Rollup merge of #143662 - obi1kenobi:pg/unsafe-attribute-wrappers, r=t-rustdoc

[rustdoc] Display unsafe attrs with edition 2024 `unsafe()` wrappers.

Use Rust 2024 edition representation for unsafe attributes in rustdoc HTML:
- `#[no_mangle]` -> `#[unsafe(no_mangle)]`
- `#[export_name = "foo"]` -> `#[unsafe(export_name = "foo")]`
- `#[link_section = ".text"]` -> `#[unsafe(link_section = ".text")]`

The 2024 edition representation is used regardless of the crate's own edition. This ensures that Rustaceans don't have to learn the rules of an outdated edition (e.g. that `unsafe()` wasn't always necessary) in order to understand a crate's documentation.

After some looking through the `T-rustdoc` issues, I was not able to find an existing issue for this. Apologies if I missed it.

r? ``````@aDotInTheVoid``````

src/librustdoc/clean/types.rs

@@ -763,13 +763,13 @@ impl Item {
             .iter()
             .filter_map(|attr| match attr {
                 hir::Attribute::Parsed(AttributeKind::LinkSection { name, .. }) => {
-                    Some(format!("#[link_section = \"{name}\"]"))
+                    Some(format!("#[unsafe(link_section = \"{name}\")]"))
                 }
                 hir::Attribute::Parsed(AttributeKind::NoMangle(..)) => {
-                    Some("#[no_mangle]".to_string())
+                    Some("#[unsafe(no_mangle)]".to_string())
                 }
                 hir::Attribute::Parsed(AttributeKind::ExportName { name, .. }) => {
-                    Some(format!("#[export_name = \"{name}\"]"))
+                    Some(format!("#[unsafe(export_name = \"{name}\")]"))
                 }
                 hir::Attribute::Parsed(AttributeKind::NonExhaustive(..)) => {
                     Some("#[non_exhaustive]".to_string())

tests/rustdoc/attribute-rendering.rs

@@ -1,7 +1,7 @@
 #![crate_name = "foo"]
 
 //@ has 'foo/fn.f.html'
-//@ has - //*[@'class="rust item-decl"]' '#[export_name = "f"] pub fn f()'
-#[export_name = "\
-f"]
+//@ has - //*[@'class="rust item-decl"]' '#[unsafe(export_name = "f")] pub fn f()'
+#[unsafe(export_name = "\
+f")]
 pub fn f() {}

tests/rustdoc/attributes-2021-edition.rs

@@ -0,0 +1,14 @@
+//@ edition: 2021
+#![crate_name = "foo"]
+
+//@ has foo/fn.f.html '//pre[@class="rust item-decl"]' '#[unsafe(no_mangle)]'
+#[no_mangle]
+pub extern "C" fn f() {}
+
+//@ has foo/fn.g.html '//pre[@class="rust item-decl"]' '#[unsafe(export_name = "bar")]'
+#[export_name = "bar"]
+pub extern "C" fn g() {}
+
+//@ has foo/fn.example.html '//pre[@class="rust item-decl"]' '#[unsafe(link_section = ".text")]'
+#[link_section = ".text"]
+pub extern "C" fn example() {}

tests/rustdoc/attributes-re-export-2021-edition.rs

@@ -0,0 +1,13 @@
+// Tests that attributes are correctly copied onto a re-exported item.
+//@ edition:2024
+#![crate_name = "re_export"]
+
+//@ has 're_export/fn.thingy2.html' '//pre[@class="rust item-decl"]' '#[unsafe(no_mangle)]'
+pub use thingymod::thingy as thingy2;
+
+mod thingymod {
+    #[unsafe(no_mangle)]
+    pub fn thingy() {
+
+    }
+}

tests/rustdoc/attributes-re-export.rs

@@ -2,7 +2,7 @@
 //@ edition:2021
 #![crate_name = "re_export"]
 
-//@ has 're_export/fn.thingy2.html' '//pre[@class="rust item-decl"]' '#[no_mangle]'
+//@ has 're_export/fn.thingy2.html' '//pre[@class="rust item-decl"]' '#[unsafe(no_mangle)]'
 pub use thingymod::thingy as thingy2;
 
 mod thingymod {

tests/rustdoc/attributes.rs

@@ -1,13 +1,18 @@
+//@ edition: 2024
 #![crate_name = "foo"]
 
-//@ has foo/fn.f.html '//pre[@class="rust item-decl"]' '#[no_mangle]'
-#[no_mangle]
+//@ has foo/fn.f.html '//pre[@class="rust item-decl"]' '#[unsafe(no_mangle)]'
+#[unsafe(no_mangle)]
 pub extern "C" fn f() {}
 
-//@ has foo/fn.g.html '//pre[@class="rust item-decl"]' '#[export_name = "bar"]'
-#[export_name = "bar"]
+//@ has foo/fn.g.html '//pre[@class="rust item-decl"]' '#[unsafe(export_name = "bar")]'
+#[unsafe(export_name = "bar")]
 pub extern "C" fn g() {}
 
+//@ has foo/fn.example.html '//pre[@class="rust item-decl"]' '#[unsafe(link_section = ".text")]'
+#[unsafe(link_section = ".text")]
+pub extern "C" fn example() {}
+
 //@ has foo/struct.Repr.html '//pre[@class="rust item-decl"]' '#[repr(C, align(8))]'
 #[repr(C, align(8))]
 pub struct Repr;

tests/rustdoc/reexport/reexport-attrs.rs

@@ -4,13 +4,13 @@
 
 extern crate reexports_attrs;
 
-//@ has 'foo/fn.f0.html' '//pre[@class="rust item-decl"]' '#[no_mangle]'
+//@ has 'foo/fn.f0.html' '//pre[@class="rust item-decl"]' '#[unsafe(no_mangle)]'
 pub use reexports_attrs::f0;
 
-//@ has 'foo/fn.f1.html' '//pre[@class="rust item-decl"]' '#[link_section = ".here"]'
+//@ has 'foo/fn.f1.html' '//pre[@class="rust item-decl"]' '#[unsafe(link_section = ".here")]'
 pub use reexports_attrs::f1;
 
-//@ has 'foo/fn.f2.html' '//pre[@class="rust item-decl"]' '#[export_name = "f2export"]'
+//@ has 'foo/fn.f2.html' '//pre[@class="rust item-decl"]' '#[unsafe(export_name = "f2export")]'
 pub use reexports_attrs::f2;
 
 //@ has 'foo/enum.T0.html' '//pre[@class="rust item-decl"]' '#[repr(u8)]'