynchronized::h9cae1c2b6b95e283
at /rustc/86c6ebee8fa0a5ad1e18e375113b06bd2849b634/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
2: 0x7f036805e6d0 - std::sys_common::backtrace::_print_fmt::h66058888c3f62113
at /rustc/86c6ebee8fa0a5ad1e18e375113b06bd2849b634/library/std/src/sys_common/backtrace.rs:66:5
3: 0x7f036805e6d0 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::hbd5c004e9efb9ba2
at /rustc/86c6ebee8fa0a5ad1e18e375113b06bd2849b634/library/std/src/sys_common/backtrace.rs:45:22
4: 0x7f03680b976e - core::fmt::write::h8f3478ef5df05a9d
at /rustc/86c6ebee8fa0a5ad1e18e375113b06bd2849b634/library/core/src/fmt/mod.rs:1202:17
5: 0x7f036804f5d5 - std::io::Write::write_fmt::habe0caeb57ead591
at /rustc/86c6ebee8fa0a5ad1e18e375113b06bd2849b634/library/std/src/io/mod.rs:1672:15
6: 0x7f0368061393 - std::sys_common::backtrace::_print::h287226fc48c2ff2f
at /rustc/86c6ebee8fa0a5ad1e18e375113b06bd2849b634/library/std/src/sys_common/backtrace.rs:48:5
7: 0x7f0368061393 - std::sys_common::backtrace::print::h780c6aa9646c0456
at /rustc/86c6ebee8fa0a5ad1e18e375113b06bd2849b634/library/std/src/sys_common/backtrace.rs:35:9
8: 0x7f0368061393 - std::panicking::default_hook::{{closure}}::hac00efbd46ee1160
at /rustc/86c6ebee8fa0a5ad1e18e375113b06bd2849b634/library/std/src/panicking.rs:295:22
9: 0x7f036806107f - std::panicking::default_hook::hd5470e8f0b27a6bd
at /rustc/86c6ebee8fa0a5ad1e18e375113b06bd2849b634/library/std/src/panicking.rs:314:9
10: 0x7f036a896a44 - rustc_driver[18fce8fcccec4a33]::DEFAULT_HOOK::{closure#0}::{closure#0}
11: 0x7f0368061bcd - std::panicking::rust_panic_with_hook::h5ec17662a20c0edd
at /rustc/86c6ebee8fa0a5ad1e18e375113b06bd2849b634/library/std/src/panicking.rs:702:17
12: 0x7f036b95a241 - std[5fd532954ff53d47]::panicking::begin_panic::<rustc_errors[5aa25185040b39a]::ExplicitBug>::{closure#0}
13: 0x7f036b95a1f6 - std[5fd532954ff53d47]::sys_common::backtrace::__rust_end_short_backtrace::<std[5fd532954ff53d47]::panicking::begin_panic<rustc_errors[5aa25185040b39a]::ExplicitBug>::{closure#0}, !>
14: 0x7f036b954ca6 - std[5fd532954ff53d47]::panicking::begin_panic::<rustc_errors[5aa25185040b39a]::ExplicitBug>
15: 0x7f036b957286 - std[5fd532954ff53d47]::panic::panic_any::<rustc_errors[5aa25185040b39a]::ExplicitBug>
16: 0x7f036a3be970 - <rustc_errors[5aa25185040b39a]::HandlerInner as core[d628f3806372268a]::ops::drop::Drop>::drop
17: 0x7f036a0d0408 - core[d628f3806372268a]::ptr::drop_in_place::<rustc_session[c8f4ed044bfefb6c]::parse::ParseSess>
18: 0x7f036a0b8233 - <alloc[2c946ccec12a76bb]::rc::Rc<rustc_session[c8f4ed044bfefb6c]::session::Session> as core[d628f3806372268a]::ops::drop::Drop>::drop
19: 0x7f036a0b778d - core[d628f3806372268a]::ptr::drop_in_place::<rustc_interface[4a84693f72592b98]::interface::Compiler>
