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Allow unsized closures in iterator adaptors #43717

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89 changes: 47 additions & 42 deletions src/libcore/iter/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1050,13 +1050,13 @@ unsafe impl<A, B> TrustedLen for Zip<A, B>
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
#[derive(Clone)]
pub struct Map<I, F> {
pub struct Map<I, F: ?Sized> {
iter: I,
f: F,
}

#[stable(feature = "core_impl_debug", since = "1.9.0")]
impl<I: fmt::Debug, F> fmt::Debug for Map<I, F> {
impl<I: fmt::Debug, F: ?Sized> fmt::Debug for Map<I, F> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
f.debug_struct("Map")
.field("iter", &self.iter)
Expand All @@ -1065,7 +1065,8 @@ impl<I: fmt::Debug, F> fmt::Debug for Map<I, F> {
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<B, I: Iterator, F> Iterator for Map<I, F> where F: FnMut(I::Item) -> B {
impl<B, I: Iterator, F: ?Sized> Iterator for Map<I, F> where F: FnMut(I::Item) -> B
{
type Item = B;

#[inline]
Expand All @@ -1078,16 +1079,17 @@ impl<B, I: Iterator, F> Iterator for Map<I, F> where F: FnMut(I::Item) -> B {
self.iter.size_hint()
}

fn fold<Acc, G>(self, init: Acc, mut g: G) -> Acc
fn fold<Acc, G>(mut self, init: Acc, mut g: G) -> Acc
where G: FnMut(Acc, Self::Item) -> Acc,
Self: Sized,
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couldn't you also just add an F: Sized bound?

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Not allowed unfortunately. Doesn't match the trait.

{
let mut f = self.f;
let f = &mut self.f;
self.iter.fold(init, move |acc, elt| g(acc, f(elt)))
}
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<B, I: DoubleEndedIterator, F> DoubleEndedIterator for Map<I, F> where
impl<B, I: DoubleEndedIterator, F: ?Sized> DoubleEndedIterator for Map<I, F> where
F: FnMut(I::Item) -> B,
{
#[inline]
Expand All @@ -1097,7 +1099,7 @@ impl<B, I: DoubleEndedIterator, F> DoubleEndedIterator for Map<I, F> where
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<B, I: ExactSizeIterator, F> ExactSizeIterator for Map<I, F>
impl<B, I: ExactSizeIterator, F: ?Sized> ExactSizeIterator for Map<I, F>
where F: FnMut(I::Item) -> B
{
fn len(&self) -> usize {
Expand All @@ -1110,16 +1112,16 @@ impl<B, I: ExactSizeIterator, F> ExactSizeIterator for Map<I, F>
}

#[unstable(feature = "fused", issue = "35602")]
impl<B, I: FusedIterator, F> FusedIterator for Map<I, F>
impl<B, I: FusedIterator, F: ?Sized> FusedIterator for Map<I, F>
where F: FnMut(I::Item) -> B {}

#[unstable(feature = "trusted_len", issue = "37572")]
unsafe impl<B, I, F> TrustedLen for Map<I, F>
unsafe impl<B, I, F: ?Sized> TrustedLen for Map<I, F>
where I: TrustedLen,
F: FnMut(I::Item) -> B {}

#[doc(hidden)]
unsafe impl<B, I, F> TrustedRandomAccess for Map<I, F>
unsafe impl<B, I, F: ?Sized> TrustedRandomAccess for Map<I, F>
where I: TrustedRandomAccess,
F: FnMut(I::Item) -> B,
{
Expand All @@ -1140,13 +1142,13 @@ unsafe impl<B, I, F> TrustedRandomAccess for Map<I, F>
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
#[derive(Clone)]
pub struct Filter<I, P> {
pub struct Filter<I, P: ?Sized> {
iter: I,
predicate: P,
}

#[stable(feature = "core_impl_debug", since = "1.9.0")]
impl<I: fmt::Debug, P> fmt::Debug for Filter<I, P> {
impl<I: fmt::Debug, P: ?Sized> fmt::Debug for Filter<I, P> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
f.debug_struct("Filter")
.field("iter", &self.iter)
Expand All @@ -1155,7 +1157,8 @@ impl<I: fmt::Debug, P> fmt::Debug for Filter<I, P> {
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<I: Iterator, P> Iterator for Filter<I, P> where P: FnMut(&I::Item) -> bool {
impl<I: Iterator, P: ?Sized> Iterator for Filter<I, P> where P: FnMut(&I::Item) -> bool
{
type Item = I::Item;

