Auto merge of #57918 - Centril:rollup, r=Centril

Rollup of 7 pull requests

Successful merges:

 - #57407 (Stabilize extern_crate_self)
 - #57703 (Make MutexGuard's Debug implementation more useful.)
 - #57764 (Fix some minor warnings)
 - #57825 (un-deprecate mem::zeroed)
 - #57827 (Ignore aarch64 in simd-intrinsic-generic-reduction)
 - #57908 (resolve: Fix span arithmetics in the import conflict error)
 - #57913 (Change crate-visibility-modifier issue number in The Unstable Book)

Failed merges:

r? @ghost

src/test/ui/feature-gates/feature-gate-extern_crate_self.rs

@@ -1,3 +0,0 @@
-extern crate self as foo; //~ ERROR `extern crate self` is unstable
-
-fn main() {}

src/test/ui/feature-gates/feature-gate-extern_crate_self.stderr

@@ -1,11 +0,0 @@
-error[E0658]: `extern crate self` is unstable (see issue #56409)
-  --> $DIR/feature-gate-extern_crate_self.rs:1:1
-   |
-LL | extern crate self as foo; //~ ERROR `extern crate self` is unstable
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = help: add #![feature(extern_crate_self)] to the crate attributes to enable
-
-error: aborting due to previous error
-
-For more information about this error, try `rustc --explain E0658`.

src/test/ui/imports/extern-crate-self/extern-crate-self-fail.rs

@@ -1,5 +1,3 @@
-#![feature(extern_crate_self)]
-
 extern crate self; //~ ERROR `extern crate self;` requires renaming
 
 #[macro_use] //~ ERROR `macro_use` is not supported on `extern crate self`

src/test/ui/imports/extern-crate-self/extern-crate-self-fail.stderr

@@ -1,11 +1,11 @@
 error: `extern crate self;` requires renaming
-  --> $DIR/extern-crate-self-fail.rs:3:1
+  --> $DIR/extern-crate-self-fail.rs:1:1
    |
 LL | extern crate self; //~ ERROR `extern crate self;` requires renaming
    | ^^^^^^^^^^^^^^^^^^ help: try: `extern crate self as name;`
 
 error: `macro_use` is not supported on `extern crate self`
-  --> $DIR/extern-crate-self-fail.rs:5:1
+  --> $DIR/extern-crate-self-fail.rs:3:1
    |
 LL | #[macro_use] //~ ERROR `macro_use` is not supported on `extern crate self`
    | ^^^^^^^^^^^^

src/test/ui/imports/extern-crate-self/extern-crate-self-macro-alias.rs

@@ -0,0 +1,16 @@
+// run-pass
+
+// Test that a macro can correctly expand the alias
+// in an `extern crate self as ALIAS` item.
+
+fn the_answer() -> usize { 42 }
+
+macro_rules! alias_self {
+    ($alias:ident) => { extern crate self as $alias; }
+}
+
+alias_self!(the_alias);
+
+fn main() {
+    assert_eq!(the_alias::the_answer(), 42);
+}

src/test/ui/imports/extern-crate-self/extern-crate-self-macro-item.rs

@@ -0,0 +1,12 @@
+// compile-pass
+
+// Test that `extern crate self;` is accepted
+// syntactically as an item for use in a macro.
+
+macro_rules! accept_item { ($x:item) => {} }
+
+accept_item! {
+    extern crate self;
+}
+
+fn main() {}

src/test/ui/imports/extern-crate-self/extern-crate-self-macro-self.rs

@@ -0,0 +1,16 @@
+// run-pass
+
+// Test that a macro can correctly expand `self` in
+// an `extern crate self as ALIAS` item.
+
+fn the_answer() -> usize { 42 }
+
+macro_rules! extern_something {
+    ($alias:ident) => { extern crate $alias as the_alias; }
+}
+
+extern_something!(self);
+
+fn main() {
+    assert_eq!(the_alias::the_answer(), 42);
+}

src/test/ui/imports/extern-crate-self/extern-crate-self-pass.rs

@@ -1,7 +1,5 @@
 // compile-pass
 
-#![feature(extern_crate_self)]
-
 extern crate self as foo;
 
 struct S;

src/test/ui/issues/issue-56411.rs

@@ -0,0 +1,17 @@
+macro_rules! import {
+    ( $($name:ident),* ) => {
+        $(
+            mod $name;
+            pub use self::$name;
+            //~^ ERROR the name `issue_56411_aux` is defined multiple times
+            //~| ERROR `issue_56411_aux` is private, and cannot be re-exported
+
+        )*
+    }
+}
+
+import!(issue_56411_aux);
+
+fn main() {
+    println!("Hello, world!");
+}

src/test/ui/issues/issue-56411.stderr

@@ -0,0 +1,31 @@
+error[E0255]: the name `issue_56411_aux` is defined multiple times
+  --> $DIR/issue-56411.rs:5:21
+   |
+LL |             mod $name;
+   |             ---------- previous definition of the module `issue_56411_aux` here
+LL |             pub use self::$name;
+   |                     ^^^^^^^^^^^
+   |                     |
+   |                     `issue_56411_aux` reimported here
+   |                     you can use `as` to change the binding name of the import
+...
+LL | import!(issue_56411_aux);
+   | ------------------------- in this macro invocation
+   |
+   = note: `issue_56411_aux` must be defined only once in the type namespace of this module
+
+error[E0365]: `issue_56411_aux` is private, and cannot be re-exported
+  --> $DIR/issue-56411.rs:5:21
+   |
+LL |             pub use self::$name;
+   |                     ^^^^^^^^^^^ re-export of private `issue_56411_aux`
+...
+LL | import!(issue_56411_aux);
+   | ------------------------- in this macro invocation
+   |
+   = note: consider declaring type or module `issue_56411_aux` with `pub`
+
+error: aborting due to 2 previous errors
+
+Some errors occurred: E0255, E0365.
+For more information about an error, try `rustc --explain E0255`.

src/test/ui/issues/issue_56411_aux.rs

@@ -0,0 +1,5 @@
+// compile-pass
+
+struct T {}
+
+fn main() {}