Merge pull request #354 from madsmtm/declare-class-method-id

Allow `#[method_id]` in `declare_class!`

Author: madsmtm

crates/objc2/CHANGELOG.md

@@ -10,6 +10,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 * Support `#[cfg(...)]` attributes in `extern_class!` macro.
 * Added support for selectors with multiple colons like `abc::` in the `sel!`,
   `extern_class!`, `extern_protocol!` and `declare_class!` macros.
+* Added ability to use `#[method_id(mySelector:)]` inside `declare_class!`,
+  just like you would do in `extern_methods!`.
 
 ### Changed
 * **BREAKING**: Using the automatic `NSError**`-to-`Result` functionality in
@@ -19,6 +21,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 ### Fixed
 * Allow empty structs in `declare_class!` macro.
 * Allow using `extern_methods!` without the `ClassType` trait in scope.
+* Fixed a few small issues with `declare_class!`.
 
 
 ## 0.3.0-beta.4 - 2022-12-24

crates/objc2/src/__macro_helpers.rs

@@ -30,6 +30,10 @@ pub use core::{compile_error, concat, panic, stringify};
 // TODO: Use `core::cell::LazyCell`
 pub use std::sync::Once;
 
+mod declare_class;
+
+pub use self::declare_class::{MaybeOptionId, MessageRecieveId};
+
 // Common selectors.
 //
 // These are put here to deduplicate the cached selector, and when using
@@ -850,6 +854,13 @@ mod tests {
         let _obj: Id<__RcTestObject, Shared> = unsafe { msg_send_id![&obj, methodReturningNull] };
     }
 
+    #[test]
+    #[should_panic = "unexpected NULL returned from -[__RcTestObject aMethod:]"]
+    fn test_normal_with_param_and_null() {
+        let obj = Id::into_shared(__RcTestObject::new());
+        let _obj: Id<__RcTestObject, Shared> = unsafe { msg_send_id![&obj, aMethod: false] };
+    }
+
     #[test]
     #[should_panic = "unexpected NULL description; receiver was NULL"]
     #[cfg(not(debug_assertions))] // Does NULL receiver checks

crates/objc2/src/__macro_helpers/declare_class.rs

@@ -0,0 +1,113 @@
+use core::mem::ManuallyDrop;
+use core::ptr;
+
+use crate::declare::__IdReturnValue;
+use crate::rc::{Allocated, Id, Ownership};
+use crate::{Message, MessageReceiver};
+
+use super::{CopyOrMutCopy, Init, MaybeUnwrap, New, Other};
+
+// One could imagine a different design where we simply had a method like
+// `fn convert_receiver()`, but that won't work in `declare_class!` since we
+// can't actually modify the `self` argument (e.g. `let self = foo(self)` is
+// not allowed).
+//
+// See `MsgSendId` and `RetainSemantics` for details on the retain semantics
+// we're following here.
+pub trait MessageRecieveId<Receiver, Ret> {
+    fn into_return(obj: Ret) -> __IdReturnValue;
+}
+
+// Receiver and return type have no correlation
+impl<Receiver, Ret> MessageRecieveId<Receiver, Ret> for New
+where
+    Receiver: MessageReceiver,
+    Ret: MaybeOptionId,
+{
+    #[inline]
+    fn into_return(obj: Ret) -> __IdReturnValue {
+        obj.consumed_return()
+    }
+}
+
+// Explicitly left unimplemented for now!
+// impl MessageRecieveId<impl MessageReceiver, Option<Allocated<T>>> for Alloc {}
+
+// Note: `MethodImplementation` allows for `Allocated` as the receiver, so we
+// restrict it here to only be when the selector is `init`.
+//
+// Additionally, the receiver and return type must have the same generic
+// generic parameter `T`.
+impl<Ret, T, O> MessageRecieveId<Allocated<T>, Ret> for Init
+where
+    T: Message,
+    O: Ownership,
+    Ret: MaybeOptionId<Input = Id<T, O>>,
+{
+    #[inline]
+    fn into_return(obj: Ret) -> __IdReturnValue {
+        obj.consumed_return()
+    }
+}
+
+// Receiver and return type have no correlation
+impl<Receiver, Ret> MessageRecieveId<Receiver, Ret> for CopyOrMutCopy
+where
+    Receiver: MessageReceiver,
+    Ret: MaybeOptionId,
+{
+    #[inline]
+    fn into_return(obj: Ret) -> __IdReturnValue {
+        obj.consumed_return()
+    }
+}
+
+// Receiver and return type have no correlation
+impl<Receiver, Ret> MessageRecieveId<Receiver, Ret> for Other
+where
+    Receiver: MessageReceiver,
+    Ret: MaybeOptionId,
+{
+    #[inline]
+    fn into_return(obj: Ret) -> __IdReturnValue {
+        obj.autorelease_return()
+    }
+}
+
+/// Helper trait for specifying an `Id<T, O>` or an `Option<Id<T, O>>`.
+///
+/// (Both of those are valid return types from declare_class! `#[method_id]`).
+pub trait MaybeOptionId: MaybeUnwrap {
+    fn consumed_return(self) -> __IdReturnValue;
+    fn autorelease_return(self) -> __IdReturnValue;
+}
+
+impl<T: Message, O: Ownership> MaybeOptionId for Id<T, O> {
+    #[inline]
+    fn consumed_return(self) -> __IdReturnValue {
+        let ptr: *mut T = Id::consume_as_ptr(ManuallyDrop::new(self));
+        __IdReturnValue(ptr.cast())
+    }
+
+    #[inline]
+    fn autorelease_return(self) -> __IdReturnValue {
+        let ptr: *mut T = Id::autorelease_return(self);
+        __IdReturnValue(ptr.cast())
+    }
+}
+
+impl<T: Message, O: Ownership> MaybeOptionId for Option<Id<T, O>> {
+    #[inline]
+    fn consumed_return(self) -> __IdReturnValue {
+        let ptr: *mut T = self
+            .map(|this| Id::consume_as_ptr(ManuallyDrop::new(this)))
+            .unwrap_or_else(ptr::null_mut);
+        __IdReturnValue(ptr.cast())
+    }
+
+    #[inline]
+    fn autorelease_return(self) -> __IdReturnValue {
+        let ptr: *mut T = Id::autorelease_return_option(self);
+        __IdReturnValue(ptr.cast())
+    }
+}

