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Tweak Library Integer Division Docs
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Improved the documentation and diagnostics related to panicking in the division-like methods in std:

* For signed methods that can overflow, clarified "results in overflow" to "self is -1 and rhs is Self::MIN." This is more concise that saying "results in overflow" and then explaining how it could overflow.
* For floor/ceil_div, corrected the documentation and made it more like the documentation in other methods.
* For signed methods that can overflow, explicitly mention that they are not affected by compiler flags.
* Removed all unused rustc_inherit_overflow_checks attributes. The non-division-like operations will never overflow.
* Added track_caller attributes to all methods that can panic. The panic messages will always be correct. For example, division methods all have / before %.
* Edited the saturating_div documentation to be consistent with similar methods.
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@NCGThompson
NCGThompson committed Jan 8, 2024
1 parent 75c68cf commit a0e94a2
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Showing 2 changed files with 34 additions and 36 deletions.
40 changes: 17 additions & 23 deletions library/core/src/num/int_macros.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1121,6 +1121,10 @@ macro_rules! int_impl {
/// Saturating integer division. Computes `self / rhs`, saturating at the
/// numeric bounds instead of overflowing.
///
/// # Panics
///
/// This function will panic if `rhs` is 0.
///
/// # Examples
///
/// Basic usage:
Expand All @@ -1131,11 +1135,6 @@ macro_rules! int_impl {
#[doc = concat!("assert_eq!(", stringify!($SelfT), "::MIN.saturating_div(-1), ", stringify!($SelfT), "::MAX);")]
///
/// ```
///
/// ```should_panic
#[doc = concat!("let _ = 1", stringify!($SelfT), ".saturating_div(0);")]
///
/// ```
#[stable(feature = "saturating_div", since = "1.58.0")]
#[rustc_const_stable(feature = "saturating_div", since = "1.58.0")]
#[must_use = "this returns the result of the operation, \
Expand Down Expand Up @@ -1913,6 +1912,7 @@ macro_rules! int_impl {
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[inline]
#[track_caller]
pub const fn overflowing_rem_euclid(self, rhs: Self) -> (Self, bool) {
if unlikely!(rhs == -1) {
(0, self == Self::MIN)
Expand Down Expand Up @@ -2152,7 +2152,8 @@ macro_rules! int_impl {
///
/// # Panics
///
/// This function will panic if `rhs` is 0 or the division results in overflow.
/// This function will panic if `rhs` is 0 or if `self` is -1 and `rhs` is
/// `Self::MIN`. This behavior is not affected by the `overflow-checks` flag.
///
/// # Examples
///
Expand All @@ -2172,7 +2173,7 @@ macro_rules! int_impl {
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[inline]
#[rustc_inherit_overflow_checks]
#[track_caller]
pub const fn div_euclid(self, rhs: Self) -> Self {
let q = self / rhs;
if self % rhs < 0 {
Expand All @@ -2190,7 +2191,8 @@ macro_rules! int_impl {
///
/// # Panics
///
/// This function will panic if `rhs` is 0 or the division results in overflow.
/// This function will panic if `rhs` is 0 or if `self` is -1 and `rhs` is
/// `Self::MIN`. This behavior is not affected by the `overflow-checks` flag.
///
/// # Examples
///
Expand All @@ -2211,7 +2213,7 @@ macro_rules! int_impl {
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[inline]
#[rustc_inherit_overflow_checks]
#[track_caller]
pub const fn rem_euclid(self, rhs: Self) -> Self {
let r = self % rhs;
if r < 0 {
Expand All @@ -2233,12 +2235,8 @@ macro_rules! int_impl {
///
/// # Panics
///
/// This function will panic if `rhs` is zero.
///
/// ## Overflow behavior
///
/// On overflow, this function will panic if overflow checks are enabled (default in debug
/// mode) and wrap if overflow checks are disabled (default in release mode).
/// This function will panic if `rhs` is 0 or if `self` is -1 and `rhs` is
/// `Self::MIN`. This behavior is not affected by the `overflow-checks` flag.
///
/// # Examples
///
Expand All @@ -2258,7 +2256,7 @@ macro_rules! int_impl {
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[inline]
#[rustc_inherit_overflow_checks]
#[track_caller]
pub const fn div_floor(self, rhs: Self) -> Self {
let d = self / rhs;
let r = self % rhs;
Expand All @@ -2273,12 +2271,8 @@ macro_rules! int_impl {
///
/// # Panics
///
/// This function will panic if `rhs` is zero.
///
/// ## Overflow behavior
///
/// On overflow, this function will panic if overflow checks are enabled (default in debug
/// mode) and wrap if overflow checks are disabled (default in release mode).
/// This function will panic if `rhs` is 0 or if `self` is -1 and `rhs` is
/// `Self::MIN`. This behavior is not affected by the `overflow-checks` flag.
