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improve the TryFrom implementations #43248

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Jul 25, 2017
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improve the TryFrom implementations #43248

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215 changes: 177 additions & 38 deletions src/libcore/num/mod.rs
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Original file line number Diff line number Diff line change
@@ -2504,76 +2504,209 @@ impl fmt::Display for TryFromIntError {
}
}

macro_rules! same_sign_try_from_int_impl {
($storage:ty, $target:ty, $($source:ty),*) => {$(
// no possible bounds violation
macro_rules! try_from_unbounded {
($source:ty, $($target:ty),*) => {$(
#[unstable(feature = "try_from", issue = "33417")]
impl TryFrom<$source> for $target {
type Error = TryFromIntError;
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Since this can never fail, shouldn't this be an empty type like enum NeverIntError {}?

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Oh-- but I see there are cfg'd impls of this for usize based on the current target's pointer width, so those would have to be kept as TryFromIntError in order to ensure target compatibility.

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I think the infallible ones are moving to a blanket impl, per #33417 (comment)

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Yep-- I was suggesting enum NeverIntError {} so that this wouldn't be blocked on never_type. Once never_type and the blanket impl land, NeverIntError can be changed to an alias for !.


#[inline]
fn try_from(u: $source) -> Result<$target, TryFromIntError> {
let min = <$target as FromStrRadixHelper>::min_value() as $storage;
let max = <$target as FromStrRadixHelper>::max_value() as $storage;
if u as $storage < min || u as $storage > max {
Err(TryFromIntError(()))
} else {
Ok(u as $target)
}
}
)*}
}

// only negative bounds
macro_rules! try_from_lower_bounded {
($source:ty, $($target:ty),*) => {$(
#[unstable(feature = "try_from", issue = "33417")]
impl TryFrom<$source> for $target {
type Error = TryFromIntError;

#[inline]
fn try_from(u: $source) -> Result<$target, TryFromIntError> {
if u >= 0 {
Ok(u as $target)
} else {
Err(TryFromIntError(()))
}
}
}
)*}
}

same_sign_try_from_int_impl!(u128, u8, u8, u16, u32, u64, u128, usize);
same_sign_try_from_int_impl!(i128, i8, i8, i16, i32, i64, i128, isize);
same_sign_try_from_int_impl!(u128, u16, u8, u16, u32, u64, u128, usize);
same_sign_try_from_int_impl!(i128, i16, i8, i16, i32, i64, i128, isize);
same_sign_try_from_int_impl!(u128, u32, u8, u16, u32, u64, u128, usize);
same_sign_try_from_int_impl!(i128, i32, i8, i16, i32, i64, i128, isize);
same_sign_try_from_int_impl!(u128, u64, u8, u16, u32, u64, u128, usize);
same_sign_try_from_int_impl!(i128, i64, i8, i16, i32, i64, i128, isize);
same_sign_try_from_int_impl!(u128, u128, u8, u16, u32, u64, u128, usize);
same_sign_try_from_int_impl!(i128, i128, i8, i16, i32, i64, i128, isize);
same_sign_try_from_int_impl!(u128, usize, u8, u16, u32, u64, u128, usize);
same_sign_try_from_int_impl!(i128, isize, i8, i16, i32, i64, i128, isize);

macro_rules! cross_sign_from_int_impl {
($unsigned:ty, $($signed:ty),*) => {$(
// unsigned to signed (only positive bound)
macro_rules! try_from_upper_bounded {
($source:ty, $($target:ty),*) => {$(
#[unstable(feature = "try_from", issue = "33417")]
impl TryFrom<$unsigned> for $signed {
impl TryFrom<$source> for $target {
type Error = TryFromIntError;

fn try_from(u: $unsigned) -> Result<$signed, TryFromIntError> {
let max = <$signed as FromStrRadixHelper>::max_value() as u128;
if u as u128 > max {
#[inline]
fn try_from(u: $source) -> Result<$target, TryFromIntError> {
if u > (<$target>::max_value() as $source) {
Err(TryFromIntError(()))
} else {
Ok(u as $signed)
Ok(u as $target)
}
}
}
)*}
}