20: 0x7f036a0b6c39 - rustc_span[593a361d701c283c]::with_source_map::<core[d628f3806372268a]::result::Result<(), rustc_errors[5aa25185040b39a]::ErrorGuaranteed>, rustc_interface[4a84693f72592b98]::interface::create_compiler_and_run<core[d628f3806372268a]::result::Result<(), rustc_errors[5aa25185040b39a]::ErrorGuaranteed>, rustc_driver[18fce8fcccec4a33]::run_compiler::{closure#1}>::{closure#1}>
21: 0x7f036a0b6462 - rustc_interface[4a84693f72592b98]::interface::create_compiler_and_run::<core[d628f3806372268a]::result::Result<(), rustc_errors[5aa25185040b39a]::ErrorGuaranteed>, rustc_driver[18fce8fcccec4a33]::run_compiler::{closure#1}>
22: 0x7f036a0b5001 - <scoped_tls[ec94400a14ecf1fb]::ScopedKey<rustc_span[593a361d701c283c]::SessionGlobals>>::set::<rustc_interface[4a84693f72592b98]::interface::run_compiler<core[d628f3806372268a]::result::Result<(), rustc_errors[5aa25185040b39a]::ErrorGuaranteed>, rustc_driver[18fce8fcccec4a33]::run_compiler::{closure#1}>::{closure#0}, core[d628f3806372268a]::result::Result<(), rustc_errors[5aa25185040b39a]::ErrorGuaranteed>>
23: 0x7f036a0b4cef - std[5fd532954ff53d47]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[4a84693f72592b98]::util::run_in_thread_pool_with_globals<rustc_interface[4a84693f72592b98]::interface::run_compiler<core[d628f3806372268a]::result::Result<(), rustc_errors[5aa25185040b39a]::ErrorGuaranteed>, rustc_driver[18fce8fcccec4a33]::run_compiler::{closure#1}>::{closure#0}, core[d628f3806372268a]::result::Result<(), rustc_errors[5aa25185040b39a]::ErrorGuaranteed>>::{closure#0}, core[d628f3806372268a]::result::Result<(), rustc_errors[5aa25185040b39a]::ErrorGuaranteed>>
24: 0x7f036a6c2719 - <<std[5fd532954ff53d47]::thread::Builder>::spawn_unchecked_<rustc_interface[4a84693f72592b98]::util::run_in_thread_pool_with_globals<rustc_interface[4a84693f72592b98]::interface::run_compiler<core[d628f3806372268a]::result::Result<(), rustc_errors[5aa25185040b39a]::ErrorGuaranteed>, rustc_driver[18fce8fcccec4a33]::run_compiler::{closure#1}>::{closure#0}, core[d628f3806372268a]::result::Result<(), rustc_errors[5aa25185040b39a]::ErrorGuaranteed>>::{closure#0}, core[d628f3806372268a]::result::Result<(), rustc_errors[5aa25185040b39a]::ErrorGuaranteed>>::{closure#1} as core[d628f3806372268a]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
25: 0x7f036806b9c3 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h4fe4faa13dc6a27b
at /rustc/86c6ebee8fa0a5ad1e18e375113b06bd2849b634/library/alloc/src/boxed.rs:1935:9
26: 0x7f036806b9c3 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h17b55ecd9f8a7fb6
at /rustc/86c6ebee8fa0a5ad1e18e375113b06bd2849b634/library/alloc/src/boxed.rs:1935:9
27: 0x7f036806b9c3 - std::sys::unix::thread::Thread::new::thread_start::ha9824217d895d25c
at /rustc/86c6ebee8fa0a5ad1e18e375113b06bd2849b634/library/std/src/sys/unix/thread.rs:108:17
28: 0x7f0367f3f609 - start_thread
29: 0x7f0367e62133 - clone
30: 0x0 - <unknown>