crates/objc2/src/declare.rs

@@ -124,6 +124,7 @@ use std::ffi::CString;
 
 use crate::encode::{Encode, EncodeArguments, Encoding, RefEncode};
 use crate::ffi;
+use crate::rc::Allocated;
 use crate::runtime::{Bool, Class, Imp, Object, Protocol, Sel};
 use crate::sel;
 use crate::Message;
@@ -196,6 +197,37 @@ macro_rules! method_decl_impl {
             }
         }
     };
+    (@<> Allocated<T>, $f:ty, $($t:ident),*) => {
+        #[doc(hidden)]
+        impl<T, $($t),*> private::Sealed for $f
+        where
+            T: Message + ?Sized,
+            $($t: Encode,)*
+        {}
+
+        #[doc(hidden)]
+        impl<T, $($t),*> MethodImplementation for $f
+        where
+            T: Message + ?Sized,
+            $($t: Encode,)*
+        {
+            type Callee = T;
+            type Ret = __IdReturnValue;
+            type Args = ($($t,)*);
+
+            fn __imp(self) -> Imp {
+                // SAFETY: `Allocated<T>` is the same as `NonNull<T>`, except
+                // with the assumption of a +1 calling convention.
+                //
+                // The calling convention is ensured to be upheld by having
+                // `__IdReturnValue` in the type, since that type is private
+                // and hence only internal macros like `#[method_id]` will be
+                // able to produce it (and that, in turn, only allows it if
+                // the selector is `init` as checked by `MessageRecieveId`).
+                unsafe { mem::transmute(self) }
+            }
+        }
+    };
     (# $abi:literal; $($t:ident),*) => {
         method_decl_impl!(@<'a> T, R, extern $abi fn(&'a T, Sel $(, $t)*) -> R, $($t),*);
         method_decl_impl!(@<'a> T, R, extern $abi fn(&'a mut T, Sel $(, $t)*) -> R, $($t),*);
@@ -207,6 +239,9 @@ macro_rules! method_decl_impl {
         method_decl_impl!(@<'a> Class, R, extern $abi fn(&'a Class, Sel $(, $t)*) -> R, $($t),*);
         method_decl_impl!(@<> Class, R, unsafe extern $abi fn(*const Class, Sel $(, $t)*) -> R, $($t),*);
         method_decl_impl!(@<'a> Class, R, unsafe extern $abi fn(&'a Class, Sel $(, $t)*) -> R, $($t),*);
+
+        method_decl_impl!(@<> Allocated<T>, extern $abi fn(Allocated<T>, Sel $(, $t)*) -> __IdReturnValue, $($t),*);
+        method_decl_impl!(@<> Allocated<T>, unsafe extern $abi fn(Allocated<T>, Sel $(, $t)*) -> __IdReturnValue, $($t),*);
     };
     ($($t:ident),*) => {
         method_decl_impl!(# "C"; $($t),*);
@@ -229,6 +264,17 @@ method_decl_impl!(A, B, C, D, E, F, G, H, I, J);
 method_decl_impl!(A, B, C, D, E, F, G, H, I, J, K);
 method_decl_impl!(A, B, C, D, E, F, G, H, I, J, K, L);
 
