diff --git a/library/core/src/iter/traits/collect.rs b/library/core/src/iter/traits/collect.rs index 2cf2ea58fd4ee..c3c7288e38990 100644 --- a/library/core/src/iter/traits/collect.rs +++ b/library/core/src/iter/traits/collect.rs @@ -492,131 +492,150 @@ impl Extend<()> for () { fn extend_one(&mut self, _item: ()) {} } -#[stable(feature = "extend_for_tuple", since = "1.56.0")] -impl Extend<(A, B)> for (ExtendA, ExtendB) -where - ExtendA: Extend, - ExtendB: Extend, -{ - /// Allows to `extend` a tuple of collections that also implement `Extend`. - /// - /// See also: [`Iterator::unzip`] - /// - /// # Examples - /// ``` - /// let mut tuple = (vec![0], vec![1]); - /// tuple.extend([(2, 3), (4, 5), (6, 7)]); - /// assert_eq!(tuple.0, [0, 2, 4, 6]); - /// assert_eq!(tuple.1, [1, 3, 5, 7]); - /// - /// // also allows for arbitrarily nested tuples as elements - /// let mut nested_tuple = (vec![1], (vec![2], vec![3])); - /// nested_tuple.extend([(4, (5, 6)), (7, (8, 9))]); - /// - /// let (a, (b, c)) = nested_tuple; - /// assert_eq!(a, [1, 4, 7]); - /// assert_eq!(b, [2, 5, 8]); - /// assert_eq!(c, [3, 6, 9]); - /// ``` - fn extend>(&mut self, into_iter: T) { - let (a, b) = self; - let iter = into_iter.into_iter(); - SpecTupleExtend::extend(iter, a, b); - } +macro_rules! spec_tuple_impl { + ( ($ty_name:ident, $var_name:ident, $extend_ty_name: ident, $trait_name:ident, $default_fn_name:ident, $cnt:tt), ) => { + spec_tuple_impl!($trait_name, $default_fn_name, #[doc(fake_variadic)] #[doc = "This trait is implemented for tuples up to twelve items long. The `impl`s for 1- and 3- through 12-ary tuples were stabilized after 2-tuples, in RUSTC_CURRENT_VERSION."] => ($ty_name, $var_name, $extend_ty_name, $cnt),); + }; + ( ($ty_name:ident, $var_name:ident, $extend_ty_name: ident, $trait_name:ident, $default_fn_name:ident, $cnt:tt), $(($ty_names:ident, $var_names:ident, $extend_ty_names:ident, $trait_names:ident, $default_fn_names:ident, $cnts:tt),)*) => { - fn extend_one(&mut self, item: (A, B)) { - self.0.extend_one(item.0); - self.1.extend_one(item.1); - } + spec_tuple_impl!($(($ty_names, $var_names, $extend_ty_names, $trait_names, $default_fn_names, $cnts),)*); + spec_tuple_impl!($trait_name, $default_fn_name, #[doc(hidden)] => ($ty_name, $var_name, $extend_ty_name, $cnt), $(($ty_names, $var_names, $extend_ty_names, $cnts),)*); + }; + ($trait_name:ident, $default_fn_name:ident, #[$meta:meta] $(#[$doctext:meta])? => $(($ty_names:ident, $var_names:ident, $extend_ty_names:ident, $cnts:tt),)*) => { + #[$meta] + $(#[$doctext])? + #[stable(feature = "extend_for_tuple", since = "1.56.0")] + impl<$($ty_names,)* $($extend_ty_names,)*> Extend<($($ty_names,)*)> for ($($extend_ty_names,)*) + where + $($extend_ty_names: Extend<$ty_names>,)* + { + /// Allows to `extend` a tuple of collections that also implement `Extend`. + /// + /// See also: [`Iterator::unzip`] + /// + /// # Examples + /// ``` + /// // Example given for a 2-tuple, but 1- through 12-tuples are supported + /// let mut tuple = (vec![0], vec![1]); + /// tuple.extend([(2, 3), (4, 5), (6, 7)]); + /// assert_eq!(tuple.0, [0, 2, 4, 6]); + /// assert_eq!