use std::cell::{RefCell, Ref};
use std::any::Any;
trait Foo: Any + AsAny {
//
}
trait AsAny {
fn as_any(&self) -> &dyn Any;
}
impl<T: Foo> AsAny for T {
fn as_any(&self) -> &dyn Any {
self
}
}
fn demo<'a, T: 'static>(cell: &'a RefCell<dyn Foo>) -> Option<&T> {
// this causes compile error correctly
// let x: Ref<'a, _> = cell.borrow();
let x = cell.borrow::<'a, _>();
x.as_any().downcast_ref::<T>()
}
fn main() {
//
}warning: cannot specify lifetime arguments explicitly if late bound lifetime parameters are present
--> src/main.rs:58:27
|
58 | let x = cell.borrow::<'a, _>();
| ^^
|
= note: #[warn(late_bound_lifetime_arguments)] on by default
= warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
= note: for more information, see issue #42868 <https://github.com/rust-lang/rust/issues/42868>
error: internal compiler error: src/librustc_typeck/check/mod.rs:2461: no type for node 121: type _ (id=121) in fcx 0x70000a15f458
thread 'rustc' panicked at 'Box<Any>', src/librustc_errors/lib.rs:620:9
stack backtrace:
0: std::sys::unix::backtrace::tracing::imp::unwind_backtrace
1: std::sys_common::backtrace::_print
2: std::panicking::default_hook::{{closure}}
3: std::panicking::default_hook
4: rustc::util::common::panic_hook
5: std::panicking::rust_panic_with_hook
6: std::panicking::begin_panic
7: rustc_errors::Handler::bug
8: rustc::util::bug::opt_span_bug_fmt::{{closure}}
9: rustc::ty::context::tls::with_opt::{{closure}}
10: rustc::ty::context::tls::with_context_opt
11: rustc::ty::context::tls::with_opt
12: rustc::util::bug::opt_span_bug_fmt
13: rustc::util::bug::bug_fmt
14: rustc_typeck::check::FnCtxt::node_ty
15: <rustc_typeck::check::writeback::WritebackCx<'cx, 'gcx, 'tcx> as rustc::hir::intravisit::Visitor<'gcx>>::visit_ty
16: rustc::hir::intravisit::walk_expr
17: <rustc_typeck::check::writeback::WritebackCx<'cx, 'gcx, 'tcx> as rustc::hir::intravisit::Visitor<'gcx>>::visit_expr
18: <rustc_typeck::check::writeback::WritebackCx<'cx, 'gcx, 'tcx> as rustc::hir::intravisit::Visitor<'gcx>>::visit_local
19: rustc::hir::intravisit::walk_expr
20: <rustc_typeck::check::writeback::WritebackCx<'cx, 'gcx, 'tcx> as rustc::hir::intravisit::Visitor<'gcx>>::visit_expr
21: rustc_typeck::check::writeback::<impl rustc_typeck::check::FnCtxt<'a, 'gcx, 'tcx>>::resolve_type_vars_in_body
22: rustc::ty::context::GlobalCtxt::enter_local
23: rustc_typeck::check::typeck_tables_of
24: rustc::ty::query::__query_compute::typeck_tables_of
25: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors<'tcx> for rustc::ty::query::queries::typeck_tables_of<'tcx>>::compute
26: rustc::dep_graph::graph::DepGraph::with_task_impl
27: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::get_query
28: rustc::ty::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::par_body_owners
29: rustc_typeck::check::typeck_item_bodies
30: rustc::ty::query::__query_compute::typeck_item_bodies
31: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors<'tcx> for rustc::ty::query::queries::typeck_item_bodies<'tcx>>::compute
32: rustc::dep_graph::graph::DepGraph::with_task_impl
33: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::get_query
34: rustc::util::common::time
35: rustc_typeck::check_crate
36: <std::thread::local::LocalKey<T>>::with
37: rustc::ty::context::TyCtxt::create_and_enter
38: rustc_driver::driver::compile_input
39: rustc_driver::run_compiler_with_pool
40: <scoped_tls::ScopedKey<T>>::set
41: rustc_driver::run_compiler
42: syntax::with_globals
43: __rust_maybe_catch_panic
44: <F as alloc::boxed::FnBox<A>>::call_box
45: std::sys::unix::thread::Thread::new::thread_start
46: _pthread_body
47: _pthread_start
query stack during panic:
#0 [typeck_tables_of] processing `demo`
#1 [typeck_item_bodies] type-checking all item bodies
end of query stack
error: aborting due to previous error
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 1.34.1 (fc50f328b 2019-04-24) running on x86_64-apple-darwin
note: compiler flags: -C debuginfo=2 -C incremental --crate-type bin
note: some of the compiler flags provided by cargo are hidden
Compiler crashes with
Also, I wonder what is the right way (or is there any way) to write a
demowith expected behavior. Thanks.