+/// Helper type for implementing `MethodImplementation` with a receiver of
+/// `Allocated<T>`, without exposing that implementation to users.
+#[doc(hidden)]
+#[repr(transparent)]
+pub struct __IdReturnValue(pub(crate) *mut Object);
+
+// SAFETY: `__IdReturnValue` is `#[repr(transparent)]`
+unsafe impl Encode for __IdReturnValue {
+    const ENCODING: Encoding = <*mut Object>::ENCODING;
+}
+
 fn method_type_encoding(ret: &Encoding, args: &[Encoding]) -> CString {
     // First two arguments are always self and the selector
     let mut types = format!("{ret}{}{}", <*mut Object>::ENCODING, Sel::ENCODING);
@@ -630,6 +676,7 @@ impl ProtocolBuilder {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use crate::rc::{Id, Shared};
     use crate::runtime::{NSObject, NSZone};
     use crate::test_utils;
     use crate::{declare_class, extern_protocol, msg_send, ClassType, ConformsTo, ProtocolType};
@@ -641,8 +688,8 @@ mod tests {
             const NAME: &'static str = "NSCopying";
 
             #[allow(unused)]
-            #[method(copyWithZone:)]
-            fn copy_with_zone(&self, _zone: *const NSZone) -> *mut Self;
+            #[method_id(copyWithZone:)]
+            fn copy_with_zone(&self, _zone: *const NSZone) -> Id<Self, Shared>;
         }
     );
 
@@ -814,9 +861,8 @@ mod tests {
             }
 
             unsafe impl ConformsTo<NSCopyingObject> for Custom {
-                #[method(copyWithZone:)]
-                #[allow(unreachable_code)]
-                fn copy_with_zone(&self, _zone: *const NSZone) -> *mut Self {
+                #[method_id(copyWithZone:)]
+                fn copy_with_zone(&self, _zone: *const NSZone) -> Id<Self, Shared> {
                     unimplemented!()
                 }
             }
@@ -910,9 +956,8 @@ mod tests {
             }
 
             unsafe impl ConformsTo<NSCopyingObject> for Custom {
-                #[method(copyWithZone:)]
-                #[allow(unreachable_code)]
-                fn copy_with_zone(&self, _zone: *const NSZone) -> *mut Self {
+                #[method_id(copyWithZone:)]
+                fn copy_with_zone(&self, _zone: *const NSZone) -> Id<Self, Shared> {
                     unimplemented!()
                 }
 
@@ -924,4 +969,50 @@ mod tests {
 
         let _cls = Custom::class();
     }
+
+    // Proof-of-concept how we could make declare_class! accept generic.
+    #[test]
+    fn test_generic() {
+        struct GenericDeclareClass<T>(T);
+
+        unsafe impl<T> RefEncode for GenericDeclareClass<T> {
+            const ENCODING_REF: Encoding = Encoding::Object;
+        }
+        unsafe impl<T> Message for GenericDeclareClass<T> {}
+
+        unsafe impl<T> ClassType for GenericDeclareClass<T> {
+            type Super = NSObject;
+            const NAME: &'static str = "GenericDeclareClass";
+
+            #[inline]
+            fn as_super(&self) -> &Self::Super {
+                unimplemented!()
+            }
+
+            #[inline]
+            fn as_super_mut(&mut self) -> &mut Self::Super {
+                unimplemented!()
+            }
+
+            fn class() -> &'static Class {
+                let superclass = NSObject::class();
+                let mut builder = ClassBuilder::new(Self::NAME, superclass).unwrap();
+
+                unsafe {
+                    builder.add_method(
+                        sel!(generic),
+                        <GenericDeclareClass<T>>::generic as unsafe extern "C" fn(_, _),
+                    );
+                }
+
+                builder.register()
+            }
+        }
+
+        impl<T> GenericDeclareClass<T> {
+            extern "C" fn generic(&self, _cmd: Sel) {}
+        }
+
+        let _ = GenericDeclareClass::<()>::class();
+    }
 }