GAT ICE: cannot directly store unsized values #68656
Description
The following ICE's:
#![feature(generic_associated_types)] trait UnsafeCopy<T: Copy> { type Item<'a>: std::ops::Deref<Target = T>; fn bug<'a>(item: &Self::Item<'a>) -> () { let x: T = **item; } } impl <T: Copy> UnsafeCopy<T> for T { type Item<'a> = T; } fn main() { <&'static str>::bug(&""); }Backtrace:
error: internal compiler error: src/librustc_codegen_ssa/mir/operand.rs:305: cannot directly store unsized values thread 'rustc' panicked at 'Box<Any>', src/librustc_errors/lib.rs:883:9 stack backtrace: 0: backtrace::backtrace::libunwind::trace at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.40/src/backtrace/libunwind.rs:88 1: backtrace::backtrace::trace_unsynchronized at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.40/src/backtrace/mod.rs:66 2: std::sys_common::backtrace::_print_fmt at src/libstd/sys_common/backtrace.rs:77 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:1052 5: std::io::Write::write_fmt at src/libstd/io/mod.rs:1426 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:204 9: std::panicking::default_hook at src/libstd/panicking.rs:224 10: rustc_driver::report_ice 11: std::panicking::rust_panic_with_hook at src/libstd/panicking.rs:476 12: std::panicking::begin_panic 13: rustc_errors::HandlerInner::bug 14: rustc_errors::Handler::bug 15: rustc::util::bug::opt_span_bug_fmt::{{closure}} 16: rustc::ty::context::tls::with_opt::{{closure}} 17: rustc::ty::context::tls::with_opt 18: rustc::util::bug::opt_span_bug_fmt 19: rustc::util::bug::bug_fmt 20: rustc_codegen_ssa::mir::operand::OperandValue<V>::store_with_flags 21: rustc_codegen_ssa::mir::rvalue::<impl rustc_codegen_ssa::mir::FunctionCx<Bx>>::codegen_rvalue 22: rustc_codegen_ssa::mir::codegen_mir 23: <rustc::mir::mono::MonoItem as rustc_codegen_ssa::mono_item::MonoItemExt>::define 24: rustc_codegen_llvm::base::compile_codegen_unit::module_codegen 25: rustc::dep_graph::graph::DepGraph::with_task 26: rustc_codegen_llvm::base::compile_codegen_unit 27: rustc_codegen_ssa::base::codegen_crate 28: <rustc_codegen_llvm::LlvmCodegenBackend as rustc_codegen_utils::codegen_backend::CodegenBackend>::codegen_crate 29: rustc_session::utils::<impl rustc_session::session::Session>::time 30: rustc_interface::passes::QueryContext::enter 31: rustc_interface::queries::Queries::ongoing_codegen 32: rustc_interface::interface::run_compiler_in_existing_thread_pool 33: scoped_tls::ScopedKey<T>::set 34: syntax::with_globals note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace. 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 1.42.0-nightly (3761dcd34 2020-01-28) running on x86_64-unknown-linux-gnu note: compiler flags: -C codegen-units=1 -C debuginfo=2 --crate-type bin note: some of the compiler flags provided by cargo are hidden query stack during panic: end of query stack error: aborting due to previous error error: could not compile `playground`.