Add method_family attribute

Spelled as `#[unsafe(method_family($family))]`.

This was previously a private "modifier" inside `#[method(...)]`, but it
makes sense to have it as a separate attribute, if not only so that we
can reduce the amount of private API that framework crates depend on.

Author: madsmtm

crates/header-translator/src/method.rs

@@ -768,20 +768,31 @@ impl fmt::Display for Method {
         }
 
         let id_mm_name = match &self.memory_management {
-            MemoryManagement::IdCopy => Some("Copy"),
-            MemoryManagement::IdMutableCopy => Some("MutableCopy"),
-            MemoryManagement::IdNew => Some("New"),
-            MemoryManagement::IdInit => Some("Init"),
-            MemoryManagement::IdOther => Some("Other"),
+            // MemoryManagement::IdAlloc => Some("alloc"), // Unsupported
+            MemoryManagement::IdCopy => Some("copy"),
+            MemoryManagement::IdMutableCopy => Some("mutableCopy"),
+            MemoryManagement::IdNew => Some("new"),
+            MemoryManagement::IdInit => Some("init"),
+            MemoryManagement::IdOther => Some("none"),
             MemoryManagement::Normal => None,
         };
         if let Some(id_mm_name) = id_mm_name {
-            write!(f, "        #[method_id(@__method_family {id_mm_name} ")?;
+            // TODO: Be explicit about when we emit this for better
+            // compile-times, and when we do it for soundness.
+            writeln!(f, "        #[unsafe(method_family({id_mm_name}))]")?;
+        };
+
+        let method_kind = if self.memory_management == MemoryManagement::Normal {
+            "method"
         } else {
-            write!(f, "        #[method(")?;
-        }
+            "method_id"
+        };
         let error_trailing = if self.is_error { "_" } else { "" };
-        writeln!(f, "{}{})]", self.selector, error_trailing)?;
+        writeln!(
+            f,
+            "        #[{}({}{})]",
+            method_kind, self.selector, error_trailing
+        )?;
 
         //
         // Signature

crates/objc2/src/__macro_helpers/method_family.rs

@@ -21,13 +21,30 @@
 #[derive(Debug)]
 pub struct MethodFamily<const INNER: u8> {}
 
+/// The `new` family.
 pub type New = MethodFamily<1>;
+/// The `alloc` family.
 pub type Alloc = MethodFamily<2>;
+/// The `init` family.
 pub type Init = MethodFamily<3>;
+/// The `copy` family.
 pub type Copy = MethodFamily<4>;
+/// The `mutableCopy` family.
 pub type MutableCopy = MethodFamily<5>;
+/// No family.
 pub type Other = MethodFamily<6>;
 
+/// Helper module where `#[method_family($family:ident)]` will import its
+/// value from.
+#[allow(non_camel_case_types)]
+pub mod method_family_import {
+    // Rename to match Clang's `__attribute__((objc_method_family(family)))`.
+    pub use super::{
+        Alloc as alloc, Copy as copy, Init as init, MutableCopy as mutableCopy, New as new,
+        Other as none,
+    };
+}
+
 pub const fn method_family(selector: &str) -> u8 {
     let selector = selector.as_bytes();
     match (

crates/objc2/src/__macro_helpers/mod.rs

@@ -41,7 +41,7 @@ pub use self::define_class::{
 pub use self::defined_ivars::DefinedIvarsHelper;
 pub use self::image_info::ImageInfo;
 pub use self::method_family::{
-    method_family, Alloc, Copy, Init, MethodFamily, MutableCopy, New, Other,
+    method_family, method_family_import, Alloc, Copy, Init, MethodFamily, MutableCopy, New, Other,
 };
 pub use self::module_info::ModuleInfo;
 pub use self::msg_send::MsgSend;