signal nymph
I have a struct that looks like this. How can i implement Copy on it? the only way i can see is to 1. make params and returns borrows, but then i need to a lifetimes everywhere and rewrite the 90% of my project. Or 2. turn the Vecs to arrays and limit the length, which i don't really want to do.
#[derive(Debug, PartialEq, Clone, Copy)]
pub struct FuncPtr {
pub ptr: usize,
pub params: Vec<TypeLiteral>,
pub returns: Vec<TypeLiteral>
}
chilly kettle
How can i implement Copy on it?
You can't.
You can, however, stick to Clone and call.clone() where needed
Copy represents a "dumb" bitwise copy: it copies the bits of the thing you have on hand. This is fine for, say, u32, but not for Vec: in the latter's case, the thing you're holding is just a (ptr, len, capacity) struct, the actual data is behind the pointer
Duplicating that struct would not duplicate the actual data
And it would lead to two vecs that both think they own it, which can trivially lead to things like use after free or double free
.clone(), on the other hand, also copies the actual data
pulsar zenith
You'll have to turn them into arrays.
There are crates for stack based, size limited Vecs that can improve the ergonomics.
chilly kettle
ArrayVec is still not Copy though
It has to be Drop, and Drop is mutally exclusive with Copy
signal nymph
think ill just remove Copy and spam .clone() everywhere. not pretty but that's the rust life 😎 . Ty anyway