ICE: Error encountered resolving bounds after type-checking

[The0x539]

Code

fn any<T>() -> T { loop {} }

trait Foo { type V; }

trait Callback<T: Foo>: Fn(&T, &T::V) {}
impl<T: Foo, F: Fn(&T, &T::V)> Callback<T> for F {}

struct Bar<T: Foo> {
    callback: Box<dyn Callback<T>>,
}

impl<T: Foo> Bar<T> {
    fn event(&self) {
        (self.callback)(any(), any());
    }
}

struct A;
struct B;
impl Foo for A { type V = B; }

fn main() {
    let foo = Bar::<A> {
        callback: Box::new(|_: &A, _: &B| ()),
    };
    foo.event();
}

Meta

rustc --version --verbose:

rustc 1.46.0-nightly (feb3536eb 2020-06-09)
binary: rustc
commit-hash: feb3536eba10c2e4585d066629598f03d5ddc7c6
commit-date: 2020-06-09
host: x86_64-unknown-linux-gnu
release: 1.46.0-nightly
LLVM version: 10.0

Error output

error: internal compiler error: src/librustc_trait_selection/traits/codegen/mod.rs:108: Encountered errors `[FulfillmentError(Obligation(predicate=Binder(TraitPredicate(<dyn for<'r, 's> Callback<A, Output = ()> as std::ops::Fn<(&A, &B)>>)), depth=1),Unimplemented)]` resolving bounds after type-checking

Backtrace

thread 'rustc' panicked at 'Box<Any>', src/librustc_errors/lib.rs:907:9
stack backtrace:
   0: backtrace::backtrace::libunwind::trace
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.46/src/backtrace/libunwind.rs:86
   1: backtrace::backtrace::trace_unsynchronized
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.46/src/backtrace/mod.rs:66
   2: std::sys_common::backtrace::_print_fmt
             at src/libstd/sys_common/backtrace.rs:78
   3: <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt
             at src/libstd/sys_common/backtrace.rs:59
   4: core::fmt::write
             at src/libcore/fmt/mod.rs:1076
   5: std::io::Write::write_fmt
             at src/libstd/io/mod.rs:1537
   6: std::sys_common::backtrace::_print
             at src/libstd/sys_common/backtrace.rs:62
   7: std::sys_common::backtrace::print
             at src/libstd/sys_common/backtrace.rs:49
   8: std::panicking::default_hook::{{closure}}
             at src/libstd/panicking.rs:198
   9: std::panicking::default_hook
             at src/libstd/panicking.rs:218
  10: rustc_driver::report_ice
  11: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:481
  12: std::panicking::begin_panic
  13: rustc_errors::HandlerInner::bug
  14: rustc_errors::Handler::bug
  15: rustc_middle::util::bug::opt_span_bug_fmt::{{closure}}
  16: rustc_middle::ty::context::tls::with_opt::{{closure}}
  17: rustc_middle::ty::context::tls::with_opt
  18: rustc_middle::util::bug::opt_span_bug_fmt
  19: rustc_middle::util::bug::bug_fmt
  20: rustc_trait_selection::traits::codegen::drain_fulfillment_cx_or_panic
  21: rustc_middle::ty::context::GlobalCtxt::enter_local
  22: rustc_trait_selection::traits::codegen::codegen_fulfill_obligation
  23: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::codegen_fulfill_obligation>::compute
  24: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  25: rustc_data_structures::stack::ensure_sufficient_stack
  26: rustc_query_system::query::plumbing::get_query_impl
  27: rustc_ty::instance::resolve_instance
  28: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::resolve_instance>::compute
  29: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  30: rustc_data_structures::stack::ensure_sufficient_stack
  31: rustc_query_system::query::plumbing::get_query_impl
  32: rustc_middle::ty::instance::Instance::resolve
  33: <rustc_mir::monomorphize::collector::MirNeighborCollector as rustc_middle::mir::visit::Visitor>::visit_terminator_kind
  34: rustc_mir::monomorphize::collector::collect_neighbours
  35: rustc_data_structures::stack::ensure_sufficient_stack
  36: rustc_mir::monomorphize::collector::collect_items_rec
  37: rustc_mir::monomorphize::collector::collect_items_rec
  38: rustc_mir::monomorphize::collector::collect_crate_mono_items
  39: rustc_mir::monomorphize::partitioning::collect_and_partition_mono_items
  40: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::collect_and_partition_mono_items>::compute
  41: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  42: rustc_query_system::query::plumbing::get_query_impl
  43: rustc_codegen_ssa::base::codegen_crate
  44: <rustc_codegen_llvm::LlvmCodegenBackend as rustc_codegen_ssa::traits::backend::CodegenBackend>::codegen_crate
  45: rustc_interface::passes::start_codegen
  46: rustc_middle::ty::context::tls::enter_global
  47: rustc_interface::queries::Queries::ongoing_codegen
  48: rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter
  49: rustc_span::with_source_map
  50: rustc_interface::interface::run_compiler_in_existing_thread_pool
  51: scoped_tls::ScopedKey<T>::set

[JohnTitor]

Triage: It's no longer ICE with the latest nightly, I think it's fixed by #77720.