Move error::Error trait from libstd to liballoc

Author: taiki-e

src/libstd/error.rs renamed to src/liballoc/error.rs

@@ -13,18 +13,19 @@
 // coherence challenge (e.g., specialization, neg impls, etc) we can
 // reconsider what crate these items belong in.
 
+use core::any::TypeId;
 use core::array;
+use core::cell;
+use core::char;
+use core::fmt::{self, Debug, Display};
+use core::mem::transmute;
+use core::num;
+use core::str;
 
 use crate::alloc::{AllocErr, LayoutErr, CannotReallocInPlace};
-use crate::any::TypeId;
 use crate::borrow::Cow;
-use crate::cell;
-use crate::char;
-use crate::fmt::{self, Debug, Display};
-use crate::mem::transmute;
-use crate::num;
-use crate::str;
-use crate::string;
+use crate::boxed::Box;
+use crate::string::{self, String};
 
 /// `Error` is a trait representing the basic expectations for error values,
 /// i.e., values of type `E` in [`Result<T, E>`]. Errors must describe
@@ -38,9 +39,9 @@ use crate::string;
 /// provide its own errors while also revealing some of the implementation for
 /// debugging via [`source`] chains.
 ///
-/// [`Result<T, E>`]: ../result/enum.Result.html
-/// [`Display`]: ../fmt/trait.Display.html
-/// [`Debug`]: ../fmt/trait.Debug.html
+/// [`Result<T, E>`]: ../../std/result/enum.Result.html
+/// [`Display`]: ../../std/fmt/trait.Display.html
+/// [`Debug`]: ../../std/fmt/trait.Debug.html
 /// [`source`]: trait.Error.html#method.source
 #[stable(feature = "rust1", since = "1.0.0")]
 pub trait Error: Debug + Display {
@@ -52,7 +53,7 @@ pub trait Error: Debug + Display {
     ///
     /// To obtain error description as a string, use `to_string()`.
     ///
-    /// [`Display`]: ../fmt/trait.Display.html
+    /// [`Display`]: ../../std/fmt/trait.Display.html
     ///
     /// # Examples
     ///
@@ -891,7 +892,7 @@ impl dyn Error + Send + Sync {
 #[cfg(test)]
 mod tests {
     use super::Error;
-    use crate::fmt;
+    use core::fmt;
 
     #[derive(Debug, PartialEq)]
     struct A;

src/liballoc/lib.rs

@@ -77,10 +77,12 @@
 #![feature(allocator_api)]
 #![feature(allow_internal_unstable)]
 #![feature(arbitrary_self_types)]
+#![feature(array_error_internals)]
 #![feature(box_into_raw_non_null)]
 #![feature(box_patterns)]
 #![feature(box_syntax)]
 #![feature(cfg_target_has_atomic)]
+#![feature(char_error_internals)]
 #![feature(coerce_unsized)]
 #![feature(const_generic_impls_guard)]
 #![feature(const_generics)]
@@ -93,9 +95,11 @@
 #![feature(fmt_internals)]
 #![feature(fn_traits)]
 #![feature(fundamental)]
+#![feature(int_error_internals)]
 #![feature(internal_uninit_const)]
 #![feature(lang_items)]
 #![feature(libc)]
+#![feature(never_type)]
 #![feature(nll)]
 #![feature(optin_builtin_traits)]
 #![feature(pattern)]
@@ -167,6 +171,8 @@ pub mod str;
 pub mod string;
 pub mod vec;
 
+pub mod error;
+
 #[cfg(not(test))]
 mod std {
     pub use core::ops; // RangeFull

src/libstd/lib.rs

@@ -447,6 +447,9 @@ pub use core::hint;
 #[stable(feature = "core_array", since = "1.36.0")]
 pub use core::array;
 
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use alloc_crate::error;
+
 pub mod f32;
 pub mod f64;
 
@@ -455,7 +458,6 @@ pub mod thread;
 pub mod ascii;
 pub mod collections;
 pub mod env;
-pub mod error;
 pub mod ffi;
 pub mod fs;
 pub mod io;