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Make Range implementation safe

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This commit is contained in:
Jacob Pratt 2021-04-01 05:06:28 -04:00
parent 641c8cd875
commit a875876027
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GPG Key ID: B80E19E4662B5AA4
3 changed files with 24 additions and 31 deletions
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2
compiler/rustc_index/src/vec.rs
View File

@ -184,7 +184,7 @@ macro_rules! newtype_index {
} }
} }
unsafe impl ::std::iter::Step for $type { impl ::std::iter::Step for $type {
#[inline] #[inline]
fn steps_between(start: &Self, end: &Self) -> Option<usize> { fn steps_between(start: &Self, end: &Self) -> Option<usize> {
<usize as ::std::iter::Step>::steps_between( <usize as ::std::iter::Step>::steps_between(

51
library/core/src/iter/range.rs
View File

@ -9,15 +9,8 @@ use super::{FusedIterator, TrustedLen, TrustedRandomAccess};
/// ///
/// The *successor* operation moves towards values that compare greater. /// The *successor* operation moves towards values that compare greater.
/// The *predecessor* operation moves towards values that compare lesser. /// The *predecessor* operation moves towards values that compare lesser.
///
/// # Safety
///
/// This trait is `unsafe` because its implementation must be correct for
/// the safety of `unsafe trait TrustedLen` implementations, and the results
/// of using this trait can otherwise be trusted by `unsafe` code to be correct
/// and fulfill the listed obligations.
#[unstable(feature = "step_trait", reason = "recently redesigned", issue = "42168")] #[unstable(feature = "step_trait", reason = "recently redesigned", issue = "42168")]
pub unsafe trait Step: Clone + PartialOrd + Sized { pub trait Step: Clone + PartialOrd + Sized {
/// Returns the number of *successor* steps required to get from `start` to `end`. /// Returns the number of *successor* steps required to get from `start` to `end`.
/// ///
/// Returns `None` if the number of steps would overflow `usize` /// Returns `None` if the number of steps would overflow `usize`
@ -237,7 +230,7 @@ macro_rules! step_integer_impls {
$( $(
#[allow(unreachable_patterns)] #[allow(unreachable_patterns)]
#[unstable(feature = "step_trait", reason = "recently redesigned", issue = "42168")] #[unstable(feature = "step_trait", reason = "recently redesigned", issue = "42168")]
unsafe impl Step for $u_narrower { impl Step for $u_narrower {
step_identical_methods!(); step_identical_methods!();
#[inline] #[inline]
@ -269,7 +262,7 @@ macro_rules! step_integer_impls {
#[allow(unreachable_patterns)] #[allow(unreachable_patterns)]
#[unstable(feature = "step_trait", reason = "recently redesigned", issue = "42168")] #[unstable(feature = "step_trait", reason = "recently redesigned", issue = "42168")]
unsafe impl Step for $i_narrower { impl Step for $i_narrower {
step_identical_methods!(); step_identical_methods!();
#[inline] #[inline]
@ -333,7 +326,7 @@ macro_rules! step_integer_impls {
$( $(
#[allow(unreachable_patterns)] #[allow(unreachable_patterns)]
#[unstable(feature = "step_trait", reason = "recently redesigned", issue = "42168")] #[unstable(feature = "step_trait", reason = "recently redesigned", issue = "42168")]
unsafe impl Step for $u_wider { impl Step for $u_wider {
step_identical_methods!(); step_identical_methods!();
#[inline] #[inline]
@ -358,7 +351,7 @@ macro_rules! step_integer_impls {
#[allow(unreachable_patterns)] #[allow(unreachable_patterns)]
#[unstable(feature = "step_trait", reason = "recently redesigned", issue = "42168")] #[unstable(feature = "step_trait", reason = "recently redesigned", issue = "42168")]
unsafe impl Step for $i_wider { impl Step for $i_wider {
step_identical_methods!(); step_identical_methods!();
#[inline] #[inline]
@ -408,7 +401,7 @@ step_integer_impls! {
} }
#[unstable(feature = "step_trait", reason = "recently redesigned", issue = "42168")] #[unstable(feature = "step_trait", reason = "recently redesigned", issue = "42168")]
unsafe impl Step for char { impl Step for char {
#[inline] #[inline]
fn steps_between(&start: &char, &end: &char) -> Option<usize> { fn steps_between(&start: &char, &end: &char) -> Option<usize> {
let start = start as u32; let start = start as u32;
@ -519,8 +512,8 @@ impl<A: Step> Iterator for ops::Range<A> {
#[inline] #[inline]
fn next(&mut self) -> Option<A> { fn next(&mut self) -> Option<A> {
if self.start < self.end { if self.start < self.end {
