cfg_if! (
if #[cfg(feature="no_std")] {
use core::char;
use core::fmt::{self, Display, Formatter};
} else {
use std::char;
use std::error::Error;
use std::fmt::{self, Display, Formatter};
}
);
use {TryFrom, TryFromIntError, Void};
impl<T> TryFrom<char> for T
where
T: TryFrom<u32, Err = TryFromIntError>,
{
type Err = TryFromIntError;
fn try_from(c: char) -> Result<T, TryFromIntError> {
T::try_from(c as u32)
}
}
#[test]
fn test_char_to_int() {
assert_eq!(u8::try_from('~'), Ok(0x7e));
assert_eq!(u8::try_from('\u{100}'), Err(TryFromIntError::Overflow));
}
macro_rules! impl_infallible {
($($ty:ty),*) => { $(
impl TryFrom<$ty> for char {
type Err = Void;
fn try_from (n: $ty) -> Result<char, Void> { Ok(n as char) }
}
)* };
}
impl_infallible!(u8, char);
#[test]
fn test_to_char_infallible() {
assert_eq!(char::try_from(0x7e), Ok('~'));
assert_eq!(char::try_from('~'), Ok('~'));
}
macro_rules! impl_int_to_char {
($($ty:ty),*) => { $(
impl TryFrom<$ty> for char {
type Err = TryFromIntToCharError;
fn try_from (n: $ty) -> Result<char, TryFromIntToCharError> {
match u32::try_from(n)? {
n @ 0...0x10ffff => match char::from_u32(n) {
None => Err(TryFromIntToCharError::Reserved),
Some(c) => Ok(c),
},
_ => Err(TryFromIntToCharError::Overflow)
}
}
}
)* };
}
impl_int_to_char!(i8, i16, i32, i64, isize, u16, u32, u64, usize);
#[test]
fn test_int_to_char() {
assert_eq!(char::try_from(-1), Err(TryFromIntToCharError::Underflow));
assert_eq!(char::try_from(0x7eu32), Ok('~'));
assert_eq!(char::try_from(0xd888), Err(TryFromIntToCharError::Reserved));
assert_eq!(char::try_from(0x10ffff), Ok('\u{10ffff}'));
assert_eq!(
char::try_from(0x110000),
Err(TryFromIntToCharError::Overflow)
);
}
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub enum TryFromIntToCharError {
Overflow,
Underflow,
Reserved,
}
impl TryFromIntToCharError {
fn as_str(self) -> &'static str {
match self {
TryFromIntToCharError::Overflow => "integer overflow",
TryFromIntToCharError::Underflow => "integer underflow",
TryFromIntToCharError::Reserved => "reserved code point",
}
}
}
impl Display for TryFromIntToCharError {
fn fmt(&self, f: &mut Formatter) -> fmt::Result {
f.write_str(self.as_str())
}
}
cfg_if! (
if #[cfg(not(feature="no_std"))] {
impl Error for TryFromIntToCharError {
fn description(&self) -> &str {
self.as_str()
}
}
}
);
impl From<TryFromIntError> for TryFromIntToCharError {
fn from(other: TryFromIntError) -> TryFromIntToCharError {
match other {
TryFromIntError::Overflow => TryFromIntToCharError::Overflow,
TryFromIntError::Underflow => TryFromIntToCharError::Underflow,
}
}
}
impl From<Void> for TryFromIntToCharError {
fn from(_: Void) -> TryFromIntToCharError {
unreachable!()
}
}