From 41e21aa1c27522c6b29c5b88e37b1f479f63e38c Mon Sep 17 00:00:00 2001 From: Martin Habovstiak Date: Mon, 13 Sep 2021 15:44:27 +0200 Subject: Implement write() method for Box> This adds method similar to `MaybeUninit::write` main difference being it returns owned `Box`. This can be used to elide copy from stack safely, however it's not currently tested that the optimization actually occurs. Analogous methods are not provided for `Rc` and `Arc` as those need to handle the possibility of sharing. Some version of them may be added in the future. This was discussed in #63291 which this change extends. --- compiler/rustc_data_structures/src/functor.rs | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) (limited to 'compiler/rustc_data_structures/src') diff --git a/compiler/rustc_data_structures/src/functor.rs b/compiler/rustc_data_structures/src/functor.rs index 920f7b1ed0a..2703af97a1b 100644 --- a/compiler/rustc_data_structures/src/functor.rs +++ b/compiler/rustc_data_structures/src/functor.rs @@ -31,11 +31,9 @@ impl IdFunctor for Box { let value = raw.read(); // SAFETY: Converts `Box` to `Box>` which is the // inverse of `Box::assume_init()` and should be safe. - let mut raw: Box> = Box::from_raw(raw.cast()); + let raw: Box> = Box::from_raw(raw.cast()); // SAFETY: Write the mapped value back into the `Box`. - raw.write(f(value)?); - // SAFETY: We just initialized `raw`. - raw.assume_init() + Box::write(raw, f(value)?) }) } } -- cgit 1.4.1-3-g733a5