no_std, #[start]: rustc core dump when defining extern main symbol with wrong type signature

[carlpaten]

Minimal test case

carl@crust:~/repro$ rustc test.rs
test.rs:6:5: 6:15 warning: foreign function is never used: `main`, #[warn(dead_code)] on by default
test.rs:6     fn main();
              ^~~~~~~~~~
rustc: /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/llvm/include/llvm/Support/Casting.h:237: typename llvm::cast_retty<X, Y*>::ret_type llvm::cast(Y*) [with X = llvm::Function; Y = llvm::Value; typename llvm::cast_retty<X, Y*>::ret_type = llvm::Function*]: Assertion `isa<X>(Val) && "cast<Ty>() argument of incompatible type!"' failed.
Aborted (core dumped)

[durka]

cc #9307

[nagisa]

Yes, a duplicate of the issue linked above.

[nagisa]

Or rather, I’ll keep this open, since it seems to refer to the #[start] attribute and not a language item.

[Mark-Simulacrum]

Can someone provide a minimal test case for this issue? The one linked in the original comment no longer exists; the linked issue does still assert, though.

[nagisa]

From comments it sounds like it was something like

#![feature(start)]

#[start]
fn main() {}

or

extern {
    fn main();
}
fn main(){}

Both of these do not ICE anymore.

Either way, since we do not have the exact reproducer and it was indicated that the issue is kinda similar to the other linked issue, I’m inclined to close.