Allows to fetch a resource in a system mutably.
If the resource isn't strictly required, you should use
T: The type of the resource
Auto Trait Implementations
impl<'a, T> !RefUnwindSafe for FetchMut<'a, T>
impl<'a, T> !UnwindSafe for FetchMut<'a, T>
type Error = Infallible
The type returned in the event of a conversion error.