diff options
Diffstat (limited to 'library/core/src')
| -rw-r--r-- | library/core/src/iter/range.rs | 30 |
1 files changed, 28 insertions, 2 deletions
diff --git a/library/core/src/iter/range.rs b/library/core/src/iter/range.rs index 2ecf9ce5b81..055ead117ea 100644 --- a/library/core/src/iter/range.rs +++ b/library/core/src/iter/range.rs @@ -183,8 +183,25 @@ pub trait Step: Clone + PartialOrd + Sized { } } -// These are still macro-generated because the integer literals resolve to different types. -macro_rules! step_identical_methods { +// Separate impls for signed ranges because the distance within a signed range can be larger +// than the signed::MAX value. Therefore `as` casting to the signed type would be incorrect. +macro_rules! step_signed_methods { + ($unsigned: ty) => { + #[inline] + unsafe fn forward_unchecked(start: Self, n: usize) -> Self { + // SAFETY: the caller has to guarantee that `start + n` doesn't overflow. + unsafe { start.checked_add_unsigned(n as $unsigned).unwrap_unchecked() } + } + + #[inline] + unsafe fn backward_unchecked(start: Self, n: usize) -> Self { + // SAFETY: the caller has to guarantee that `start - n` doesn't overflow. + unsafe { start.checked_sub_unsigned(n as $unsigned).unwrap_unchecked() } + } + }; +} + +macro_rules! step_unsigned_methods { () => { #[inline] unsafe fn forward_unchecked(start: Self, n: usize) -> Self { @@ -197,7 +214,12 @@ macro_rules! step_identical_methods { // SAFETY: the caller has to guarantee that `start - n` doesn't overflow. unsafe { start.unchecked_sub(n as Self) } } + }; +} +// These are still macro-generated because the integer literals resolve to different types. +macro_rules! step_identical_methods { + () => { #[inline] #[allow(arithmetic_overflow)] #[rustc_inherit_overflow_checks] @@ -238,6 +260,7 @@ macro_rules! step_integer_impls { #[unstable(feature = "step_trait", reason = "recently redesigned", issue = "42168")] impl Step for $u_narrower { step_identical_methods!(); + step_unsigned_methods!(); #[inline] fn steps_between(start: &Self, end: &Self) -> Option<usize> { @@ -270,6 +293,7 @@ macro_rules! step_integer_impls { #[unstable(feature = "step_trait", reason = "recently redesigned", issue = "42168")] impl Step for $i_narrower { step_identical_methods!(); + step_signed_methods!($u_narrower); #[inline] fn steps_between(start: &Self, end: &Self) -> Option<usize> { @@ -334,6 +358,7 @@ macro_rules! step_integer_impls { #[unstable(feature = "step_trait", reason = "recently redesigned", issue = "42168")] impl Step for $u_wider { step_identical_methods!(); + step_unsigned_methods!(); #[inline] fn steps_between(start: &Self, end: &Self) -> Option<usize> { @@ -359,6 +384,7 @@ macro_rules! step_integer_impls { #[unstable(feature = "step_trait", reason = "recently redesigned", issue = "42168")] impl Step for $i_wider { step_identical_methods!(); + step_signed_methods!($u_wider); #[inline] fn steps_between(start: &Self, end: &Self) -> Option<usize> { |