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Remove unreachable panics from VecDeque
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bugadani committed Jan 14, 2021
1 parent c87ef0a commit 744f885
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Showing 2 changed files with 23 additions and 5 deletions.
9 changes: 4 additions & 5 deletions library/alloc/src/collections/vec_deque/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1292,7 +1292,7 @@ impl<T> VecDeque<T> {
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn front(&self) -> Option<&T> {
if !self.is_empty() { Some(&self[0]) } else { None }
self.get(0)
}

/// Provides a mutable reference to the front element, or `None` if the
Expand All @@ -1316,7 +1316,7 @@ impl<T> VecDeque<T> {
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn front_mut(&mut self) -> Option<&mut T> {
if !self.is_empty() { Some(&mut self[0]) } else { None }
self.get_mut(0)
}

/// Provides a reference to the back element, or `None` if the `VecDeque` is
Expand All @@ -1336,7 +1336,7 @@ impl<T> VecDeque<T> {
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn back(&self) -> Option<&T> {
if !self.is_empty() { Some(&self[self.len() - 1]) } else { None }
self.get(self.len().wrapping_sub(1))
}

/// Provides a mutable reference to the back element, or `None` if the
Expand All @@ -1360,8 +1360,7 @@ impl<T> VecDeque<T> {
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn back_mut(&mut self) -> Option<&mut T> {
let len = self.len();
if !self.is_empty() { Some(&mut self[len - 1]) } else { None }
self.get_mut(self.len().wrapping_sub(1))
}

/// Removes the first element and returns it, or `None` if the `VecDeque` is
Expand Down
19 changes: 19 additions & 0 deletions src/test/codegen/vecdeque_no_panic.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,19 @@
// This test checks that `VecDeque::front[_mut]()` and `VecDeque::back[_mut]()` can't panic.

// compile-flags: -O
// ignore-debug: the debug assertions get in the way

#![crate_type = "lib"]

use std::collections::VecDeque;

// CHECK-LABEL: @dont_panic
#[no_mangle]
pub fn dont_panic(v: &mut VecDeque<usize>) {
// CHECK-NOT: expect
// CHECK-NOT: panic
v.front();
v.front_mut();
v.back();
v.back_mut();
}

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