Auto merge of #62086 - petrochenkov:builtout, r=eddyb

Define built-in macros through libcore

This PR defines built-in macros through libcore using a scheme similar to lang items (attribute `#[rustc_builtin_macro]`).
All the macro properties (stability, visibility, etc.) are taken from the source code in libcore, with exception of the expander function transforming input tokens/AST into output tokens/AST, which is still provided by the compiler.

The macros are made available to user code through the standard library prelude (`{core,std}::prelude::v1`), so they are still always in scope.
As a result **built-in macros now have stable absolute addresses in the library**, like `core::prelude::v1::line!()`, this is an insta-stable change.

Right now `prelude::v1` is the only publicly available absolute address for these macros, but eventually they can be moved into more appropriate locations with library team approval (e.g. `Clone` derive -> `core::clone::Clone`).

Now when built-in macros have canonical definitions they can be imported or reexported without issues (https://github.com/rust-lang/rust/issues/61687).

Other changes:
- You can now define a derive macro with a name matching one of the built-in derives (https://github.com/rust-lang/rust/issues/52269). This was an artificial restriction that could be worked around with import renaming anyway.

Known regressions:
- Empty library crate with a crate-level `#![test]` attribute no longer compiles without `--test`. Previously it didn't compile *with* `--test` or with the bin crate type.

Fixes https://github.com/rust-lang/rust/issues/61687
Fixes https://github.com/rust-lang/rust/issues/61804
r? @eddyb

1 files changed, 5 insertions, 5 deletions

diff --git a/src/libstd/error.rs b/src/libstd/error.rs
index 5b1e78a1139..117a430eec6 100644
--- a/src/libstd/error.rs
+++ b/src/libstd/error.rs
@@ -254,8 +254,8 @@ impl<'a, E: Error + 'a> From<E> for Box<dyn Error + 'a> {
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a, E: Error + Send + Sync + 'a> From<E> for Box<dyn Error + Send + Sync + 'a> {
-    /// Converts a type of [`Error`] + [`Send`] + [`Sync`] into a box of dyn [`Error`] +
-    /// [`Send`] + [`Sync`].
+    /// Converts a type of [`Error`] + [`trait@Send`] + [`trait@Sync`] into a box of
+    /// dyn [`Error`] + [`trait@Send`] + [`trait@Sync`].
     ///
     /// [`Error`]: ../error/trait.Error.html
     ///
@@ -298,7 +298,7 @@ impl<'a, E: Error + Send + Sync + 'a> From<E> for Box<dyn Error + Send + Sync +
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl From<String> for Box<dyn Error + Send + Sync> {
-    /// Converts a [`String`] into a box of dyn [`Error`] + [`Send`] + [`Sync`].
+    /// Converts a [`String`] into a box of dyn [`Error`] + [`trait@Send`] + [`trait@Sync`].
     ///
     /// [`Error`]: ../error/trait.Error.html
     ///
@@ -362,7 +362,7 @@ impl From<String> for Box<dyn Error> {
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a> From<&str> for Box<dyn Error + Send + Sync + 'a> {
-    /// Converts a [`str`] into a box of dyn [`Error`] + [`Send`] + [`Sync`].
+    /// Converts a [`str`] into a box of dyn [`Error`] + [`trait@Send`] + [`trait@Sync`].
     ///
     /// [`Error`]: ../error/trait.Error.html
     ///
@@ -405,7 +405,7 @@ impl From<&str> for Box<dyn Error> {
 
 #[stable(feature = "cow_box_error", since = "1.22.0")]
 impl<'a, 'b> From<Cow<'b, str>> for Box<dyn Error + Send + Sync + 'a> {
-    /// Converts a [`Cow`] into a box of dyn [`Error`] + [`Send`] + [`Sync`].
+    /// Converts a [`Cow`] into a box of dyn [`Error`] + [`trait@Send`] + [`trait@Sync`].
     ///
     /// [`Cow`]: ../borrow/enum.Cow.html
     /// [`Error`]: ../error/trait.Error.html