// all other cases
macro_rules! try_from_both_bounded {
($source:ty, $($target:ty),*) => {$(
#[unstable(feature = "try_from", issue = "33417")]
impl TryFrom<$signed> for $unsigned {
impl TryFrom<$source> for $target {
type Error = TryFromIntError;

fn try_from(u: $signed) -> Result<$unsigned, TryFromIntError> {
let max = <$unsigned as FromStrRadixHelper>::max_value() as u128;
if u < 0 || u as u128 > max {
#[inline]
fn try_from(u: $source) -> Result<$target, TryFromIntError> {
let min = <$target>::min_value() as $source;
let max = <$target>::max_value() as $source;
if u < min || u > max {
Err(TryFromIntError(()))
} else {
Ok(u as $unsigned)
Ok(u as $target)
}
}
}
)*}
}

cross_sign_from_int_impl!(u8, i8, i16, i32, i64, i128, isize);
cross_sign_from_int_impl!(u16, i8, i16, i32, i64, i128, isize);
cross_sign_from_int_impl!(u32, i8, i16, i32, i64, i128, isize);
cross_sign_from_int_impl!(u64, i8, i16, i32, i64, i128, isize);
cross_sign_from_int_impl!(u128, i8, i16, i32, i64, i128, isize);
cross_sign_from_int_impl!(usize, i8, i16, i32, i64, i128, isize);
macro_rules! rev {
($mac:ident, $source:ty, $($target:ty),*) => {$(
$mac!($target, $source);
)*}
}

/// intra-sign conversions
try_from_unbounded!(u8, u8, u16, u32, u64, u128);
try_from_unbounded!(u16, u16, u32, u64, u128);
try_from_unbounded!(u32, u32, u64, u128);
try_from_unbounded!(u64, u64, u128);
try_from_unbounded!(u128, u128);
try_from_upper_bounded!(u16, u8);
try_from_upper_bounded!(u32, u16, u8);
try_from_upper_bounded!(u64, u32, u16, u8);
try_from_upper_bounded!(u128, u64, u32, u16, u8);

try_from_unbounded!(i8, i8, i16, i32, i64, i128);
try_from_unbounded!(i16, i16, i32, i64, i128);
try_from_unbounded!(i32, i32, i64, i128);
try_from_unbounded!(i64, i64, i128);
try_from_unbounded!(i128, i128);
try_from_both_bounded!(i16, i8);
try_from_both_bounded!(i32, i16, i8);
try_from_both_bounded!(i64, i32, i16, i8);
try_from_both_bounded!(i128, i64, i32, i16, i8);

// unsigned-to-signed
try_from_unbounded!(u8, i16, i32, i64, i128);
try_from_unbounded!(u16, i32, i64, i128);
try_from_unbounded!(u32, i64, i128);
try_from_unbounded!(u64, i128);
try_from_upper_bounded!(u8, i8);
try_from_upper_bounded!(u16, i8, i16);
try_from_upper_bounded!(u32, i8, i16, i32);
try_from_upper_bounded!(u64, i8, i16, i32, i64);
try_from_upper_bounded!(u128, i8, i16, i32, i64, i128);

// signed-to-unsigned
try_from_lower_bounded!(i8, u8, u16, u32, u64, u128);
try_from_lower_bounded!(i16, u16, u32, u64, u128);
try_from_lower_bounded!(i32, u32, u64, u128);
try_from_lower_bounded!(i64, u64, u128);
try_from_lower_bounded!(i128, u128);
try_from_both_bounded!(i16, u8);
try_from_both_bounded!(i32, u16, u8);
try_from_both_bounded!(i64, u32, u16, u8);
try_from_both_bounded!(i128, u64, u32, u16, u8);

#[unstable(feature = "try_from", issue = "33417")]
pub use self::ptr_try_from_impls::*;
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What is this for? You can't (and don't need to) reexport impls.

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Really? Because the pub makes them visible where the mods are not. I deem them implementation detail, so I chose to keep them private.

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Impls are always visible, even if they're in private modules.


