diff --git a/src/liballoc/string.rs b/src/liballoc/string.rs index 84c35c6f1bd..b714df5d36b 100644 --- a/src/liballoc/string.rs +++ b/src/liballoc/string.rs @@ -486,7 +486,7 @@ impl String { /// [`str::from_utf8`]: ../../std/str/fn.from_utf8.html /// [`as_bytes`]: struct.String.html#method.as_bytes /// [`FromUtf8Error`]: struct.FromUtf8Error.html - /// [`Err`]: ../../stdresult/enum.Result.html#variant.Err + /// [`Err`]: ../../std/result/enum.Result.html#variant.Err #[inline] #[stable(feature = "rust1", since = "1.0.0")] pub fn from_utf8(vec: Vec) -> Result { @@ -2073,48 +2073,17 @@ impl ops::DerefMut for String { /// [`String`]: struct.String.html /// [`from_str`]: ../../std/str/trait.FromStr.html#tymethod.from_str #[stable(feature = "str_parse_error", since = "1.5.0")] -#[derive(Copy)] -pub enum ParseError {} +pub type ParseError = core::convert::Infallible; #[stable(feature = "rust1", since = "1.0.0")] impl FromStr for String { - type Err = ParseError; + type Err = core::convert::Infallible; #[inline] fn from_str(s: &str) -> Result { Ok(String::from(s)) } } -#[stable(feature = "str_parse_error", since = "1.5.0")] -impl Clone for ParseError { - fn clone(&self) -> ParseError { - match *self {} - } -} - -#[stable(feature = "str_parse_error", since = "1.5.0")] -impl fmt::Debug for ParseError { - fn fmt(&self, _: &mut fmt::Formatter<'_>) -> fmt::Result { - match *self {} - } -} - -#[stable(feature = "str_parse_error2", since = "1.8.0")] -impl fmt::Display for ParseError { - fn fmt(&self, _: &mut fmt::Formatter<'_>) -> fmt::Result { - match *self {} - } -} - -#[stable(feature = "str_parse_error", since = "1.5.0")] -impl PartialEq for ParseError { - fn eq(&self, _: &ParseError) -> bool { - match *self {} - } -} - -#[stable(feature = "str_parse_error", since = "1.5.0")] -impl Eq for ParseError {} /// A trait for converting a value to a `String`. /// diff --git a/src/libcore/array.rs b/src/libcore/array.rs index 3a27a39af4a..9c6ecc43502 100644 --- a/src/libcore/array.rs +++ b/src/libcore/array.rs @@ -49,7 +49,7 @@ unsafe impl> FixedSizeArray for A { } /// The error type returned when a conversion from a slice to an array fails. -#[unstable(feature = "try_from", issue = "33417")] +#[stable(feature = "try_from", since = "1.34.0")] #[derive(Debug, Copy, Clone)] pub struct TryFromSliceError(()); @@ -138,7 +138,7 @@ macro_rules! array_impls { } } - #[unstable(feature = "try_from", issue = "33417")] + #[stable(feature = "try_from", since = "1.34.0")] impl<'a, T> TryFrom<&'a [T]> for [T; $N] where T: Copy { type Error = TryFromSliceError; @@ -147,7 +147,7 @@ macro_rules! array_impls { } } - #[unstable(feature = "try_from", issue = "33417")] + #[stable(feature = "try_from", since = "1.34.0")] impl<'a, T> TryFrom<&'a [T]> for &'a [T; $N] { type Error = TryFromSliceError; @@ -161,7 +161,7 @@ macro_rules! array_impls { } } - #[unstable(feature = "try_from", issue = "33417")] + #[stable(feature = "try_from", since = "1.34.0")] impl<'a, T> TryFrom<&'a mut [T]> for &'a mut [T; $N] { type Error = TryFromSliceError; diff --git a/src/libcore/char/convert.rs b/src/libcore/char/convert.rs index 4a1a236b669..6a5abfb408f 100644 --- a/src/libcore/char/convert.rs +++ b/src/libcore/char/convert.rs @@ -218,7 +218,7 @@ impl FromStr for char { } -#[unstable(feature = "try_from", issue = "33417")] +#[stable(feature = "try_from", since = "1.34.0")] impl TryFrom for char { type Error = CharTryFromError; @@ -233,11 +233,11 @@ impl TryFrom for char { } /// The error type returned when a conversion from u32 to char fails. -#[unstable(feature = "try_from", issue = "33417")] +#[stable(feature = "try_from", since = "1.34.0")] #[derive(Copy, Clone, Debug, PartialEq, Eq)] pub struct CharTryFromError(()); -#[unstable(feature = "try_from", issue = "33417")] +#[stable(feature = "try_from", since = "1.34.0")] impl fmt::Display for CharTryFromError { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { "converted integer out of range for `char`".fmt(f) diff --git a/src/libcore/char/mod.rs b/src/libcore/char/mod.rs index 15e153bdfad..f3369c4d940 100644 --- a/src/libcore/char/mod.rs +++ b/src/libcore/char/mod.rs @@ -30,7 +30,7 @@ pub use self::convert::{from_u32, from_digit}; pub use self::convert::from_u32_unchecked; #[stable(feature = "char_from_str", since = "1.20.0")] pub use self::convert::ParseCharError; -#[unstable(feature = "try_from", issue = "33417")] +#[stable(feature = "try_from", since = "1.34.0")] pub use self::convert::CharTryFromError; #[stable(feature = "decode_utf16", since = "1.9.0")] pub use self::decode::{decode_utf16, DecodeUtf16, DecodeUtf16Error}; diff --git a/src/libcore/convert.rs b/src/libcore/convert.rs index b8d751cfbb6..5ecfa9cde03 100644 --- a/src/libcore/convert.rs +++ b/src/libcore/convert.rs @@ -41,6 +41,8 @@ #![stable(feature = "rust1", since = "1.0.0")] +use fmt; + /// An identity function. /// /// Two things are important to note about this function: @@ -367,22 +369,26 @@ pub trait From: Sized { /// /// [`TryFrom`]: trait.TryFrom.html /// [`Into`]: trait.Into.html -#[unstable(feature = "try_from", issue = "33417")] +#[stable(feature = "try_from", since = "1.34.0")] pub trait TryInto: Sized { /// The type returned in the event of a conversion error. + #[stable(feature = "try_from", since = "1.34.0")] type Error; /// Performs the conversion. + #[stable(feature = "try_from", since = "1.34.0")] fn try_into(self) -> Result; } /// Attempt to construct `Self` via a conversion. -#[unstable(feature = "try_from", issue = "33417")] +#[stable(feature = "try_from", since = "1.34.0")] pub trait TryFrom: Sized { /// The type returned in the event of a conversion error. + #[stable(feature = "try_from", since = "1.34.0")] type Error; /// Performs the conversion. + #[stable(feature = "try_from", since = "1.34.0")] fn try_from(value: T) -> Result; } @@ -450,7 +456,7 @@ impl From for T { // TryFrom implies TryInto -#[unstable(feature = "try_from", issue = "33417")] +#[stable(feature = "try_from", since = "1.34.0")] impl TryInto for T where U: TryFrom { type Error = U::Error; @@ -462,9 +468,9 @@ impl TryInto for T where U: TryFrom // Infallible conversions are semantically equivalent to fallible conversions // with an uninhabited error type. -#[unstable(feature = "try_from", issue = "33417")] +#[stable(feature = "try_from", since = "1.34.0")] impl TryFrom for T where U: Into { - type Error = !; + type Error = Infallible; fn try_from(value: U) -> Result { Ok(U::into(value)) @@ -496,3 +502,115 @@ impl AsRef for str { self } } + +//////////////////////////////////////////////////////////////////////////////// +// THE NO-ERROR ERROR TYPE +//////////////////////////////////////////////////////////////////////////////// + +/// The