Overflow while adding drop-check rules.

[kaminsod]

Not sure if this is a bug or something I missed in my code, but seems to be the same as #29844. Issue present in stable, beta and nightly.

https://play.rust-lang.org/?gist=5d30e353c7fac8f23e871367f774f9b0&version=stable&backtrace=0

#[derive(Debug)]
enum E1<T> {
    V1(T),
    V2(Box<E1<E2<T>>>)
}

#[derive(Debug)]
enum E2<T> {
    V1(usize, T),
    V2(usize, T, T)
}

fn main() {
    let wub = E1::V2(Box::new(E1::V1(E2::V1(1, "wub"))));

    println!("{:?}", wub);
}

Issues on stable (similar issues on beta and nightly):

:14:9: 14:12 error: overflow while adding drop-check rules for E1<&str> [E0320]
:14 let wub = E1::V2(Box::new(E1::V1(E2::V1(1, "wub"))));
^~~
:14:9: 14:12 note: overflowed on enum E2 variant V1 field #0 type: usize
:14 let wub = E1::V2(Box::new(E1::V1(E2::V1(1, "wub"))));
^~~
:14:15: 14:57 error: overflow while adding drop-check rules for E1<&str> [E0320]
:14 let wub = E1::V2(Box::new(E1::V1(E2::V1(1, "wub"))));
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
:14:15: 14:57 note: overflowed on enum E2 variant V1 field #0 type: usize
:14 let wub = E1::V2(Box::new(E1::V1(E2::V1(1, "wub"))));
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
:14:22: 14:56 error: overflow while adding drop-check rules for Box<E1<E2<&str>>> [E0320]
:14 let wub = E1::V2(Box::new(E1::V1(E2::V1(1, "wub"))));
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
:14:22: 14:56 note: overflowed on enum E1 variant V1 field #0 type: E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<E2<&str>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
:14 let wub = E1::V2(Box::new(E1::V1(E2::V1(1, "wub"))));
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
:14:31: 14:55 error: overflow while adding drop-check rules for E1<E2<&str>> [E0320]
:14 let wub = E1::V2(Box::new(E1::V1(E2::V1(1, "wub"))));
^~~~~~~~~~~~~~~~~~~~~~~~
:14:31: 14:55 note: overflowed on enum E2 variant V1 field #0 type: usize
:14 let wub = E1::V2(Box::new(E1::V1(E2::V1(1, "wub"))));

[kaminsod]

Slightly simplified version of code producing same issue.

#[derive(Debug)]
enum A<T> {
    A1(T),
    A2(Box<A<B<T>>>)
}

#[derive(Debug)]
enum B<T> {
    B(T)
}

fn main() {
    let wub = A::A2(Box::new(A::A1(B::B("wub"))));

    println!("{:?}", wub);
}

https://play.rust-lang.org/?gist=b5faaff96db3a386eb7906461f81d5a8&version=stable&backtrace=0

[nagisa]

Even more minimal:

enum A<T> {
    A1(T),
    A2(Box<A<::std::marker::PhantomData<T>>>)
}

fn main() {
    A::A1(());
}

[pnkfelix]

I think this is a duplicate of #4287

[Mark-Simulacrum]

Closing in favor of #4287.