Merge pull request #523 from madsmtm/restrict-this-declare-class

Restrict `this` parameters to `Self`-like types in `declare_class!`

crates/objc2/CHANGELOG.md

@@ -81,6 +81,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 * Allow cloning `Id<AnyObject>`.
 * **BREAKING**: Restrict message sending to `&mut` references to things that
   implement `IsAllowedMutable`.
+* Disallow the ability to use non-`Self`-like types as the receiver in
+  `declare_class!`.
 
 ### Removed
 * **BREAKING**: Removed `ProtocolType` implementation for `NSObject`.

crates/objc2/src/__macro_helpers/declare_class.rs

@@ -1,9 +1,20 @@
+#[cfg(all(debug_assertions, feature = "verify"))]
+use alloc::vec::Vec;
+use core::marker::PhantomData;
+#[cfg(all(debug_assertions, feature = "verify"))]
+use std::collections::HashSet;
+
+#[cfg(all(debug_assertions, feature = "verify"))]
+use crate::runtime::{AnyProtocol, MethodDescription};
+
 use objc2_encode::Encoding;
 
+use crate::declare::{ClassBuilder, IvarType};
 use crate::encode::Encode;
 use crate::rc::{Allocated, Id};
+use crate::runtime::{AnyClass, MethodImplementation, Sel};
 use crate::runtime::{AnyObject, MessageReceiver};
-use crate::{ClassType, Message};
+use crate::{ClassType, Message, ProtocolType};
 
