CFI breaks on trait Address Taken functions

[maurer]

mmaurer@anyblade:~/github/rust-lang$ rustc -Z sanitizer=cfi -C lto -C codegen-units=1 badsample.rs
mmaurer@anyblade:~/github/rust-lang$ ./badsample 
Illegal instruction
mmaurer@anyblade:~/github/rust-lang$ rustc -C lto -C codegen-units=1 badsample.rs
mmaurer@anyblade:~/github/rust-lang$ ./badsample
mmaurer@anyblade:~/github/rust-lang$ cat badsample.rs 

trait Foo {
    fn foo(&self);
}

struct S;

impl Foo for S {
    fn foo(&self) {}
}

struct S2 {
    f: fn(&S)
}

impl S2 {
    fn foo(&self, s: &S) {
        (self.f)(s)
    }
}

fn main() {
    S2 { f: <S as Foo>::foo }.foo(&S)
}

This appears to happen because <S as Foo>::foo has CFI-type fn(&dyn Foo) rather than fn(&S).

cc @rcvalle

[rcvalle]

@rustbot claim