Edit `rustc_arena::DropArena` docs
- Add a "Safety" section, edit formatting for clarity - Add missing punctuation in code comments
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@ -568,10 +568,13 @@ impl Drop for DropType {
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}
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/// An arena which can be used to allocate any type.
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///
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/// # Safety
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///
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/// Allocating in this arena is unsafe since the type system
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/// doesn't know which types it contains. In order to
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/// allocate safely, you must store a PhantomData<T>
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/// alongside this arena for each type T you allocate.
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/// allocate safely, you must store a `PhantomData<T>`
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/// alongside this arena for each type `T` you allocate.
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#[derive(Default)]
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pub struct DropArena {
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/// A list of destructors to run when the arena drops.
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@ -589,7 +592,7 @@ impl DropArena {
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ptr::write(mem, object);
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let result = &mut *mem;
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// Record the destructor after doing the allocation as that may panic
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// and would cause `object`'s destructor to run twice if it was recorded before
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// and would cause `object`'s destructor to run twice if it was recorded before.
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self.destructors
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.borrow_mut()
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.push(DropType { drop_fn: drop_for_type::<T>, obj: result as *mut T as *mut u8 });
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@ -607,16 +610,16 @@ impl DropArena {
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let start_ptr = self.arena.alloc_raw(Layout::array::<T>(len).unwrap()) as *mut T;
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let mut destructors = self.destructors.borrow_mut();
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// Reserve space for the destructors so we can't panic while adding them
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// Reserve space for the destructors so we can't panic while adding them.
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destructors.reserve(len);
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// Move the content to the arena by copying it and then forgetting
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// the content of the SmallVec
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// the content of the SmallVec.
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vec.as_ptr().copy_to_nonoverlapping(start_ptr, len);
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mem::forget(vec.drain(..));
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// Record the destructors after doing the allocation as that may panic
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// and would cause `object`'s destructor to run twice if it was recorded before
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// and would cause `object`'s destructor to run twice if it was recorded before.
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for i in 0..len {
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destructors
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.push(DropType { drop_fn: drop_for_type::<T>, obj: start_ptr.add(i) as *mut u8 });
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