///
/// # Examples
///
Expand All @@ -2298,7 +2292,7 @@ macro_rules! int_impl {
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[inline]
#[rustc_inherit_overflow_checks]
#[track_caller]
pub const fn div_ceil(self, rhs: Self) -> Self {
let d = self / rhs;
let r = self % rhs;
Expand Down
30 changes: 17 additions & 13 deletions library/core/src/num/uint_macros.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1123,6 +1123,10 @@ macro_rules! uint_impl {
/// Saturating integer division. Computes `self / rhs`, saturating at the
/// numeric bounds instead of overflowing.
///
/// # Panics
///
/// This function will panic if `rhs` is 0.
///
/// # Examples
///
/// Basic usage:
Expand All @@ -1131,16 +1135,12 @@ macro_rules! uint_impl {
#[doc = concat!("assert_eq!(5", stringify!($SelfT), ".saturating_div(2), 2);")]
///
/// ```
///
/// ```should_panic
#[doc = concat!("let _ = 1", stringify!($SelfT), ".saturating_div(0);")]
///
/// ```
#[stable(feature = "saturating_div", since = "1.58.0")]
#[rustc_const_stable(feature = "saturating_div", since = "1.58.0")]
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[inline]
#[track_caller]
pub const fn saturating_div(self, rhs: Self) -> Self {
// on unsigned types, there is no overflow in integer division
self.wrapping_div(rhs)
Expand Down Expand Up @@ -1275,6 +1275,7 @@ macro_rules! uint_impl {
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[inline(always)]
#[track_caller]
pub const fn wrapping_div(self, rhs: Self) -> Self {
self / rhs
}
Expand Down Expand Up @@ -1304,6 +1305,7 @@ macro_rules! uint_impl {
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[inline(always)]
#[track_caller]
pub const fn wrapping_div_euclid(self, rhs: Self) -> Self {
self / rhs
}
Expand Down Expand Up @@ -1331,6 +1333,7 @@ macro_rules! uint_impl {
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[inline(always)]
#[track_caller]
pub const fn wrapping_rem(self, rhs: Self) -> Self {
self % rhs
}
Expand Down Expand Up @@ -1361,6 +1364,7 @@ macro_rules! uint_impl {
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[inline(always)]
#[track_caller]
pub const fn wrapping_rem_euclid(self, rhs: Self) -> Self {
self % rhs
}
Expand Down Expand Up @@ -1743,6 +1747,7 @@ macro_rules! uint_impl {
#[rustc_const_stable(feature = "const_overflowing_int_methods", since = "1.52.0")]
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[track_caller]
pub const fn overflowing_div(self, rhs: Self) -> (Self, bool) {
(self / rhs, false)
}
Expand Down Expand Up @@ -1773,6 +1778,7 @@ macro_rules! uint_impl {
#[rustc_const_stable(feature = "const_euclidean_int_methods", since = "1.52.0")]
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[track_caller]
pub const fn overflowing_div_euclid(self, rhs: Self) -> (Self, bool) {
(self / rhs, false)
}
Expand Down Expand Up @@ -1800,6 +1806,7 @@ macro_rules! uint_impl {
#[rustc_const_stable(feature = "const_overflowing_int_methods", since = "1.52.0")]
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[track_caller]
pub const fn overflowing_rem(self, rhs: Self) -> (Self, bool) {
(self % rhs, false)
}
Expand Down Expand Up @@ -1830,6 +1837,7 @@ macro_rules! uint_impl {
#[rustc_const_stable(feature = "const_euclidean_int_methods", since = "1.52.0")]
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[track_caller]
pub const fn overflowing_rem_euclid(self, rhs: Self) -> (Self, bool) {
(self % rhs, false)
}
Expand Down Expand Up @@ -2065,7 +2073,7 @@ macro_rules! uint_impl {
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[inline(always)]
#[rustc_inherit_overflow_checks]
#[track_caller]
pub const fn div_euclid(self, rhs: Self) -> Self {
self / rhs
}
Expand Down Expand Up @@ -2094,7 +2102,7 @@ macro_rules! uint_impl {
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[inline(always)]
#[rustc_inherit_overflow_checks]
#[track_caller]
pub const fn rem_euclid(self, rhs: Self) -> Self {
self % rhs
}
Expand All @@ -2119,6 +2127,7 @@ macro_rules! uint_impl {
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[inline(always)]
#[track_caller]
pub const fn div_floor(self, rhs: Self) -> Self {
self / rhs
}
Expand All @@ -2129,11 +2138,6 @@ macro_rules! uint_impl {
///
/// This function will panic if `rhs` is zero.
///
/// ## Overflow behavior
///
/// On overflow, this function will panic if overflow checks are enabled (default in debug
/// mode) and wrap if overflow checks are disabled (default in release mode).
///
/// # Examples
///
/// Basic usage:
Expand All @@ -2146,7 +2150,7 @@ macro_rules! uint_impl {
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[inline]
#[rustc_inherit_overflow_checks]
#[track_caller]
pub const fn div_ceil(self, rhs: Self) -> Self {
let d = self / rhs;
let r = self % rhs;
Expand Down

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