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* Refactor the `[[HostDefined]]` implementation. Currently `[[HostDefined]]` doesn't permit you to mutably borrow two objects from the `[[HostDefined]]` field since the `FxHashMap` is wrapped under a `GcRefCell`. This commit implements a `get_mut_many` (from `hashbrown`'s `HashMap`) method to permit accessing several `NativeObject`s using a `NativeTuple`. Additionally, this commit takes the opportunity to provide automatic downcasting on the `insert` and `remove` methods for `[[HostDefined]]`. * Update `[[HostDefined]]` example.pull/3462/head
Alistair
12 months ago
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GitHub
6 changed files with 204 additions and 85 deletions
@ -1,111 +1,154 @@
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use std::any::TypeId; |
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use boa_gc::{GcRef, GcRefCell, GcRefMut}; |
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use boa_macros::{Finalize, Trace}; |
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use rustc_hash::FxHashMap; |
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use hashbrown::hash_map::HashMap; |
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use crate::object::NativeObject; |
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/// Map used to store the host defined objects.
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#[doc(hidden)] |
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type HostDefinedMap = FxHashMap<TypeId, Box<dyn NativeObject>>; |
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/// This represents a `ECMASCript` specification \[`HostDefined`\] field.
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///
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/// This allows storing types which are mapped by their [`TypeId`].
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#[derive(Default, Trace, Finalize)] |
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#[allow(missing_debug_implementations)] |
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pub struct HostDefined { |
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state: GcRefCell<HostDefinedMap>, |
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// INVARIANT: All key-value pairs `(id, obj)` satisfy:
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// `id == TypeId::of::<T>() && obj.is::<T>()`
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// for some type `T : NativeObject`.
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types: HashMap<TypeId, Box<dyn NativeObject>>, |
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} |
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// TODO: Track https://github.com/rust-lang/rust/issues/65991 and
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// https://github.com/rust-lang/rust/issues/90850 to remove this
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// when those are stabilized.
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fn downcast_boxed_native_object_unchecked<T: NativeObject>(obj: Box<dyn NativeObject>) -> Box<T> { |
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let raw: *mut dyn NativeObject = Box::into_raw(obj); |
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// SAFETY: We know that `obj` is of type `T` (due to the INVARIANT of `HostDefined`).
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// See `HostDefined::insert`, `HostDefined::insert_default` and `HostDefined::remove`.
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unsafe { Box::from_raw(raw.cast::<T>()) } |
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} |
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impl HostDefined { |
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/// Insert a type into the [`HostDefined`].
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///
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/// # Panics
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///
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/// Panics if [`HostDefined`] field is borrowed.
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#[track_caller] |
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pub fn insert_default<T: NativeObject + Default>(&self) -> Option<Box<dyn NativeObject>> { |
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self.state |
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.borrow_mut() |
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pub fn insert_default<T: NativeObject + Default>(&mut self) -> Option<Box<T>> { |
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self.types |
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.insert(TypeId::of::<T>(), Box::<T>::default()) |
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.map(downcast_boxed_native_object_unchecked) |
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} |
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/// Insert a type into the [`HostDefined`].
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///
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/// # Panics
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///
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/// Panics if [`HostDefined`] field is borrowed.
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#[track_caller] |
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pub fn insert<T: NativeObject>(&self, value: T) -> Option<Box<dyn NativeObject>> { |
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self.state |
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.borrow_mut() |
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pub fn insert<T: NativeObject>(&mut self, value: T) -> Option<Box<T>> { |
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self.types |
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.insert(TypeId::of::<T>(), Box::new(value)) |
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.map(downcast_boxed_native_object_unchecked) |
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} |
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/// Check if the [`HostDefined`] has type T.
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///
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/// # Panics
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///
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/// Panics if [`HostDefined`] field is borrowed mutably.
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#[must_use] |
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#[track_caller] |
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pub fn has<T: NativeObject>(&self) -> bool { |
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self.state.borrow().contains_key(&TypeId::of::<T>()) |
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self.types.contains_key(&TypeId::of::<T>()) |
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} |
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/// Remove type T from [`HostDefined`], if it exists.
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///
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/// Returns [`Some`] with the object if it exits, [`None`] otherwise.
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///
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/// # Panics
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///
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/// Panics if [`HostDefined`] field is borrowed.
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#[track_caller] |
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pub fn remove<T: NativeObject>(&self) -> Option<Box<dyn NativeObject>> { |
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self.state.borrow_mut().remove(&TypeId::of::<T>()) |
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pub fn remove<T: NativeObject>(&mut self) -> Option<Box<T>> { |
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self.types |
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.remove(&TypeId::of::<T>()) |
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.map(downcast_boxed_native_object_unchecked) |
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} |
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/// Get type T from [`HostDefined`], if it exits.