#[cfg(target_pointer_width = "16")]
mod ptr_try_from_impls {
use super::TryFromIntError;
use convert::TryFrom;

try_from_upper_bounded!(usize, u8);
try_from_unbounded!(usize, usize, u16, u32, u64, u128);
try_from_upper_bounded!(usize, i8, i16, isize);
try_from_unbounded!(usize, i32, i64, i128);

try_from_both_bounded!(isize, u8);
try_from_lower_bounded!(isize, usize, u16, u32, u64, u128);
try_from_both_bounded!(isize, i8);
try_from_unbounded!(isize, i16, i32, i64, i128);
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This looks like it's missing isize to isize. It might be clearer to put the following outside these target specific modules:

try_from_unbounded!(usize, usize);
try_from_upper_bounded!(usize, isize);
try_from_lower_bounded!(isize, usize);
try_from_unbounded!(isize, isize);


rev!(try_from_unbounded, usize, u8, u16);
rev!(try_from_upper_bounded, usize, u32, u64, u128);
rev!(try_from_lower_bounded, usize, i8, i16);
rev!(try_from_both_bounded, usize, i32, i64, i128);

rev!(try_from_unbounded, isize, u8);
rev!(try_from_upper_bounded, isize, u16, u32, u64, u128);
rev!(try_from_unbounded, isize, i8, i16);
rev!(try_from_both_bounded, isize, i32, i64, i128);
}

#[cfg(target_pointer_width = "32")]
mod ptr_try_from_impls {
use super::TryFromIntError;
use convert::TryFrom;

try_from_upper_bounded!(usize, u8, u16);
try_from_unbounded!(usize, usize, u32, u64, u128);
try_from_upper_bounded!(usize, i8, i16, i32, isize);
try_from_unbounded!(usize, i64, i128);

try_from_both_bounded!(isize, u8, u16);
try_from_lower_bounded!(isize, usize, u32, u64, u128);
try_from_both_bounded!(isize, i8, i16);
try_from_unbounded!(isize, i32, i64, i128);

rev!(try_from_unbounded, usize, u8, u16, u32);
rev!(try_from_upper_bounded, usize, u64, u128);
rev!(try_from_lower_bounded, usize, i8, i16, i32);
rev!(try_from_both_bounded, usize, i64, i128);

rev!(try_from_unbounded, isize, u8, u16);
rev!(try_from_upper_bounded, isize, u32, u64, u128);
rev!(try_from_unbounded, isize, i8, i16, i32);
rev!(try_from_both_bounded, isize, i64, i128);
}

#[cfg(target_pointer_width = "64")]
mod ptr_try_from_impls {
use super::TryFromIntError;
use convert::TryFrom;

try_from_upper_bounded!(usize, u8, u16, u32);
try_from_unbounded!(usize, usize, u64, u128);
try_from_upper_bounded!(usize, i8, i16, i32, i64, isize);
try_from_unbounded!(usize, i128);

try_from_both_bounded!(isize, u8, u16, u32);
try_from_lower_bounded!(isize, usize, u64, u128);
try_from_both_bounded!(isize, i8, i16, i32);
try_from_unbounded!(isize, i64, i128);

rev!(try_from_unbounded, usize, u8, u16, u32, u64);
rev!(try_from_upper_bounded, usize, u128);
rev!(try_from_lower_bounded, usize, i8, i16, i32, i64);
rev!(try_from_both_bounded, usize, i128);

rev!(try_from_unbounded, isize, u8, u16, u32);
rev!(try_from_upper_bounded, isize, u64, u128);
rev!(try_from_unbounded, isize, i8, i16, i32, i64);
rev!(try_from_both_bounded, isize, i128);
}

#[doc(hidden)]
trait FromStrRadixHelper: PartialOrd + Copy {
@@ -2587,15 +2720,21 @@ trait FromStrRadixHelper: PartialOrd + Copy {

macro_rules! doit {
($($t:ty)*) => ($(impl FromStrRadixHelper for $t {
#[inline]
fn min_value() -> Self { Self::min_value() }
#[inline]
fn max_value() -> Self { Self::max_value() }
#[inline]
fn from_u32(u: u32) -> Self { u as Self }
#[inline]
fn checked_mul(&self, other: u32) -> Option<Self> {
Self::checked_mul(*self, other as Self)
}
#[inline]
fn checked_sub(&self, other: u32) -> Option<Self> {
Self::checked_sub(*self, other as Self)
}
#[inline]
fn checked_add(&self, other: u32) -> Option<Self> {
Self::checked_add(*self, other as Self)
}
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