error type for errors that can never happen. +/// +/// Since this enum has no variant, a value of this type can never actually exist. +/// This can be useful for generic APIs that use [`Result`] and parameterize the error type, +/// to indicate that the result is always [`Ok`]. +/// +/// For example, the [`TryFrom`] trait (conversion that returns a [`Result`]) +/// has a blanket implementation for all types where a reverse [`Into`] implementation exists. +/// +/// ```ignore (illustrates std code, duplicating the impl in a doctest would be an error) +/// impl TryFrom for T where U: Into { +/// type Error = Infallible; +/// +/// fn try_from(value: U) -> Result { +/// Ok(U::into(value)) // Never returns `Err` +/// } +/// } +/// ``` +/// +/// # Future compatibility +/// +/// This enum has the same role as [the `!` “never” type][never], +/// which is unstable in this version of Rust. +/// When `!` is stabilized, we plan to make `Infallible` a type alias to it: +/// +/// ```ignore (illustrates future std change) +/// pub type Infallible = !; +/// ``` +/// +/// … and eventually deprecate `Infallible`. +/// +/// +/// However there is one case where `!` syntax can be used +/// before `!` is stabilized as a full-fleged type: in the position of a function’s return type. +/// Specifically, it is possible implementations for two different function pointer types: +/// +/// ``` +/// trait MyTrait {} +/// impl MyTrait for fn() -> ! {} +/// impl MyTrait for fn() -> std::convert::Infallible {} +/// ``` +/// +/// With `Infallible` being an enum, this code is valid. +/// However when `Infallible` becomes an alias for the never type, +/// the two `impl`s will start to overlap +/// and therefore will be disallowed by the language’s trait coherence rules. +/// +/// [`Ok`]: ../result/enum.Result.html#variant.Ok +/// [`Result`]: ../result/enum.Result.html +/// [`TryFrom`]: trait.TryFrom.html +/// [`Into`]: trait.Into.html +/// [never]: ../../std/primitive.never.html +#[stable(feature = "convert_infallible", since = "1.34.0")] +#[derive(Copy)] +pub enum Infallible {} + +#[stable(feature = "convert_infallible", since = "1.34.0")] +impl Clone for Infallible { + fn clone(&self) -> Infallible { + match *self {} + } +} + +#[stable(feature = "convert_infallible", since = "1.34.0")] +impl fmt::Debug for Infallible { + fn fmt(&self, _: &mut fmt::Formatter<'_>) -> fmt::Result { + match *self {} + } +} + +#[stable(feature = "convert_infallible", since = "1.34.0")] +impl fmt::Display for Infallible { + fn fmt(&self, _: &mut fmt::Formatter<'_>) -> fmt::Result { + match *self {} + } +} + +#[stable(feature = "convert_infallible", since = "1.34.0")] +impl PartialEq for Infallible { + fn eq(&self, _: &Infallible) -> bool { + match *self {} + } +} + +#[stable(feature = "convert_infallible", since = "1.34.0")] +impl Eq for Infallible {} + +#[stable(feature = "convert_infallible", since = "1.34.0")] +impl PartialOrd for Infallible { + fn partial_cmp(&self, _other: &Self) -> Option { + match *self {} + } +} + +#[stable(feature = "convert_infallible", since = "1.34.0")] +impl Ord for Infallible { + fn cmp(&self, _other: &Self) -> crate::cmp::Ordering { + match *self {} + } +} + +#[stable(feature = "convert_infallible", since = "1.34.0")] +impl From for Infallible { + fn from(x: !) -> Self { + x + } +} diff --git a/src/libcore/num/mod.rs b/src/libcore/num/mod.rs index 5b7d5f45d92..3ceba83afee 100644 --- a/src/libcore/num/mod.rs +++ b/src/libcore/num/mod.rs @@ -2,7 +2,7 @@ #![stable(feature = "rust1", since = "1.0.0")] -use convert::TryFrom; +use convert::{TryFrom, Infallible}; use fmt; use intrinsics; use mem; @@ -2000,7 +2000,6 @@ assert_eq!