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Improve btree's unwrap_unchecked #74693

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19 changes: 10 additions & 9 deletions library/alloc/src/collections/btree/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -13,15 +13,16 @@ trait Recover<Q: ?Sized> {
fn replace(&mut self, key: Self::Key) -> Option<Self::Key>;
}

/// Same purpose as `Option::unwrap` but doesn't always guarantee a panic
/// if the option contains no value.
/// SAFETY: the caller must ensure that the option contains a value.
#[inline(always)]
pub unsafe fn unwrap_unchecked<T>(val: Option<T>) -> T {
val.unwrap_or_else(|| {
if cfg!(debug_assertions) {
panic!("'unchecked' unwrap on None in BTreeMap");
} else {
unsafe {
core::intrinsics::unreachable();
}
}
})
if cfg!(debug_assertions) {
val.expect("'unchecked' unwrap on None in BTreeMap")
} else {
val.unwrap()
// val.unwrap_or_else(|| unsafe { core::hint::unreachable_unchecked() })
// ...is considerably slower
}
}