Rename TryFrom's associated type and implement str::parse using TryFrom.
Per discussion on the tracking issue, naming `TryFrom`'s associated type `Error` is generally more consistent with similar traits in the Rust ecosystem, and what people seem to assume it should be called. It also helps disambiguate from `Result::Err`, the most common "Err". See https://github.com/rust-lang/rust/issues/33417#issuecomment-269108968. TryFrom<&str> and FromStr are equivalent, so have the latter provide the former to ensure that. Using TryFrom in the implementation of `str::parse` means types that implement either trait can use it. When we're ready to stabilize `TryFrom`, we should update `FromStr` to suggest implementing `TryFrom<&str>` instead for new code. See https://github.com/rust-lang/rust/issues/33417#issuecomment-277175994 and https://github.com/rust-lang/rust/issues/33417#issuecomment-277253827. Refs #33417.
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@ -209,10 +209,10 @@ impl From<u8> for char {
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#[unstable(feature = "try_from", issue = "33417")]
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impl TryFrom<u32> for char {
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type Err = CharTryFromError;
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type Error = CharTryFromError;
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#[inline]
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fn try_from(i: u32) -> Result<Self, Self::Err> {
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fn try_from(i: u32) -> Result<Self, Self::Error> {
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if (i > MAX as u32) || (i >= 0xD800 && i <= 0xDFFF) {
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Err(CharTryFromError(()))
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} else {
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@ -48,6 +48,8 @@
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#![stable(feature = "rust1", since = "1.0.0")]
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use str::FromStr;
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/// A cheap, reference-to-reference conversion.
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///
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/// `AsRef` is very similar to, but different than, [`Borrow`]. See
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@ -212,20 +214,20 @@ pub trait From<T>: Sized {
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#[unstable(feature = "try_from", issue = "33417")]
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pub trait TryInto<T>: Sized {
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/// The type returned in the event of a conversion error.
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type Err;
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type Error;
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/// Performs the conversion.
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fn try_into(self) -> Result<T, Self::Err>;
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fn try_into(self) -> Result<T, Self::Error>;
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}
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/// Attempt to construct `Self` via a conversion.
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#[unstable(feature = "try_from", issue = "33417")]
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pub trait TryFrom<T>: Sized {
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/// The type returned in the event of a conversion error.
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type Err;
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type Error;
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/// Performs the conversion.
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fn try_from(value: T) -> Result<Self, Self::Err>;
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fn try_from(value: T) -> Result<Self, Self::Error>;
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}
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////////////////////////////////////////////////////////////////////////////////
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@ -290,9 +292,9 @@ impl<T> From<T> for T {
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// TryFrom implies TryInto
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#[unstable(feature = "try_from", issue = "33417")]
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impl<T, U> TryInto<U> for T where U: TryFrom<T> {
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type Err = U::Err;
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type Error = U::Error;
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fn try_into(self) -> Result<U, U::Err> {
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fn try_into(self) -> Result<U, U::Error> {
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U::try_from(self)
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}
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}
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@ -322,3 +324,13 @@ impl AsRef<str> for str {
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self
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}
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}
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// FromStr implies TryFrom<&str>
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#[unstable(feature = "try_from", issue = "33417")]
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impl<'a, T> TryFrom<&'a str> for T where T: FromStr {
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type Error = <T as FromStr>::Err;
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fn try_from(s: &'a str) -> Result<T, Self::Error> {
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FromStr::from_str(s)
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}
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}
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@ -2591,7 +2591,7 @@ macro_rules! same_sign_try_from_int_impl {
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($storage:ty, $target:ty, $($source:ty),*) => {$(
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#[unstable(feature = "try_from", issue = "33417")]
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impl TryFrom<$source> for $target {
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type Err = TryFromIntError;
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type Error = TryFromIntError;
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fn try_from(u: $source) -> Result<$target, TryFromIntError> {
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let min = <$target as FromStrRadixHelper>::min_value() as $storage;
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@ -2623,7 +2623,7 @@ macro_rules! cross_sign_from_int_impl {
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($unsigned:ty, $($signed:ty),*) => {$(
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#[unstable(feature = "try_from", issue = "33417")]
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impl TryFrom<$unsigned> for $signed {
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type Err = TryFromIntError;
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type Error = TryFromIntError;
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fn try_from(u: $unsigned) -> Result<$signed, TryFromIntError> {
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let max = <$signed as FromStrRadixHelper>::max_value() as u128;
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@ -2637,7 +2637,7 @@ macro_rules! cross_sign_from_int_impl {
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#[unstable(feature = "try_from", issue = "33417")]
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impl TryFrom<$signed> for $unsigned {
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type Err = TryFromIntError;
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type Error = TryFromIntError;
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fn try_from(u: $signed) -> Result<$unsigned, TryFromIntError> {
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let max = <$unsigned as FromStrRadixHelper>::max_value() as u128;
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@ -18,6 +18,7 @@ use self::pattern::Pattern;
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use self::pattern::{Searcher, ReverseSearcher, DoubleEndedSearcher};
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use char;
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use convert::TryFrom;
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use fmt;
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use iter::{Map, Cloned, FusedIterator};
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use mem;
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@ -1746,7 +1747,7 @@ pub trait StrExt {
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#[stable(feature = "core", since = "1.6.0")]
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fn is_empty(&self) -> bool;
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#[stable(feature = "core", since = "1.6.0")]
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fn parse<T: FromStr>(&self) -> Result<T, T::Err>;
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fn parse<'a, T: TryFrom<&'a str>>(&'a self) -> Result<T, T::Error>;
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}
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// truncate `&str` to length at most equal to `max`
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@ -2045,7 +2046,9 @@ impl StrExt for str {
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fn is_empty(&self) -> bool { self.len() == 0 }
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#[inline]
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fn parse<T: FromStr>(&self) -> Result<T, T::Err> { FromStr::from_str(self) }
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fn parse<'a, T>(&'a self) -> Result<T, T::Error> where T: TryFrom<&'a str> {
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T::try_from(self)
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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