src/test/ui/issue-54302-cases.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.

trait Mirror {
    type Image;
    fn coerce(self) -> Self::Image;
}

impl<T> Mirror for T {
    type Image = T;
    fn coerce(self) -> Self { self }
}

trait Foo<'x, T> {
    fn foo(self) -> &'x T;
}

impl<'s, 'x, T: 'x> Foo<'x, T> for &'s T where &'s T: Foo2<'x, T> {
    fn foo(self) -> &'x T { self.foo2() }
}

trait Foo2<'x, T> {
    fn foo2(self) -> &'x T;
}

// example 1 - fails leak check
impl<'x> Foo2<'x, u32> for &'x u32
{
    fn foo2(self) -> &'x u32 { self }
}

// example 2 - OK with this issue
impl<'x, 'a: 'x> Foo2<'x, i32> for &'a i32
{
    fn foo2(self) -> &'x i32 { self }
}

// example 3 - fails due to issue #XYZ + Leak-check
impl<'x, T> Foo2<'x, u64> for T
    where T: Mirror<Image=&'x u64>
{
    fn foo2(self) -> &'x u64 { self.coerce() }
}

// example 4 - fails due to issue #XYZ
impl<'x, 'a: 'x, T> Foo2<'x, i64> for T
    where T: Mirror<Image=&'a i64>
{
    fn foo2(self) -> &'x i64 { self.coerce() }
}


trait RefFoo<T> {
    fn ref_foo(&self) -> &'static T;
}

impl<T> RefFoo<T> for T where for<'a> &'a T: Foo<'static, T> {
    fn ref_foo(&self) -> &'static T {
        self.foo()
    }
}


fn coerce_lifetime1(a: &u32) -> &'static u32
{
    <u32 as RefFoo<u32>>::ref_foo(a)
    //~^ ERROR the trait bound `for<'a> &'a u32: Foo2<'_, u32>` is not satisfied
}

fn coerce_lifetime2(a: &i32) -> &'static i32
{
    <i32 as RefFoo<i32>>::ref_foo(a)
    //~^ ERROR the requirement `for<'a> 'a : ` is not satisfied
}

fn coerce_lifetime3(a: &u64) -> &'static u64
{
    <u64 as RefFoo<u64>>::ref_foo(a)
    //~^ ERROR type mismatch resolving `for<'a> <&'a u64 as Mirror>::Image == &u64`
}

fn coerce_lifetime4(a: &i64) -> &'static i64
{
    <i64 as RefFoo<i64>>::ref_foo(a)
    //~^ ERROR type mismatch resolving `for<'a> <&'a i64 as Mirror>::Image == &i64`
}

fn main() {}