bjoernager/rust
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Rollup merge of #122437 - Nadrieril:no-after-max, r=compiler-errors

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pattern analysis: remove `MaybeInfiniteInt::JustAfterMax`

It was inherited from before half-open ranges, but it doesn't pull its weight anymore. We lose a tiny bit of diagnostic precision as can be seen in the test. I'm generally in favor of half-open ranges over explicit `x..=MAX` ranges anyway.
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Matthias Krüger 2024-03-13 20:01:57 +01:00 • committed by GitHub
commit 5c2aa6dc6f
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4 changed files with 18 additions and 21 deletions
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13
compiler/rustc_pattern_analysis/src/constructor.rs
View file

@ -195,8 +195,6 @@ pub enum MaybeInfiniteInt {
/// Encoded value. DO NOT CONSTRUCT BY HAND; use `new_finite_{int,uint}`.
#[non_exhaustive]
Finite(u128),
/// The integer after `u128::MAX`. We need it to represent `x..=u128::MAX` as an exclusive range.
JustAfterMax,
PosInfinity,
}
@ -232,18 +230,18 @@ impl MaybeInfiniteInt {
pub fn minus_one(self) -> Option<Self> {
match self {
Finite(n) => n.checked_sub(1).map(Finite),
JustAfterMax => Some(Finite(u128::MAX)),
x => Some(x),
}
}
/// Note: this will not turn a finite value into an infinite one or vice-versa.
/// Note: this will turn `u128::MAX` into `PosInfinity`. This means `plus_one` and `minus_one`
/// are not strictly inverses, but that poses no problem in our use of them.
/// this will not turn a finite value into an infinite one or vice-versa.
pub fn plus_one(self) -> Option<Self> {
match self {
Finite(n) => match n.checked_add(1) {
Some(m) => Some(Finite(m)),
None => Some(JustAfterMax),
None => Some(PosInfinity),
},
JustAfterMax => None,
x => Some(x),
}
}
@ -277,8 +275,7 @@ impl IntRange {
}
/// Construct a range with these boundaries.
/// `lo` must not be `PosInfinity` or `JustAfterMax`. `hi` must not be `NegInfinity`.
/// If `end` is `Included`, `hi` must also not be `JustAfterMax`.
/// `lo` must not be `PosInfinity`. `hi` must not be `NegInfinity`.
#[inline]
pub fn from_range(lo: MaybeInfiniteInt, mut hi: MaybeInfiniteInt, end: RangeEnd) -> IntRange {
if end == RangeEnd::Included {

2
compiler/rustc_pattern_analysis/src/rustc.rs
View file

@ -706,7 +706,7 @@ impl<'p, 'tcx: 'p> RustcPatCtxt<'p, 'tcx> {
None => PatRangeBoundary::PosInfinity,
}
}
JustAfterMax | PosInfinity => PatRangeBoundary::PosInfinity,
PosInfinity => PatRangeBoundary::PosInfinity,
}
}