Compiler crash with self.into::<i64>()

[jD91mZM2]

I got a compiler crash and idk what any of it means but here you go.

I tried this code:
compiler-crash branch on jrust.

cargo check --example concat

I expected to see this happen:
stuff would work

Instead, this happened:
Rust was eaten by velociraptors.

Meta

Backtrace

rustc --version --verbose:

rustc 1.28.0 (9634041f0 2018-07-30)
binary: rustc
commit-hash: 9634041f0e8c0f3191d2867311276f19d0a42564
commit-date: 2018-07-30
host: x86_64-unknown-linux-gnu
release: 1.28.0
LLVM version: 6.0

[jD91mZM2]

Smaller example:

pub trait JavaAdd<T> {
    type Target;

    fn add(self, other: T) -> Self::Target;
}

macro_rules! impl_add {
    ($($primitive:ident),*) => {
        $(impl<T: Into<i64>> JavaAdd<T> for $primitive {
            type Target = i64;

            fn add(self, other: T) -> Self::Target {
                self.into::<i64>() + other.into::<i64>()
            }
        })*
    }
}

impl_add!(i8, i16);

[dtolnay]

Reduced some more:

struct S;

impl S {
    fn f() {}
}

macro_rules! impl_add {
    ($($n:ident)*) => {
        $(
            fn $n() {
                S::f::<i64>();
            }
        )*
    }
}

impl_add!(a b);