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Rollup merge of #116481 - scottmcm:tweak-combinators, r=cuviper

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Reuse existing `Some`s in `Option::(x)or`

LLVM still has trouble re-using discriminants sometimes when rebuilding a two-variant enum, so when we have the correct variant already built, just use it.

That's shorter in the Rust code, as well as simpler in MIR and the optimized LLVM, so might as well: <https://rust.godbolt.org/z/KhdE8eToW>

Thanks to `@veber-alex` for pointing out this opportunity in https://github.com/rust-lang/rust/issues/101210#issuecomment-1732470941
This commit is contained in:
Matthias Krüger 2023-10-06 21:17:50 +02:00 • committed by GitHub
commit f8dae0c20a
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1 changed files with 4 additions and 4 deletions
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8
library/core/src/option.rs
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@ -1475,7 +1475,7 @@ impl<T> Option<T> {
#[stable(feature = "rust1", since = "1.0.0")]
pub fn or(self, optb: Option<T>) -> Option<T> {
match self {
Some(x) => Some(x),
x @ Some(_) => x,
None => optb,
}
}
@ -1500,7 +1500,7 @@ impl<T> Option<T> {
F: FnOnce() -> Option<T>,
{
match self {
Some(x) => Some(x),
x @ Some(_) => x,
None => f(),
}
}
@ -1530,8 +1530,8 @@ impl<T> Option<T> {
#[stable(feature = "option_xor", since = "1.37.0")]
pub fn xor(self, optb: Option<T>) -> Option<T> {
match (self, optb) {
(Some(a), None) => Some(a),
(None, Some(b)) => Some(b),
(a @ Some(_), None) => a,
(None, b @ Some(_)) => b,
_ => None,
}
}