#[inline]
Expand Down Expand Up @@ -1186,7 +1189,9 @@ impl<I: Iterator, P> Iterator for Filter<I, P> where P: FnMut(&I::Item) -> bool
// Using the branchless version will also simplify the LLVM byte code, thus
// leaving more budget for LLVM optimizations.
#[inline]
fn count(mut self) -> usize {
fn count(mut self) -> usize
where Self: Sized
{
let mut count = 0;
for x in &mut self.iter {
count += (self.predicate)(&x) as usize;
Expand All @@ -1196,7 +1201,7 @@ impl<I: Iterator, P> Iterator for Filter<I, P> where P: FnMut(&I::Item) -> bool
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<I: DoubleEndedIterator, P> DoubleEndedIterator for Filter<I, P>
impl<I: DoubleEndedIterator, P: ?Sized> DoubleEndedIterator for Filter<I, P>
where P: FnMut(&I::Item) -> bool,
{
#[inline]
Expand All @@ -1211,7 +1216,7 @@ impl<I: DoubleEndedIterator, P> DoubleEndedIterator for Filter<I, P>
}

#[unstable(feature = "fused", issue = "35602")]
impl<I: FusedIterator, P> FusedIterator for Filter<I, P>
impl<I: FusedIterator, P: ?Sized> FusedIterator for Filter<I, P>
where P: FnMut(&I::Item) -> bool {}

/// An iterator that uses `f` to both filter and map elements from `iter`.
Expand All @@ -1224,13 +1229,13 @@ impl<I: FusedIterator, P> FusedIterator for Filter<I, P>
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
#[derive(Clone)]
pub struct FilterMap<I, F> {
pub struct FilterMap<I, F: ?Sized> {
iter: I,
f: F,
}

#[stable(feature = "core_impl_debug", since = "1.9.0")]
impl<I: fmt::Debug, F> fmt::Debug for FilterMap<I, F> {
impl<I: fmt::Debug, F: ?Sized> fmt::Debug for FilterMap<I, F> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
f.debug_struct("FilterMap")
.field("iter", &self.iter)
Expand All @@ -1239,7 +1244,7 @@ impl<I: fmt::Debug, F> fmt::Debug for FilterMap<I, F> {
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<B, I: Iterator, F> Iterator for FilterMap<I, F>
impl<B, I: Iterator, F: ?Sized> Iterator for FilterMap<I, F>
where F: FnMut(I::Item) -> Option<B>,
{
type Item = B;
Expand All @@ -1262,7 +1267,7 @@ impl<B, I: Iterator, F> Iterator for FilterMap<I, F>
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<B, I: DoubleEndedIterator, F> DoubleEndedIterator for FilterMap<I, F>
impl<B, I: DoubleEndedIterator, F: ?Sized> DoubleEndedIterator for FilterMap<I, F>
where F: FnMut(I::Item) -> Option<B>,
{
#[inline]
Expand All @@ -1277,7 +1282,7 @@ impl<B, I: DoubleEndedIterator, F> DoubleEndedIterator for FilterMap<I, F>
}

#[unstable(feature = "fused", issue = "35602")]
impl<B, I: FusedIterator, F> FusedIterator for FilterMap<I, F>
impl<B, I: FusedIterator, F: ?Sized> FusedIterator for FilterMap<I, F>
where F: FnMut(I::Item) -> Option<B> {}

/// An iterator that yields the current count and the element during iteration.
Expand Down Expand Up @@ -1534,14 +1539,14 @@ impl<I: Iterator> Peekable<I> {
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
#[derive(Clone)]
pub struct SkipWhile<I, P> {
pub struct SkipWhile<I, P: ?Sized> {
iter: I,
flag: bool,
predicate: P,
}