// SAFETY: just checked precondition let n =
let n = unsafe { Step::forward_unchecked(self.start.clone(), 1) }; Step::forward_checked(self.start.clone(), 1).expect("`Step` invariants not upheld");
Some(mem::replace(&mut self.start, n)) Some(mem::replace(&mut self.start, n))
} else { } else {
None None
@ -541,8 +534,8 @@ impl<A: Step> Iterator for ops::Range<A> {
fn nth(&mut self, n: usize) -> Option<A> { fn nth(&mut self, n: usize) -> Option<A> {
if let Some(plus_n) = Step::forward_checked(self.start.clone(), n) { if let Some(plus_n) = Step::forward_checked(self.start.clone(), n) {
if plus_n < self.end { if plus_n < self.end {
// SAFETY: just checked precondition self.start =
self.start = unsafe { Step::forward_unchecked(plus_n.clone(), 1) }; Step::forward_checked(plus_n.clone(), 1).expect("`Step` invariants not upheld");
return Some(plus_n); return Some(plus_n);
} }
} }
@ -632,8 +625,8 @@ impl<A: Step> DoubleEndedIterator for ops::Range<A> {
#[inline] #[inline]
fn next_back(&mut self) -> Option<A> { fn next_back(&mut self) -> Option<A> {
if self.start < self.end { if self.start < self.end {
// SAFETY: just checked precondition self.end =
self.end = unsafe { Step::backward_unchecked(self.end.clone(), 1) }; Step::backward_checked(self.end.clone(), 1).expect("`Step` invariants not upheld");
Some(self.end.clone()) Some(self.end.clone())
} else { } else {
None None
@ -644,8 +637,8 @@ impl<A: Step> DoubleEndedIterator for ops::Range<A> {
fn nth_back(&mut self, n: usize) -> Option<A> { fn nth_back(&mut self, n: usize) -> Option<A> {
if let Some(minus_n) = Step::backward_checked(self.end.clone(), n) { if let Some(minus_n) = Step::backward_checked(self.end.clone(), n) {
if minus_n > self.start { if minus_n > self.start {
// SAFETY: just checked precondition self.end =
self.end = unsafe { Step::backward_unchecked(minus_n, 1) }; Step::backward_checked(minus_n, 1).expect("`Step` invariants not upheld");
return Some(self.end.clone()); return Some(self.end.clone());
} }
} }
@ -711,8 +704,8 @@ impl<A: Step> Iterator for ops::RangeInclusive<A> {
} }
let is_iterating = self.start < self.end; let is_iterating = self.start < self.end;
Some(if is_iterating { Some(if is_iterating {
// SAFETY: just checked precondition let n =
let n = unsafe { Step::forward_unchecked(self.start.clone(), 1) }; Step::forward_checked(self.start.clone(), 1).expect("`Step` invariants not upheld");
mem::replace(&mut self.start, n) mem::replace(&mut self.start, n)
} else { } else {
self.exhausted = true; self.exhausted = true;
@ -774,8 +767,8 @@ impl<A: Step> Iterator for ops::RangeInclusive<A> {
let mut accum = init; let mut accum = init;
while self.start < self.end { while self.start < self.end {
// SAFETY: just checked precondition let n =
let n = unsafe { Step::forward_unchecked(self.start.clone(), 1) }; Step::forward_checked(self.start.clone(), 1).expect("`Step` invariants not upheld");
let n = mem::replace(&mut self.start, n); let n = mem::replace(&mut self.start, n);
accum = f(accum, n)?; accum = f(accum, n)?;
} }
@ -828,8 +821,8 @@ impl<A: Step> DoubleEndedIterator for ops::RangeInclusive<A> {
} }
let is_iterating = self.start < self.end; let is_iterating = self.start < self.end;
Some(if is_iterating { Some(if is_iterating {
// SAFETY: just checked precondition let n =
let n = unsafe { Step::backward_unchecked(self.end.clone(), 1) }; Step::backward_checked(self.end.clone(), 1).expect("`Step` invariants not upheld");
mem::replace(&mut self.end, n) mem::replace(&mut self.end, n)
} else { } else {
self.exhausted = true; self.exhausted = true;
@ -879,8 +872,8 @@ impl<A: Step> DoubleEndedIterator for ops::RangeInclusive<A> {
let mut accum = init; let mut accum = init;
while self.start < self.end { while self.start < self.end {
// SAFETY: just checked precondition let n =
let n = unsafe { Step::backward_unchecked(self.end.clone(), 1) }; Step::backward_checked(self.end.clone(), 1).expect("`Step` invariants not upheld");
let n = mem::replace(&mut self.end, n); let n = mem::replace(&mut self.end, n);
accum = f(accum, n)?; accum = f(accum, n)?;
} }

2
src/test/ui/impl-trait/example-calendar.rs
View File

@ -157,7 +157,7 @@ impl<'a, 'b> std::ops::Add<&'b NaiveDate> for &'a NaiveDate {
} }
} }
unsafe impl std::iter::Step for NaiveDate { impl std::iter::Step for NaiveDate {
fn steps_between(_: &Self, _: &Self) -> Option<usize> { fn steps_between(_: &Self, _: &Self) -> Option<usize> {
unimplemented!() unimplemented!()
} }