src/test/ui/impl-trait/impl_trait_projections.rs

// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use std::fmt::Debug;
use std::option;

fn parametrized_type_is_allowed() -> Option<impl Debug> {
    Some(5i32)
}

fn path_parametrized_type_is_allowed() -> option::Option<impl Debug> {
    Some(5i32)
}

fn projection_is_disallowed(x: impl Iterator) -> <impl Iterator>::Item {
//~^ ERROR `impl Trait` is not allowed in path parameters
//~^^ ERROR ambiguous associated type
    x.next().unwrap()
}

fn projection_with_named_trait_is_disallowed(x: impl Iterator)
    -> <impl Iterator as Iterator>::Item
//~^ ERROR `impl Trait` is not allowed in path parameters
{
    x.next().unwrap()
}

fn projection_with_named_trait_inside_path_is_disallowed()
    -> <::std::ops::Range<impl Debug> as Iterator>::Item
//~^ ERROR `impl Trait` is not allowed in path parameters
{
    (1i32..100).next().unwrap()
}

fn projection_from_impl_trait_inside_dyn_trait_is_disallowed()
    -> <dyn Iterator<Item = impl Debug> as Iterator>::Item
//~^ ERROR `impl Trait` is not allowed in path parameters
{
    panic!()
}

fn main() {}