rust/src/test/ui/impl-trait/issues/issue-57979-impl-trait-in-path.rs

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// rust-lang/rust#57979 : the initial support for `impl Trait` didn't
// properly check syntax hidden behind an associated type projection.
// Here we test behavior of occurrences of `impl Trait` within a path
// component in that context.
mod allowed {
#![allow(nested_impl_trait)]
pub trait Bar { }
pub trait Quux<T> { type Assoc; }
pub fn demo(_: impl Quux<(), Assoc=<() as Quux<impl Bar>>::Assoc>) { }
impl<T> Quux<T> for () { type Assoc = u32; }
}
mod warned {
#![warn(nested_impl_trait)]
pub trait Bar { }
pub trait Quux<T> { type Assoc; }
pub fn demo(_: impl Quux<(), Assoc=<() as Quux<impl Bar>>::Assoc>) { }
//~^ WARN `impl Trait` is not allowed in path parameters
//~| WARN will become a hard error in a future release!
impl<T> Quux<T> for () { type Assoc = u32; }
}
mod denied {
#![deny(nested_impl_trait)]
pub trait Bar { }
pub trait Quux<T> { type Assoc; }
pub fn demo(_: impl Quux<(), Assoc=<() as Quux<impl Bar>>::Assoc>) { }
//~^ ERROR `impl Trait` is not allowed in path parameters
//~| WARN will become a hard error in a future release!
impl<T> Quux<T> for () { type Assoc = u32; }
}
fn main() { }