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Implement SliceIndex for R: RangeBounds<usize> #51464

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Implement SliceIndex for R: RangeBounds<usize> #51464

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65 changes: 54 additions & 11 deletions src/libcore/slice/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1985,6 +1985,8 @@ mod private_slice_index {
#[stable(feature = "slice_get_slice", since = "1.28.0")]
impl Sealed for usize {}
#[stable(feature = "slice_get_slice", since = "1.28.0")]
impl<R: ops::RangeBounds<usize>> Sealed for R {}
#[stable(feature = "slice_get_slice", since = "1.28.0")]
impl Sealed for ops::Range<usize> {}
#[stable(feature = "slice_get_slice", since = "1.28.0")]
impl Sealed for ops::RangeTo<usize> {}
Expand Down Expand Up @@ -2086,10 +2088,61 @@ impl<T> SliceIndex<[T]> for usize {
}
}

// Given a RangeBounds, pick the appropriate concrete RangeXXX type and call the
// given method on an instance of that concrete type.
macro_rules! call_method_on_range_bounds {
($slf:ident, $method:ident, $slc:ident) => (
match ($slf.start_bound(), $slf.end_bound()) {
(ops::Bound::Included(x), ops::Bound::Included(y)) => (*x..=*y).$method($slc),
(ops::Bound::Included(x), ops::Bound::Excluded(y)) => (*x..*y).$method($slc),
(ops::Bound::Included(x), ops::Bound::Unbounded) => (*x..).$method($slc),
(ops::Bound::Excluded(x), ops::Bound::Included(y)) => ((x+1)..=*y).$method($slc),
(ops::Bound::Excluded(x), ops::Bound::Excluded(y)) => ((x+1)..*y).$method($slc),
(ops::Bound::Excluded(x), ops::Bound::Unbounded) => ((x+1)..).$method($slc),
(ops::Bound::Unbounded, ops::Bound::Included(y)) => (..=*y).$method($slc),
(ops::Bound::Unbounded, ops::Bound::Excluded(y)) => (..*y).$method($slc),
(ops::Bound::Unbounded, ops::Bound::Unbounded) => (..).$method($slc),
}
);
}

#[stable(feature = "slice-get-slice-impls", since = "1.15.0")]
impl<T> SliceIndex<[T]> for ops::Range<usize> {
impl<T, R: ops::RangeBounds<usize>> SliceIndex<[T]> for R {
type Output = [T];

#[inline]
default fn get(self, slice: &[T]) -> Option<&[T]> {
call_method_on_range_bounds!(self, get, slice)
}

#[inline]
default fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> {
call_method_on_range_bounds!(self, get_mut, slice)
}

#[inline]
default unsafe fn get_unchecked(self, slice: &[T]) -> &[T] {
call_method_on_range_bounds!(self, get_unchecked, slice)
}

#[inline]
default unsafe fn get_unchecked_mut(self, slice: &mut [T]) -> &mut [T] {
call_method_on_range_bounds!(self, get_unchecked_mut, slice)
}

#[inline]
default fn index(self, slice: &[T]) -> &[T] {
call_method_on_range_bounds!(self, index, slice)
}

#[inline]
default fn index_mut(self, slice: &mut [T]) -> &mut [T] {
call_method_on_range_bounds!(self, index_mut, slice)
}
}

#[stable(feature = "slice-get-slice-impls", since = "1.15.0")]
impl<T> SliceIndex<[T]> for ops::Range<usize> {
#[inline]
fn get(self, slice: &[T]) -> Option<&[T]> {
if self.start > self.end || self.end > slice.len() {
Expand Down Expand Up @@ -2149,8 +2202,6 @@ impl<T> SliceIndex<[T]> for ops::Range<usize> {

#[stable(feature = "slice-get-slice-impls", since = "1.15.0")]
impl<T> SliceIndex<[T]> for ops::RangeTo<usize> {
type Output = [T];

#[inline]
fn get(self, slice: &[T]) -> Option<&[T]> {
(0..self.end).get(slice)
Expand Down Expand Up @@ -2184,8 +2235,6 @@ impl<T> SliceIndex<[T]> for ops::RangeTo<usize> {

#[stable(feature = "slice-get-slice-impls", since = "1.15.0")]
impl<T> SliceIndex<[T]> for ops::RangeFrom<usize> {
type Output = [T];

#[inline]
fn get(self, slice: &[T]) -> Option<&[T]> {
(self.start..slice.len()).get(slice)
Expand Down Expand Up @@ -2219,8 +2268,6 @@ impl<T> SliceIndex<[T]> for ops::RangeFrom<usize> {

#[stable(feature = "slice-get-slice-impls", since = "1.15.0")]
impl<T> SliceIndex<[T]> for ops::RangeFull {
type Output = [T];

#[inline]
fn get(self, slice: &[T]) -> Option<&[T]> {
Some(slice)
Expand Down Expand Up @@ -2255,8 +2302,6 @@ impl<T> SliceIndex<[T]> for ops::RangeFull {

#[stable(feature = "inclusive_range", since = "1.26.0")]
impl<T> SliceIndex<[T]> for ops::RangeInclusive<usize> {
type Output = [T];

#[inline]
fn get(self, slice: &[T]) -> Option<&[T]> {
if self.end == usize::max_value() { None }
Expand Down Expand Up @@ -2294,8 +2339,6 @@ impl<T> SliceIndex<[T]> for ops::RangeInclusive<usize> {

#[stable(feature = "inclusive_range", since = "1.26.0")]
impl<T> SliceIndex<[T]> for ops::RangeToInclusive<usize> {
type Output = [T];

#[inline]
fn get(self, slice: &[T]) -> Option<&[T]> {
(0..=self.end).get(slice)
Expand Down