Intrinsics can be declared and defined

[arielb1]

Meta

$ rustc -V
rustc 1.14.0-nightly (9c31d76e9 2016-10-03)

STR

#![feature(intrinsics)]

trait Foo {
    extern "rust-intrinsic" fn foo(&self);
}

impl Foo for () {
    extern "rust-intrinsic" fn foo(&self) {
        hello();
    }
}

extern "rust-intrinsic" fn hello() {
    println!("Hello, World!");
}

fn main() {
    ().foo();
}

Actual Result

error: internal compiler error: ../src/librustc_trans/intrinsic.rs:558: unknown intrinsic 'hello'

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

thread 'rustc' panicked at 'Box<Any>', ../src/librustc_errors/lib.rs:656
note: Run with `RUST_BACKTRACE=1` for a backtrace.

[arielb1]

cc #34123

[istankovic]

Still reproducible with rustc 1.26.0-nightly (adf2135ad 2018-03-17).