(tuple.1, [1, 3, 5, 7]); + /// + /// // also allows for arbitrarily nested tuples as elements + /// let mut nested_tuple = (vec![1], (vec![2], vec![3])); + /// nested_tuple.extend([(4, (5, 6)), (7, (8, 9))]); + /// + /// let (a, (b, c)) = nested_tuple; + /// assert_eq!(a, [1, 4, 7]); + /// assert_eq!(b, [2, 5, 8]); + /// assert_eq!(c, [3, 6, 9]); + /// ``` + fn extend>(&mut self, into_iter: T) { + let ($($var_names,)*) = self; + let iter = into_iter.into_iter(); + $trait_name::extend(iter, $($var_names,)*); + } - fn extend_reserve(&mut self, additional: usize) { - self.0.extend_reserve(additional); - self.1.extend_reserve(additional); - } + fn extend_one(&mut self, item: ($($ty_names,)*)) { + $(self.$cnts.extend_one(item.$cnts);)* + } - unsafe fn extend_one_unchecked(&mut self, item: (A, B)) { - // SAFETY: Those are our safety preconditions, and we correctly forward `extend_reserve`. - unsafe { - self.0.extend_one_unchecked(item.0); - self.1.extend_one_unchecked(item.1); - } - } -} + fn extend_reserve(&mut self, additional: usize) { + $(self.$cnts.extend_reserve(additional);)* + } -fn default_extend_tuple( - iter: impl Iterator, - a: &mut ExtendA, - b: &mut ExtendB, -) where - ExtendA: Extend, - ExtendB: Extend, -{ - fn extend<'a, A, B>( - a: &'a mut impl Extend, - b: &'a mut impl Extend, - ) -> impl FnMut((), (A, B)) + 'a { - move |(), (t, u)| { - a.extend_one(t); - b.extend_one(u); + unsafe fn extend_one_unchecked(&mut self, item: ($($ty_names,)*)) { + // SAFETY: Those are our safety preconditions, and we correctly forward `extend_reserve`. + unsafe { + $(self.$cnts.extend_one_unchecked(item.$cnts);)* + } + } } - } - let (lower_bound, _) = iter.size_hint(); - if lower_bound > 0 { - a.extend_reserve(lower_bound); - b.extend_reserve(lower_bound); - } + trait $trait_name<$($ty_names),*> { + fn extend(self, $($var_names: &mut $ty_names,)*); + } - iter.fold((), extend(a, b)); -} + fn $default_fn_name<$($ty_names,)* $($extend_ty_names,)*>( + iter: impl Iterator, + $($var_names: &mut $extend_ty_names,)* + ) where + $($extend_ty_names: Extend<$ty_names>,)* + { + fn extend<'a, $($ty_names,)*>( + $($var_names: &'a mut impl Extend<$ty_names>,)* + ) -> impl FnMut((), ($($ty_names,)*)) + 'a { + #[allow(non_snake_case)] + move |(), ($($extend_ty_names,)*)| { + $($var_names.extend_one($extend_ty_names);)* + } + } -trait SpecTupleExtend { - fn extend(self, a: &mut A, b: &mut B); -} + let (lower_bound, _) = iter.size_hint(); + if lower_bound > 0 { + $($var_names.extend_reserve(lower_bound);)* + } -impl SpecTupleExtend for Iter -where - ExtendA: Extend, - ExtendB: Extend, - Iter: Iterator, -{ - default fn extend(self, a: &mut ExtendA, b: &mut ExtendB) { - default_extend_tuple(self, a, b); - } -} + iter.fold((), extend($($var_names,)*)); + } -impl SpecTupleExtend for Iter -where - ExtendA: Extend, - ExtendB: Extend, - Iter: TrustedLen, -{ - fn extend(self, a: &mut ExtendA, b: &mut ExtendB) { - fn extend<'a, A, B>( - a: &'a mut impl Extend, - b: &'a mut impl Extend, - ) -> impl FnMut((), (A, B)) + 'a { - // SAFETY: We reserve enough space for the `size_hint`, and the iterator is `TrustedLen` - // so its `size_hint` is exact. - move |(), (t, u)| unsafe { - a.extend_one_unchecked(t); - b.extend_one_unchecked(u); + impl<$($ty_names,)* $($extend_ty_names,)* Iter> $trait_name<$($extend_ty_names),*> for Iter + where + $($extend_ty_names: Extend<$ty_names>,)* + Iter: Iterator, + { + default fn extend(self, $($var_names: &mut $extend_ty_names),*) { + $default_fn_name(self, $($var_names),*); } } - let (lower_bound, upper_bound) = self.size_hint(); + impl<$($ty_names,)* $($extend_ty_names,)* Iter> $trait_name<$($extend_ty_names),*> for Iter + where + $($extend_ty_names: Extend<$ty_names>,)* + Iter: TrustedLen, + { + fn extend(self, $($var_names: &mut $extend_ty_names,)*) { + fn extend<'a, $($ty_names,)*>( + $($var_names: &'a mut impl Extend<$ty_names>,)* + ) -> impl FnMut((), ($($ty_names,)*)) + 'a { + #[allow(non_snake_case)] + // SAFETY: We reserve enough space for the `size_hint`, and the iterator is `TrustedLen` + // so its `size_hint` is exact. + move |(), ($($extend_ty_names,)*)| unsafe { + $($var_names.extend_one_unchecked($extend_ty_names);)* + } + } - if upper_bound.is_none() { - // We cannot reserve more than `usize::MAX` items, and this is likely to go out of memory anyway. - default_extend_tuple(self, a, b); - return; - } + let (lower_bound, upper_bound) = self.size_hint(); - if lower_bound > 0 { - a.extend_reserve(lower_bound); - b.extend_reserve(lower_bound); - } + if upper_bound.is_none() { + // We cannot reserve more than `usize::MAX` items, and this is likely to go out of memory anyway. + $default_fn_name(self, $($var_names,)*); + return; + } - self.fold((), extend(a, b)); + if lower_bound > 0 { + $($var_names.extend_reserve(lower_bound);)* + } + + self.fold((), extend($($var_names,)*)); + } } + + }; } + +spec_tuple_impl!( + (L, l, EL, TraitL, default_extend_tuple_l, 11), + (K, k, EK, TraitK, default_extend_tuple_k, 10), + (J, j, EJ, TraitJ, default_extend_tuple_j, 9), + (I, i, EI, TraitI, default_extend_tuple_i, 8), + (H, h, EH, TraitH, default_extend_tuple_h, 7), + (G, g, EG, TraitG, default_extend_tuple_g, 6), + (F, f, EF, TraitF, default_extend_tuple_f, 5), + (E, e, EE, TraitE, default_extend_tuple_e, 4), + (D, d, ED, TraitD, default_extend_tuple_d, 3), + (C, c, EC, TraitC, default_extend_tuple_c, 2), + (B, b, EB, TraitB, default_extend_tuple_b, 1), + (A, a, EA, TraitA, default_extend_tuple_a, 0), +); diff --git a/library/core/tests/iter/traits/iterator.rs b/library/core/tests/iter/traits/iterator.rs index 93ef9c0812b16..76f1e3319d42e 100644 --- a/library/core/tests/iter/traits/iterator.rs +++ b/library/core/tests/iter/traits/iterator.rs @@ -617,6 +617,19 @@ fn test_next_chunk() { assert_eq!(it.next_chunk::<0>().unwrap(), []); } +#[test] +fn test_collect_into_tuples() { + let a = vec![(1, 2, 3), (4, 5, 6), (7, 8, 9)]; + let b = vec![1, 4, 7]; + let c = vec![2, 5, 8]; + let d = vec![3, 6, 9]; + let mut e = (Vec::new(), Vec::new(), Vec::new()); + a.iter().cloned().collect_into(&mut e); + assert!(e.0 == b); + assert!(e.1 == c); + assert!(e.2 == d); +} + // just tests by whether or not this compiles fn _empty_impl_all_auto_traits() { use std::panic::{RefUnwindSafe, UnwindSafe};