#[stable(feature = "core_impl_debug", since = "1.9.0")]
impl<I: fmt::Debug, P> fmt::Debug for SkipWhile<I, P> {
impl<I: fmt::Debug, P: ?Sized> fmt::Debug for SkipWhile<I, P> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
f.debug_struct("SkipWhile")
.field("iter", &self.iter)
Expand All @@ -1551,7 +1556,7 @@ impl<I: fmt::Debug, P> fmt::Debug for SkipWhile<I, P> {
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<I: Iterator, P> Iterator for SkipWhile<I, P>
impl<I: Iterator, P: ?Sized> Iterator for SkipWhile<I, P>
where P: FnMut(&I::Item) -> bool
{
type Item = I::Item;
Expand All @@ -1575,7 +1580,7 @@ impl<I: Iterator, P> Iterator for SkipWhile<I, P>
}

#[unstable(feature = "fused", issue = "35602")]
impl<I, P> FusedIterator for SkipWhile<I, P>
impl<I, P: ?Sized> FusedIterator for SkipWhile<I, P>
where I: FusedIterator, P: FnMut(&I::Item) -> bool {}

/// An iterator that only accepts elements while `predicate` is true.
Expand All @@ -1588,14 +1593,14 @@ impl<I, P> FusedIterator for SkipWhile<I, P>
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
#[derive(Clone)]
pub struct TakeWhile<I, P> {
pub struct TakeWhile<I, P: ?Sized> {
iter: I,
flag: bool,
predicate: P,
}

#[stable(feature = "core_impl_debug", since = "1.9.0")]
impl<I: fmt::Debug, P> fmt::Debug for TakeWhile<I, P> {
impl<I: fmt::Debug, P: ?Sized> fmt::Debug for TakeWhile<I, P> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
f.debug_struct("TakeWhile")
.field("iter", &self.iter)
Expand All @@ -1605,7 +1610,7 @@ impl<I: fmt::Debug, P> fmt::Debug for TakeWhile<I, P> {
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<I: Iterator, P> Iterator for TakeWhile<I, P>
impl<I: Iterator, P: ?Sized> Iterator for TakeWhile<I, P>
where P: FnMut(&I::Item) -> bool
{
type Item = I::Item;
Expand Down Expand Up @@ -1634,7 +1639,7 @@ impl<I: Iterator, P> Iterator for TakeWhile<I, P>
}

#[unstable(feature = "fused", issue = "35602")]
impl<I, P> FusedIterator for TakeWhile<I, P>
impl<I, P: ?Sized> FusedIterator for TakeWhile<I, P>
where I: FusedIterator, P: FnMut(&I::Item) -> bool {}

/// An iterator that skips over `n` elements of `iter`.
Expand Down Expand Up @@ -1851,15 +1856,15 @@ impl<B, I, St, F> Iterator for Scan<I, St, F> where
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
#[derive(Clone)]
pub struct FlatMap<I, U: IntoIterator, F> {
pub struct FlatMap<I, U: IntoIterator, F: ?Sized> {
iter: I,
f: F,
frontiter: Option<U::IntoIter>,
backiter: Option<U::IntoIter>,
f: F,
}

#[stable(feature = "core_impl_debug", since = "1.9.0")]
impl<I: fmt::Debug, U: IntoIterator, F> fmt::Debug for FlatMap<I, U, F>
impl<I: fmt::Debug, U: IntoIterator, F: ?Sized> fmt::Debug for FlatMap<I, U, F>
where U::IntoIter: fmt::Debug
{
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
Expand All @@ -1872,7 +1877,7 @@ impl<I: fmt::Debug, U: IntoIterator, F> fmt::Debug for FlatMap<I, U, F>
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<I: Iterator, U: IntoIterator, F> Iterator for FlatMap<I, U, F>
impl<I: Iterator, U: IntoIterator, F: ?Sized> Iterator for FlatMap<I, U, F>
where F: FnMut(I::Item) -> U,
{
type Item = U::Item;
Expand Down Expand Up @@ -1905,7 +1910,7 @@ impl<I: Iterator, U: IntoIterator, F> Iterator for FlatMap<I, U, F>
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<I: DoubleEndedIterator, U, F> DoubleEndedIterator for FlatMap<I, U, F> where
impl<I: DoubleEndedIterator, U, F: ?Sized> DoubleEndedIterator for FlatMap<I, U, F> where
F: FnMut(I::Item) -> U,
U: IntoIterator,
U::IntoIter: DoubleEndedIterator
Expand All @@ -1927,7 +1932,7 @@ impl<I: DoubleEndedIterator, U, F> DoubleEndedIterator for FlatMap<I, U, F> wher
}