(value, ", $swap_op, "); When starting from a slice rather than an array, fallible conversion APIs can be used: ``` -#![feature(try_from)] use std::convert::TryInto; fn read_be_", stringify!($SelfT), "(input: &mut &[u8]) -> ", stringify!($SelfT), " { @@ -2032,7 +2031,6 @@ assert_eq!(value, ", $swap_op, "); When starting from a slice rather than an array, fallible conversion APIs can be used: ``` -#![feature(try_from)] use std::convert::TryInto; fn read_be_", stringify!($SelfT), "(input: &mut &[u8]) -> ", stringify!($SelfT), " { @@ -2074,7 +2072,6 @@ assert_eq!(value, ", $swap_op, "); When starting from a slice rather than an array, fallible conversion APIs can be used: ``` -#![feature(try_from)] use std::convert::TryInto; fn read_be_", stringify!($SelfT), "(input: &mut &[u8]) -> ", stringify!($SelfT), " { @@ -3767,7 +3764,6 @@ assert_eq!(value, ", $swap_op, "); When starting from a slice rather than an array, fallible conversion APIs can be used: ``` -#![feature(try_from)] use std::convert::TryInto; fn read_be_", stringify!($SelfT), "(input: &mut &[u8]) -> ", stringify!($SelfT), " { @@ -3799,7 +3795,6 @@ assert_eq!(value, ", $swap_op, "); When starting from a slice rather than an array, fallible conversion APIs can be used: ``` -#![feature(try_from)] use std::convert::TryInto; fn read_be_", stringify!($SelfT), "(input: &mut &[u8]) -> ", stringify!($SelfT), " { @@ -3841,7 +3836,6 @@ assert_eq!(value, ", $swap_op, "); When starting from a slice rather than an array, fallible conversion APIs can be used: ``` -#![feature(try_from)] use std::convert::TryInto; fn read_be_", stringify!($SelfT), "(input: &mut &[u8]) -> ", stringify!($SelfT), " { @@ -4504,7 +4498,7 @@ macro_rules! from_str_radix_int_impl { from_str_radix_int_impl! { isize i8 i16 i32 i64 i128 usize u8 u16 u32 u64 u128 } /// The error type returned when a checked integral type conversion fails. -#[unstable(feature = "try_from", issue = "33417")] +#[stable(feature = "try_from", since = "1.34.0")] #[derive(Debug, Copy, Clone, PartialEq, Eq)] pub struct TryFromIntError(()); @@ -4519,24 +4513,34 @@ impl TryFromIntError { } } -#[unstable(feature = "try_from", issue = "33417")] +#[stable(feature = "try_from", since = "1.34.0")] impl fmt::Display for TryFromIntError { fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result { self.__description().fmt(fmt) } } -#[unstable(feature = "try_from", issue = "33417")] +#[stable(feature = "try_from", since = "1.34.0")] +impl From for TryFromIntError { + fn from(x: Infallible) -> TryFromIntError { + match x {} + } +} + +#[unstable(feature = "never_type", issue = "35121")] impl From for TryFromIntError { fn from(never: !) -> TryFromIntError { - never + // Match rather than coerce to make sure that code like + // `From for TryFromIntError` above will keep working + // when `Infallible` becomes an alias to `!