ICE: 'cannot copy unsized immediates' creating Box of trait object with generics

[qwertz19281]

While cargo check succeeds without warnings, cargo build fails on nightly on this code.

On stable 1.64.0, both checking and building succeed without warnings.

Code (playground)

pub trait Widget<E> {
    fn boxed<'w>(self) -> Box<dyn WidgetDyn<E>+'w> where Self: Sized + 'w;
}

pub trait WidgetDyn<E> {}

impl<T,E> WidgetDyn<E> for T where T: Widget<E> {}

impl<E> Widget<E> for dyn WidgetDyn<E> + '_ {
    fn boxed<'w>(self) -> Box<dyn WidgetDyn<E>+'w> where Self: Sized + 'w {
        Box::new(self) //ICE: cannot copy unsized immediates
    }
}

Meta

rustc --version --verbose:

rustc 1.66.0-nightly (8ce3204af 2022-09-30)
binary: rustc
commit-hash: 8ce3204af9463db3192ea1eb31c45c2f6d4b5ae6
commit-date: 2022-09-30
host: x86_64-unknown-linux-gnu
release: 1.66.0-nightly
LLVM version: 15.0.2

Error output

thread 'rustc' panicked at 'cannot copy unsized immediates', /rustc/8ce3204af9463db3192ea1eb31c45c2f6d4b5ae6/compiler/rustc_const_eval/src/interpret/place.rs:643:17

