Auto merge of #55012 - kennytm:rollup, r=kennytm

Rollup of 16 pull requests

Successful merges:

 - #54755 (Documents reference equality by address (#54197))
 - #54811 (During rustc bootstrap, make default for `optimize` independent of `debug`)
 - #54825 (NLL says "borrowed content" instead of more precise "dereference of raw pointer")
 - #54860 (Add doc comments about safest way to initialize a vector of zeros)
 - #54869 (Fix mobile docs)
 - #54891 (Fix tracking issue for Once::is_completed)
 - #54913 (doc fix: it's auto traits that make for automatic implementations)
 - #54920 (Fix handling of #[must_use] on unit and uninhabited types)
 - #54932 (A handful of random string-related improvements)
 - #54936 (impl Eq+Hash for TyLayout)
 - #54950 (std: Synchronize global allocator on wasm32)
 - #54956 ("(using ..." doesn't have the matching ")")
 - #54958 (add a macro for static (compile-time) assertions)
 - #54967 (Remove incorrect span for second label inner macro invocation)
 - #54983 (Fix slice's benchmarks)
 - #54989 (Fix spelling in the documentation to htmldocck.py)

Failed merges:

r? @ghost

src/test/rustdoc/inline_cross/issue-31948-1.rs

@@ -22,13 +22,13 @@ extern crate rustdoc_nonreachable_impls;
 pub use rustdoc_nonreachable_impls::hidden::Wobble;
 
 // @has issue_31948_1/trait.Bark.html
-// FIXME(33025): has - '//code' 'for Foo'
+// @has - '//code' 'for Foo'
 // @has - '//code' 'for Wobble'
 // @!has - '//code' 'for Wibble'
 pub use rustdoc_nonreachable_impls::Bark;
 
 // @has issue_31948_1/trait.Woof.html
-// FIXME(33025): has - '//code' 'for Foo'
+// @has - '//code' 'for Foo'
 // @has - '//code' 'for Wobble'
 // @!has - '//code' 'for Wibble'
 pub use rustdoc_nonreachable_impls::Woof;

src/test/rustdoc/inline_cross/issue-31948-2.rs

@@ -22,7 +22,7 @@ extern crate rustdoc_nonreachable_impls;
 pub use rustdoc_nonreachable_impls::hidden::Wobble;
 
 // @has issue_31948_2/trait.Qux.html
-// FIXME(33025): has - '//code' 'for Foo'
+// @has - '//code' 'for Foo'
 // @has - '//code' 'for Wobble'
 pub use rustdoc_nonreachable_impls::hidden::Qux;
 

src/test/ui/borrowck/borrowck-move-from-unsafe-ptr.nll.stderr

@@ -1,10 +1,10 @@
-error[E0507]: cannot move out of borrowed content
+error[E0507]: cannot move out of dereference of raw pointer
   --> $DIR/borrowck-move-from-unsafe-ptr.rs:13:13
    |
 LL |     let y = *x; //~ ERROR cannot move out of dereference of raw pointer
    |             ^^
    |             |
-   |             cannot move out of borrowed content
+   |             cannot move out of dereference of raw pointer
    |             help: consider removing the `*`: `x`
 
 error: aborting due to previous error

src/test/ui/issues/issue-20801.nll.stderr

@@ -16,22 +16,22 @@ LL |     let b = unsafe { *imm_ref() };
    |                      cannot move out of borrowed content
    |                      help: consider removing the `*`: `imm_ref()`
 
-error[E0507]: cannot move out of borrowed content
+error[E0507]: cannot move out of dereference of raw pointer
   --> $DIR/issue-20801.rs:42:22
    |
 LL |     let c = unsafe { *mut_ptr() };
    |                      ^^^^^^^^^^
    |                      |
-   |                      cannot move out of borrowed content
+   |                      cannot move out of dereference of raw pointer
    |                      help: consider removing the `*`: `mut_ptr()`
 
-error[E0507]: cannot move out of borrowed content
+error[E0507]: cannot move out of dereference of raw pointer
   --> $DIR/issue-20801.rs:45:22
    |
 LL |     let d = unsafe { *const_ptr() };
    |                      ^^^^^^^^^^^^
    |                      |
-   |                      cannot move out of borrowed content
+   |                      cannot move out of dereference of raw pointer
    |                      help: consider removing the `*`: `const_ptr()`
 
 error: aborting due to 4 previous errors

src/test/ui/lint/must_use-unit.rs

@@ -0,0 +1,17 @@
+#![feature(never_type)]
+
+#![deny(unused_must_use)]
+
+#[must_use]
+fn foo() {}
+
+#[must_use]
+fn bar() -> ! {
+    unimplemented!()
+}
+
+fn main() {
+    foo(); //~ unused return value of `foo`
+
+    bar(); //~ unused return value of `bar`
+}

src/test/ui/lint/must_use-unit.stderr

@@ -0,0 +1,20 @@
+error: unused return value of `foo` which must be used
+  --> $DIR/must_use-unit.rs:14:5
+   |
+LL |     foo(); //~ unused return value of `foo`
+   |     ^^^^^^
+   |
+note: lint level defined here
+  --> $DIR/must_use-unit.rs:3:9
+   |
+LL | #![deny(unused_must_use)]
+   |         ^^^^^^^^^^^^^^^
+
+error: unused return value of `bar` which must be used
+  --> $DIR/must_use-unit.rs:16:5
+   |
+LL |     bar(); //~ unused return value of `bar`
+   |     ^^^^^^
+
+error: aborting due to 2 previous errors
+

src/test/ui/macros/issue-54441.stderr

@@ -1,9 +1,6 @@
 error: expected one of `crate`, `fn`, `pub`, `static`, or `type`, found `let`
   --> $DIR/issue-54441.rs:5:9
    |
-LL | #![feature(macros_in_extern)]
-   | - expected one of `crate`, `fn`, `pub`, `static`, or `type` here
-...
 LL |         let //~ ERROR expected
    |         ^^^ unexpected token
 ...