`. + match never {} } } // no possible bounds violation macro_rules! try_from_unbounded { ($source:ty, $($target:ty),*) => {$( - #[unstable(feature = "try_from", issue = "33417")] + #[stable(feature = "try_from", since = "1.34.0")] impl TryFrom<$source> for $target { type Error = TryFromIntError; @@ -4551,7 +4555,7 @@ macro_rules! try_from_unbounded { // only negative bounds macro_rules! try_from_lower_bounded { ($source:ty, $($target:ty),*) => {$( - #[unstable(feature = "try_from", issue = "33417")] + #[stable(feature = "try_from", since = "1.34.0")] impl TryFrom<$source> for $target { type Error = TryFromIntError; @@ -4570,7 +4574,7 @@ macro_rules! try_from_lower_bounded { // unsigned to signed (only positive bound) macro_rules! try_from_upper_bounded { ($source:ty, $($target:ty),*) => {$( - #[unstable(feature = "try_from", issue = "33417")] + #[stable(feature = "try_from", since = "1.34.0")] impl TryFrom<$source> for $target { type Error = TryFromIntError; @@ -4589,7 +4593,7 @@ macro_rules! try_from_upper_bounded { // all other cases macro_rules! try_from_both_bounded { ($source:ty, $($target:ty),*) => {$( - #[unstable(feature = "try_from", issue = "33417")] + #[stable(feature = "try_from", since = "1.34.0")] impl TryFrom<$source> for $target { type Error = TryFromIntError; diff --git a/src/libcore/tests/lib.rs b/src/libcore/tests/lib.rs index 4cd734bad90..d0021376389 100644 --- a/src/libcore/tests/lib.rs +++ b/src/libcore/tests/lib.rs @@ -26,7 +26,6 @@ #![feature(str_internals)] #![feature(test)] #![feature(trusted_len)] -#![feature(try_from)] #![feature(try_trait)] #![feature(align_offset)] #![feature(reverse_bits)] diff --git a/src/librustc_apfloat/lib.rs b/src/librustc_apfloat/lib.rs index 46d046d7b41..1b0bcdd0b5b 100644 --- a/src/librustc_apfloat/lib.rs +++ b/src/librustc_apfloat/lib.rs @@ -35,7 +35,6 @@ #![deny(rust_2018_idioms)] #![feature(nll)] -#![feature(try_from)] // See librustc_cratesio_shim/Cargo.toml for a comment explaining this. #[allow(unused_extern_crates)] extern crate rustc_cratesio_shim; diff --git a/src/librustc_mir/lib.rs b/src/librustc_mir/lib.rs index e0fee10cd00..06e79dc4e70 100644 --- a/src/librustc_mir/lib.rs +++ b/src/librustc_mir/lib.rs @@ -23,7 +23,6 @@ Rust MIR: a lowered representation of Rust. Also: an experiment! #![feature(unicode_internals)] #![feature(step_trait)] #![feature(slice_concat_ext)] -#![feature(try_from)] #![feature(reverse_bits)] #![feature(try_blocks)] diff --git a/src/libstd/error.rs b/src/libstd/error.rs index ef8c97bebdf..17e50a649fa 100644 --- a/src/libstd/error.rs +++ b/src/libstd/error.rs @@ -466,14 +466,14 @@ impl Error for num::ParseIntError { } } -#[unstable(feature = "try_from", issue = "33417")] +#[stable(feature = "try_from", since = "1.34.0")] impl Error for num::TryFromIntError { fn description(&self) -> &str { self.__description() } } -#[unstable(feature = "try_from", issue = "33417")] +#[stable(feature = "try_from", since = "1.34.0")] impl Error for array::TryFromSliceError { fn description(&self) -> &str { self.