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///
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/// # Panics
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///
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/// Panics if [`HostDefined`] field is borrowed.
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/// Get type T from [`HostDefined`], if it exists.
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#[track_caller] |
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pub fn get<T: NativeObject>(&self) -> Option<GcRef<'_, T>> { |
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GcRef::try_map(self.state.borrow(), |state| { |
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state |
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pub fn get<T: NativeObject>(&self) -> Option<&T> { |
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self.types |
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.get(&TypeId::of::<T>()) |
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.map(Box::as_ref) |
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.and_then(<dyn NativeObject>::downcast_ref::<T>) |
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}) |
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} |
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/// Get type T from [`HostDefined`], if it exits.
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///
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/// # Panics
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///
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/// Panics if [`HostDefined`] field is borrowed.
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/// Get type T from [`HostDefined`], if it exists.
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#[track_caller] |
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pub fn get_mut<T: NativeObject>(&self) -> Option<GcRefMut<'_, HostDefinedMap, T>> { |
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GcRefMut::try_map( |
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self.state.borrow_mut(), |
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|state: &mut FxHashMap<TypeId, Box<dyn NativeObject>>| { |
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state |
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pub fn get_mut<T: NativeObject>(&mut self) -> Option<&mut T> { |
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self.types |
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.get_mut(&TypeId::of::<T>()) |
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.map(Box::as_mut) |
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.and_then(<dyn NativeObject>::downcast_mut::<T>) |
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}, |
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) |
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} |
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/// Get type a tuple of types from [`HostDefined`], if they exist.
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#[track_caller] |
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pub fn get_many_mut<T, const SIZE: usize>(&mut self) -> Option<T::NativeTupleMutRef<'_>> |
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where |
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T: NativeTuple<SIZE>, |
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{ |
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let ids = T::as_type_ids(); |
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let refs: [&TypeId; SIZE] = ids |
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.iter() |
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.collect::<Vec<_>>() |
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.try_into() |
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.expect("tuple should be of size `SIZE`"); |
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self.types.get_many_mut(refs).and_then(T::mut_ref_from_anys) |
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} |
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/// Clears all the objects.
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///
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/// # Panics
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///
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/// Panics if [`HostDefined`] field is borrowed.
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#[track_caller] |
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pub fn clear(&self) { |
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self.state.borrow_mut().clear(); |
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pub fn clear(&mut self) { |
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self.types.clear(); |
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} |
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} |
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/// This trait represents a tuple of [`NativeObject`]s capable of being
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/// used in [`HostDefined`].
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///
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/// This allows accessing multiple types from [`HostDefined`] at once.
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pub trait NativeTuple<const SIZE: usize> { |
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type NativeTupleMutRef<'a>; |
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fn as_type_ids() -> Vec<TypeId>; |
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fn mut_ref_from_anys( |
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anys: [&'_ mut Box<dyn NativeObject>; SIZE], |
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) -> Option<Self::NativeTupleMutRef<'_>>; |
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} |
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macro_rules! impl_native_tuple { |
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($size:literal $(,$name:ident)* ) => { |
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impl<$($name: NativeObject,)*> NativeTuple<$size> for ($($name,)*) { |
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type NativeTupleMutRef<'a> = ($(&'a mut $name,)*); |
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fn as_type_ids() -> Vec<TypeId> { |
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vec![$(TypeId::of::<$name>(),)*] |
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} |
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fn mut_ref_from_anys( |
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anys: [&'_ mut Box<dyn NativeObject>; $size], |
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) -> Option<Self::NativeTupleMutRef<'_>> { |
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#[allow(unused_variables, unused_mut)] |
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let mut anys = anys.into_iter(); |
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Some(($( |
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anys.next().expect("Expect `anys` to be of length `SIZE`").downcast_mut::<$name>()?, |
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)*)) |
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} |
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} |
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} |
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} |
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impl_native_tuple!(0); |
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impl_native_tuple!(1, A); |
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impl_native_tuple!(2, A, B); |
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impl_native_tuple!(3, A, B, C); |
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impl_native_tuple!(4, A, B, C, D); |
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impl_native_tuple!(5, A, B, C, D, E); |
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impl_native_tuple!(6, A, B, C, D, E, F); |
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impl_native_tuple!(7, A, B, C, D, E, F, G); |
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impl_native_tuple!(8, A, B, C, D, E, F, G, H); |
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impl_native_tuple!(9, A, B, C, D, E, F, G, H, I); |
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impl_native_tuple!(10, A, B, C, D, E, F, G, H, I, J); |
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impl_native_tuple!(11, A, B, C, D, E, F, G, H, I, J, K); |
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impl_native_tuple!(12, A, B, C, D, E, F, G, H, I, J, K, L); |
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