When we match a pattern that contains variables, the matching data values are moved into the variables (unless their data type has the Copy trait). For example, this will cause the compiler to report an error, even though at first glance it seems reasonable, especially for people who are used to other programming languages:
let source5 = DemoStruct { id: 40, name: String::from("A Surprising Thing"), probability: 0.93 };
if let DemoStruct {id: 41, name: x, probability: _} = source5 {
println!("Extracted name: {}", x);
}
println!("source5.name is {}", source5.name);
The problem is that, after the if let, source5.name does not (or at least might not) contain a value anymore, because that value was moved to the x variable. The compiler can't be sure that the final println! command will always be valid, which...