 use super::{CopyOrMutCopy, Init, MaybeUnwrap, New, Other};
 use crate::mutability;
@@ -52,7 +63,7 @@ where
 // 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`.
+// parameter `T`.
 impl<Ret, T> MessageRecieveId<Allocated<T>, Ret> for Init
 where
     T: Message,
@@ -190,3 +201,237 @@ where
 {
     // Noop
 }
+
+#[derive(Debug)]
+pub struct ClassBuilderHelper<T: ?Sized> {
+    builder: ClassBuilder,
+    p: PhantomData<T>,
+}
+
+#[track_caller]
+fn failed_declaring_class(name: &str) -> ! {
+    panic!("could not create new class {name}. Perhaps a class with that name already exists?")
+}
+
+impl<T: ?Sized + ClassType> ClassBuilderHelper<T> {
+    #[inline]
+    #[track_caller]
+    #[allow(clippy::new_without_default)]
+    pub fn new() -> Self
+    where
+        T::Super: ClassType,
+    {
+        let builder = match ClassBuilder::new(T::NAME, <T::Super as ClassType>::class()) {
+            Some(builder) => builder,
+            None => failed_declaring_class(T::NAME),
+        };
+
+        Self {
+            builder,
+            p: PhantomData,
+        }
+    }
+
+    #[inline]
+    pub fn add_protocol_methods<P>(&mut self) -> ClassProtocolMethodsBuilder<'_, T>
+    where
+        P: ?Sized + ProtocolType,
+    {
+        let protocol = P::protocol();
+
+        if let Some(protocol) = protocol {
+            self.builder.add_protocol(protocol);
+        }
+
+        #[cfg(all(debug_assertions, feature = "verify"))]
+        {
+            ClassProtocolMethodsBuilder {
+                builder: self,
+                protocol,
+                required_instance_methods: protocol
+                    .map(|p| p.method_descriptions(true))
+                    .unwrap_or_default(),
+                optional_instance_methods: protocol
+                    .map(|p| p.method_descriptions(false))
+                    .unwrap_or_default(),
+                registered_instance_methods: HashSet::new(),
+                required_class_methods: protocol
+                    .map(|p| p.class_method_descriptions(true))
+                    .unwrap_or_default(),
+                optional_class_methods: protocol
+                    .map(|p| p.class_method_descriptions(false))
+                    .unwrap_or_default(),
+                registered_class_methods: HashSet::new(),
+            }
+        }
+
+        #[cfg(not(all(debug_assertions, feature = "verify")))]
+        {
+            ClassProtocolMethodsBuilder { builder: self }
+        }
+    }
+
+    // Addition: This restricts to callee `T`
+    #[inline]
+    pub unsafe fn add_method<F>(&mut self, sel: Sel, func: F)
+    where
+        F: MethodImplementation<Callee = T>,
+    {
+        // SAFETY: Checked by caller
+        unsafe { self.builder.add_method(sel, func) }
+    }
+
+    #[inline]
+    pub unsafe fn add_class_method<F>(&mut self, sel: Sel, func: F)
+    where
+        F: MethodImplementation<Callee = AnyClass>,
+    {
+        // SAFETY: Checked by caller
+        unsafe { self.builder.add_class_method(sel, func) }
+    }
+
+    #[inline]
+    pub fn add_static_ivar<I: IvarType>(&mut self) {
+        self.builder.add_static_ivar::<I>()
+    }
+
+    #[inline]
+    pub fn register(self) -> &'static AnyClass {
+        self.builder.register()
+    }
+}
+
+/// Helper for ensuring that:
+/// - Only methods on the protocol are overriden.
+/// - TODO: The methods have the correct signature.
+/// - All required methods are overridden.
+#[derive(Debug)]
+pub struct ClassProtocolMethodsBuilder<'a, T: ?Sized> {
+    builder: &'a mut ClassBuilderHelper<T>,
+    #[cfg(all(debug_assertions, feature = "verify"))]
+    protocol: Option<&'static AnyProtocol>,
+    #[cfg(all(debug_assertions, feature = "verify"))]
+    required_instance_methods: Vec<MethodDescription>,
+    #[cfg(all(debug_assertions, feature = "verify"))]
+    optional_instance_methods: Vec<MethodDescription>,
+    #[cfg(all(debug_assertions, feature = "verify"))]
+    registered_instance_methods: HashSet<Sel>,
+    #[cfg(all(debug_assertions, feature = "verify"))]
+    required_class_methods: Vec<MethodDescription>,
+    #[cfg(all(debug_assertions, feature = "verify"))]
+    optional_class_methods: Vec<MethodDescription>,
+    #[cfg(all(debug_assertions, feature = "verify"))]
+    registered_class_methods: HashSet<Sel>,
+}
+
+impl<T: ?Sized + ClassType> ClassProtocolMethodsBuilder<'_, T> {
+    // Addition: This restricts to callee `T`
+    #[inline]
+    pub unsafe fn add_method<F>(&mut self, sel: Sel, func: F)
+    where
+        F: MethodImplementation<Callee = T>,
+    {
+        #[cfg(all(debug_assertions, feature = "verify"))]
+        if let Some(protocol) = self.protocol {
+            let _types = self
+                .required_instance_methods
+                .iter()
+                .chain(&self.optional_instance_methods)
+                .find(|desc| desc.sel == sel)
+                .map(|desc| desc.types)
+                .unwrap_or_else(|| {
+                    panic!(
+                        "failed overriding protocol method -[{protocol} {sel}]: method not found"
+                    )
+                });
+        }
+
+        // SAFETY: Checked by caller
+        unsafe { self.builder.add_method(sel, func) };
+
+        #[cfg(all(debug_assertions, feature = "verify"))]
+        if !self.registered_instance_methods.insert(sel) {
+            unreachable!("already added")
+        }
+    }
+
+    #[inline]
+    pub unsafe fn add_class_method<F>(&mut self, sel: Sel, func: F)
+    where
+        F: MethodImplementation<Callee = AnyClass>,
+    {
+        #[cfg(all(debug_assertions, feature = "verify"))]
+        if let Some(protocol) = self.protocol {
+            let _types = self
+                .required_class_methods
+                .iter()
+                .chain(&self.optional_class_methods)
+                .find(|desc| desc.sel == sel)
+                .map(|desc| desc.types)
+                .unwrap_or_else(|| {
+                    panic!(
+                        "failed overriding protocol method +[{protocol} {sel}]: method not found"
+                    )
+                });
+        }
+
+        // SAFETY: Checked by caller
+        unsafe { self.builder.add_class_method(sel, func) };
+
+        #[cfg(all(debug_assertions, feature = "verify"))]
+        if !self.registered_class_methods.insert(sel) {
+            unreachable!("already added")
+        }
+    }
+
+    #[cfg(all(debug_assertions, feature = "verify"))]
+    pub fn finish(self) {
+        let superclass = self.builder.builder.superclass();
+
+        if let Some(protocol) = self.protocol {
+            for desc in &self.required_instance_methods {
+                if self.registered_instance_methods.contains(&desc.sel) {
+                    continue;
+                }
+
+                // TODO: Don't do this when `NS_PROTOCOL_REQUIRES_EXPLICIT_IMPLEMENTATION`
+                if superclass
+                    .and_then(|superclass| superclass.instance_method(desc.sel))
+                    .is_some()
+                {
+                    continue;
+                }
+
+                panic!(
+                    "must implement required protocol method -[{protocol} {}]",
+                    desc.sel
+                )
+            }
+        }
+
+        if let Some(protocol) = self.protocol {
+            for desc in &self.required_class_methods {
+                if self.registered_class_methods.contains(&desc.sel) {
+                    continue;
+                }
+
+                // TODO: Don't do this when `NS_PROTOCOL_REQUIRES_EXPLICIT_IMPLEMENTATION`
+                if superclass
+                    .and_then(|superclass| superclass.class_method(desc.sel))
+                    .is_some()
+                {
+                    continue;
+                }
+
+                panic!(
+                    "must implement required protocol method +[{protocol} {}]",
+                    desc.sel
+                );
+            }
+        }
+    }
+
+    #[inline]
+    #[cfg(not(all(debug_assertions, feature = "verify")))]
+    pub fn finish(self) {}
+}