#[unstable(feature = "fused", issue = "35602")]
impl<I, U, F> FusedIterator for FlatMap<I, U, F>
impl<I, U, F: ?Sized> FusedIterator for FlatMap<I, U, F>
where I: FusedIterator, U: IntoIterator, F: FnMut(I::Item) -> U {}

/// An iterator that yields `None` forever after the underlying iterator
Expand Down Expand Up @@ -2090,21 +2095,21 @@ impl<I> ExactSizeIterator for Fuse<I> where I: ExactSizeIterator {
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
#[derive(Clone)]
pub struct Inspect<I, F> {
pub struct Inspect<I, F: ?Sized> {
iter: I,
f: F,
}

#[stable(feature = "core_impl_debug", since = "1.9.0")]
impl<I: fmt::Debug, F> fmt::Debug for Inspect<I, F> {
impl<I: fmt::Debug, F: ?Sized> fmt::Debug for Inspect<I, F> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
f.debug_struct("Inspect")
.field("iter", &self.iter)
.finish()
}
}

impl<I: Iterator, F> Inspect<I, F> where F: FnMut(&I::Item) {
impl<I: Iterator, F: ?Sized> Inspect<I, F> where F: FnMut(&I::Item) {
#[inline]
fn do_inspect(&mut self, elt: Option<I::Item>) -> Option<I::Item> {
if let Some(ref a) = elt {
Expand All @@ -2116,7 +2121,7 @@ impl<I: Iterator, F> Inspect<I, F> where F: FnMut(&I::Item) {
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<I: Iterator, F> Iterator for Inspect<I, F> where F: FnMut(&I::Item) {
impl<I: Iterator, F: ?Sized> Iterator for Inspect<I, F> where F: FnMut(&I::Item) {
type Item = I::Item;

#[inline]
Expand All @@ -2132,7 +2137,7 @@ impl<I: Iterator, F> Iterator for Inspect<I, F> where F: FnMut(&I::Item) {
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<I: DoubleEndedIterator, F> DoubleEndedIterator for Inspect<I, F>
impl<I: DoubleEndedIterator, F: ?Sized> DoubleEndedIterator for Inspect<I, F>
where F: FnMut(&I::Item),
{
#[inline]
Expand All @@ -2143,7 +2148,7 @@ impl<I: DoubleEndedIterator, F> DoubleEndedIterator for Inspect<I, F>
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<I: ExactSizeIterator, F> ExactSizeIterator for Inspect<I, F>
impl<I: ExactSizeIterator, F: ?Sized> ExactSizeIterator for Inspect<I, F>
where F: FnMut(&I::Item)
{
fn len(&self) -> usize {
Expand All @@ -2156,5 +2161,5 @@ impl<I: ExactSizeIterator, F> ExactSizeIterator for Inspect<I, F>
}

#[unstable(feature = "fused", issue = "35602")]
impl<I: FusedIterator, F> FusedIterator for Inspect<I, F>
impl<I: FusedIterator, F: ?Sized> FusedIterator for Inspect<I, F>
where F: FnMut(&I::Item) {}
13 changes: 13 additions & 0 deletions src/libcore/tests/iter.rs
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1288,3 +1288,16 @@ fn test_step_replace_no_between() {
assert_eq!(x, 1);
assert_eq!(y, 5);
}

#[test]
fn test_unsized_closures_in_map_etc() {
fn an_iterator<I: Iterator + ?Sized>(iter: &mut I) { let _ = iter.next(); }

an_iterator::<Filter<_, FnMut(&_) -> _>>(&mut (0..10).filter(|_| true));
an_iterator::<FilterMap<_, FnMut(_) -> _>>(&mut (0..10).filter_map(|i| Some(i)));
an_iterator::<FlatMap<_, _, FnMut(_) -> _>>(&mut (0..10).flat_map(|i| 0..i));
an_iterator::<Inspect<_, FnMut(&_)>>(&mut (0..10).inspect(|_| {}));
an_iterator::<Map<_, FnMut(_) -> _>>(&mut (0..10).map(|x| x + 1));
an_iterator::<SkipWhile<_, FnMut(&_) -> _>>(&mut (0..10).skip_while(|_| true));
an_iterator::<TakeWhile<_, FnMut(&_) -> _>>(&mut (0..10).take_while(|_| true));
}