Crash on Implementing !Trait, Not Trait: thread 'rustc' panicked at 'called `Option::unwrap()` on a `None` value', src\libcore\option.rs:345:21

[Jon-Davis]

So this probably isn't valid Rust code but it did crash the compiler rather then sending me a warning so I thought I'd at least file a bug. I have a struct Wrapper<T> and a trait Releasable, I wanted to implement Releasable on Wrapper in the cases where T implemented Releasable, and in the case where T did not implement !Releasable. Im not sure if this is even valid rust code although I did notice things like RefCell not implementing !Sync so I thought I'd give it a try.

pub struct Wrapper<T>(T);

pub trait Releasable {
    fn release(&mut self);
}

impl<T: Releasable> Releasable for Wrapper<T> {
    fn release(&mut self) {
        self.0.release();
    }
}

impl<T : !Releasable> Releasable for Wrapper<T>{
    fn release(&mut self){}
}

impl<T> Drop for Wrapper<T>{
    fn drop(&mut self) {
        self.release();
    }
}

Meta

thread 'rustc' panicked at 'called Option::unwrap() on a None value', src\libcore\option.rs:345:21
note: Run with RUST_BACKTRACE=1 environment variable to display a backtrace.

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/blob/master/CONTRIBUTING.md#bug-reports

note: rustc 1.35.0-nightly (87a4363 2019-03-03) running on x86_64-pc-windows-msvc

note: compiler flags: -C debuginfo=2 -C incremental --crate-type lib

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

stack backtrace:
   0: std::sys_common::alloc::realloc_fallback
   1: std::panicking::take_hook
   2: std::panicking::take_hook
   3: std::panicking::rust_panic_with_hook
   4: std::panicking::begin_panic_fmt
   5: rust_begin_unwind
   6: core::panicking::panic_fmt
   7: core::panicking::panic
   8: syntax::parse::parser::Parser::parse_block
   9: syntax::parse::parser::Parser::parse_block
  10: syntax::parse::parser::Parser::parse_block
  11: syntax::parse::parser::Parser::default_submod_path
  12: syntax::parse::parser::Parser::default_submod_path
  13: syntax::parse::parser::Parser::parse_item
  14: syntax::parse::parser::Parser::parse_visibility
  15: syntax::parse::parser::Parser::default_submod_path
  16: syntax::parse::parser::Parser::default_submod_path
  17: syntax::parse::parser::Parser::parse_item
  18: syntax::parse::parser::Parser::parse_visibility
  19: syntax::parse::parser::Parser::parse_crate_mod
  20: syntax::parse::parse_crate_from_file
  21: <env_logger::fmt::WriteStyle as core::default::Default>::default
  22: <env_logger::fmt::WriteStyle as core::default::Default>::default
  23: rustc_driver::driver::phase_1_parse_input
  24: rustc_driver::driver::compile_input
  25: rustc_driver::run_compiler
  26: <env_logger::Logger as log::Log>::flush
  27: rustc_driver::run_compiler
  28: <env_logger::Logger as log::Log>::flush
  29: <env_logger::fmt::WriteStyle as core::default::Default>::default
  30: _rust_maybe_catch_panic
  31: <env_logger::fmt::WriteStyle as core::default::Default>::default
  32: std::sys::windows::thread::Thread::new
  33: BaseThreadInitThunk
  34: RtlUserThreadStart

[estebank]

Will be fixed by #58861. Duplicate of #58857.