__description() @@ -548,7 +548,7 @@ impl Error for cell::BorrowMutError { } } -#[unstable(feature = "try_from", issue = "33417")] +#[stable(feature = "try_from", since = "1.34.0")] impl Error for char::CharTryFromError { fn description(&self) -> &str { "converted integer out of range for `char`" diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs index 6dd3a6cc0fd..7af569ab350 100644 --- a/src/libstd/lib.rs +++ b/src/libstd/lib.rs @@ -296,7 +296,6 @@ #![feature(str_internals)] #![feature(thread_local)] #![feature(toowned_clone_into)] -#![feature(try_from)] #![feature(try_reserve)] #![feature(unboxed_closures)] #![feature(untagged_unions)] diff --git a/src/libstd/path.rs b/src/libstd/path.rs index 240b92a17db..9f91a9f89eb 100644 --- a/src/libstd/path.rs +++ b/src/libstd/path.rs @@ -78,7 +78,6 @@ use iter::{self, FusedIterator}; use ops::{self, Deref}; use rc::Rc; use str::FromStr; -use string::ParseError; use sync::Arc; use ffi::{OsStr, OsString}; @@ -1533,7 +1532,7 @@ impl From for PathBuf { #[stable(feature = "path_from_str", since = "1.32.0")] impl FromStr for PathBuf { - type Err = ParseError; + type Err = core::convert::Infallible; fn from_str(s: &str) -> Result { Ok(PathBuf::from(s)) diff --git a/src/test/run-pass/try-from-int-error-partial-eq.rs b/src/test/run-pass/try-from-int-error-partial-eq.rs index 83ede675925..e9b53f2d1c8 100644 --- a/src/test/run-pass/try-from-int-error-partial-eq.rs +++ b/src/test/run-pass/try-from-int-error-partial-eq.rs @@ -1,4 +1,3 @@ -#![feature(try_from)] #![allow(unused_must_use)] use std::convert::TryFrom; diff --git a/src/test/run-pass/try_from.rs b/src/test/run-pass/try_from.rs index 4522ce3a8d6..e42f2c3e393 100644 --- a/src/test/run-pass/try_from.rs +++ b/src/test/run-pass/try_from.rs @@ -4,9 +4,9 @@ // This test was added to show the motivation for doing this // over `TryFrom` being blanket impl for all `T: From` -#![feature(try_from, never_type)] +#![feature(never_type)] -use std::convert::TryInto; +use std::convert::{TryInto, Infallible}; struct Foo { t: T, @@ -32,6 +32,6 @@ impl Into> for Foo { } pub fn main() { - let _: Result, !> = Foo { t: 10 }.try_into(); + let _: Result, Infallible> = Foo { t: 10 }.try_into(); } diff --git a/src/test/ui/e0119/conflict-with-std.rs b/src/test/ui/e0119/conflict-with-std.rs index e639bc5db5e..6dc81f33dfc 100644 --- a/src/test/ui/e0119/conflict-with-std.rs +++ b/src/test/ui/e0119/conflict-with-std.rs @@ -1,4 +1,3 @@ -#![feature(try_from)] use std::marker::PhantomData; use std::convert::{TryFrom, AsRef}; diff --git a/src/test/ui/e0119/conflict-with-std.stderr b/src/test/ui/e0119/conflict-with-std.stderr index c2ae321aa5e..1cfb3c1daba 100644 --- a/src/test/ui/e0119/conflict-with-std.stderr +++ b/src/test/ui/e0119/conflict-with-std.stderr @@ -1,5 +1,5 @@ error[E0119]: conflicting implementations of trait `std::convert::AsRef` for type `std::boxed::Box`: - --> $DIR/conflict-with-std.rs:7:1 + --> $DIR/conflict-with-std.rs:6:1 | LL | impl AsRef for Box { //~ ERROR conflicting implementations | ^^^^^^^^^^^^^^^^^^^^^^^^ @@ -9,7 +9,7 @@ LL | impl AsRef for Box { //~ ERROR conflicting implementations where T: ?Sized; error[E0119]: conflicting implementations of trait `std::convert::From` for type `S`: - --> $DIR/conflict-with-std.rs:14:1 + --> $DIR/conflict-with-std.rs:13:1 | LL | impl From for S { //~ ERROR conflicting implementations | ^^^^^^^^^^^^^^^^^^ @@ -18,7 +18,7 @@ LL | impl From for S { //~ ERROR conflicting implementations - impl std::convert::From for T; error[E0119]: conflicting implementations of trait `std::convert::TryFrom` for type `X`: - --> $DIR/conflict-with-std.rs:21:1 + --> $DIR/conflict-with-std.rs:20:1 | LL | impl TryFrom for X { //~ ERROR conflicting implementations | ^^^^^^^^^^^^^^^^^^^^^