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Implement conversion traits for primitive integer types #28921

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Oct 15, 2015
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43 changes: 43 additions & 0 deletions src/libcore/num/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,7 @@ use self::wrapping::OverflowingOps;

use char::CharExt;
use cmp::{Eq, PartialOrd};
use convert::From;
use fmt;
use intrinsics;
use marker::{Copy, Sized};
Expand Down Expand Up @@ -1471,3 +1472,45 @@ impl fmt::Display for ParseIntError {
}

pub use num::dec2flt::ParseFloatError;

// Conversion traits for primitive integer types
// Conversions T -> T are covered by a blanket impl and therefore excluded
// Some conversions from and to usize/isize are not implemented due to portability concerns
macro_rules! impl_from {
($Small: ty, $Large: ty) => {
#[stable(feature = "lossless_int_conv", since = "1.5.0")]
impl From<$Small> for $Large {
#[stable(feature = "lossless_int_conv", since = "1.5.0")]
#[inline]
fn from(small: $Small) -> $Large {
small as $Large
}
}
}
}

// Unsigned -> Unsigned
impl_from! { u8, u16 }
impl_from! { u8, u32 }
impl_from! { u8, u64 }
impl_from! { u8, usize }
impl_from! { u16, u32 }
impl_from! { u16, u64 }
impl_from! { u32, u64 }

// Signed -> Signed
impl_from! { i8, i16 }
impl_from! { i8, i32 }
impl_from! { i8, i64 }
impl_from! { i8, isize }
impl_from! { i16, i32 }
impl_from! { i16, i64 }
impl_from! { i32, i64 }

// Unsigned -> Signed
impl_from! { u8, i16 }
impl_from! { u8, i32 }
impl_from! { u8, i64 }
impl_from! { u16, i32 }
impl_from! { u16, i64 }
impl_from! { u32, i64 }
40 changes: 40 additions & 0 deletions src/libcoretest/num/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -137,4 +137,44 @@ mod tests {
assert_eq!("+".parse::<i8>().ok(), None);
assert_eq!("".parse::<u8>().ok(), None);
}

macro_rules! test_impl_from {
($fn_name: ident, $Small: ty, $Large: ty) => {
#[test]
fn $fn_name() {
let small_max = <$Small>::max_value();
let small_min = <$Small>::min_value();
let large_max: $Large = small_max.into();
let large_min: $Large = small_min.into();
assert_eq!(large_max as $Small, small_max);
assert_eq!(large_min as $Small, small_min);
}
}
}

// Unsigned -> Unsigned
test_impl_from! { test_u8u16, u8, u16 }
test_impl_from! { test_u8u32, u8, u32 }
test_impl_from! { test_u8u64, u8, u64 }
test_impl_from! { test_u8usize, u8, usize }
test_impl_from! { test_u16u32, u16, u32 }
test_impl_from! { test_u16u64, u16, u64 }
test_impl_from! { test_u32u64, u32, u64 }

// Signed -> Signed
test_impl_from! { test_i8i16, i8, i16 }
test_impl_from! { test_i8i32, i8, i32 }
test_impl_from! { test_i8i64, i8, i64 }
test_impl_from! { test_i8isize, i8, isize }
test_impl_from! { test_i16i32, i16, i32 }
test_impl_from! { test_i16i64, i16, i64 }
test_impl_from! { test_i32i64, i32, i64 }

// Unsigned -> Signed
test_impl_from! { test_u8i16, u8, i16 }
test_impl_from! { test_u8i32, u8, i32 }
test_impl_from! { test_u8i64, u8, i64 }
test_impl_from! { test_u16i32, u16, i32 }
test_impl_from! { test_u16i64, u16, i64 }
test_impl_from! { test_u32i64, u32, i64 }
}