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Use subslice patterns in slice methods #69706

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merged 1 commit into from
Mar 7, 2020
Merged

Use subslice patterns in slice methods #69706

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30 changes: 8 additions & 22 deletions src/libcore/slice/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -103,7 +103,7 @@ impl<T> [T] {
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn first(&self) -> Option<&T> {
self.get(0)
if let [first, ..] = self { Some(first) } else { None }
}

/// Returns a mutable pointer to the first element of the slice, or `None` if it is empty.
Expand All @@ -121,7 +121,7 @@ impl<T> [T] {
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn first_mut(&mut self) -> Option<&mut T> {
self.get_mut(0)
if let [first, ..] = self { Some(first) } else { None }
}

/// Returns the first and all the rest of the elements of the slice, or `None` if it is empty.
Expand All @@ -139,7 +139,7 @@ impl<T> [T] {
#[stable(feature = "slice_splits", since = "1.5.0")]
#[inline]
pub fn split_first(&self) -> Option<(&T, &[T])> {
if self.is_empty() { None } else { Some((&self[0], &self[1..])) }
if let [first, tail @ ..] = self { Some((first, tail)) } else { None }
}

/// Returns the first and all the rest of the elements of the slice, or `None` if it is empty.
Expand All @@ -159,12 +159,7 @@ impl<T> [T] {
#[stable(feature = "slice_splits", since = "1.5.0")]
#[inline]
pub fn split_first_mut(&mut self) -> Option<(&mut T, &mut [T])> {
if self.is_empty() {
None
} else {
let split = self.split_at_mut(1);
Some((&mut split.0[0], split.1))
}
if let [first, tail @ ..] = self { Some((first, tail)) } else { None }
}

/// Returns the last and all the rest of the elements of the slice, or `None` if it is empty.
Expand All @@ -182,8 +177,7 @@ impl<T> [T] {
#[stable(feature = "slice_splits", since = "1.5.0")]
#[inline]
pub fn split_last(&self) -> Option<(&T, &[T])> {
let len = self.len();
if len == 0 { None } else { Some((&self[len - 1], &self[..(len - 1)])) }
if let [init @ .., last] = self { Some((last, init)) } else { None }
}

/// Returns the last and all the rest of the elements of the slice, or `None` if it is empty.
Expand All @@ -203,13 +197,7 @@ impl<T> [T] {
#[stable(feature = "slice_splits", since = "1.5.0")]
#[inline]
pub fn split_last_mut(&mut self) -> Option<(&mut T, &mut [T])> {
let len = self.len();
if len == 0 {
None
} else {
let split = self.split_at_mut(len - 1);
Some((&mut split.1[0], split.0))
}
if let [init @ .., last] = self { Some((last, init)) } else { None }
}

/// Returns the last element of the slice, or `None` if it is empty.
Expand All @@ -226,8 +214,7 @@ impl<T> [T] {
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn last(&self) -> Option<&T> {
let last_idx = self.len().checked_sub(1)?;
self.get(last_idx)
if let [.., last] = self { Some(last) } else { None }
}

/// Returns a mutable pointer to the last item in the slice.
Expand All @@ -245,8 +232,7 @@ impl<T> [T] {
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn last_mut(&mut self) -> Option<&mut T> {
let last_idx = self.len().checked_sub(1)?;
self.get_mut(last_idx)
if let [.., last] = self { Some(last) } else { None }
}

/// Returns a reference to an element or subslice depending on the type of
Expand Down