summaryrefslogtreecommitdiffstats
path: root/src/test/ui/higher-rank-trait-bounds/issue-30786.rs
diff options
context:
space:
mode:
Diffstat (limited to 'src/test/ui/higher-rank-trait-bounds/issue-30786.rs')
-rw-r--r--src/test/ui/higher-rank-trait-bounds/issue-30786.rs134
1 files changed, 0 insertions, 134 deletions
diff --git a/src/test/ui/higher-rank-trait-bounds/issue-30786.rs b/src/test/ui/higher-rank-trait-bounds/issue-30786.rs
deleted file mode 100644
index e5f46f711..000000000
--- a/src/test/ui/higher-rank-trait-bounds/issue-30786.rs
+++ /dev/null
@@ -1,134 +0,0 @@
-// rust-lang/rust#30786: the use of `for<'b> &'b mut A: Stream<Item=T`
-// should act as assertion that item does not borrow from its stream;
-// but an earlier buggy rustc allowed `.map(|x: &_| x)` which does
-// have such an item.
-//
-// This tests double-checks that we do not allow such behavior to leak
-// through again.
-
-pub trait Stream {
- type Item;
- fn next(self) -> Option<Self::Item>;
-}
-
-// Example stream
-pub struct Repeat(u64);
-
-impl<'a> Stream for &'a mut Repeat {
- type Item = &'a u64;
- fn next(self) -> Option<Self::Item> {
- Some(&self.0)
- }
-}
-
-pub struct Map<S, F> {
- stream: S,
- func: F,
-}
-
-impl<'a, A, F, T> Stream for &'a mut Map<A, F>
-where
- &'a mut A: Stream,
- F: FnMut(<&'a mut A as Stream>::Item) -> T,
-{
- type Item = T;
- fn next(self) -> Option<T> {
- match self.stream.next() {
- Some(item) => Some((self.func)(item)),
- None => None,
- }
- }
-}
-
-pub struct Filter<S, F> {
- stream: S,
- func: F,
-}
-
-impl<'a, A, F, T> Stream for &'a mut Filter<A, F>
-where
- for<'b> &'b mut A: Stream<Item = T>, // <---- BAD
- F: FnMut(&T) -> bool,
-{
- type Item = <&'a mut A as Stream>::Item;
- fn next(self) -> Option<Self::Item> {
- while let Some(item) = self.stream.next() {
- if (self.func)(&item) {
- return Some(item);
- }
- }
- None
- }
-}
-
-pub trait StreamExt
-where
- for<'b> &'b mut Self: Stream,
-{
- fn mapx<F>(self, func: F) -> Map<Self, F>
- where
- Self: Sized,
- for<'a> &'a mut Map<Self, F>: Stream,
- {
- Map { func: func, stream: self }
- }
-
- fn filterx<F>(self, func: F) -> Filter<Self, F>
- where
- Self: Sized,
- for<'a> &'a mut Filter<Self, F>: Stream,
- {
- Filter { func: func, stream: self }
- }
-
- fn countx(mut self) -> usize
- where
- Self: Sized,
- {
- let mut count = 0;
- while let Some(_) = self.next() {
- count += 1;
- }
- count
- }
-}
-
-impl<T> StreamExt for T where for<'a> &'a mut T: Stream {}
-
-fn identity<T>(x: &T) -> &T {
- x
-}
-
-fn variant1() {
- let source = Repeat(10);
-
- // Here, the call to `mapx` returns a type `T` to which `StreamExt`
- // is not applicable, because `for<'b> &'b mut T: Stream`) doesn't hold.
- //
- // More concretely, the type `T` is `Map<Repeat, Closure>`, and
- // the where clause doesn't hold because the signature of the
- // closure gets inferred to a signature like `|&'_ Stream| -> &'_`
- // for some specific `'_`, rather than a more generic
- // signature.
- //
- // Why *exactly* we opt for this signature is a bit unclear to me,
- // we deduce it somehow from a reuqirement that `Map: Stream` I
- // guess.
- let map = source.mapx(|x: &_| x);
- let filter = map.filterx(|x: &_| true);
- //~^ ERROR the method
-}
-
-fn variant2() {
- let source = Repeat(10);
-
- // Here, we use a function, which is not subject to the vagaries
- // of closure signature inference. In this case, we get the error
- // on `countx` as, I think, the test originally expected.
- let map = source.mapx(identity);
- let filter = map.filterx(|x: &_| true);
- let count = filter.countx();
- //~^ ERROR the method
-}
-
-fn main() {}