Implement the unsafe-fields RFC.

Co-Authored-By: Jacob Pratt <jacob@jhpratt.dev>

src/tools/rustfmt/src/items.rs

@@ -1916,15 +1916,15 @@ pub(crate) fn rewrite_struct_field_prefix(
     field: &ast::FieldDef,
 ) -> RewriteResult {
     let vis = format_visibility(context, &field.vis);
+    let safety = format_safety(field.safety);
     let type_annotation_spacing = type_annotation_spacing(context.config);
     Ok(match field.ident {
         Some(name) => format!(
-            "{}{}{}:",
-            vis,
+            "{vis}{safety}{}{}:",
             rewrite_ident(context, name),
             type_annotation_spacing.0
         ),
-        None => vis.to_string(),
+        None => format!("{vis}{safety}"),
     })
 }
 

src/tools/rustfmt/tests/source/unsafe-field.rs

@@ -0,0 +1,16 @@
+struct Foo {
+    unsafe
+    field: (),
+}
+
+enum Bar {
+    Variant {
+        unsafe
+        field: (),
+    },
+}
+
+union Baz {
+    unsafe
+    field: (),
+}

src/tools/rustfmt/tests/target/unsafe-field.rs

@@ -0,0 +1,11 @@
+struct Foo {
+    unsafe field: (),
+}
+
+enum Bar {
+    Variant { unsafe field: () },
+}
+
+union Baz {
+    unsafe field: (),
+}