Backtrace

   Compiling playground v0.0.1 (/playground)
thread 'rustc' panicked at 'cannot copy unsized immediates', /rustc/8ce3204af9463db3192ea1eb31c45c2f6d4b5ae6/compiler/rustc_const_eval/src/interpret/place.rs:643:17
stack backtrace:
   0:     0x7f20d3308470 - std::backtrace_rs::backtrace::libunwind::trace::h48a6b877947e3b61
                               at /rustc/8ce3204af9463db3192ea1eb31c45c2f6d4b5ae6/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   1:     0x7f20d3308470 - std::backtrace_rs::backtrace::trace_unsynchronized::hfe09011594941abe
                               at /rustc/8ce3204af9463db3192ea1eb31c45c2f6d4b5ae6/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f20d3308470 - std::sys_common::backtrace::_print_fmt::h9ce2ad36264dcd3e
                               at /rustc/8ce3204af9463db3192ea1eb31c45c2f6d4b5ae6/library/std/src/sys_common/backtrace.rs:66:5
   3:     0x7f20d3308470 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h4f730349406daa4f
                               at /rustc/8ce3204af9463db3192ea1eb31c45c2f6d4b5ae6/library/std/src/sys_common/backtrace.rs:45:22
   4:     0x7f20d336330e - core::fmt::write::h4545826f01b877ac
                               at /rustc/8ce3204af9463db3192ea1eb31c45c2f6d4b5ae6/library/core/src/fmt/mod.rs:1209:17
   5:     0x7f20d32f90f5 - std::io::Write::write_fmt::hac4d3a613c78c8e4
                               at /rustc/8ce3204af9463db3192ea1eb31c45c2f6d4b5ae6/library/std/src/io/mod.rs:1679:15
   6:     0x7f20d330b213 - std::sys_common::backtrace::_print::ha560f7b733dc8a6e
                               at /rustc/8ce3204af9463db3192ea1eb31c45c2f6d4b5ae6/library/std/src/sys_common/backtrace.rs:48:5
   7:     0x7f20d330b213 - std::sys_common::backtrace::print::hcca78599db59c8b4
                               at /rustc/8ce3204af9463db3192ea1eb31c45c2f6d4b5ae6/library/std/src/sys_common/backtrace.rs:35:9
   8:     0x7f20d330b213 - std::panicking::default_hook::{{closure}}::h0d6a74e6cb8499ce
                               at /rustc/8ce3204af9463db3192ea1eb31c45c2f6d4b5ae6/library/std/src/panicking.rs:267:22
   9:     0x7f20d330aeea - std::panicking::default_hook::hcb5d3609ae810fb1
                               at /rustc/8ce3204af9463db3192ea1eb31c45c2f6d4b5ae6/library/std/src/panicking.rs:286:9
  10:     0x7f20d5b6a7d1 - rustc_driver[6635a35d3e701dd7]::DEFAULT_HOOK::{closure#0}::{closure#0}
  11:     0x7f20d330ba4b - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::hba26835306149e75
                               at /rustc/8ce3204af9463db3192ea1eb31c45c2f6d4b5ae6/library/alloc/src/boxed.rs:1952:9
  12:     0x7f20d330ba4b - std::panicking::rust_panic_with_hook::h4f2461a1c1c1a86e
                               at /rustc/8ce3204af9463db3192ea1eb31c45c2f6d4b5ae6/library/std/src/panicking.rs:673:13
  13:     0x7f20d330b861 - std::panicking::begin_panic_handler::{{closure}}::hcad64e5dfff8b9ed
                               at /rustc/8ce3204af9463db3192ea1eb31c45c2f6d4b5ae6/library/std/src/panicking.rs:558:13
  14:     0x7f20d330891c - std::sys_common::backtrace::__rust_end_short_backtrace::h2a66b4ccd8d28c5b
                               at /rustc/8ce3204af9463db3192ea1eb31c45c2f6d4b5ae6/library/std/src/sys_common/backtrace.rs:138:18
  15:     0x7f20d330b5c2 - rust_begin_unwind
                               at /rustc/8ce3204af9463db3192ea1eb31c45c2f6d4b5ae6/library/std/src/panicking.rs:556:5
  16:     0x7f20d335fee3 - core::panicking::panic_fmt::h443d402932f5c508
                               at /rustc/8ce3204af9463db3192ea1eb31c45c2f6d4b5ae6/library/core/src/panicking.rs:142:14
  17:     0x7f20d52394a9 - <rustc_const_eval[596954f8d26f1fb9]::interpret::eval_context::InterpCx<rustc_mir_transform[aa15e105a635a786]::const_prop::ConstPropMachine>>::eval_rvalue_into_place
  18:     0x7f20d4f6a2e9 - <rustc_mir_transform[aa15e105a635a786]::const_prop_lint::ConstPropagator as rustc_middle[cea04118b266f04d]::mir::visit::Visitor>::visit_body
  19:     0x7f20d4f61ccc - <rustc_mir_transform[aa15e105a635a786]::const_prop_lint::ConstProp as rustc_mir_transform[aa15e105a635a786]::pass_manager::MirLint>::run_lint
  20:     0x7f20d460b2f5 - rustc_mir_transform[aa15e105a635a786]::pass_manager::run_passes_no_validate
  21:     0x7f20d4608524 - rustc_mir_transform[aa15e105a635a786]::run_analysis_to_runtime_passes
  22:     0x7f20d4607542 - rustc_mir_transform[aa15e105a635a786]::mir_drops_elaborated_and_const_checked
  23:     0x7f20d510eed3 - rustc_query_system[effbf359c8fbf60]::query::plumbing::try_execute_query::<rustc_query_impl[7290f92e0d30aec0]::plumbing::QueryCtxt, rustc_query_system[effbf359c8fbf60]::query::caches::DefaultCache<rustc_middle[cea04118b266f04d]::ty::WithOptConstParam<rustc_span[ea709073fc09e903]::def_id::LocalDefId>, &rustc_data_structures[83030b31f5a5da14]::steal::Steal<rustc_middle[cea04118b266f04d]::mir::Body>>>
  24:     0x7f20d5aabcce - <rustc_query_impl[7290f92e0d30aec0]::Queries as rustc_middle[cea04118b266f04d]::ty::query::QueryEngine>::mir_drops_elaborated_and_const_checked
