Allow #[cppgc] &mut T in sync ops

Closes #787

Author: littledivy

core/cppgc.rs

@@ -41,10 +41,16 @@ pub fn make_cppgc_object<'a, T: 'static>(
   obj
 }
 
+#[repr(C)]
+struct InnerMember {
+  inner: [usize; 2],
+  ptr: *mut (),
+}
+
 #[allow(clippy::needless_lifetimes)]
 pub fn try_unwrap_cppgc_object<'sc, T: 'static>(
   val: v8::Local<'sc, v8::Value>,
-) -> Option<&'sc T> {
+) -> Option<&'sc mut T> {
   let Ok(obj): Result<v8::Local<v8::Object>, _> = val.try_into() else {
     return None;
   };
@@ -60,13 +66,13 @@ pub fn try_unwrap_cppgc_object<'sc, T: 'static>(
   // The object can only be created by `make_cppgc_object`.
   let member = unsafe {
     let ptr = obj.get_aligned_pointer_from_internal_field(SLOT_OFFSET);
-    let obj = &*(ptr as *const v8::cppgc::InnerMember);
-    obj.get::<CppGcObject<T>>()
+    let obj = &*(ptr as *mut InnerMember);
+    obj.ptr.cast::<CppGcObject<T>>().as_mut().unwrap()
   };
 
   if member.tag != TypeId::of::<T>() {
     return None;
   }
 
-  Some(&member.member)
+  Some(&mut member.member)
 }

core/runtime/ops.rs

@@ -608,6 +608,7 @@ mod tests {
       op_arraybuffer_slice,
       op_test_get_cppgc_resource,
       op_test_make_cppgc_resource,
+      op_test_set_cppgc_resource,
       op_external_make,
       op_external_process,
       op_external_make_ptr,
@@ -1907,14 +1908,24 @@ mod tests {
     resource.value
   }
 
+  #[op2(fast)]
+  pub fn op_test_set_cppgc_resource(
+    #[cppgc] resource: &mut TestResource,
+    value: u32,
+  ) {
+    resource.value = value;
+  }
+
   #[test]
   pub fn test_op_cppgc_object() -> Result<(), Box<dyn std::error::Error>> {
     run_test2(
       10,
-      "op_test_make_cppgc_resource, op_test_get_cppgc_resource",
+      "op_test_make_cppgc_resource, op_test_get_cppgc_resource, op_test_set_cppgc_resource",
       r"
       const resource = op_test_make_cppgc_resource();
-      assert(op_test_get_cppgc_resource(resource) == 42);",
+      assert(op_test_get_cppgc_resource(resource) == 42);
+      op_test_set_cppgc_resource(resource, 43);
+      assert(op_test_get_cppgc_resource(resource) == 43);",
     )?;
     Ok(())
   }

ops/op2/dispatch_async.rs

@@ -47,7 +47,7 @@ pub(crate) fn generate_dispatch_async(
   let mut output = TokenStream::new();
 
   let with_self = if generator_state.needs_self {
-    with_self(generator_state, &signature.ret_val)
+    with_self(generator_state, true, &signature.ret_val)
       .map_err(V8SignatureMappingError::NoSelfMapping)?
   } else {
     quote!()

ops/op2/dispatch_slow.rs

@@ -92,7 +92,7 @@ pub(crate) fn generate_dispatch_slow(
   )?);
 
   let with_self = if generator_state.needs_self {
-    with_self(generator_state, &signature.ret_val)
+    with_self(generator_state, false, &signature.ret_val)
       .map_err(V8SignatureMappingError::NoSelfMapping)?
   } else {
     quote!()
@@ -246,6 +246,7 @@ pub(crate) fn with_js_runtime_state(
 
 pub(crate) fn with_self(
   generator_state: &mut GeneratorState,
+  is_async: bool,
   ret_val: &RetVal,
 ) -> Result<TokenStream, V8MappingError> {
   generator_state.needs_opctx = true;
@@ -254,6 +255,7 @@ pub(crate) fn with_self(
     format!("expected {}", &generator_state.self_ty),
   )?;
   let tokens = if matches!(ret_val, RetVal::Future(_) | RetVal::FutureResult(_))
+    || is_async
   {
     let tokens = gs_quote!(generator_state(self_ty, fn_args, scope) => {
       let Some(self_) = deno_core::_ops::CppGcObjectGuard::<#self_ty>::try_new_from_cppgc_object(&mut *#scope, #fn_args.this().into()) else {

ops/op2/signature.rs

@@ -1470,12 +1470,10 @@ fn parse_type_state(ty: &Type) -> Result<Arg, ArgError> {
 
 fn parse_cppgc(position: Position, ty: &Type) -> Result<Arg, ArgError> {
   match (position, ty) {
-    (Position::Arg, Type::Reference(of)) if of.mutability.is_none() => {
-      match &*of.elem {
-        Type::Path(of) => Ok(Arg::CppGcResource(stringify_token(&of.path))),
-        _ => Err(ArgError::InvalidCppGcType(stringify_token(ty))),
-      }
-    }
+    (Position::Arg, Type::Reference(of)) => match &*of.elem {
+      Type::Path(of) => Ok(Arg::CppGcResource(stringify_token(&of.path))),
+      _ => Err(ArgError::InvalidCppGcType(stringify_token(ty))),
+    },
     (Position::RetVal, Type::Path(of)) => {
       Ok(Arg::CppGcResource(stringify_token(&of.path)))
     }

ops/op2/test_cases/sync/cppgc_resource.out

@@ -12,3 +12,6 @@ fn op_make_cppgc_object() -> Wrap {
 
 #[op2(fast)]
 fn op_use_cppgc_object(#[cppgc] _wrap: &Wrap) {}
+
+#[op2(fast)]
+fn op_use_cppgc_object_mut(#[cppgc] _wrap: &mut Wrap) {}

ops/op2/test_cases/sync/cppgc_resource.rs

@@ -11,3 +11,6 @@ fn op_use_cppgc_object(#[cppgc] _wrap: &'static Wrap) {}
 
 #[op2(fast)]
 fn op_use_buffer(#[buffer] _buffer: &'static [u8]) {}
+
+#[op2(async)]
+async fn op_use_cppgc_object_mut_async(#[cppgc] _wrap: &mut Wrap) {}