You need to implement Add on &Vector rather than on Vector. impl<‘a, ‘b> Add<&’b Vector> for &’a Vector { type Output = Vector; fn add(self, other: &’b Vector) -> Vector { Vector { x: self.x + other.x, y: self.y + other.y, } } } In its definition, Add::add always takes self by value. But references … Read more
The question you asked TL;DR: No, you cannot return a reference to a variable that is owned by a function. This applies if you created the variable or if you took ownership of the variable as a function argument. Solutions Instead of trying to return a reference, return an owned object. String instead of &str, … Read more
It’s easiest to understand what non-lexical lifetimes are by understanding what lexical lifetimes are. In versions of Rust before non-lexical lifetimes are present, this code will fail: fn main() { let mut scores = vec![1, 2, 3]; let score = &scores[0]; scores.push(4); } The Rust compiler sees that scores is borrowed by the score variable, … Read more
The other answers all have salient points (fjh’s concrete example where an explicit lifetime is needed), but are missing one key thing: why are explicit lifetimes needed when the compiler will tell you you’ve got them wrong? This is actually the same question as “why are explicit types needed when the compiler can infer them”. … Read more
Managing the lifetimes of garbage-collected objects [closed]
Let’s look at a simple implementation of this: struct Parent { count: u32, } struct Child<‘a> { parent: &’a Parent, } struct Combined<‘a> { parent: Parent, child: Child<‘a>, } impl<‘a> Combined<‘a> { fn new() -> Self { let parent = Parent { count: 42 }; let child = Child { parent: &parent }; Combined { … Read more
The lifetime of function static variables begins the first time[0] the program flow encounters the declaration and it ends at program termination. This means that the run-time must perform some book keeping in order to destruct it only if it was actually constructed. Additionally, since the standard says that the destructors of static objects must … Read more