  25:     0x7f20d4688fdb - rustc_mir_transform[aa15e105a635a786]::optimized_mir
  26:     0x7f20d45a2562 - rustc_query_system[effbf359c8fbf60]::query::plumbing::try_execute_query::<rustc_query_impl[7290f92e0d30aec0]::plumbing::QueryCtxt, rustc_query_system[effbf359c8fbf60]::query::caches::DefaultCache<rustc_span[ea709073fc09e903]::def_id::DefId, &rustc_middle[cea04118b266f04d]::mir::Body>>
  27:     0x7f20d5aac0bf - <rustc_query_impl[7290f92e0d30aec0]::Queries as rustc_middle[cea04118b266f04d]::ty::query::QueryEngine>::optimized_mir
  28:     0x7f20d4e1974f - <rustc_metadata[c2fa7c38f8bdc238]::rmeta::encoder::EncodeContext>::encode_crate_root
  29:     0x7f20d487f872 - rustc_metadata[c2fa7c38f8bdc238]::rmeta::encoder::encode_metadata_impl
  30:     0x7f20d4865cbe - rustc_data_structures[83030b31f5a5da14]::sync::join::<rustc_metadata[c2fa7c38f8bdc238]::rmeta::encoder::encode_metadata::{closure#0}, rustc_metadata[c2fa7c38f8bdc238]::rmeta::encoder::encode_metadata::{closure#1}, (), ()>
  31:     0x7f20d4865b99 - rustc_metadata[c2fa7c38f8bdc238]::rmeta::encoder::encode_metadata
  32:     0x7f20d4864de3 - rustc_metadata[c2fa7c38f8bdc238]::fs::encode_and_write_metadata
  33:     0x7f20d4858d72 - <rustc_interface[c5619889e11552cd]::passes::QueryContext>::enter::<<rustc_interface[c5619889e11552cd]::queries::Queries>::ongoing_codegen::{closure#0}::{closure#0}, core[7ac8aee7065c0cc9]::result::Result<alloc[31d53a49c811d0c6]::boxed::Box<dyn core[7ac8aee7065c0cc9]::any::Any>, rustc_errors[fbe8c5f47b14aa4]::ErrorGuaranteed>>
  34:     0x7f20d481b343 - <rustc_interface[c5619889e11552cd]::queries::Queries>::ongoing_codegen
  35:     0x7f20d48195ca - rustc_interface[c5619889e11552cd]::interface::create_compiler_and_run::<core[7ac8aee7065c0cc9]::result::Result<(), rustc_errors[fbe8c5f47b14aa4]::ErrorGuaranteed>, rustc_driver[6635a35d3e701dd7]::run_compiler::{closure#1}>
  36:     0x7f20d4817ed1 - <scoped_tls[d196d212a4d59b56]::ScopedKey<rustc_span[ea709073fc09e903]::SessionGlobals>>::set::<rustc_interface[c5619889e11552cd]::interface::run_compiler<core[7ac8aee7065c0cc9]::result::Result<(), rustc_errors[fbe8c5f47b14aa4]::ErrorGuaranteed>, rustc_driver[6635a35d3e701dd7]::run_compiler::{closure#1}>::{closure#0}, core[7ac8aee7065c0cc9]::result::Result<(), rustc_errors[fbe8c5f47b14aa4]::ErrorGuaranteed>>
  37:     0x7f20d4817bbf - std[25baae9c6c77129a]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[c5619889e11552cd]::util::run_in_thread_pool_with_globals<rustc_interface[c5619889e11552cd]::interface::run_compiler<core[7ac8aee7065c0cc9]::result::Result<(), rustc_errors[fbe8c5f47b14aa4]::ErrorGuaranteed>, rustc_driver[6635a35d3e701dd7]::run_compiler::{closure#1}>::{closure#0}, core[7ac8aee7065c0cc9]::result::Result<(), rustc_errors[fbe8c5f47b14aa4]::ErrorGuaranteed>>::{closure#0}, core[7ac8aee7065c0cc9]::result::Result<(), rustc_errors[fbe8c5f47b14aa4]::ErrorGuaranteed>>
  38:     0x7f20d59cfbd0 - <<std[25baae9c6c77129a]::thread::Builder>::spawn_unchecked_<rustc_interface[c5619889e11552cd]::util::run_in_thread_pool_with_globals<rustc_interface[c5619889e11552cd]::interface::run_compiler<core[7ac8aee7065c0cc9]::result::Result<(), rustc_errors[fbe8c5f47b14aa4]::ErrorGuaranteed>, rustc_driver[6635a35d3e701dd7]::run_compiler::{closure#1}>::{closure#0}, core[7ac8aee7065c0cc9]::result::Result<(), rustc_errors[fbe8c5f47b14aa4]::ErrorGuaranteed>>::{closure#0}, core[7ac8aee7065c0cc9]::result::Result<(), rustc_errors[fbe8c5f47b14aa4]::ErrorGuaranteed>>::{closure#1} as core[7ac8aee7065c0cc9]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  39:     0x7f20d3315663 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h15b2b49f1be836c1
                               at /rustc/8ce3204af9463db3192ea1eb31c45c2f6d4b5ae6/library/alloc/src/boxed.rs:1938:9
  40:     0x7f20d3315663 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h2e516647663708b1
                               at /rustc/8ce3204af9463db3192ea1eb31c45c2f6d4b5ae6/library/alloc/src/boxed.rs:1938:9
  41:     0x7f20d3315663 - std::sys::unix::thread::Thread::new::thread_start::hf5914966a92465bd
                               at /rustc/8ce3204af9463db3192ea1eb31c45c2f6d4b5ae6/library/std/src/sys/unix/thread.rs:108:17
  42:     0x7f20d31e8609 - start_thread
  43:     0x7f20d310b133 - clone
  44:                0x0 - <unknown>

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/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: rustc 1.66.0-nightly (8ce3204af 2022-09-30) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type lib -C embed-bitcode=no -C codegen-units=1 -C debuginfo=2

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
#0 [mir_drops_elaborated_and_const_checked] elaborating drops for `<impl at src/lib.rs:9:1: 9:44>::boxed`
#1 [optimized_mir] optimizing MIR for `<impl at src/lib.rs:9:1: 9:44>::boxed`
end of query stack
error: could not compile `playground`

[compiler-errors]

this has to do with the trivially false Self: Sized predicate. Perhaps we should skip const prop if the where clauses of the function have any where clause predicates known to be false...