Description
When a function returns Option<T> and the function is basically a wrapper on an Arc<RwLock<Option<T>>> but T does not implement Clone then the code self.value.read().unwrap().as_ref().map(|value| value.clone()) will show a compile error "mismatched types" as the return type is Option<_> and found Option<&_>. This suggests that I need to clone the value, but I am already doing that. Trying to dereference the value also fails with the error that the T does not implement Copy (nor do I want it to).
Example:
struct MyStruct<T>
{
value: Arc<RwLock<Option<T>>>,
}
impl<T> MyStruct<T>
{
fn get_value(&self) -> Option<T> {
let locked_value = self.value.read().unwrap();
locked_value.as_ref().map(|value| value.clone())
}
}
I expected to see this happen:
The underlying issue of "no method named clone found for type" is the true underlying problem that is hidden from the developer.
Instead, this happened:
I was misdirected to the return type being invalid.
I was under the impression that bad or misleading error messages in Rust are considered bugs, but if that is not the case please let me know what I need to do to help resolve this issue. Thank you.
Edit:
While constructing the more complete example, I noticed that omitting the .as_ref() then caused the compiler to properly call out the lack of Clone. When I added T: Clone then an error would appear since I was missing .as_ref(). This bug demonstrates that if you already start with .as_ref() included, that the compiler fails to point you to the lack of Clone.