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Add a test for #55731

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varkor committed Feb 25, 2019
1 parent 776411b commit b7763af5267be200ffcb75e1ed35a0f3979c7d51
Showing with 64 additions and 0 deletions.
  1. +52 −0 src/test/ui/issues/issue-55731.rs
  2. +12 −0 src/test/ui/issues/issue-55731.stderr
@@ -0,0 +1,52 @@
use std::marker::PhantomData;

trait DistributedIterator {
fn reduce(self)
where
Self: Sized,
{
unreachable!()
}
}

trait DistributedIteratorMulti<Source> {
type Item;
}

struct Connect<I>(PhantomData<fn(I)>);
impl<I: for<'a> DistributedIteratorMulti<&'a ()>> DistributedIterator for Connect<I> where {}

struct Cloned<Source>(PhantomData<fn(Source)>);
impl<'a, Source> DistributedIteratorMulti<&'a Source> for Cloned<&'a Source> {
type Item = ();
}

struct Map<I, F> {
i: I,
f: F,
}
impl<I: DistributedIteratorMulti<Source>, F, Source> DistributedIteratorMulti<Source> for Map<I, F>
where
F: A<<I as DistributedIteratorMulti<Source>>::Item>,
{
type Item = ();
}

trait A<B> {}

struct X;
impl A<()> for X {}

fn multi<I>(_reducer: I)
where
I: for<'a> DistributedIteratorMulti<&'a ()>,
{
DistributedIterator::reduce(Connect::<I>(PhantomData))
}

fn main() {
multi(Map { //~ ERROR implementation of `DistributedIteratorMulti` is not general enough
i: Cloned(PhantomData),
f: X,
});
}
@@ -0,0 +1,12 @@
error: implementation of `DistributedIteratorMulti` is not general enough
--> $DIR/issue-55731.rs:48:5
|
LL | multi(Map { //~ ERROR implementation of `DistributedIteratorMulti` is not general enough
| ^^^^^
|
= note: Due to a where-clause on `multi`,
= note: `Map<Cloned<&()>, X>` must implement `DistributedIteratorMulti<&'0 ()>`, for any lifetime `'0`
= note: but `Map<Cloned<&()>, X>` actually implements `DistributedIteratorMulti<&'1 ()>`, for some specific lifetime `'1`

error: aborting due to previous error

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