box: fixup map/try_map deallocate calls

@@ -731,12 +731,16 @@ impl<T, A: Allocator> Box<T, A> {         let (value, allocation) = Box::take(this);         let (raw, alloc) = Box::into_non_null_with_allocator(allocation);         if size_of::<T>() == size_of::<U>() && align_of::<T>() == align_of::<U>() {-            // ignore-tidy-undocumented-unsafe+            // SAFETY: We checked that the memory requirements are the same for both types+            // and `raw` is already a valid pointer for the requisite memory.             let allocation = unsafe { Box::from_non_null_in(raw.cast::<MaybeUninit<U>>(), alloc) };             Box::write(allocation, f(value))         } else {-            // ignore-tidy-undocumented-unsafe-            unsafe { alloc.deallocate(raw.cast(), Layout::for_value(&value)) }+            if size_of::<T>() != 0 {+                // SAFETY: `raw` isn't dangling since it points to a non-zero-sized+                // allocation and is never used again after this point.+                unsafe { alloc.deallocate(raw.cast(), Layout::for_value(&value)) }+            }             Box::new_in(f(value), alloc)         }     }@@ -773,12 +777,16 @@ impl<T, A: Allocator> Box<T, A> {         let (raw, alloc) = Box::into_non_null_with_allocator(allocation);         if size_of::<T>() == size_of::<R::Output>() && align_of::<T>() == align_of::<R::Output>() {             let allocation =-                // ignore-tidy-undocumented-unsafe+                // SAFETY: We checked that the memory requirements are the same for both types+                // and `raw` is already a valid pointer for the requisite memory.                 unsafe { Box::from_non_null_in(raw.cast::<MaybeUninit<R::Output>>(), alloc) };             try { Box::write(allocation, f(value)?) }         } else {-            // ignore-tidy-undocumented-unsafe-            unsafe { alloc.deallocate(raw.cast(), Layout::for_value(&value)) }+            if size_of::<T>() != 0 {+                // SAFETY: `raw` isn't dangling since it points to a non-zero-sized+                // allocation and is never used again after this point.+                unsafe { alloc.deallocate(raw.cast(), Layout::for_value(&value)) }+            }             try { Box::new_in(f(value)?, alloc) }         }     }