A few memory management questions

[niu]

I am new to rust. As I known, rust has no GC. So I am confused a few things.
First,

struct node {
name: String,
x: float64,
y: float64,
}

let mut n = node{
name: "test".to_string(),
x: 1.0,
y: 1.0,
}

// If I want to change the node's name like this.
n.name = String::from("test1");
//where is the "test".to_string(), will the memory of it be released ?

// If I want to change the node's name like this.
n.name = String::from("test1");
//where is the "test".to_string(), will the memory of it be released ?

And I am confused about some other data structures, such like name is a Vec or some other data which will allocate memory on heap. When it is changed, is the memory been released ?
Another simple example.

let mut x = "where am i".to_string();
x = "you are changed".to_string();
//where is the "where am i".to_string() now?

//where is the "where am i".to_string() now? is it been released?

And I am confused about many examples. Such as vector and hashmap, hashmap 's key's value is always changed, will the value's memory be released? If someone knows it ,please help me! thx!

[Hyeonu]

Structs and collections own its fields/elements. When the field/element is overwritten, the previous value is not owned by anyone so it will be dropped just before the assignment.

Note that the struct/collection owns the field/element doesn't implies they can't stores the references. Vec<&String> owns the &Strings but the &String doesn't own its buffer since it's just an reference.

[niu]

Ok, I got it, how about the simple example? What if a string value changed? Is it the same thing?

let mut x = "where am i".to_string();
x = "you are changed".to_string();
//where is the "where am i".to_string() now?

[Hyeonu]

Yes. Variables owns its value.