//@ revisions: current next
//@ ignore-compare-mode-next-solver (explicit revisions)
//@[next] compile-flags: -Znext-solver
//@[next] check-pass
//@[current] known-bug: unknown
//@[current] failure-status: 101
//@[current] dont-check-compiler-stderr

// Tests that rebasing from the concrete impl to the default impl also processes the
// `[u32; 0]: IntoIterator<Item = ?U>` predicate to constrain the `?U` impl arg.
// This test also makes sure that we don't do anything weird when rebasing the args
// is ambiguous.

#![feature(specialization)]
//[next]~^ WARN the feature `specialization` is incomplete

trait Spec {
    type Assoc;
}

default impl<T, U> Spec for T where T: IntoIterator<Item = U> {
    type Assoc = U;
}

impl<T> Spec for [T; 0] {}

fn main() {
    let x: <[_; 0] as Spec>::Assoc = 1;
}